XC racer #8 in a series

[G Norsworthy]

This build log will cover the 8th XC racer in a series built over the last 20 years. It includes influence from the XCBD, Supra, Wiley, and assorted experience collected over 20 years. I will try not to repeat what Anker has shown recently in the XCBD log, only what is different. I will show the entire process through flight. The design is targeted at the west coast races, but would be ideal for the Level V tasks as well.

[G Norsworthy]

Templates were printed on paper and cut from plastic laminate. Cores were cut using a Feathercut. For the longer sections a homemade bow with lots of tension gave better results. There was a bit of a learning curve at the beginning, so there is more spackle than I would like, but the next one will be very nice. The wing and stab tips, and LE were hand sanded with cardboard templates.

[danstrider]

Subscribed! I'm interested to see this one come together :-)

Dan

[G Norsworthy]

Here is a breakdown for enough stuff to build two of these. The only major item lacking is the glass for the wing which was left over from the last one. Two rolls from Thayer runs about $100 and is enough to build at least three, maybe more.

item quantity each total
formica 1 16 16
foam 3 26.66 79.98
resin,tape 96.81
ACP mylar, bags, carbon 1 97.88 97.88
US Comp kevlar, crowfoot 1 139.45 139.45
plywood 1 19.66 19.66
double stick 1 9 9


total
458.78

[G Norsworthy]

Extruded foam always has internal stresses that relax when cut. No matter how careful you are in the blocking step, the angles at the transitions will never match. That is why I cut them very slightly over and plan to match them up later. We will be building on the bottom. I cut the templates as tall as possible and went through the top in a few places near the root. Consequently there was more spackle and sand time than I would like but we must press on. The templates will be adjusted down 1/8" before the next cutting session. These templates were drawn with the top point constant and the bottom rising towards the tip as the airfoils get thinner. This adds a slight dihedral effect and looks better to the eye.

Lay out some masking tape in case you don't want to use a sharpie on the landlady's granite countertop and draw the sweep. Use the LE because that is where we lined up the templates when we cut the cores. Sand the bottom beds until they fit over the lines, glue and weigh. Once the beds are finished you can follow with the cores.

[G Norsworthy]

I must admit I neglected to account for the short center section and designed in 3/8" Al rods for joiners. In 20 years I've never bent or broken one except in contact with dry lake beds, hillsides, etc but those were all 7-8 ft center sections. It's already in so we go ahead with it but in the future there is room for 1/2" rods.

I drew out the geometry for the (now 1/2") joiner rods plus brass tube to verify that it fits in the space at 9" width. The dimensions are not on the PDF because it will mess up the scaling on the big drawing but you get the idea.

Next I plot the ribs and half ribs on paper with two concentric circles for drilling the hole for the tube, one for the pilot hole and one for the big drill. The paper is stuck on with glue stick and the ribs are cut out with band saw and belt sander. Next the holes are drilled as carefully as possible.

[G Norsworthy]

Slide the root and half ribs onto brass tube and sand as needed to make sure the bottoms are all even. We will be referencing the bottom for all the glueing and from here on it is more important that the bottoms match than the ribs fit the foam perfectly.



Assign pairs to each side of the poly joint for cutting and fitting. Adjust the holes in the root/half pair so that the tube will fit at an angle. Match the foam at the joint and hand sand the core roots to approximately 4 degrees. The exact amount is not critical because we will sand again after the ribs are bagged on.

Cut slots for the half ribs so that the total distance from end to end is 9" through the joint, including both sides. Use the master drawing to position the ribs correctly. The rod should go through the high point of whatever airfoil is in use. Part of the reason I deviated from my usual straight trailing edge is the rods are much easier to place and install if the high point of the wing is in a straight line from tip to tip. Check the fit of the pieces to make sure the bottom matches the core, and grind off any area away from the holes that sticks out the bottom. Do not cut near the holes as this is where we are referencing.

Glue the root and half ribs with 30 minute epoxy. This gives a little extra time, especially if it is hot. Use a minimum of glue as this is just for placement. Later steps up to and including bagging will fill and anchor permanently. Do this in the bottom beds with the cores weighed down well and the ribs pushed down against the bottom bed so all the bottoms are lined up.

[G Norsworthy]

Sharpen one of the brass tubes and cut through the foam to the half rib. You can start with a Dremel and a 1/8" drill bit to get halfway first. Cut as needed to get the tube into the hole in the half rib. Go a little past the rib and mark the location where to cut the tube. We want the brass tube all the way through the rib and jammed against the foam so there is no path for laminating resin to get inside when we bag.

Install all the tubes and check the angle of the rod against a flat table with a ruler. If all the bottoms lined up all four sides will be exactly the same. Rough up the tubes and glue in.

Grind down the ribs to match the cores. Open a 1/8" channel to fill with epoxy and microballoons to fill any gaps around the tube and tie the tubes to the skin. See Anker's thread for details.

http://www.rcgroups.com/forums/showthread.php?t=992455&page=3&highlight=building+xcbd

[Kai@UCSB]

Went to Greg's place to take a look of this project :D

http://i463.photobucket.com/albums/qq355/popov_kai/IMG_4268.jpg

[G Norsworthy]

Let's switch gears here and do the fuse layup. There are many ways of going about this, and all make a good product with good technique and experience. This method evolved over a period of about 10 years of off and on possession of the GJ fuse mold.

The fuse layup will be 3 oz glass for the skin and 5 oz kevlar for the inside layer. It will deviate from previous versions in that the scrap kevlar will be cut up to build up the interior where the solid wood cross pieces go for the wing bolts. In previous editions the area was reinforced with 1/8 ply but the curvature of the fuse requires lots of microballoons and clamps, and it never bonds across the whole length anyway. This way will utilize all the kevlar scrap. There are four strips of 3.5 carbon uni in the tail boom to prevent flex.

The first step is to use a paper pattern of the inside to trace cut lines on the glass and kevlar. The glass will overlap the flange by about 1/2", and the kevlar is cut carefully to remain entirely within the flange. If successful we do not have to cut any kevlar at all after the layup.

[G Norsworthy]

At this point the photographer had to leave so you will have to take my word for it. The next step is to lay in peel ply over the wet cloth. Then a layer of paper towels over the peel ply. Use masking tape if needed to keep things in place. Now slide the whole thing into a tubular bag and seal the ends with clips. Pull down to about 8" of Hg and leave it overnight.

Yes, we are going to join this with some of the 3 oz glass pinched between the flanges. It is not very thick, and it protects the flange. This is the best way to bag the halves and be sure there is coverage all the way out. We will wet sand off the flashing later. Not very elegant but then if you saw how dusty it is in Cal Valley you would see it doesn't matter. The other way to do it is a lap seam. That way works well too but the glass/resin is not as good as a bagged fuse.

Once the peel ply is out and the flange is cleaned up we are ready to seam the halves together.

[G Norsworthy]

Forgot to mention the 5 oz kevlar is crowfoot, and is a double layer from the nose to about 5" behind the TE of the wing.

[Kai@UCSB]

Went to Greg's workshop again this afternoon where Greg was working putting the two half-fuselage together.

[yyz]

Right on, Greg. Thanks for doing this build thread. I know a lot of people will be watching and learning from this.

Mike

[danstrider]

Can you explain what I'm looking at in the last picture? I can tell it's down the tube of the tail with the vertical fin going up, but what's the flap? Is that the joining tape before it's smoothed out?

Thanks and it's great to see so many pictures! Keep them coming please :-)
Dan

[G Norsworthy]

A few words about joining the fuse halves. Start with the halves open on the bench. Cut some 4 mil plastic bag material in strips 1" wider than the joiner tape. Measure and cut the joiner tapes, top and bottom. Lay out the tape on top of the plastic sheet.

Mix a batch of slow hardening laminating resin. We are now using the US Composites with the 2:1 hardener. Plenty of working time but needs a couple days and heat to really harden.

Wet out the joiner tape on top of the plastic using a small roller. It should be on the wet side, just for this part.

Mix a side batch of resin with cabosil or microballoons. Not too thick, just enough to fill any open weave on the fuse layup.

Paint the bond area with pure resin first and then the resin/filler mixture using a short paint brush. Paint enough on to ensure a good bond between the fuse and the joiner tape.

Place the joiner tapes on the fuse sides, top on one side and bottom on the other side, lining up the center of the tape with the seam. Pick up one side, turn it over, and place it over the other side, offset until the flanges touch. Now slide the two halves together until the keys lock. Bolt or clamp the two sides together.

Now use a combination of stick, gloved finger, and small tailwheel on the end of a stick to roll down the joiner tape. Because we are rolling on plastic, there is no danger of unravelling the tape, or sticking it to the wheel/stick and pulling it back up. Keep rolling periodically until the resin get a little tacky to ensure there are no bubbles.

The last step is to take the slightly tacky resin and mix in a little microballoons. Stand the mold on its nose and pour some thickened resin to cast a solid plug in the nose.

Tonight we unbolt it and see what kind of troll pops out.

[yyz]

Putting the seam tape on the plastic and then rolling the plastic is a hot tip! Joining the halves is the step that drives me to drink. :mad:

Where in the world are you obtaining the blue foam in California? I looked all over for that stuff. It's relatively cheap and easy to find in cold parts of the country; not so much in the warmer climates.




A few words about joining the fuse halves. Start with the halves open on the bench. Cut some 4 mil plastic bag material in strips 1" wider than the joiner tape. Measure and cut the joiner tapes, top and bottom. Lay out the tape on top of the plastic sheet.

Mix a batch of slow hardening laminating resin. We are now using the US Composites with the 2:1 hardener. Plenty of working time but needs a couple days and heat to really harden.

Wet out the joiner tape on top of the plastic using a small roller. It should be on the wet side, just for this part.

Mix a side batch of resin with cabosil or microballoons. Not too thick, just enough to fill any open weave on the fuse layup.

Paint the bond area with pure resin first and then the resin/filler mixture using a short paint brush. Paint enough on to ensure a good bond between the fuse and the joiner tape.

Place the joiner tapes on the fuse sides, top on one side and bottom on the other side, lining up the center of the tape with the seam. Pick up one side, turn it over, and place it over the other side, offset until the flanges touch. Now slide the two halves together until the keys lock. Bolt or clamp the two sides together.

Now use a combination of stick, gloved finger, and small tailwheel on the end of a stick to roll down the joiner tape. Because we are rolling on plastic, there is no danger of unravelling the tape, or sticking it to the wheel/stick and pulling it back up. Keep rolling periodically until the resin get a little tacky to ensure there are no bubbles.

The last step is to take the slightly tacky resin and mix in a little microballoons. Stand the mold on its nose and pour some thickened resin to cast a solid plug in the nose.

Tonight we unbolt it and see what kind of troll pops out.

[G Norsworthy]

This is the rewarding or frustrating part, depending on how it goes. I saw this done with something like a 40 foot boat mold, and those guys knew what they were doing. Some water, compressed air, a few popping noises and it slid right out.

After unbolting the flanges, use a hose to run some water down the crack to start dissolving the PVA. Wait a bit, go to dinner, and come back later. Now start prying the mold apart wherever it appears loose. In this case one side just lifted off. Then the other side peeled out. This was the first time I brushed on the PVA and I must admit it was easier than spraying. The finish was just as good or better.

Success. I'll take it to work tomorrow to weigh it. Not as good as Europlastic, but then I only do one of these every few years and the mold is not perfect either. Next step is to fill, sand, and paint the seam to your level of satisfaction.

The jury is still out on the US Composites with the 2:1 hardener. For this amount of time the MGS was much harder, but I will give this some time in the hot box. The scrap kevlar in the wing saddle is much stiffer than previous versions but still may need some plywood for the wood screws in the cross pieces.

[G Norsworthy]

http://www.whitecap.com/\

They stock it in San Fran and brought it to the local branch for me. if there is no local source I might be willing to make a deal. Will PM with details.

I'm using hiload 40, which seems to be fine given the thickness of the skins. Word is hiload 60 is even better but the learning curve for cutting is longer. I built 5 and 6 from spyderfoam. Again hard to cut and the source has dried up.

[yyz]

Greg,

Did you paint the mold prior to layup or using a coloring agent in the gelcoat layer? The white looks really nice in the photos.

Mike




This is the rewarding or frustrating part, depending on how it goes. I saw this done with something like a 40 foot boat mold, and those guys knew what they were doing. Some water, compressed air, a few popping noises and it slid right out.

After unbolting the flanges, use a hose to run some water down the crack to start dissolving the PVA. Wait a bit, go to dinner, and come back later. Now start prying the mold apart wherever it appears loose. In this case one side just lifted off. Then the other side peeled out. This was the first time I brushed on the PVA and I must admit it was easier than spraying. The finish was just as good or better.

Success. I'll take it to work tomorrow to weigh it. Not as good as Europlastic, but then I only do one of these every few years and the mold is not perfect either. Next step is to fill, sand, and paint the seam to your level of satisfaction.

The jury is still out on the US Composites with the 2:1 hardener. For this amount of time the MGS was much harder, but I will give this some time in the hot box. The scrap kevlar in the wing saddle is much stiffer than previous versions but still may need some plywood for the wood screws in the cross pieces.

[G Norsworthy]

Mike,

The white is car paint, and it was painted in the mold.

Greg

[G Norsworthy]

This design will have a T tail. I looked at all the options and with some improvements in building learned from DLG planes it makes the most sense. The stab will be bolted on and the elevator will be hinged. I looked at the Supra scheme, but it gives up a lot of moment arm in front of the fin. Construction borrows heavily from the Supra.

The stabs are cut, trued, and glued at the root just like the wing joint. The top of the templates lines up so that the hinge line is straight. Two pieces of end grain balsa are inset full depth where the bolts will go through. Two smaller pieces of 1/8" thick carbon plate are then inset on the bottom of the wood, where the bolts will go through.

Two pultruded carbon rods are inset in the foam, described well here.

http://www.rcgroups.com/forums/showthread.php?t=1065719

The hinge line is cut and faced with 1.5 oz glass as described here. I am using the tape over wood filler like Phil Barnes uses on the elevator. The fin is thicker and the triangle cutout is reasonable to deal with. The surfaces are held on with small tabs of 1.5 oz glass (not bias) and double stick. I like the tape better than 3M77 because it is easier to control and doesn't mess up the shop. You also always know how much you have left, and the nozzle does not plug.

http://www.rcgroups.com/forums/showthread.php?p=12386533&highlight=prefaced#post12386533

LE is wrapped with 1.5 oz glass and double stick tape, and the stab is ready to bag.

[Kai@UCSB]

Greg,

Will you use Kevlar as hinge line?

-Kai

[G Norsworthy]

The tails will be skinnd in kevlar. Single layer on the stab, maybe double on the fin. The skin is the hinge, same as a Taboo wing. If I double the fin, there will still be only a single layer over the hinge line, otherwise it will not bend very well.

[G Norsworthy]

Fuse finished out just under 15 oz. Got the center section and tails in the bag tonight.

[dbaya]

Subscribed. Epoxy still sticky!

[G Norsworthy]

A few photos of the fin during assembly. The fin also has two pieces of 1/8"carbon plate embedded in the tip where the bolts will go. They are then covered in end grain balsa, which is cut oversize and fit to the stab after bagging.

The stab layup is 1 layer of 1.7 oz kevlar on the bias. The fin layup is one layer of 1.7 oz kevlar, a second layer of 1.7 kevlar forward of but not covering the hinge, and a 2" layer of 4.5 oz carbon uni over the high point, expanded at the tip to cover the second carbon insert. Something I forgot on this one but will use in the future is to run a 1/2" wide strip of 1.5 oz glass between the kevlar and the paint, poking out past the LE of the mylar, to encapsulate the kevlar should some finish work be required on the LE.

The hinge reinforcement, LE, and balsa inserts were wet out with extra resin for a good bond. The assemblys were packed inside denim cloth with plastic covering on the inside as a vacuum conduit. This is re-usable and conducts very well. The final vacuum was pulled with some weight distributed over the top bed, and me pushing on it as well to ensure that the bottom bed is flat on the table. Once the vaccum is pulled, the TE is checked with a long straightedge to make sure it is not warped.

[G Norsworthy]

A maple block is glued into the center section about 2.5" back from the LE to make a hard point for the bolts. It is deep enough to take countersunk bolts if we go that route.

The layup is 1.5 oz bias glass, 2 layers of 6 oz uni glass top and bottom, one layer of 6 oz top and bottom over the middle 12", and cross direction uni patches over the brass tubes. Took a mix of 15 oz of resin, and a little was left over. The final vacuum was pulled under a bit of weight to verify that the beds are down on the bench. The alternate is to use double stick but then you have to clean it up. The TE was checked with a long straightedge to make sure it is not warped. So far this is the best looking XC wing I have made at this point. I credit Anker's idea not to remove any skin thickness so that the wing is supported by the bed all the way to the TE. The parts are scheduled to come out Sunday.

[yyz]

What the hell, Greg? It's like you quit building and went back to work. What's up with that? :( :( Seriously though, watching this and learning a ton.

Thanks again,

Mike

[G Norsworthy]

Social service, actually. Plus I bagged the center section last week and uncertain of the US Comp slow resin I asked dbaya not to open the bags until the weekend no matter how many times I begged. Not to fear I have the centers and tails in my posession and bagged the tips tonight. I'll post it all as soon as I can get some time.

[G Norsworthy]

The tip layup is 3 layers of 1.2 oz glass on the bias out to the tip, 4 layers from the poly joint to 42 inches out, 1 layer of 6 oz uni glass 22 inches out, and a patch of 6 oz uni glass at 90 degrees over the brass tube. All this glass was cut and stacked with the corners marked to ensure it matches. I remember buying balanced weave, and there are enough layers that it should not matter, but better to be safe.

The 1.2 is all wet out in one step, then dried with a paper towel and hard roller. Next the uni layers are put on, wet out, dried, and checked with a squeegee to make sure all the excess is out. Roll extra epoxy on the LE and root ribs. Stack it all together and put in the bag. We used paper towels top and bottom for bleeder cloth this time.

[G Norsworthy]

The bag is carefully positioned over the bottom bed on a flat table. Pull out most of the air with the vacuum and then stack magazines and weight, evenly distributed. We lost the photographer so what is not shown is two people pushing down in addition to the weight for the final draw. Once it is under vacuum you can let go. Two days under vacuum and one in the hot box then we can peel.

Also shown is the hatch mold. About 10 layers of 1.2 scrap, oriented as found. No time to paint the mold so we will paint after cutting them to shape.

The US Composites 2:1 does cure but it takes a while and some heat. It is not as hard as the MGS and probably not the best choice for DLG but for thick layups like this it works fine.

Next we go back to the center section and tails for trimming, and some cosmetic work on the fuse seam.

Anybody know an elegant way to hold the wings together at the poly joint without tape?

[G Norsworthy]

I found some wicked strong magnets. I may try to embed an opposed pair in the ply root ribs.

[Keith Kindrick]

Do you have an estimated weight of the tips using this layup?

[G Norsworthy]

The E374 plane has something similar and is labeled 10.5, but the tip is shorter and I didn't know about rolling out the glass with paper towels.

We mixed 12 oz of resin per tip and didn't use it all.

I guess the right answer is I will take them to work and weigh them, probably Monday.

[G Norsworthy]

The JW layup spreadsheet is telling me 33 oz per half. This comes to 66 or 4.125 lbs for the wing. Throw in the ply root ribs and joiners, and we round up to 5 lbs out of my 11 lb budget. The fuse is 15 oz plus a little filler on the seam, make it an even pound. This takes me to 6. A pound of lead in the nose is customary. I like to leave 1/2 to 1 lb for repairs and come out at 10. This means I have 3 pounds left for the tails, radio, and wing mount. I'll have everything but the tips trimmed out by tonight so we can start to get some real weights by tomorrow.

Attached is an overlay plot of RG15, MH32, DS19, and AG23. Not too far off, especially considering wire cut and bagged wings.

[G Norsworthy]

The center section and tails are out of the bag. They look very good, better than any large wings I have made to date. The LE of the center section is trimmed with car body scissors and wet sanded to shape. The ends are cut off with scissors and a knife, finished with wet permagrit sander. We managed not to fill the joiner tube with epoxy. The TE is cut close to the line with car body scissors, very easy since it is mostly uni, then wet sanded with the permagrit. I'll check the LE with templates after the tips are sanded. There may be one round of fill and sand, or they may be fine the way they are. White electrical tape is the easiest but JW told me the bump at the edge is not good for the flow. I didn't want to say anything until they were out but the black is flat Krylon rattle can and came out pretty good. Not really flat since it backs up against waxed mylar, but releases well, covers well, and seems durable.

The tails are treated more or less in the same fashion. The fin needed some LE work as the kevlar did not conform all the way forward. If you are really careful and the foam is well epoxied, you can hit the kevlar with fast CA and wet sand immediately. Otherwise use epoxy and wait. Wet sanding with kevlar is much better than dry sanding. The stab came out almost perfect with almost no LE work.

Find the hinge lines and slit the skin on the open side. Use a new blade on the kevlar skin or it makes a mess. On the fin, open it up enough to expose the foam triangle. Now use a curved permagrit to pick/grind out the foam. Cut the skin back to the facing, ca and wet sand, and you have a prefaced hinge ready to use.

On the elevator, slit the hinge and start bending it back, cutting on the wood as it is exposed. At some point it will make a loud crack as the insert releases from the facing, or the wood cracks. Now you can peel out the insert and finish out the hinge line.

Twe rounds of fill and wet sand with epoxy and microballoons then spot putty on the fuse seam. This is not absolutely necessary, but this one looks good and I want to take it all the way.

Next we move on to the tips, and fitting the tails and center section to the fuse. Weights Monday.

[yyz]

<snip> Not too far off, especially considering wire cut and bagged wings.

Wow, not much visible difference at all....

Does any part of your wing (eg, tips) even come close to the low Re where Mark Drela suggests that the MH32 "starts falling apart" and wasn't that a major part of his effort on the Aegea sections?

Also, weren't the MH32 and RG15 originally pylon racing airfoils?

Greg, would have fully expected you to have both cruising and thermaling polars in that diagram :)

It's looking great. Love the red skunk stripe down the fuselage, by the way....

Mike

[G Norsworthy]

The Re range was considered in the design as follows: Root at 80 mph is 904,000, tip at 22 mph per John Ellias SBXC testing 22 mph 93,000. The previous version of this plane had a DS21/DS19 combo per JW but I had not learned from Anker not to subtract the skin thickness, plus the foam cutting left a bit to be desired. I think either combo is a viable plane but I went with the good Dr's foils because they were purpose designed for no camber change. The polars are in one of the older XC threads and I did compare them to the MH32, which according to my notes has a narrower drag bucket. I also noted that the AG24 looked similar to the RG15 at 200K but better at 100K. Plus we are not flying the AG24 at the tip but AG27 optimized for the chord.

#4 had an "MH32" if you could call it that by the time you subtract the spar bump and the distorted TE. I thought it flew a bit slow but it didn't last long in competition. I went with the max spar min skin approach and the plane had no finger dent resistance, and we blew the ailerons off it at 1400m. Still flew on the rudder.

Got the tips out of the bag tonight. 21.6 and 21.7 oz so we are consistant. Rest of the weights should follow when I have access to the good scale on Monday.

The fuse mold is not perfect, but it sure beats starting over.

Thanks again to dbaya for the tools and labor. From here on it is all back in my garage awaiting assembly.

[Kiesling]

Nice work Greg - looking forward to hearing the flight reports.

Tom

[dbaya]

Greg,

Thanks for letting me work with you on this project! What a huge plane. It looks great assembled.

Dom

[yyz]

Amen to that! Looks great w/ the T-tail. Nice work, Greg. Beautiful.



Greg,

Thanks for letting me work with you on this project! What a huge plane. It looks great assembled.

Dom

[G Norsworthy]

Next we will glue on the rudder and mount the stab. Rough up the paint on the side of the fin where it is glued to the subfin on the fuse. Round the bottom of the fin where it touches the bottom of the fuse. We will be glueing the fin to the fuse here. In this case the kevlar fuzz is fine since it gives some nice surface area to glue on. Rough up the joiner tape where it will touch the fin. Remember we used poly sheet to get a nice smooth finish on the joiner tape. Finally rough up the inside of the subfin. We used peel ply so it doesn't take much.

At this point I had to run out and buy another clamp because one was not enough. Set up a dry run of the fin clamped to the fuse with some foam rubber to spread the load and protect the paint. Check the alignment, it should be fine as long as the the two subfin sides are free as the clamps are tightened. Now take it back apart, cover the surfaces with 30 minute epoxy, and put it back together with clamps and tape. Let the California sun do its work for a while. Once the glue is cured, take it apart and peel the masking tape.

[G Norsworthy]

These stupid things never match no matter how careful you are fitting them to the raw cores. For lack of better tools I matched them with a Dremel and permagrit sander. Not half bad. I reached the limit of how much rib I want to grind off before compromising the joiner. When I get the resin back we will try a little saran wrap and tape trick to match these up. I want a joint I don't have to tape.

A word about the US Composites 2:1 slow system. In a hot garage or out in the sun the tip area where all the fibers are 45 degrees the wing feels a little floppy. Not a disaster as there is not much stress out here and it feels great in torsion. This is after 8h in a hotbox at 120F. I need to call them Monday and see what it will take to harden this stuff up. Once the wing cools it stiffens up again but California Valley is quite warm at times. I don't remember this happening with MGS or stinky 13:1 Shell. The thicker laminates like the center section and the double layer of kevlar on the nose feel fine.

[G Norsworthy]

Use the foam cutting template to make a rough outline of where to cut the vertical grain wood for the stab mount. Cut and sand as needed to seat the stab on top of the fin.

Mark the locations of the through holes in the stab for the mounting bolts. Drill a pilot hole and make sure it lines up reasonably well. Now drill the through holes. Line up the stab to the fin using the shadow of the foam joint. Mark the location of the holes on the fin using a pencil. Drill a pilot hole then the tap hole through the carbon plates embedded in the top of the fin. Tap the holes in the fin then CA and tap again. Countersink the top of the stab, add CA, and cut out the kevlar fuzz with a sharp blade. If everything went right, bolt the stab onto the fin. I will try to get ahold of an incidence meter to rig this, as it is impossible to tell by eye where the T-tail is. I'll hold off on the fillet for either the wing or the stab until after it is trimmed in case it needs adjustment. There is plenty of meat left in the wood on top of the fin in case it needs to be cut down.

[big jer]

Greg Pal
I used to build X/C models. I don't know how you did it so quickly. Looks good in the photos. See ya at Visalia.

JDK

[G Norsworthy]

Hi Jerry,

Part of it was building ahead and starting the thread later. Part of it is currently having zero obligations outside work, food, and sleep. A big part of it is 20 years experience and lots of tips over the years from guys like you.

Visalia, eh, not too far to drive.

[will_newton]

Nice work Greg! I've been having a good time reading your build while the XCBD is on a short hiatus awaiting Anker's testing of the completed build. You've done in weeks what has taken me months. I hope that by the time we are on our 8th build things are going as well. It would be interesting to see a version history of your series of planes to see how the design has gotten tweaked with each build.

[G Norsworthy]

The US Composites 2:1 slow is not really suited to making parts. The working time is nice but it never gets hard enough. I put the tips and the stab in a homemade hotbox for two days at 130-140F and the tips are barely usable. I ordered another bottle of the 3:1 medium hardener and will work faster if needed. The 2:1 is fine for secondary bonds, glueing, fillets, etc.

[G Norsworthy]

This is one of the most dreaded parts of the build, but turned out not so bad because of careful measurements at the foam fitting stage. The GJ fuse has the wing set about 2" forward of where it belongs on this design, so cut out the fuse as needed and trim the opening to fit the bottom surface of the wing. Then cut out two cross braces to accept the wing bolts. I have had good success with either maple block or two stacked pieces of 1/4" ply. The landlady's contractors were nice enough to leave a table saw in the corner of the garage. Things go much faster with power tools. Laminate the ply together with epoxy or wood glue. Now shape the parts to fit inside the fuse with about a 1/8" gap between the top of the fuse wall and the ply brace. Glue the parts in.

Cut some strips from the 6 oz uni glass left from the wing layup. We will install about 6 per location above the brace to help prevent it from being pulled out. Let this cure before the next step.

Now place the wing over the fuse and trace the approximate location of the joint on the bottom of the wing. Put two strips of masking tape over the line to cover the joint area. Now install the center section on the fuse as close to the correct position as possible. Tape it down hard with masking tape. Tape a piece of carpet thread or other stiff string centered at the forward base of the fin. Pull the thread to one corner of the wing and put on a tape flag. Now go back and forth between the two corners, adjusting as necessary to center the wing. When the two sides are equal, put more tape on the wing to hold it tight. Set the plane up on a table and install the wingtips. Repeat the triangulation to the tips to verify that everything is straight. Sight the fin to make sure the wing is aligned 90 degrees. When everything is aligned, take the tips off, turn it over, and glue, yes glue, the wing to the fuse in four spots. Make sure you have time to finish this procedure in one session, because we want the epoxy to still be a little soft at the end so we can pick it off. The hard part is done.

Line up the following tools: small pilot drill, #7, 1/4", 1/4-20 tap, and countersink. Mark the locations on the top of the wing where the holes will go. 2-1/2" forward and 2" rear is good spacing. You did write down the location of the maple block before bagging the wing, right? Now drill the pilot hole and follow with the #7, all the way through the ply brace in the fuse. Flip the plane over and pick out the still slightly soft epoxy glue joint. Tap the holes in the fuse, one, then CA, then once more, and drill out the 1/4" holes in the wing. Finally counter sink and clean up the holes so the bolts will go through. We will use countersunk forward and flat head rear. There is not enough thickness to countersink the rear ones and the fairing will cover most of them anyway. Bolt the wing on to check the fit and we are done.

[G Norsworthy]

Will,

I'll dig through the pics tonight and try to round up a scanner. It helps having a fuse mold and friends with tools.

[yyz]

Greg,

The short-winged version in the last photo is for 2-meter cross-country events, right? :)

Do you have a date in mind for its maiden flight? I'm putting my Thermik together and should be done in a week or so. Also, I just found some 200 lb mono on Ebay so we're locked and loaded for launching if you want to come down to CV.

Mike

ps: I've had really good luck w/ West Systems and it's "usable" w/in a couple of days. Never hot boxed it (curing, anyway) but my shop gets pretty warm.


This is one of the most dreaded parts of the build, but turned out not so bad because of careful measurements at the foam fitting stage. The GJ fuse has the wing set about 2" forward of where it belongs on this design, so cut out the fuse as needed and trim the opening to fit the bottom surface of the wing. Then cut out two cross braces to accept the wing bolts. I have had good success with either maple block or two stacked pieces of 1/4" ply. The landlady's contractors were nice enough to leave a table saw in the corner of the garage. Things go much faster with power tools. Laminate the ply together with epoxy or wood glue. Now shape the parts to fit inside the fuse with about a 1/8" gap between the top of the fuse wall and the ply brace. Glue the parts in.

Cut some strips from the 6 oz uni glass left from the wing layup. We will install about 6 per location above the brace to help prevent it from being pulled out. Let this cure before the next step.

Now place the wing over the fuse and trace the approximate location of the joint on the bottom of the wing. Put two strips of masking tape over the line to cover the joint area. Now install the center section on the fuse as close to the correct position as possible. Tape it down hard with masking tape. Tape a piece of carpet thread or other stiff string centered at the forward base of the fin. Pull the thread to one corner of the wing and put on a tape flag. Now go back and forth between the two corners, adjusting as necessary to center the wing. When the two sides are equal, put more tape on the wing to hold it tight. Set the plane up on a table and install the wingtips. Repeat the triangulation to the tips to verify that everything is straight. Sight the fin to make sure the wing is aligned 90 degrees. When everything is aligned, take the tips off, turn it over, and glue, yes glue, the wing to the fuse in four spots. Make sure you have time to finish this procedure in one session, because we want the epoxy to still be a little soft at the end so we can pick it off. The hard part is done.

Line up the following tools: small pilot drill, #7, 1/4", 1/4-20 tap, and countersink. Mark the locations on the top of the wing where the holes will go. 2-1/2" forward and 2" rear is good spacing. You did write down the location of the maple block before bagging the wing, right? Now drill the pilot hole and follow with the #7, all the way through the ply brace in the fuse. Flip the plane over and pick out the still slightly soft epoxy glue joint. Tap the holes in the fuse, one, then CA, then once more, and drill out the 1/4" holes in the wing. Finally counter sink and clean up the holes so the bolts will go through. We will use countersunk forward and flat head rear. There is not enough thickness to countersink the rear ones and the fairing will cover most of them anyway. Bolt the wing on to check the fit and we are done.

[G Norsworthy]

Mike,

These things always drag on near the end but I don't see any deal killers and I already own everything I need to finish it except the lead. Depends on how much time I have but I can't see more than 2 weeks. I'll probably try some hand launches and a low winch to check the incidence and CG at a local field before the final fillets go on.

I'd be up for a weekend in Cal Valley even if a contest doesn't happen. Maybe the second or third weekend in August.

[G Norsworthy]

I've used West fast and slow, Shell, MGS, and some other thing I got in Texas 20 years ago, and they all made usable parts. This is the first one I have seen that was really too soft to use. From what they told me and what other people have told me the faster cure hardener makes a harder product also.

[P-51flyer]

Looking good Greg! Can't wait to see that puppy fly!

Aaron

BTW- We are all West systems over here ;)

[G Norsworthy]

The radio tray is cut from 1/8" ply and hinged about halfway so it will go past the wing mounts. A 1/4" ply block with two 8-32 tapped holes is glued to the floor. The tray is then bolted down to this block. This makes radio installation very easy, and you can still get your hand up the nose to play with the lead later.

The elevator servo is put in just like a wing servo. I used an HS5125 MG which fits nicely in the base of the fin. MG is nice and worth the weight because we don't want to take this one out for a chipped tooth later. One error is I forgot to cut a hole for the wire and ended up using a long drill bit to get through the base of the fin. Not so elegant and used up most of my evening to get the servo in.

A few more weights:

Tips 21.6, 21.7=43.3
Center 42.8 total wing without rods 86.1 or just over 5 lbs, about what I expected.

Fuse with fin and wing blocks 20.3
Stab 2.4
Total so far 108.8 or 6.8 lbs This leaves about 3.5 lbs for the radio, battery, and lead. I think we can make it, and I know I can get a few ounces out of the center section on the next one if needed.

[yyz]

Thought you were doing RDS on the rudder but realized that's the elevator servo. Can't wait to see this masterpiece fly!


The radio tray is cut from 1/8" ply and hinged about halfway so it will go past the wing mounts. A 1/4" ply block with two 8-32 tapped holes is glued to the floor. The tray is then bolted down to this block. This makes radio installation very easy, and you can still get your hand up the nose to play with the lead later.

The elevator servo is put in just like a wing servo. I used an HS5125 MG which fits nicely in the base of the fin. MG is nice and worth the weight because we don't want to take this one out for a chipped tooth later. One error is I forgot to cut a hole for the wire and ended up using a long drill bit to get through the base of the fin. Not so elegant and used up most of my evening to get the servo in.

A few more weights:

Tips 21.6, 21.7=43.3
Center 42.8 total wing without rods 86.1 or just over 5 lbs, about what I expected.

Fuse with fin and wing blocks 20.3
Stab 2.4
Total so far 108.8 or 6.8 lbs This leaves about 3.5 lbs for the radio, battery, and lead. I think we can make it, and I know I can get a few ounces out of the center section on the next one if needed.

[G Norsworthy]

Here are some photos and links to the older planes.

#1 was a copy of a Wiley copy made in a 1 bedroom apartment. Same basic construction as #8 but no kevlar and wood sheeted stabs. The fuse was artistic and clean but the boom was extended on the plug somewhat like a broomstick and we pulled a new mold off it. The diameter was a bit small but it lasted for 10 years. Got me my 2 hour and 10K, if I remember correctly both without a vario. When it was plugged in it had an Ace vario which is slightly better than nothing. I had no idea what I was doing but they were really good times. Blew the tail off really high over Lancaster, either from the above thin boom or too small stab wires. The wing followed soon after. See the Aloft wreckage for similarities.

#2 was 3/32 balsa over white foam with spruce spars. X and V tail tried, both flew well. S4233 root, S7037 tip. I had gotten tired of not being able to thermal #1 and figured I could give up some speed for thermalling performance. It thermalled great, probably better than anything I have owned, but I still didn't know what I was doing, and without experience and a good vario I still never got out on the road much. Sold to Gary Fogel for atmospheric experiments.

#3 was another Wiley copy, this time with the GJ fuse, and a conversation with JW himself. Simple layup, all glass, about 9.5 lbs empty. 12" root is a little hard to see but we did take it to 1780m. E374 again and not a great example of it but it works. It's the white one in between the two yellow ones. The real Wiley below.

http://xcsoaring.com/contests/cvccr/2004/cvcr04.htm

#3 set the speed record at Montague 2007 with me at the sticks and JW calling. This one started with a Multiplex vario and now uses a Picolario. Funny how it is not so much the plane...I still have it. It has gotten two 2k, a 10k, and a 25K pin for other pilots. Very easy to fly, tracks straight, but needs good lift and got outrun by an MXC in front of my eyes at Montague 2009.

#4 was MH 32 after watching some of the early Europlastic. Heavily Drela influenced with carbon spars and thin glass skin. Lots of distortion in the TE. Thermalled OK, seemed a little slow. Blew the ailerons off at 1400m in Cal Valley. Seemed a bit sluggish in the turns...Far left at Montague with the solar cells on the wing. Repaired and used for camera experiments.

http://xcsoaring.com/contests/mccc/2005/xc05.htm

#5 No pics but see #6, same design. This one had the DS21 airfoil, bagged carbon over spyderfoam. Still learning on the TE but much better than #4. 3 oz bias carbon makes a really nice, light tip. Flaps and ailerons. Very short lifetime. Met its end in the soda lake at Cal Valley. With a Picolario and some experience got us miles on the scoresheet finally.

#6 Same as #5, used some recycled parts.

http://xcsoaring.com/contests/mccc/2004/matt_photos/15.jpg

Sleddriver gets his 10K. This was a really sweet plane. Finally got the TE distortion under control. With camber you cruised down the road, steering and pulling camber as the vario directs. This is also the far right plane in the above photo with myself, Julian, Beverly, and Nowell. That day we flew 92 miles for 3RD place. JW flew it that Sunday for a quick lap and said it was an honest airplane. Got me my 100K. Met its end splattered over a mountainside in Cal Valley. Got most of the pieces back. Too far to say what happened but broke through the flap servo cutout at 45 degrees suspiciously like the Aloft wreckage. At this point we simplified...

#7 14" root poly design in response to #6 crash and poor air quality at Cal Valley. DS21-DS19 airfoils. All glass, the tips were a bit delicate. Great visibility, wingloading maybe a bit low but thermalled great. Same construction as what I am building in this thread. Not great foam cutting. Won Montague 2007. Crashed in Cal Valley this year, flown too far down the road and lost visual. Fixable but moved on to #8.

http://xcsoaring.com/contests/mccc/2007/photo2.htm

[G Norsworthy]

We're going to take the opportunity to knock out a couple more of these while there is time available and the momentum to build. I'll fill in some details and changes made so nobody repeats my mistakes.

Here is the blank sheet for cutting the raw foam. I measured off the LE because that is where the templates are referenced. The gravity cutter introduces a bit of wire sag, and also ripples if it is not set up right, especially on the 32 inch panel. We had better luck with a smaller diameter wire and as much tension as possible on the bow. If you have not cut big panels before, plan on burning some foam in the learning curve. I am sure there are tips here on RCG. Better yet, buy the cores from somebody who knows how to cut them hint hint.

I like to cut the blank span about 1/8" long, since the foam always distorts after cutting and that leaves a little room to sand and fit before glueing the panels together.

[flyonline]

Great info there greg, thanks. I really like hearing about the lineage and influences of other models.

Coupla quick questions.
1. How does a balsa sheeted wing + spar stack up (specifically aimed at an entry level scratch built plane) compared to an all glass?
2. Considering Joe flew Wiley for years and set many records, would a simple RES/REF be the best place to start for a beginner.
3. I'm interested that you've used the DS19/21, are there many other XC planes with these foils out there, and will you continue to use them in the future?

Thanks

Steve

[G Norsworthy]

How does a balsa sheeted wing + spar stack up (specifically aimed at an entry level scratch built plane) compared to an all glass?

I know of at least four balsa sheeted wings, the one above and another 7032 wing that flew like giant TD ships. Not too fast but very easy to fly and thermal well. I helped someone build an E-374 wing on a Sealy fuse in FL but I moved away before it flew. I heard it was good. The last was the Brian Agnew Roadkill shown below. This was a sort of copy of my Wiley copy. 13" root, 8" tip, flat center section. I watched him thermal this plane out from treetop height twice in a row. It came back with a Casio altimiter watch over 5k feet. I also watched him make three 10K runs in one day, each faster than the last. On the last one he blew by me at cloud base and speed limit from the trunk of his Honda Accord yelling go go go go! I daresay that plane was as competitive as my Wiley copy is now. If you know what you are doing I think you can make an entry level raceable plane from white foam, spruce, and 3/32 balsa. That said, the skill set to make a good wood wing is about the same as a bagged glass wing, and the glass wing is more durable and won't wrinkle in the sun.

Considering Joe flew Wiley for years and set many records, would a simple RES/REF be the best place to start for a beginner.

I've flown poly XC and full house XC, and after 20 years I prefer the poly. They are easier to track, easier to thermal, and you can't fly down the road by accident with the flap halfway down because you bumped the stick. Flying out of a truck is much harder than flying off a field, with the noise, wind, sun, and vario to keep track of. When it all comes together the camber change on a nice long run is sweet, but the airfoils the good Dr. provided should fly fine without camber change. Any servo, linkage, etc that you put in your 11 lb budget is something you have to take out of the structure. Plus any hinged surface is a potential failure site. I think part of the reason Wiley and my copy lasted so long is they are simple and robust.
As far as spoilers or flaps, any hole in the wing is bad in my opinion. That is where they always fail. The one time I actually got so high I had to bring it down, it was the poly E374 and I was able to spiral it down carefully. It all depends on where you fly and the landing options, but if the plane is built purely for racing, I would be reluctant to use anything but R/E. That said, the MXC is a really nice plane and the last conversation I had with JW he said he had a plane designed in his head and it was full house.

I'm interested that you've used the DS19/21, are there many other XC planes with these foils out there, and will you continue to use them in the future?

I liked the DS 21 planes a lot, especially the ones with camber change. I don't know of anybody else who finished a plane with these. Take a look at the pdf with the four foils plotted over each other. We're not talking about much difference here. I'm sold on the current set because one, they should not need camber change, and two, they are designed as a progression to match the airfoil to the Re as the wing tapers. The proof is in the flying, and if it doesn't work I would consider going back to the DS series. If all goes well I should have an answer in about a week.

[G Norsworthy]

Roadkill. Nobody in FL could touch Brian with this 20 years ago.

[flyonline]

Greg
thanks for the info. I've kinda figured that a glass wing would probably end up being cheaper than a balsa one anyway - balsa is so expensive down here that such a wide wing chord would eat up a LOT of balsa sheets.

I flew with a guy that had an OD TD ship with a 3 piece wing and 5 surfaces. The middle section was just for camber change/crow and the plug in tips were ailerons + camber. My idea was to do a 3 piece for portability and have different plug in tips if camber/braking was required.

Can you remember the EDA on the poly ships??

Thanks again.

Steve

[DEAN GRADWELL]

Greg,
This is a great thread. Thanks for sharing.
Regards Dean

[G Norsworthy]

Can you remember the EDA on the poly ships

I'm working off this. I checked it against the Wiley copy and they are very close. Too much and they Dutch roll. Not enough and you can't work the low thermals and they get difficult to put into a tight field.

http://www.rcgroups.com/forums/showthread.php?t=992133

It depends on your geography and task, but part of the competition is knowing the course, where the lift, sink, open areas, legal cuts, and obstructions are. A good driver helps a lot here. This is where hooking up with an experienced team helps. I learned more in one 27 mile lap calling for JW than I did in the 10 years previous.

Where I was going with that is if you can possibly fly the course safely without using flaps, I would recommend it. In extreme situations I have learned to value simplicity.

[yyz]

<snip> I helped someone build an E-374 wing on a Sealy fuse in FL but I moved away before it flew. I heard it was good. .

Does anyone have contact info for Bob Sealy and does anyone know if he still has the molds and/or plug for the stretched Sagitta XC fuselage?

Thanks,

Mike

ps: What is a "legal cut"????

[G Norsworthy]

ps: What is a "legal cut"????

There are places where the road is not the shortest distance between two turn points. At Cal Valley along the soda lake there are curves around a few hills. At Montague when you cross the freeway there is a huge triangular cut that can save lots of time. If the driver watches the map and calls it out the spotter can direct the pilot to take a certain tack off the road. Knowing the course in your head helps even more because you can believe the caller when they steer you away.

[G Norsworthy]

Lots to organize here, but all in bits and pieces. Let's go back to the poly joint. This worked so I can show it. Put a little packing tape over the wing rod hole, about 1/4" bigger than the hole, all four locations. Cut out the hole. Now wrap the wingtip rib in saran wrap and tape it down tight. For lack of wax I rubbed the wing rods lightly with 3 in 1 oil and inserted them. run masking tape along the bottom of the center section under the root rib, split half the width, and fold it back a little. Now mix up a batch of epoxy and microballoons stiff enough to stay on a vertical surface. Smear an excess on the center section ply rib but avoid the rod. Now take off the tape on the bottom of the wing and replace it with a new piece. Now shove the tip on, push it hard, and tape the two pieces together. Use the tape on the bottom of the joint and some cross pieces. Use tape around the TE to maintain alignment. Block up the tip for stress relief and repeat on the other side. Add more epoxy back into the mixture. Hog out the foam from inside the rear two bolt holes. Tape over the bottom and fill the vacancy with epoxy and microballoons so the bolt will not be compressing foam.

Skipping ahead a day, take off the tape and pull the tip off. I didn't even have to yank on it, it just came right off. Take off the saran wrap and packing tape. Grind off the flashing with a wet permagrit and check the fit. We have a tapeless joint.

Now cut two alignment pins from 1/4" carbon arrowshaft. 2" long, and 3/4" will stick out. Mark the spot in the center section 5" behind the rod and halfway between the skins. Start with a pilot then a 1/4" drill. Try to line up the angle with the wing rod. Glue the alignment pins in and go work on something else.

Now plug the two halves together and mark the tip where the alignment pins hit. Drill out the hole with a pilot and a 1/4" drill. In one case we hit it just right and the other one was slightly off. Adjust the hole with a small Dremel bit and CA soaked balsa on top or bottom as needed. When it matches we are done. Now we wait for those super magnets.

[G Norsworthy]

Drill out holes for two each small wood screws through the skin and into the wing hold down blocks. Avoid the already tapped 1/4-20 holes. Countersink the skin enough to mostly bury the screws. Kevlar is messy, so alternate among countersink, CA, and sharp blade until the level is correct. Mix up a batch of epoxy and screw/glue the wood screws into the blocks. These are not coming out again. Good time also to add the rudder servo rails and towhook block. Glass in the rudder servo rails with strips like the wing hold down.

Strap down the radio to the sliding tray using tiewraps, mylar straps, or whatever is convenient. Hook up the power so we can use it. Wire the elevator servo.

Now the elevator pushrod. For lack of planning I had to hand drill the passage with a bit on the end of a brass tube. Not elegant and I will try to build something in before bagging the next one. I also had to drill through the rudder hinge line since the two hinges were lined up. It works but on the next one I will put the elevator hinge forward of the rudder so they do not interfere. I picked up a graphite tube that looked pretty stiff and light. I then tried glueing a threaded rod with clevis on one side and wire with L-bend on the other side. I used Goop, which is usually good for anything, then wrapped the end with carpet thread and CA. The next day I was able to pull both sides out easily. Everything has to be tested. You don't want to drive a day to get to a contest then find some little thing that is buried inside that knocks you out for the day. Next was to cut an angle in the carbon tube to expose about half of the wire insert. Then the wire insert was cleaned with sandpaper and very lightly notched with a Dremel cutoff wheel for grip. Then the wire on the clevis side was glued in with 30 minute epoxy and wrapped with carpet thread. A little time in the sun and this now passed both the shock test and the long slow pull. The position of the L-bend wire was set by assembling the tail and tacking in the wire with CA. Now the L-bend wire was permanently glued with epoxy like the other end. Use the threads to adjust the center, then wrap the servo with packing tape and glue it in. A little white tape over the servo and the elevator is finished.

Now the rudder. I like closed metal loops with a long threaded portion for adjustment. Make a horn out of something durable, in this case 1/8 ply with carbon plate laminated on one side. Install it in the rudder with the hinge line on the center. It looks awkward but it has to be this way. Relieve as necessary to clear the rudder. When it is cured pull the strings through the fuse. I use spectra fishing line, doubled for security. On one side a cut had to be made through the skin. Tie the rudder side and stretch the servo side until it is tight with the threads almost all the way out. Crimp the line with an aluminum tube and leave it for a few days. The line will stretch a little. Come back and replace the crimp as needed, then use the threads to take up any remaining slack. Once the lines are stable, coat the crimp and the threads with Goop so it will not let go later. Now hook up the radio and adjust the throws.

[G Norsworthy]

Cut out the rear hatch with car body scissors until it is close. Notch for screws as needed. Wet sand with permagrit the final touches. When the fit is perfect, glue it to the wing with Goop.

Make two front hatch blocks from 1/8" ply. Round as needed with the Dremel. Glue these two pieces in with Goop and leave for a day.

There is not much left. Need to cut and glue the outer poly joint, pending the receipt and testing of the faster hardener. Add the magnets to the wing joint. Fit up the front hatch. Put in vario and GPS mount. Add a tube for the radio antenna. Test fly, adjust incidence and CG, add fairings, and paint. If all goes well we fly it Sunday at Dartmouth.

[pval3]

This is a beautiful bird

great work and great thread.

Phil

[G Norsworthy]

Thanks for the compliments. These big planes are actually easier to build than a DLG. The parts are a lot bigger and not so delicate.

Cut the front hatch with car body scissors, cut and fit, cut and fit. When the fit is good, tape it on and drill and countersink for two small screws to hold it on the fuse.

Next we cut and join the outer poly joint. Same as Anker's thread, no magic here. Tracking says the hardener comes in tomorrow and we can add the cloth.

For the magnets, use the Dremel to hollow out the root rib to fit the magnet. The magnet should be slightly below the surface. Glue it in with epoxy and wipe the excess off the rib.

http://www.rare-earth-magnets.com/

After it hardened I tested the force and it was a little low. I will probably add another set ahead of the wing rod for security. I will also leave only a thin film of epoxy and not set the magnet so deep. Still trying to go tape free.

Cut an angle in the bottom of the rudder so it does not hit the ground on landing. Cover the bare foam with a piece of balsa. Still on target if all goes well. Maybe an assembled photo tomorrow.

[flyonline]

I've got a piece of felt on the inside the root rib on my TWF wings which give a nice clean join against the fuse but still allows movement (they're pitcherons), or in your case a bit of squish for the magnets to pull together.

Steve

[yyz]

Greg,

Looks like you can see the light at the end of the tunnel... and know that it's not a freight train. This looks like another winner design.

Are the magnets seriously for holding the tip panels to the root?

Mike



Thanks for the compliments. These big planes are actually easier to build than a DLG. The parts are a lot bigger and not so delicate.

Cut the front hatch with car body scissors, cut and fit, cut and fit. When the fit is good, tape it on and drill and countersink for two small screws to hold it on the fuse.

Next we cut and join the outer poly joint. Same as Anker's thread, no magic here. Tracking says the hardener comes in tomorrow and we can add the cloth.

For the magnets, use the Dremel to hollow out the root rib to fit the magnet. The magnet should be slightly below the surface. Glue it in with epoxy and wipe the excess off the rib.

http://www.rare-earth-magnets.com/

After it hardened I tested the force and it was a little low. I will probably add another set ahead of the wing rod for security. I will also leave only a thin film of epoxy and not set the magnet so deep. Still trying to go tape free.

Cut an angle in the bottom of the rudder so it does not hit the ground on landing. Cover the bare foam with a piece of balsa. Still on target if all goes well. Maybe an assembled photo tomorrow.

[G Norsworthy]

Are the magnets seriously for holding the tip panels to the root?

That's the idea. Out of the box you can't pull these apart, you have to slide them. With the extra gap from the epoxy and the extra grip on the wing I could pull the wings apart. There may be some experimentation here but I really want a permanent solution to the tape problem. I heard there is a piece of hardware from Hobby Lobby for wing roots but I was not able to find it in the online catalog.

[G Norsworthy]

Next step is to glass the outer poly joint. The medium hardener showed up and I mixed a small batch to watch during the day in order to decide to proceed or not. It looked promising so ahead we go. Nothing unusual here, sand off the paint and cut 1" strips of 6 oz uni and 1.25" strips of 1.5 ounce skin coat. Just a hand layup with a bit of Saran wrap over the top to make it smooth. Plenty of working time with the faster hardener. This was cooked a day in a hot car and came out nice and crinkly, like it is supposed to.

The vario is attached to the side of the fuse with hook and loop. Don't know if you can get them anymore but the picolario has withstood numerous crashes including one full disintigration at altitude. The radio plugs are bent inside the case but it still works. The vario is connected via a double headed Futaba style plug to the flap stick. It is programmed to play the altitude and voltage when you pull the flap stick. In front of the hatch is the total energy probe. It is held on with short pieces of silicone tubing. This one was personally bent by JW. He also programmed the vario to the least sensitive setting so it does not indicate marginal lift.

A word about varios. If you have never flown with one it is like having a third eye. It is almost impossible to fly even a short task without one. The total energy probe is not absolutely necessary but really smooths things out when you are bouncing down the road with lots of distractions and noise.

Next the CG. Brian Agnew flew the Sagitta at 38% of root on a similar planform. We will target about 35% to start and see how it goes. JW says to fly them noseheavy for stability. I don't like them quite as forward as he does but you want to be well away of something that would tuck. Takes about a pound of shot as it stands now. We will start with a bag and do a little trick with plaster later after all the fairings are added and we know where to balance it.

Now the towhook. I use a #10 wood screw heated red hot, bent to 90 degrees, and dropped in a bucket of water. Hard as a rock and about the right size. Grind off the threads after the bend. I never had one fail Drill a few holes in the fuse and start one hole forward of the cg. I make a batch every 10 years or so. Add CA or epoxy once the final location is determined.

A little cosmetic work and we are ready to fly. If all goes well I will have a flight report for Sunday.

[danstrider]

Looks terrific standing up on a wing Greg! I'm eagerly waiting for a flight report!

Might you explain in a bit more detail the reasoning for a tape-less joint? I've only seen chord-wise tape seams and haven't convinced myself why that ridge would be incredibly detrimental, so I'm looking for some schooling :-)

I suppose I'm also wondering if performance percentage-wise it makes sense to look at the fuselage/wing junction with potential for simple blended fairings. You're the one building and it's a lot easier to type ideas, but that's what RCG is for right?!

Thanks and again it looks good!
Dan

[G Norsworthy]

The tapeless joint is to get rid of the gummy tape problem in the heat at Cal Valley. I just want to see if I can pull it off.

I will be installing a fairing at the wing/fuse joint. First I need to fly it to make sure the wing and tail are rigged at the right angle. I only want to paint once.

[flyonline]

The elevator servo is put in just like a wing servo. I used an HS5125 MG which fits nicely in the base of the fin. MG is nice and worth the weight because we don't want to take this one out for a chipped tooth later.
Meant to ask you about this earlier and forgot. Have you used the 5125 in this application before? I've had nothing but stellar service from my 5125s in my destiny including some very bad crashes but I know many others have had serious problems with them with poor centering, broken gears etc.

Some more great info, thanks for taking the time to post :)

Steve

[G Norsworthy]

I've only owned one 5125MG, the one in the picture. It was in a DS plane I took to 126mph, not that impressive but it was the same design T-tail and never had a problem. The T-tail puts a lot of stress on the base of the fin but insulates the servo from shock pretty well because we don't expect the elevator to hit anything. I thought about putting in a Volz that I had but I needed it for something else first.

[G Norsworthy]

Both wing tips were warped, probably from the soft resin and repeated heating and cooling cycles. One had slight washout, which I left, and the other had more washin which looked bad. After a little research on RCG I tried steam, two cycles of boiling water, heat gun, and finally iron with wet cloth. The iron trick finally worked but we hit it so hard the fibers let go in a few areas. I will have to rub in some epoxy later and maybe add some reinforcement, but for now it feels fine to fly.

We had about 5 minutes of daylight left so we ran to the park for a hand toss.

Tips 21.6, 21.7=43.3
Center 42.8 total wing without rods 86.1 or just over 5 lbs, about what I expected.

Fuse with fin and wing blocks 20.3
Stab 2.4
Total so far 108.8

Lead 16.3
Radio tray 12.4
Total rtf lacking only fairings, 8.59 lbs plus rods, tail servo, and a few odds and ends.

Looks like we have about a pound to play with to make it a bit stronger.

[yyz]

If you keep flying even when the sprinklers come on...... YOU JUST MIGHT BE A HARD CORE SAILPLANE PILOT!!!!!

Nice work, Greg. It's looks fantastic,

Mike

ps: Did you have the vario on for the hand toss? ;)



Both wing tips were warped, probably from the soft resin and repeated heating and cooling cycles. One had slight washout, which I left, and the other had more washin which looked bad. After a little research on RCG I tried steam, two cycles of boiling water, heat gun, and finally iron with wet cloth. The iron trick finally worked but we hit it so hard the fibers let go in a few areas. I will have to rub in some epoxy later and maybe add some reinforcement, but for now it feels fine to fly.

We had about 5 minutes of daylight left so we ran to the park for a hand toss.

Tips 21.6, 21.7=43.3
Center 42.8 total wing without rods 86.1 or just over 5 lbs, about what I expected.

Fuse with fin and wing blocks 20.3
Stab 2.4
Total so far 108.8

Lead 16.3
Radio tray 12.4
Total rtf lacking only fairings, 8.59 lbs plus rods, tail servo, and a few odds and ends.

Looks like we have about a pound to play with to make it a bit stronger.

[G Norsworthy]

Did you have the vario on for the hand toss?

No, but I have it for tomorrow.

[Jonas M.]

Wow, that ship looks awesome!

Thanks for sharing all the info on this build.

Jonas

[alstrahm]

I actually got to see the maiden today and it was awesome! Greg, Dom and crew did a great job, man does that plane fly! On the maiden I think Greg was at 150' at one time and specked it out . Second flight I had to leave he was up so long.
Al

whose foto skills suck

[G Norsworthy]

Thanks to everyone who came out in support of the maiden flight. I think it was a record crowd at Dartmouth.

The first launch was uneventful, as I had hoped. The wing as it sits on the fuse and the stab incidence as cut on the fin were very close. The first flight showed the CG to be a bit forward of where I like, so I landed and took out some shot. I also ground down the stab mount a little to keep the elevator neutral. The CG is now sitting about 38% of root, where I thought it might end up.

The plane circles very well. The handling of the double angle poly is very nice. Forget rolling or inverted passes but the bank angle is way sharper than I can do with the E-374 plane. The plane can also read and work lift better than anything I have flown, including #2 with the 7037/S4233. It takes a while to adjust to the appearance of the T-tail but the response is very good and there is no problem with blanking out on the launch. I installed about a pound of ballast to bring it to just under 10 lbs. No doubt it will carry the full limit and only on the lightest days can I imagine flying it under. The speed range appears good but only a test on the road will show the full capabilites. Did we hit the bar of the MXC? Probably, but it needs to be proven in competition. I have maybe close to an hour on the airfoils and at first impression I would say that the good Dr. did his homework on this one. The L/D looks fantastic. On the last flight I was trying to circle it down in the corner of the field to land and it just kept going and going and going... I took it to 500m and the visibility is good. Not quite as good as the X-tail but subjectively the handling on the T-tail is so nice it is worth it.

Now I will go through a little procedure I got from JW to set the plane up to race safely. The biggest danger at altitude is to tuck the plane. You won't even know what happened, you will just see the confetti. Launch the plane and climb it out to about 200m. Push the trim to its limits and see what the plane does. In this case the plane went from past tuck to stall. The trim is too sensitive. Make a guess how much to cut the trim authority and try to center the trim so that the full range spans from just shy of tuck at high speed to almost mushy stall. Fly again and readjust as needed. In this case the trim authority is only 21% of full. Now relaunch and find a thermal. Fly the plane at full up trim in the thermal. Crank it hard and make sure it does not stall. Straighten out and fly for a while to make sure it does not stall. Do a dive test and look for a pullout short of looping but enough to be certain it is positive. Push the trim forward and let the plane run. Try to estimate the speed. You want it to run at about 55 mph on its own. Make sure the plane still has a slight pullout at full down trim. I set the elevator throw to be on the sensitive side, but using the inner hole on the servo arm and all the throw. You want as much control as possible without being twitchy in order to land in tight spots. The full range of servo travel helps ensure good centering with the trim. The carbon pushrod helps with temperature stability. Now you have a plane that will run safely at altitude using only the elevator trim for pitch, and in the mad dash for the finish line at lower altitude you can push harder with the stick and watch the speed by eye for safety.

A side note, I defeat all the dual rates, modes, presets, etc. Low level saves are flown just like a DLG, banging the sticks if necessary, but on the road at altitude I use my right thumb on the rudder and left fingers on the elevator trim only. With all the other distractions you want the setup to be as simple as possible with nothing to mess up. Remember there are times when the plane is in a position where you absolutely cannot take your eyes off it to look at where the switches are on the transmitter. Everything has to be done by feel and has to be repeatable.

The warp in the wing is still there. Some can be ajusted out with the wing locator pins but in the long run this copy is not a keeper.

Stay tuned for the next copy. It will include carbon cloth in the wing, rectangular wing joiners, and most importantly a different epoxy system. Up for testing are the US Composites medium, MGS, and West.

[David Forbes]

Greg,
Look into Pro-set resin as well. I think it might be a West product. It's thin like MGS (or so I've heard, the hazardous shipping charges have made MGS a non-starter for me) and gives a very crisp wing with 120 degree post cure. I've used the USC resins, and still use them for molds and general bonding and splooge, but there is no substitute for a purpose made laminating resin when making wings. The Pro-set might be easier for you to get a hold of than the MGS, but I don't think the medium USC is what you're looking for.
Thanks for posting, I know it's a lot of extra work, but we all learn something. Great looking plane.
Dave

[G Norsworthy]

Dave, thanks for the tip. I looked at proset but was tempted by the long working time for the USC, having spent many an afternoon laying up parts in the San Fernando Valley at 100+ degrees. Wish I had gone with proset, or any of the other candidates on the list. I think #3 was built with West, and it has lasted 10 years with no problems. Some resins are harder than others but the XC planes are pretty tolerant, being thick layups, and the USC slow is the only one I have ever seen that just never gets there. Will probably go with proset on the next one. Does it kick hard enough at room temp to survive the transfer to the hotbox without moving, or do you need to kick it hot in one place?

Next we put the fairings on the wing and stab. Sight the stab, fin, and center section carefully, using a t-square on the stab. It will probably have moved during the trimming procedure. Mark the CG carefully because it will move in this step. Add or grind as necessary but try not to change the incidence. Now rough up the area under the surface a little. Take off the surfaces and put plastic wrap around the fillet area. Put the surfaces back on and mix up some epoxy and microballoons. Fill the area oversize and let it cure. If you want to make it really stout, put in a layer of chopped fiber and epoxy first. Patch any deficient areas from previous fills using the extra.


In a separate step, add tubes to hold the antennae for the radio and vario. they are different bands but try to keep them separate anyway.

[dbaya]

Here are some more pictures

[Kai@UCSB]

Good job !!

[Kirkgh]

Here are some more pictures

very nice if I do say so myself!!!

[OZPAF]

Greg,

Thats a really good looking aircraft. I'm a great fan of T tails and articulated Stabs, which i believe is a very effecient way to go.

I have been following your build with interest, Thanks for all the info you have shared - both building tips and trim/setup.

Its interesting to see how well the DS21 airfoil launches and thermals. It has a good reputation on small DS models as well - it sounds like it may be a very interesting foil.

Best of luck with your #8.

John

[David Forbes]

Greg,
For more info on Pro-set http://www.prosetepoxy.com/laminating_epoxies.html
I use the 125-229 combo, gives me adequate working time even in Florida summer. I'm not saying this is the only way to go, but I've been happy with it.
Dave

[yyz]

Greg,

Can you post a few words on your thoughts about the handling w/ the T tail version vs the C tail? You mentioned improved handling in several posts and I'm curious about your observations, preference/taste, etc.

I love the tall, high a/r fin and rudder combo. Looks great! The whole plane looks amazing.

Mike

[G Norsworthy]

The excel spreadsheet says you can use a smaller tail if it is a T-tail. Plus it is farther back so it can be smaller yet and has a mechanical advantage for a given amount of throw. I have to believe this because at first glance I thought the elevator would not have enough throw because of the small gap in the hinge line, but it is in fact very effective. The fixed stab with elevator also seems to respond better than the full flying, especially around the center. It works best with a T-tail because you don't have to split the elevator around the rudder or the rudder around the elevator. This makes a cleaner plane, which was the biggest thing I was after in this design. I went round and round on this one, looking at the Dynamic 160 design, which is quite elegant, and several other configurations, but I kept coming back to the T.

I copied the design off a DS plane I built a few years ago, and that one also had exceptional handling in pitch.

[yyz]

Thanks Greg.

The practicality of having the stab up and out of harm's way is attractive as it seems like you could make it lighter knowing that it is less likely to be exposed to sage brush, hay stubble, etc. Only an issue if you land out, right? :)

I'm curious, are you a natural south paw or did you learn to throw lefty to be able to winch and DLG launch with your right hand on the stick?

Can't wait to see this fly out in the Burmuda Triangle (CV), which by the way looked like it was booming on Saturday (could see streeted Cu from 50 miles west).

Mike




The excel spreadsheet says you can use a smaller tail if it is a T-tail. Plus it is farther back so it can be smaller yet and has a mechanical advantage for a given amount of throw. I have to believe this because at first glance I thought the elevator would not have enough throw because of the small gap in the hinge line, but it is in fact very effective. The fixed stab with elevator also seems to respond better than the full flying, especially around the center. It works best with a T-tail because you don't have to split the elevator around the rudder or the rudder around the elevator. This makes a cleaner plane, which was the biggest thing I was after in this design. I went round and round on this one, looking at the Dynamic 160 design, which is quite elegant, and several other configurations, but I kept coming back to the T.

I copied the design off a DS plane I built a few years ago, and that one also had exceptional handling in pitch.

[dbaya]

Blanking out foam for the next two :)

[Kai@UCSB]

Blanking out foam for the next two :)

:eek: :eek: :eek:

[ShredAir]

Nice hat, Greg... : )
This thread is a very good read. Would you mind if we placed a link to it on the xcsoaring.com website?

Dieter Mahlein, ShredAir

[G Norsworthy]

I'm curious, are you a natural south paw or did you learn to throw lefty to be able to winch and DLG launch with your right hand on the stick?

I'm right handed and fly DLG right handed. It never occurred to me throw a plane off a winch any other way than with my right thumb on the stick, especially with other peoples planes that may not be set up so well...

Would you mind if we placed a link to it on the xcsoaring.com website?
Sure, go ahead. My face is all over it through the years anyway.


Only an issue if you land out, right?
In XC there is almost no such thing as landing in.