Dodgson Designs Windsong, the New Fangled Way

[jtlsf5]

I know there have already been a couple of threads on building a Dodgson Designs plane here on RCG, but to my read, both were pretty much standard builds. This one will be a little different and will document the techniques I developed in the 1980's while building around 100 or so of Bob's various designs (no jive, I built a lot of these planes, and I know some are still flying today). Couple the techniques of then with some more modern touches and that is what you will see.

I have just completed a my second Lovesong built to more modern standards by modifying some of Bob's original construction techniques, Included are adding a little bit of glass and carbon here and there in the wing and stab, a modern 6 servo setup to get away from the complex mechanical mixing, and vacuum bagging the wings and tail surfaces with epoxy.

I don't recall the exact all up weight of the Lovesong I built in 2002 (currently residing in Oregon with Ken Eaton), but the one I just finished came in at 76 oz ready to fly. Not too bad considering the original Lovesong spec weight of 68 oz. I put five Airtonics 94141 servos (Ail, Flap, Rud) and one 94732 (Stab) in this plane, a 2500 mah NiMH battery, Airtronics 8 channel PCM receiver for control, and added about 6 oz in glass/carbon/epoxy. The plane took 70 gm of lead shot to balance. I know I could have made the plane a bit lighter with a more judicious choice of servos, but I'm not over the top about getting too light.

While this plane was nearing completion, a Windsong kit came available here on RCG, and my buddy Rob Glover latched onto it with the intent that I build it for him. He and I are good friends, and when I get in a building mood, I build. So he gets a Windsong this spring, and I will document the build. I hope you enjoy. On to the fun.

First task was to straighten out the fuse. Anyone that has built one of these planes know that even with the best packing and planning, the fuse always arrives a bit twisted. Probably a function of Bob boxing the fuses within a couple days of pulling them. Polyester takes about a week to fully cure, and thats a long time in the life of a starving kit manufacturer. Nuff said, the fix is easy. I gently warm up the main section of the fuse with a heat gun, then hold a little opposite twist and let it cool. Took a couple of rounds of this to get it nice and straight. There were some ripples along the tail boom. The fix to these was to warm with the heat gun, the put the warmed section on the bench and press gently with a piece of 1/4" ply, about 12" long until it cooled. Fuse was nice and straight after about 10 minutes of adjustment.

First session with polyester laminating resin to adhere the fuse doublers and towhook block. This is shown in the first couple of pix. While you can't really see the doublers, they are hiding under all the clothespins. I found this was the easiest way to keep these parts in good contact with the fuse while the laminating resin sets up. This is easy to see visually because there aren't any air bubbles between the wood and fiberglass fuse. Once I had the sides aligned and pinned, I propped it up on the bench and resined in the towhook block. Working time with the resin was about 30 minutes to the gel point, where the resin becomes too viscous to work. I will leave this overnight then the next few pieces will go into the fuse.

JT

[cynjon]

Subscribed... :)

[wifeswarrior]

Jim,
Song #1 is still doing well. Even the dumb thumb, stupid decision, "hey - watch this" and 2 minute torture drills have failed to change how beautiful it looks and flies. Put up enough flights and things will eventually "happen". Either you have a responsive plane - strong enough to hold together through recovery, or you don't. I do, and can launch with the best of them. The subtle changes along with things you've added revive a great plane back to having potential for "stardom".

AUW of Song #1 when purchased from you 77 oz. Now 79.5 oz.

Thanks for doing this build log. I may still try to come to you for building the Song kit I have, but if not -- now I'll know how to do it "right"

Looking forward to the day SONGS #1 and #2 can share the same sky.
:cool: How will we tell which is which in a thermal? Oh, that's right - mine will be the lower one...



Ken Eaton

[ka7cse]

Good job Jim!!! Will look forward to watching your build...

Mike Hansow
Auburn, WA

[O.L. Adcock]

Good job Mike, will watch for old time sake! :)....O.L.

[Robglover]

JT -

I've always wanted to try a 'Song, everybody says good things and all. But the smell of that resin drives me nuts. And I don't have that many clothespins...

Thanks Buddy - maybe one day I'll have to quit pickin on you about your timing skills. :p

[jtlsf5]

Its 18 hours later and the clothespins were removed to use in the second step. The first picture below shows the parts that go in next. The long spruce pieces are the tail boom rails, the nose deck and former are joined and ready to install, and the other piece is the two stab pivot plates tack CA'd to a crutch of 1/4" ply. This stab assembly allows the whole thing to be clamped from the outside, as the picture will show. Once cured a gentle twist on the crutch and it comes loose.

First bit of preparation was to carefully clean out the polyester resin that had "sweated" into the mounting channels at the front (nose deck) and rear (tail boom rails). I did this by scraping with the X-acto spade blade visible in one of the pictures, a great tool. The installation of these parts with polyester proceeded as normal. Clothespins to clamp the tail boom rails, masking tape to hold the nose together, and pinch clamps for the stab pivot blocks.

A little aside on polyester: this material is very different in use from the epoxies that we use regularly. Epoxy comes pretty much viscosity matched to be used in very specific ratios (1:1, 1:3, 1:5). For large amounts you use a ratioing pump; for small amounts you weigh with an accurate scale or by using similar length lines (1:1 types). Polyester is a different beast. The resin is of a similar viscosity to epoxy resin, but the catalyst is a water thin liquid that definately degrades over time. My current mix is 1.5 drops (from a glass dropper) per 1 mL of resin. I determined this analytically using measured amounts of resin (typically 10 mL in graduated mixing cups), then adding a predetermined number of drops. Mix well with a toothpick and wait, periodically stirring to see when the resin begins to gel (starts to get thick and lumpy). This is the gel point and determines the working time with the resin. I shoot for 30 minutes of working time (gel point around 40 minutes), enough to give me adequate time for the job at hand, but not so long that the final cure takes too long. I do this with every new batch of catalyst, usually it takes one or two samples to determine the right mix. Also, the smell from polyester is styrene, which is a diluent for the vinyl ester monomer in the resin, and neither component is that nice to breath. Be sure to use polyester in a well ventilated space.

Time for my real job and to let the resin cure up enough to handle (12-16 hours).

JT (a chemist in real life, could you guess?)

[kzimmerm]

Brings back good memories when I build LS for my best friend....

[John Cole]

Jim, thank you for the thread. I'm taking notes.

John

[jtlsf5]

Jim, thank you for the thread. I'm taking notes.

John


OK, I get a cut if you publish! ;)

JT

[ka7cse]

I miss the smell of curing resin in the garage......

[jtlsf5]

About 12 hours later, unpinned, unclamped and untaped everything. Looks pretty good. First couple of shots show the doubler laminations with no significant voids. For comparison, there are some minor visible voids in the third picture. If there were alot of these, I would worry about a bonding failure under load; a couple small ones aren't a problem.

Time for the first round of reinforcement while the nose is still accessible. The bulkhead serves as a barrier to the lead shot that will be used to balance the plane from leaving the compartment they belong in. I like to seal the key seams with strips of glass. The next picture shows the 8 pieces I use for this cycle of fiberglassing. The large one on the left goes over the towhook block, the next two between the nose deck and fuse-side/doubler, and the final five for the bulkhead-fuse joint.

First, I retaped the nose securely and ran some resin by the bottom of the bulkhead (its not a snug fit) down the bottom of the fuse. This is to pool in the nose while the fuse is stood upright to provide a larger bonded surface at the tip of the nose; contest landings, you know. Then the various pieces of cloth were resined in place. Next couple of pictures are of the glass on the towhook block and glass in the nose. You can see all the seams that were glassed. My camera just fits far enough into the unobstructed fuse to get this shot. In practice I use an old dental mirror to see what I have done in non-visible corners. Last shot is a bit fuzzy, but you can see the upper forward right corner in the mirror. Ask your dentist to save any old mirrors that they are going to scrap. They may be past their lifetime in the office, but will provide years of use to you in the shop.

Stood the fuse on the nose and left it until tomorrow. Next will be the two mid-deck pieces, then the wings get done to the point that they can be mated to the fuse.

JT

[jtlsf5]

I miss the smell of curing resin in the garage......

I sure don't!!! We are having remarkably good weather just now. I have the garage door and a rear door open to provide some flow through so the fumes don't get to be too overpowering. Gotta love Sactown!!

JT

[ka7cse]

I sure don't!!! We are having remarkably good weather just now. I have the garage door and a rear door open to provide some flow through so the fumes don't get to be too overpowering. Gotta love Sactown!!

JT

There is a skateboard/surfboard shop near where I work that works in the evenings and provides me with needed fumes from time to time!!!!! :p

[Robglover]

For those who are interested in how this got started:
http://www.rcgroups.com/forums/showthread.php?t=811780

I really like to fly these things. I also like to build them, but having an expert friend build one for me is even better. This is one of those times when the stars seem to have come into alignment. One of the really nice things about this hobby is the friends.

[IBWALT]

Jim, I can smell the polyester resin here in Houston and am looking forward to following your Windsong build. Are you going to build it complete with the FART?

Walt

PS: I still have the balsa block that I made with the raised rib to sand in the groove on the wings for the spruce spars. It is still in excellent condition and you are welcome to it. Just pm me your address in Sac'o'tomatoes and I will mail it to you. Don't know why I kept this thing all these years. Pack rat I guess or maybe my mind is still fogged by the resin fumes. :D

[jtlsf5]

Walt,
Thanks for the offer. I still have mine, used it on the last Song, and will use it on this Song (to add spar extensions even though the Windsong didn't have them). Also made one of the two X-acto #11 blade things to cut the lap seam on the 1/16" balsa sheeting. After 20 years of disuse, it didn't work so well (on a test piece), so junked it in favor of a 1/32" ply sanding stop. I'll show this set up when I get to the sheeting.

No AFART on these later planes. The advent of computer radios makes the plumber's nightmare obsolete. In its time it was revolutionary, but technology always catches up. This will be a 6 servo setup, and will use 6 Airtronics 94761's for the install.

You wouldn't be Walt Holsclaw would ya?

JT

[IBWALT]

You wouldn't be Walt Holsclaw would ya?

JT

No, Walt Higgins. I'm a friend of Julian Tamez. We met years ago at the 90 NATS.

Walt

[jtlsf5]

Time to install the two mid-decks. This step sets the basic alignment of the wings-nose-tail, so I took time to be sure it was right. The final alignment will happen after the wings are done and the rear tailboom cap is installed.

The first picture shows what will be installed. There are the two deck pieces and I will add the two small blocks to the canopy, the front to carry an alignment dowel, the rear already notched for the rubber band hold down. Second picture shows the channel where the deck pieces will install. It has been cleaned of residual resin, and the doublers carefully trimmed to allow maximum contact for the deck pieces to the fuse/doubler. The next two pictures show the parts resined and curing. The clamps help relieve the tension on the joint while the resin cures.

After this step, the final item before the wings will be to add glass reinforcements to both of the deck-doubler seams. I won't show this, its too hard to see. Same procedure as the reinforcements to the nose area, and it does add strength and integrity to the fuselage.

Its gorgeous here in Sactown, gonna go fly MY Song and Supra today. Eat your hearts out Snowbirds!! :D

JT

[jtlsf5]

No, Walt Higgins. I'm a friend of Julian Tamez. We met years ago at the 90 NATS.

Walt

Holy !@#$ :eek: Great to see you back. Say hi to JT for me. Saw him a couple of years ago at the Masters, just like old times.

JT

[lincoln]

If I'm not mistaken, it's possible to get a good joint on polyester resin with epoxy. Lots of good surface prep and maybe an epoxy meant for bonding instead of laminating. I suppose you'd have to test first, which means you'd have to find some polyester scrap.

If I'm not mistaken, the "taco shell" fuse as it comes out of the box is a very simple shape. Basically, two flat planes tangent to a cylinder. It wouldn't be hard to mold it. I'm told guy in our local club used to make "taco shell" style fuselages from thin aircraft plywood. (1/32" for a two meter, I think). That's probably the easy way out, and you could just add a bit of glass, or even another layer of ply, after you formed it. If I was doing it, I'd make sure the ply was waterproof by boiling it, and then soak it in water for a couple of days, form it, and let it dry for a long time, maybe with heat. I know it would spring back some, but this would help to hold the shape.

Clothespins are dirt cheap compared to six 9141's.

Anyone out there ever flown both and Anthem and a Lovesong or Windsong? I've only flown the Anthem, and I found it a bit of a handful.
JT -

I've always wanted to try a 'Song, everybody says good things and all. But the smell of that resin drives me nuts. And I don't have that many clothespins...

Thanks Buddy - maybe one day I'll have to quit pickin on you about your timing skills. :p

[ka7cse]

JT

I have seen several others use a fuse jig for alignment. I see you are not. Care to make any comments?

Mike

[jtlsf5]

JT

I have seen several others use a fuse jig for alignment. I see you are not. Care to make any comments?

Mike

OK. I'm a one decimal kind of guy, not a 4 decimal engineer. Every Dodgson plane is hand built anyways, so you would expect a little variation. Regarding the fuse, perfect alignment of the fuse is good, but not critical. What is critical is the alignment of wings, stabs and fin, as long as the fuse is reasonably straight and stiff. So I don't go crazy trying for the perfect fuse as long as it sights reasonably straight. I spend my time mounting the wings with zero camber difference and square to the bottom rear tip of the fuse; then the fin aligned to the wings. Finally, the stabs are trued to the fuse and fin. End result is a pretty square plane, without worrying so much about the fuse.

JT

[jtlsf5]

If I'm not mistaken, it's possible to get a good joint on polyester resin with epoxy. Lots of good surface prep and maybe an epoxy meant for bonding instead of laminating. I suppose you'd have to test first, which means you'd have to find some polyester scrap.

If I'm not mistaken, the "taco shell" fuse as it comes out of the box is a very simple shape. Basically, two flat planes tangent to a cylinder. It wouldn't be hard to mold it. I'm told guy in our local club used to make "taco shell" style fuselages from thin aircraft plywood. (1/32" for a two meter, I think). That's probably the easy way out, and you could just add a bit of glass, or even another layer of ply, after you formed it. If I was doing it, I'd make sure the ply was waterproof by boiling it, and then soak it in water for a couple of days, form it, and let it dry for a long time, maybe with heat. I know it would spring back some, but this would help to hold the shape.

Clothespins are dirt cheap compared to six 9141's.

Anyone out there ever flown both and Anthem and a Lovesong or Windsong? I've only flown the Anthem, and I found it a bit of a handful.

Lincoln
You are willing to go to a heck of alot more trouble to avoid working with polyester resin than I am. Why would you want to risk a plane that would take many hours of construction labor on a questionable at best bonding technique? If it works for you, go for it. As for me, I understand how to use polyester properly and do so to very good affect.

Your comment regarding clothespins and 94141 servos escapes me for two reasons. One, I said this plane would use 94761 servos, Rob's choice which I support (I used 94141s on mine). Both are quality servos for a quality plane. Two, what the heck do servos have to do with clothespins? Please PM offline, I'm not interested in diverting this thread from its purpose, the construction of a Windsong. And if you want to start one on the flying characteristics of the variants of this design, please do so but not here. Thanks

JT

[ka7cse]

[QUOTE=jtlsf5]OK. I'm a one decimal kind of guy, not a 4 decimal engineer.

I am with ya JT. Keep the build going. We are watching what you post. Great pictures as well.....

Mike


Lincoln,

Taco fuse's are still available from Shawn Lenci, either polyester or epoxy...

Lenci1938e@aol.com

Mike

[schrederman]

IBWALT wrote: maybe my mind is still fogged by the resin fumes.

Thanks for clearing that up for us, Walter, ol' bud... Many of us were wondering...:)...

Your bud in Clovis...

Jack

OBTW... where are the Hawks? Why didn't you guys come to Phoenix... bit of a drive, for sure.

[lenci1938e]

Mike,

Actually, we are only making the new fuses in West Systems epoxy so if you don't like the "smell" of polyester you are in lucki. The new ones are really nice and are being primed in the mold for a very smooth finish with virtually no pinholes. We are currently working on the Maestro and Saber along with the Windsong, Camano/Pixy and Pivot that are available now. Hopefully we will do the Todi as well. The two piece fuses are being done with a lap seam and not tape as the originals were.

Shawn

[jtlsf5]

Mike,

Actually, we are only making the new fuses in West Systems epoxy so if you don't like the "smell" of polyester you are in lucki. The new ones are really nice and are being primed in the mold for a very smooth finish with virtually no pinholes. We are currently working on the Maestro and Saber along with the Windsong, Camano/Pixy and Pivot that are available now. Hopefully we will do the Todi as well. The two piece fuses are being done with a lap seam and not tape as the originals were.

Shawn


I have to add my two bits for Shawn. He has done some really nice work with the Dodgson molds and tooling he acquired a few years back. I saw Bill Ervins fuses and they were nice. If I didn't like playing with all the polyester I still have, I'd be doing epoxy. Support Shawn, he has helped keep the Dodgson flame burning.

And now back to building.

JT

[jtlsf5]

One more small task before setting the fuselage aside and building the wings. The hatch is a pretty quick item to get out of the way, so here it is. The first picture shows the hatch ready to mount. It has been fitted to its spot between the mid deck pieces and fuse sides. I have added two ply tongues at the back which fit under the rear deck, and one in the front to take the locking pin. On the original Songs, there was only one rear tongue which had to stay out of the way of the flap drive system. On these modern planes, there is no plumbing aft of the antirotation pin, so more locater tongues will work.

The second picture shows the hole drilled (angled) in the front deck, with a piece of 1/16" music wire taped to the nose. This acts as a jig for the bushing installation. The 1/16" x 2" brass tube bushing that the pin rides in will be roughed with sandpaper, put in place inside the fuse against the underside of the front deck, then attached. I use baking soda and CA for this. With all in place, I trowel in some baking soda around the tube, using my finger to push and shape a mound over the tube. This ensures the tube is fully supported. Then carefully drip some thin CA into the baking soda, and voila, modern brick and mortar. Once the tube was secured, I cut the locking pin to size. A little ink from a Razor Point pen on the end of the wire allowed me to accurately mark where to drill the hole for the locking pin on the end of the hatch. It was right at the seam, so I used an awl to start the hole, then drilled a 1/16" hole. CA in the hole to strengthen it, then drill again to clean out and it was done. Last shot shows the fuse with hatch installed.

Now on to the wings. This is the next logical step in the build sequence, and allows time for all of the polyester to fully cure up before I return to the fuselage in a few days.

JT

[jtlsf5]

So as I was starting on the wings I thought of a few more pieces I could put in the fuse, and did. First picture shows the three pushrod guides, second shows them installed. Now, on to the wings.

First, I cut the correct angle into the roots of the cores. A consequence of the fuse sides not being parallel. Better to do this now before installing spars and antirotation pins than after. Third picture shows the angle. Fourth picture shows the parts for the spars. I am going to do a couple of LoveSong mods to this plane. One, an 11/32" joiner instead of the 5/16" joiner of the Windsong. The balsa spar cores are 3/8", so the necessary 3/8" OD brass tubing will fit without a problem. Two, I am going to add spar extensions set into the cores just like the LoveSong. I don't have spruce thinner than 1/8", so I will just lap joint an 18" piece of 1/8" x 3/8" onto the 36" 1/8" x 3/8" main spars. This should take the spar safely out into the aileron and well past the aileron servo box.

JT

[jtlsf5]

Spars are now nearly done. Here is the sequence. First the spars and spar extensions were matched and the lap seams sanded. They are marked for easily matching once in the wing. First picture shows these. The next picture shows how I piece the spars together. I use a long straightedge and lead bars to align things as I add each balsa spar core. I usually do the bottom of the spar first to establish a straight surface. This will install flush with the bottom of the wing when the spars are finished. Balsa spar caps will fill any voids to make solid contact with the top surface. The third picture shows the spars together and ready to install the shear webs. Note the tip end of the spars in the fourth picture, all of the laps are facing out to make the mating joint easy. Fifth picture shows the spars jigged with a spacer to ensure both the top and bottom of the spar are straight, and thick CA in place just before setting the shear web. Next picture is the two spars with the rear shear webs, already trimmed, sanded and ready to install the tubes and front shear web. The tubes have been capped with a piece of balsa to ensure that no epoxy wicks in from the tip end of the tube. Next picture shows one tube set in and the other with its balsa cap.

The tubes are now epoxied (5 min) in place, working quickly to be certain the entire tube (prescuffed) is wetted and there are no voids. I do this by mixing up my epoxy, then putting a generous amount in the open channel The open end sits on wax paper because the next bit is a mess. The tube is then started at the tip end of the spar and forced down towards the root end. Excess epoxy will squeeze out the end of the tube. Then press down on the tube all along its length and it will seat and more epoxy will squeeze out. Spread epoxy along the top and the wood mating surface adjacent to the tube, then CA the remaining joining area of the shear web. Finally, place the shear web, press to set the CA, then securely tape the joiner box area. Final picture shows the spars standing to cure. It may not show, but there is epoxy all the way around each tube, with no unfilled area. This is also the reason the tubes are a bit longer than the spar, so epoxy doesn't back into the tube. They will get trimmed later. Time to take a break.

JT

[jtlsf5]

With the spars built and only needing some Kevlar thread whipping around the joiner box, its time to get the cores ready for the spars. The first thing was already done, namely cutting the root angles. Next is to sand slots for the extended spars, add the spider foam blocks where the servos will go and to fill the existing areas routed out for the mechanical linkage. This is all wing core prep which will be done before the spars are glued in.

First picture shows the extension to the spar slot for the extra 4" of spar. One of the spar extensions is used to confirm the proper depth. Walt H., here is my 23 year old sanding block which I use for these slots. One side is for the 3/32" extensions used in the Lovesong; the other is for 1/8" which I must have done before and am doing now.

Next was to cut the pieces I will use to add/replace foam. The pieces shown in the next picture are: 4 spider foam blocks (lower left) to be inserted to accept the wing servos, and all the rest are to fill in the existing routed areas for the aileron belcrank plate and wire channel. The last picture shows one of the cutouts for the spider foam block. I used an X-acto whittling blade and the insert block itself as a cutting guide. Makes for a tight fit. Also note the locating lines. If you do this modification be sure to measure and write down the exact center of these blocks. You want to be able to find this same point once the wings are sheeted and covered. For reference, the flap center is 9" from the root and 4.5" perpendicular from the LE, and the aileron center is 39" from the root and 3.75" perpendicular from the LE. This isn't dead center on each trailing edge surface, but the stiffening elements that will be added to the flap and aileron will give a good flutter-free setup.

JT

[jtlsf5]

All the changes to the cores are complete and they are ready for installation of the spars. First picture shows the Kevlar whipping on the spars. The two areas are at either end of the joiner rod tube, mainly to prevent the shear webs from delaminating in the event of a very hard landing where those long wings have a tendancy to swing forward. Second picture shows the cores with the foam bits and pieces installed and sanded down. Third picture shows the set up to install the spars. Its important to establish a flush mount to the bottom of the core, so the wings will align easily. I use aliphatic resin glue for this to give me a little time to get everything taped up and into the beds to set. They are taped top and bottom with a little tension to hold the core tightly to the spar. After about a half hour, they can be removed to finish drying. Pictures four and five show the result just out of the beds, bottom of spar flush with core, a gap at the top that will get filled with a balsa cap. The last picture shows a LoveSong modification, 1/64" shear webs on the antirotation pin tube carrier. Very little weight, lots of strength and stability.

JT

[IBWALT]

Jim, that's a mighty fine looking vintage sanding block. But I wonder what Bob would sa sa sa sa say about some of your mods. :D Keep up the good work. I'm off to the auto parts store to get some polyester resin. So I can sniff along with your build.

Walt

[John Cole]

Jim, great thread. I appreciate you taking the time to lay this info out.

I remember adding spar extensions to my Windsong long ago, after seeing a few fold up on the winch.

Dumb question: What is spider foam?

John

[jtlsf5]

Jim, great thread. I appreciate you taking the time to lay this info out.

I remember adding spar extensions to my Windsong long ago, after seeing a few fold up on the winch.

Dumb question: What is spider foam?

John

Spider foam is a type of closed cell polystyrene, similar in composition to the gray, blue and pink foams used in traditional vacuum bagged wings. The difference is that spider foam was developed so it has structure in the thickness direction which makes it much stronger (with no weight difference) than the other closed cell foams. First I saw this used was Mark Levoe on the Super V series. Nice stuff, excellent strength and crush resistance.
JT

[jtlsf5]

Took the cores from spars glued in to ready to join the tip sections. This involved the following steps:

1. Install the antirotation pins assemblies. This has to be done carefully to be sure the wing is square. First picture shows the result sitting on the bench.

2. Add the sandable spar caps and sand to match the top of the core. Second picture shows this.

3. Cut the wire channels and backfill the keyhole. The next group of pictures show the sequence. I use a keyhole cutter I made years ago when I was scratch building a lot of bagged wings. It kind of looks like the line guide on a fishing pole, at least thats what inspired this design. One picture shows the keyhole cutter and the test piece I use to set the voltage properly. It is set so the hole is about 1/8" below the surface that I cut along. Another picture shows the my power setup. It is a lab variac (rememeber, I'm a chemist and had access to some neat surplus lab stuff) hooked up through a stepdown transformer. I use the 5V tap off the transformer, then adjust the variac voltage until I get the right power. Next picture shows the result of the cut. The rod of foam that was cut is laying on the core, full length next to the channel. Then I use a 1/4" carbon tube I had laying around the shop as a form for the inside of the channel. This is inserted all the way to the end of the cut. I fill the keyhole slot with light water based pre-mix spackling and twist out the carbon rod to leave the filler to dry. The balsa wouldn't collapse into the channel, but I don't want epoxy wicking into the wire channel during the vacuum bagging step. While filling the channel I also filled a few of the voids around the foam pieces I put in to fill the old pushrod channels. This is shown in the last couple of pictures. Thats probably enough for today. Time to take a break.

JT

[jtlsf5]

Jim, that's a mighty fine looking vintage sanding block. But I wonder what Bob would sa sa sa sa say about some of your mods. :D Keep up the good work. I'm off to the auto parts store to get some polyester resin. So I can sniff along with your build.

Walt

Walt, I think you've been doing this too long. Scratch and sniff with polyester? ;)

JT

[O.L. Adcock]

There is no problem using epoxy for gluing and finishing with the polyester fuselages. It works as well or better. The one thing you can't do is use polyester with the epoxy fuselages...Good work JT!.....O.L.

[ka7cse]

JT

Are those E214 cores?

Mike

[jtlsf5]

JT

Are those E214 cores?

Mike

Mike,
Sure are. This is a 1984 vintage Windsong based on the newspaper I pulled out when I received the kit. Even had a discount coupon good until May 1984, I guess its a bit late to use, ya think? :D

During the mid-80s I built some 3021 modified planes, one Windsong and a hybrid 3M ship I called "Gracie". Gracie used a Camano fuse converted to a T-tail (ala K-Minnow), and scratch built 3M S-3021 wings. Nice flying plane which almost got me my 2 hour thermal task for LSF 5 (about 11 minutes short). I sold it to Nick Trubov in the later 80's. I hear from Nick every now and then, he still has her and (I assume) still flies her. Nice to know this plane is still around.

JT

[jtlsf5]

There is no problem using epoxy for gluing and finishing with the polyester fuselages. It works as well or better. The one thing you can't do is use polyester with the epoxy fuselages...Good work JT!.....O.L.

O.L.,
I still don't buy it. As a chemist knowledgable in the chemistries involved with the two different resin-catalyst systems, I just don't see how one can bond to the other. They are chemically incompatible and polymerize (cure) by different chemical reactions.

The success you seem to have had is probably a function of the tenacity of epoxy to hold on to just about anything. I suspect there is very little true chemical bonding, and a whole lot of surface tension and secondary forces at work in these mixed systems.

I will always believe that the best and most robust method is polyester with polyester, and epoxy with epoxy. Just my $0.02 worth.

JT

[ka7cse]

Wow Jim, you are building an antique! Will ask Bob when I see him about the coupon. LOL

Mike

[O.L. Adcock]

JT, Yep, most everything we do is "over built" so less then ideal will still work. I can see tacky laminating polyester getting a chemical bond if done while the surface is still tacky but once it's cured, it's a mechanical bond either way. All I know is many dozens were built using epoxy with no noticeable differences. Be careful as some of the mid-late 80's Love/Windsongs were epoxy and many won't be able to tell the difference by looking at them. I know cause I made them for Bob....O.L.

[jtlsf5]

JT, Yep, most everything we do is "over built" so less then ideal will still work. I can see tacky laminating polyester getting a chemical bond if done while the surface is still tacky but once it's cured, it's a mechanical bond either way. All I know is many dozens were built using epoxy with no noticeable differences. Be careful as some of the mid-late 80's Love/Windsongs were epoxy and many won't be able to tell the difference by looking at them. I know cause I made them for Bob....O.L.


O.L.,
Doesn't work that way. The two chemistries are different. My gut tells me (and I have no intention of trying the experiment), that if you added polyester resin to an epoxy mix, it would do nothing except get in the way. Similarly, adding epoxy resin to catalyzed polyester would also result in a mess. The "tacky ends" don't intereact with the other chemistry. Polyester is free radical, epoxy is nucleophilic epoxide ring opening (and you thought I wouldn't slip some chemistry in).

Sometimes a mechanical bond is enough. I wouldn' trust it. BTW, there is actually an easy way to tell epoxy from polyester. Sand a little bit from the inside of the fuse. Under below the surface there will be a hint of the odor of either styrene or the diamine epoxy catalyst. I've checked 20 year old fuses this way and can tell what is what.

JT

[O.L. Adcock]

JT, I'd hope no one would ever mix uncured of either together and that's not what I was suggesting. Those that balk at building these planes because they think they have to use polyester need not use that for an excuse cause using epoxy has proven to work just fine in real life, not theory.....O.L.

[IBWALT]

Under below the surface there will be a hint of the odor of either styrene or the diamine epoxy catalyst. I've checked 20 year old fuses this way and can tell what is what. JT

Scratch and sniff. The tried and true method.

Walt

[O.L. Adcock]

What about the Vinylester ones? Some of those were made too along with some Kevlar. :)....O.L.

[jtlsf5]

Looks like it was kind of a slow day for all of us. ;)

My real job kind of got in the way of making significant progress, but I still managed to get a little work done. I ended up using the same full length joined beds that I used on my own Lovesong, so didn't need to do anything with the Windsong beds. A bit of trimming on the root end of the foam tip extensions, then they were joined to the main cores with foam friendly CA. Once joined, the spar extensions were installed with aliphatic resin. Same procedure as the spar installation once the channels were sanded in with my 20+ year old special block. The extensions were glued and taped, then placed in the beds and weighted down for about an hour. Then they came out of the beds and were allowed to air dry before removing the tape. The result is shown below.

JT

[Robglover]

Cool.
I'd forgotten what long straight wings look like. :)

[atjurhs]

Looks like a new pair of water skis to me. Hey and Bubba's got a boat :D

[jtlsf5]

Today I took the cores to the level of ready to skin. Three basic steps. One, install 3/8" balsa for the wing TE/Flap-Aileron LE. This is a Lovesong mod and is a real improvement over the original Wingsong. The Windsong had the TE surfaces cut free, then faced with balsa. It was very hard to keep them true and warp free with this technique. The embedded balsa provides the material as part of the core, so when the surfaces are cut free, they are already faced. Net result, no warps. Two, install the dowel inserts into the wing root. These will receive the modified eye hooks that are used to retain the wings on the finished plane. Three, fill all the remaining surface imperfections, holes, sanding scuffs, etc. I will have one last job to do, then the cores are ready to bagged. That will be to gently sand the filled areas and brush or vacuum the cores. Pictures should be self explanatory.

JT

[jtlsf5]

Looks like a new pair of water skis to me. Hey and Bubba's got a boat :D

OK Todd, one of these = two of your dainty little 2M things. :p

[Robglover]

OK Todd, one of these = two of your dainty little 2M things. :p

Nah, JT you haven't seen the way Todd builds wings. He has a lot more material in a 2 meter wing than you would put into an XC wing. Todd has never built anything that I'd describe as "dainty".

I'd probably be able to use some of Todds wings as water skis, but my boat only has a 90 hp engine so it might not pull them. :rolleyes:

[atjurhs]

stop, stop, I'm laughing so hard it hurts!

[jtlsf5]

Bubba, good news-bad news. Good news, Todd's been getting outside advice recently on building techniques. Bad news, I've been giving him the advice. ;)

[Robglover]

Bubba, good news-bad news. Good news, Todd's been getting outside advice recently on building techniques. Bad news, I've been giving him the advice. ;)

Yeah, I've tried to give the Todd advice too. He seems to have trouble hearing. He's a Marine who escaped, but he still seems to have his head stuck in that jar. He seems genetically predisposed to build in a "robust" fashion. ;)

[jtlsf5]

Back to the Windsong. The cores were sanded to smooth and prepared for sheeting. The other prep work before the actual bagging will include preparing the sheeting, and fiberglass and carbon reinforcements. The original design (transfer tape method) used pieces of 1/64" ply to reinforce the butt joint between the 4' and 18" sheeting and for the trailing edge. I will use a lap joint (like the Lovesong) for the sheeting joint, and use 2 oz. fiberglass cloth reinforcements for the TE (top and bottom), wing roots, lap joint, and top/bottom at the servo cutouts. I will also add some uni carbon top and bottom (full span) over the spars. For fun I will weigh everything before and after. Here are the weights of the cores and main sheeting. I might have to add one or two sheets of 3" x 36" balsa to fill out the tapers, but here is what I have so far (weighed on a commercial lab balance, accurate to 0.01 g, reported to 0.1 g; yeah, there's that chemist thing again...):

Left core: 163.2 g
Right core: 164.8 g

8 sheets 4" x 48" plus 5 sheets 3" x 36" balsa: 291.5 g

I individally weighed the balsa sheets, then sorted and matched to give as close to even weight to both the right and left wings. The picture below shows the main 6 pieces of balsa for each wing (weights and wing designation).

Based on this, the left core plus 6 sheets weight 301.2 g, the right core plus 6 sheets weigh 300.8 g. Close enough.

Next bit of prep work will be to join and trim the sheets to exact size, and cut the glass and carbon. I'll report on this a little later today, and may be able to bag the first wing this evening.

JT

[jtlsf5]

I got the skins ready, glass and carbon cut, and everything is ready to bag the wings. I used to glue skins together, and this was necessary with the transfer tape skinning technique. Later on when I started bagging wings with epoxy, I learned that this glueing was unnecessary. The epoxy that is being used to attach the skins will do a wonderful job of wicking into the seams and glueing them as part of the overall bagging process.

First job was to join all the balsa into mains and tip sections, just taped together. This kind of shows in the first picture, and is more apparent in later ones. The first picture shows my sanding jig for the lap joint. Its just a straightedge to run the sanding bar against, and the sandpaper surface rides on 1/32" ply pieces. This is adequate to establish the lap (1/2" wide here) and gets the joint to about 90%. A little finish sanding without the ply rails leads to a perfect fit. Second picture is getting ready to glue the lap seam, first on the bottom (inner) surface, then the top. After glueing the inner, it gets gently block sanded which removes the excess CA and fills the seam with balsa dust. Next picture shows the result along with a 5' rule.

With the skins all joined, it was time to prepare everything to attach the skins. First I cut the glass and carbon to size. This is shown in the next picture laying on the skin in the approximate position it will go on the inside of the skin. Total weight for the glass and carbon for both wings was 77.6 g.

The skins were marked with reference lines for the carbon (along the spar), and the servo pocket centers, shown in the next picture. All the other glass goes along the trailing edge, wing root and over the lap seam, all easy to locate.

Time to clear the bench. The tools for the epoxying step are pretty simple, a couple of spreaders and a mixing cup. Next picture is my vacuum pump setup, which I turn on in advance to allow to hit and hold my chosen level of vacuum, and to ensure all is operational for the 12 or so hours of time the part will be in the bag. I use a Barnant pressure-vacuum pump hooked up through a one-way valve to a surge tank (3 gallon Freon tank), vacuum switch, and guage, then finally to the part. The system is set to about 200 mmHg of vacuum (3.7 psi or 7.9"Hg), about right for white bead foam, and is running. It doesn't show, but the hose leading up to the right has a clamp on it. Once connected to the bag and everything aligned, I will release the clamp and apply vacuum to the bag/part.

The vacuum switch is something I ran across years ago in the lab. Its a really nice little unit, cost about $60. It has a small vacuum bellows connected to an adjustable switch that controls a relay. The relay primary is connected to AC power, the secondary to the vacuum pump. The net result is set the vacuum level and forget about it. The switch will turn on the pump when the vacuum falls to about 180 mmHg and run until the vacuum goes back over 200 mmHg, then shut off. I like the use it and forget about it aspect. I've used this system for everything from white bead foam (as will be done here) to making laminated parts like control horns, bellcranks, etc. which I do at about 650 mmHg, about the max this pump will pull. All the different settings were easy to hit and held reliably.

The bag (note breather rope already placed), bag seal and carbon/glass is arranged and ready to use in the final picture. Next step, epoxy and bag away.

JT

[jtlsf5]

Had dinner, then it was back to the shop to get the first wing in the bag. With all the set up earlier, this was pretty easy. Newspaper on the bench, laid out the sheeting for the left wing, moved the glass and carbon to the bench within easy reach and got to it. I measured out 69 g of West Systems with the 206 slow hardener and started. Both top and bottom skin wetted and scraped fairly dry. Then I added in order the TE pieces, the root and lap seam pieces, the servo area reinforcements, and finally the carbon spar caps. All were wetted and scraped. Once all was ready, the core was placed using the root and LE as references, the top folded over, a few pieces of tape at the root, tip, and along the LE to keep all aligned, then into the bag. The bench was cleared again, the bag sealed, placed into the beds and aligned/weighted, then applied vacuum. All was well. I took a couple of pix, one of the whole thing finished, and one sighting along the TE, nice and straight (not sure if this really shows in the picture). A bit of clean up, then weighed the mixing cup and found that I used 62 g of the 69 I mixed up. Not bad. Enough for tonight.

JT

[lenci1938e]

JT,

There is some pretty good stuff here. What weight cloth are you using on the TE reinforcement? I have done the same as you have in the past and put the glass cloth on the "inside" of the wing TE and not the "outside" as Bob had suggested. I used some 1.4 0z or 2.0? stuff that came from K&B. I think the stuff that Bob supplied was .75 oz. but I thought that was too light.

I am interested to see what you do with the fuse. I am thinking on my next Windsong of going with a carbon or G10 bellcrank (probably from hilauch.com) as the Kraft Hayes nylon is a little to flexible even with the brace that Bob added. I believe there is a better way. I will also go with carbon pushrods next time to get all the "steel" out of the boom and tail along with carbon stab joiners and aluminum tube instead of brass.

I too have used a 11/32" ejector pin for a wing rod and have never bent one on tow. I used to have a heck of a time getting my wings to fit the fuse properly with the carbon rods that Bob supplied. I finally figure out one day that I rarely had a straight wing rod in one of the kits. I'd put the wings on, then try to fit and sand. Put them on again and the fit would be worse. Once I went to the ejector pins I found that they were true and the problem of fitting the wings went magically away. I was considering going with a carbon rod but that may be overkill for a plane of this type. Plus I have a lot of ejector pins here in the shop.

Shawn

[jtlsf5]

Shawn,
Nice to see you here. I used 2.0 oz glass throughout on this plane. You are correct, 3/4 oz is what Bob supplied. It had to be put on exterior, since glass cloth was not compatible with the transfer tape method. I find that the internal balsa LE/TE plus the cloth makes for a very stiff surface.

And the nylon bellcrank goes too. I used a carbon on mine and will on this one. While I could go to carbon pushrods, I kind of like the steel ones, they don't require any special bushings and are easy to solder with silver solder. I am preserving as much of the original as possible. My current Song and this will have 1/8" carbon stab joiner pins. Saves 5 g over a 1/8" steel, or 1/2 oz overall.

I wouldn't go to a carbon main joiner unless you increase diameter to at least 1/2", but that would mean significant modification to the whole joiner system. Ejector pins are the way to go. I have used them on both of my recent Lovesongs, and would like to use one on this.

I'm currently out of 11/32", any chance of getting a couple from you for this project and as a backup? Contact me offline if so, and if you're coming up to Davis anytime soon.

Regards,
JT

[ka7cse]

I was kind of thinking of only using 5 servos next time. Using the original type flap linkage and the flap servo in the nose would save a little weigh and I hardly ever use the flaps for turning anyways. Maybe even RDS the ailerons as well :-)

Mike


Good job on the build JT!!!

[jtlsf5]

[QUOTE=ka7cse]Using the original type flap linkage and the flap servo in the nose would save a little weigh and I hardly ever use the flaps for turning anyways. QUOTE]

Mike,
This was a nice solution at the time, but with more aggressive setups and launch equipment, the end of the surface is absolutely the wrong place to drive the flap and aileron. With the lighter, stronger servos available now, there is no reason not to use them and improve mechanical advantage to control the wing. Plus, no big weight penalty as all this is on/ahead of the CG.

Regards,
JT

[ka7cse]

Your probably right Jim but was just trying to save a little weight. Could probably stiffen up the flap some with judicious use of Cf but the added would probably wipe out the weight saved from the extra servo. Build on JT, build on....

Mike

[jtlsf5]

Early Friday morning and 12 hours in the bag has elapsed. Wing is out and LE, TE and root trimmed and lightly sanded. Bagged weight is 394 g. Going back over the weights to here: core plus wood 301.2 g, epoxy 62 g, glass/carbon 38.5 = 401.7 g. Looks about right considering the strip of about 1/2" I trimmed from the TE. So far so good. Picture shows the top surface seams where the epoxy has wicked through to bond the skins together as they were bonded to the core. Next up is the right wing. Same procedure as last night.

JT

[kzimmerm]

It is refreshing to see a "true modeler"... JT, you are up working on your Lovesong... and got to post before 9:00am... reminds me of the days where I'd get 4 hrs sleep with lots of building time...

Great job so far. Thanks so much for the pictorial building log.

Kurt

[rdwoebke]

I was kind of thinking of only using 5 servos next time. Using the original type flap linkage and the flap servo in the nose would save a little weigh and I hardly ever use the flaps for turning anyways.

I don't think you want to do that. Dr. Drela posted some information on getting the best turning on full house ships and he feels you need the flaps to mirror the airlerons by about 50%.

After messing with it some in my Psyko, I agree.

Ryan

[jtlsf5]

It is refreshing to see a "true modeler"... JT, you are up working on your Lovesong... and got to post before 9:00am... reminds me of the days where I'd get 4 hrs sleep with lots of building time...

Great job so far. Thanks so much for the pictorial building log.

Kurt

Kurt,
The really scary thing is I'm on the west coast, make that before 600 am.
JT

[jtlsf5]

I don't think you want to do that. Dr. Drela posted some information on getting the best turning on full house ships and he feels you need the flaps to mirror the airlerons by about 50%.
After messing with it some in my Psyko, I agree.
Ryan

Each design has its own demands, quirks, etc. You should check the history of the design and airfoil used on the Windsong before making this kind of blanket statement. The 214 was developed for non-camber changing applications, thus flaps in the modern sense of independently controlled was not possible when this airfoil was designed by Dr. Eppler and adopted by Bob Dodgson for the Windsong. No disrespect to Dr. Drela, but the Windsong design was introduced in 1982, long before most knowledgeable soaring enthusiasts were aware of Drela and long before his contributions to soaring existed (to my knowledge).

JT

[atjurhs]

Jim,

Back on post #37, can you tell us how much voltage/current/wattage the key-hole wire loop is seeing (what's comming out of the transformer). In order to make one of these contraptions, it would be really helpful to have a basic idea of these parameters.

Thanks!

[kzimmerm]

Each design has its own demands, quirks, etc. You should check the history of the design and airfoil used on the Windsong before making this kind of blanket statement. The 214 was developed for non-camber changing applications, thus flaps in the modern sense of independently controlled was not possible when this airfoil was designed by Dr. Eppler and adopted by Bob Dodgson for the Windsong. No disrespect to Dr. Drela, but the Windsong design was introduced in 1982, long before most knowledgeable soaring enthusiasts were aware of Drela and long before his contributions to soaring existed (to my knowledge).

JT


It's been quite a while since I flew the Lovesong but from what I recall I thought there was adequate amount of roll authority. I have coupled flaps/ailerons to improve roll authority when ailerons were not sufficient (due to the fact they lacked surface area).

Just as a side note I recall a friend of mine crafted a new set of wings for his 'song w/ SD7037 airfoil. He was not very impressed with the performance. I tried to help him but he refused to let me run his 'song through it's paces. Ultimately he went back to his E214 wings and cleaned up at the local contests.

JT, have you crafted a set of glass skinned wings for the 'song? Would be interesting to see if weight differences...

WEATHER REPORT FOR NYC Metro area..... stuck home due to a "good" snow storm... 6"-12" expected... Too bad I don't have a building table set up... :(

Kurt

[Robglover]

I've been digging through my old Soartechs and refreshing my memory on the E214. It is indeed a different beast than the more recently designed airfoils. It's going to be fun to see how this translates into setups and flying techniques. I believe that it can be made to work.

Will it keep up with a Supra? Sometimes yes, sometimes no. Will it be a joy to fly? Always. :D

[kzimmerm]

I've been digging through my old Soartechs and refreshing my memory on the E214. It is indeed a different beast than the more recently designed airfoils. It's going to be fun to see how this translates into setups and flying techniques. I believe that it can be made to work.

Will it keep up with a Supra? Sometimes yes, sometimes no. Will it be a joy to fly? Always. :D


Kind of reminds me of seeing an old Bentley on the road.... Who cares about the ride.... they just look great!!!! Brings a smile to your face too!

Kurt

[rdwoebke]

Each design has its own demands, quirks, etc. You should check the history of the design and airfoil used on the Windsong before making this kind of blanket statement.

Fair enough. I should keep my mouth shut....

My bad.

;-)

You are a fantastic craftsman, a L5, and much more knowlegable/better at this stuff than this me....

Ryan

[O.L. Adcock]

In part Bob selected the 214 for it's 11+% thickness which would give it better strength/stiffness BC (Before Carbon)....The physics of that still work even with carbon. Got a ship similar to what JT is doing, balsa skinned, carbon/glass under it in the same places. I've seen zero flex on stout winches and have bent 3/8" case hardened steel wing rods!....O.L.

[Ercoupe Ed]

I've been watching this thread with some interest. I have an old Windsong, that basically only the fuselage is left. and in very good condition, plus I have a Lovesong that I bought which has been partially started( fuse).Considering the luck and performance a local friend and fellow flyer (Ray Hayes) has had with his redesigned Bird of Time series and OlyIII sailplanes with the newer 3014 airfoil, does anyone have any comments on possibly trying a 3014 wing on these older Windsongs aor Lovesongs?
I can easily cut my own cores, as I have a complete Feather Cut setup on one of my workbenches.
I do agree with JT on using the latest technology on using servos in the wings in place of the old "spaghetti drive" system .It was unique and ingenious for its time, but also driving flaps and ailerons from their ends just doesn't set well with me either.
The elimination of long mechanical linkages also reduces "slop" quite siginificantly, and as wings flex under flight loads, binding of linkages, etc, is eliminated.Just my two cents worth.

Ed

[jtlsf5]

JT, have you crafted a set of glass skinned wings for the 'song? Would be interesting to see if weight differences...
Kurt

Kurt, never did a glass skin wing on a Dodgson plane, though did a S-3021 winged Song. It was very different in flying characteristics than the 214. Not better, not worse, just different. Weight was no different (as I recall), but not enough of a perceivable performance gain to compenstate for the thinner section which gave "floppier" wings.

As I mentioned earlier, a hybrid 3021 3M wing on a Camano fuse with a T-tail was a really good flying plane. It just seemed to work on this combination, much more improvement than I saw on the Song with the 3021.

JT

[jtlsf5]

Jim,

Back on post #37, can you tell us how much voltage/current/wattage the key-hole wire loop is seeing (what's comming out of the transformer). In order to make one of these contraptions, it would be really helpful to have a basic idea of these parameters.

Thanks!
Todd,
I have never measured the output, but the Variac is set at 20/120, and the stepdown is a 120 VAC primary-5V DC secondary. You electrical wizards can figure out what I really did.

JT

[jtlsf5]

...does anyone have any comments on possibly trying a 3014 wing on these older Windsongs aor Lovesongs?



Ed, please see posts 41 and 78. The 3014 is a slightly thinner (decambered) version of the 3021. I say don't bother, on the Song the 214 flies just fine, and you will end up with a more flexy wing that will neutralize any performance gain due to airfoil alone.

JT

[jtlsf5]

Right wing is now in the bag. Got this one done a little quicker than the left last night, so the epoxy was not quite as thick when I finished. Net amount used was 58 g. More later.

JT

[jfrickie]

Jim, great thread! There was a time long ago when I and another friend (Gary Gasser) built 4 Lovesongs, 3 Caminos, 3 Pixes and 2 Pivots.
I think I can still smell the resin :) :D

[jtlsf5]

Jim, great thread! There was a time long ago when I and another friend (Gary Gasser) built 4 Lovesongs, 3 Caminos, 3 Pixes and 2 Pivots.
I think I can still smell the resin :) :D

Jim,
Glad to have you along. Enjoy the build. Best to Kathy.

JT

[jtlsf5]

Right wing is out of the bag and trimmed as was the left wing. Weight = 398 g, for a 4 g difference in the two wings at this stage.

JT

[soholingo]

I have so many questions but I am going to stick too two:

1. The carbon on the skins, means it is not wrapped/bound to the wood spar. If its not an issue here is it really needed with other balsa skinned planes?

2. How did you bag and pull the wing in less than 12 hours? What epoxy are you using? And how hot is your bagging environment?

Thanks.

[jtlsf5]

I have so many questions but I am going to stick too two:

1. The carbon on the skins, means it is not wrapped/bound to the wood spar. If its not an issue here is it really needed with other balsa skinned planes?

2. How did you bag and pull the wing in less than 12 hours? What epoxy are you using? And how hot is your bagging environment?

Thanks.

1. The carbon is an added element to the conventional spar. It is in contact and fully bound to the spar caps as part of the layup process. Overkill, maybe, but from experience it adds significant stiffness to these wings with little weight penalty.

2. I work efficiently. The layup took 30 minutes from mixing epoxy to in the bag. 12 hours later the West Systems (105 resin, 206 hardener) was sufficiently set up (judged by the remaining resin in the mixing cup) to allow the wing to be removed. Doesn't mean its ready to go out and fly, but it is available to work. I work in a heated garage, and it was about 68 F throughout. No hot box or other means to accelerate resin cure. Regardless, all I do immediately is the first trim (excess at LE, root, TE), then put the wings back in their beds and allow to rest and further cure on the bench for another 24 hours before sanding or any other operation. There is plenty left to do before putting the wings under flight stress, and I recall reading that 4-5 days was required to bring this resin system to full cure.

JT

[soholingo]

Thanks JT. That helps a lot.

Jay

[rdwoebke]

Jim,

Can you go a bit more into the spar on this plane? It has been a while since I have seen a Dogson plane built (and it was not my plane being built).

Looking at the pictures, the spar looks like spruce spar caps with a spar core (is that balsa, hardwood?) and then ply sides. Is this an accurate assesment?

Either way, this is a neat build thread. I'm sure it will be a neat plane and hopefully I'll get to see Rob fly it some day.

Ryan

[jtlsf5]

Jim,

Can you go a bit more into the spar on this plane? It has been a while since I have seen a Dogson plane built (and it was not my plane being built).

Looking at the pictures, the spar looks like spruce spar caps with a spar core (is that balsa, hardwood?) and then ply sides. Is this an accurate assesment?

Either way, this is a neat build thread. I'm sure it will be a neat plane and hopefully I'll get to see Rob fly it some day.

Ryan

Ryan,
You are correct. 3/8" balsa core out to 32", 1/8"x3/8" spruce spar caps out 36" with 1/8"x3/8" x18" spar extensions joined in a 3/4" lap seam. Front shear web is 1/32" ply 12" long, rear shear web is 1/32" x 12" plus another piece 4". Kevlar whipping at both ends of the joiner tube box. The final touch to the spar is unidirectional carbon (don't know the weight), and tapers from 2.0" at the root to 0.5" at 60" out.

Now that the wings have cured up a bit, they're pretty stiff.

JT

[jtlsf5]

Today will be devoted to prepping and bagging the stabs and rudder. I plan to do all three pieces at one time (as I have the last two Songs). First item was to prepare the joiner tubes for the stabs. The main tubes for the this plane will be a variation of the Lovesong design. The joiner rod will be 1/8" carbon, so this required 5/32"OD brass tubing. The 1 7/8" brass tubes for the stabs and a 7/8" tube for the bellcrank pivot in the fuse were cut. Some 1/32" balsa was cut for spacers on the main joiner tubes. This turned out to exactly center the 5/32" brass tubes in the core. First picture shows the formed front joiner, and one finished and one partial rear joiner. The partial has the brass tube, 1/8" square spruce stop, and 1/32" balsa spacers glued together. The finished has the 1/64" ply shear webs glued on and the whole joiner trimmed. The extra space showing in the partial is relief for the tube that will protrude on either side of the fin and key into the stab. Next picture shows the joiners finished and installed in the cores. Finally, the skins and pieces of glass cut to reinforce the root (stab only) and trailing edges is laying on the respective beds. I will use 3/4 oz glass for the rudder, and 2 oz for the stab.

JT

[jtlsf5]

Tail feathers are now in the bag and on the clock. I used 12 g of resin to get these parts wetted out with their glass and mated to the cores. First picture shows the three parts in the bag. Plenty of lead to keep the pieces firmly aligned inside their beds. The stabs are restacked in their beds on the right.

Second picture shows the connection between vacuum hose and bag. I make sure that the fitting sits directly on the piece of cotton rope that I use as a breather. This fitting came out of the lab and is used for connecting a hose to a gas sample bag. Seemed to be a natural match to vacuum bagging as done in the hobby. I tried to get close up shots of the actual bag fitting itself. Third picture is the outside the bag, fourth is inside. The fitting is machined one piece stainless installed with seals and a retainer nut. It seals with a ribbed teflon washer on the inside, and a rubber gasket compressed by a smooth teflon washer outside, compressed by the retainer nut. This is visible in the pictures; sorry if it's a bit fuzzy (its hard to hold the fitting just right and take the picture one handed).

JT

[jtlsf5]

Everything came out of the bag fine, and I started trimming. First picture shows the tailfeathers with stab LEs attached. Sanded the LE, then attached the tips and angled root plates. Dried and sanded, leading to the stabs ready to mate to the fuse when the fuse is ready. At this point the rudder weighs 9 g, and the stabs with joiner pins weight 42 g. Stabs are shown in second picture.

Next step is to build and install the fin frame. The frame is shown in the third picture. Installation requires installing the bell crank and its drive wire, as I will lose access once the fin frame is bonded to the fuse. Another mod was planned, namely to replace the nylon bellcrank that was supplied with one of the more modern composite bellcranks. Weights were 2.2 g for the nylon and 4.1 g for the carbon crank, quite acceptable.

Prior to installing the bellcrank in the fuse, I wanted to be sure everything lined up okay with the bushings and everything. Its a good thing I did this because guess what, it didn't fit. Neither the nylon bellcrank or the planned replacement fit well enough to use. Bummer. Next two pictures show the problem. In both pictures the rear rod hole is perfecly lined up over the rod (even if the camera parallax makes it look off). The close up directly over the front pin shows the problem. The carbon crank front hole can't be elongated enough to fit, and I still don't want to use the nylon, too flexy. Fortunately the solution was already in my shop.

Years ago in my composite scratch building days (early 90's), I built an F3B capable Thermal Eagle. It used a Thermal Eagle fuse and everything else was scratch built from foam, glass and carbon. For the stab bellcrank, I didn't like any of the commercial stuff that was available (mainly nylon or thin aluminum), so I fabricated my own. The basic material was a laminate of fiberglass, carbon and aircraft ply. VERY STIFF. This was the answer to the bellcrank problem.

I cut a piece to size and located and drilled the holes appropriately. I used a brass bushing in the bellcrank as I felt over time even the composites would gaul and develop slop if a hole in the bellcrank was all that rode on the main bushing. The next three pictures show the bellcrank side view, a shot end on showing the laminations, and the bellcrank installed (easily) on the stab.

And the build goes on.

JT

[jtlsf5]

Now safely past the little problem with the bellcrank. BTW, the composite unit I put together weighs 4.1 g, exactly what the carbon crank weighs, so no change here. With the bellcrank ready, the bushing/reinforcing epoxy-glass fiber mix was trimmed down to the same overall thickness as the other cranks, just to be sure there is no binding once installed. The drive rod was fabricated by soldering two 36" lengths of music wire together and cutting the ends so the joint was midway between the first cross brace and one that I will install later to support the drive rods and carry the wing wiring plugs. Picture shows the fin frame clamped in place. Enought for today.

JT

[bobby legue]

JT,
You may want to try inserting the ends of the music wire into a small roll pin and give it a squeeze, then solder them togather. Works like a charm!
Bob

[jtlsf5]

JT,
You may want to try inserting the ends of the music wire into a small roll pin and give it a squeeze, then solder them togather. Works like a charm!
Bob

Is there another way? Standard practice on Dodgson planes, and how I've been doing it for 25 years. The joiner used is commercially available at any LHS, already sized to 1/16", pretinned, etc. Requred nothing more than lining up and silver soldering.

But thanks for the tip. :D

JT

[atjurhs]

Jim,

Can you share more of what you did to the FG fuse tail area where the pivot rod will go through? How did you install the pivot rod's tube into the fuse's tail?

[jtlsf5]

Todd,
In one of my earliest posts in this sequence I installed a pair of 3/32" thick, 3/4" square ply plates (with the help of the stab plate crutch) that will receive the pivot tube. The fuse alone is not enough material to support the stab. To install the fin frame I needed to mount the bellcrank. The Windsong fuse has mold marks where the pivot tube will go. I used the crutch again as a support and drilled each side plate to take the 5/32" OD tube. The bellcrank was placed so the fin frame could be bonded in place.

This is close to the right spot, but is not necessarily the final set point; I will make the final adjustment later when the fuse rear deck is installed and the fuse glassed. At this point the fuse-fin alignment is fixed and the stab alignment can be finalized.

Just added a couple of detail shots of this.

JT

[bobby legue]

JT,
I olny learned this trick a couple of years ago and thought it was the bees knees. Now Im a little embarrassed that it was done this way for a couple of generations and I am just finding out about it. When I read the post I imagined that you were laying the wire side by side and soldering them togather. That set off a warning bell in my head and I didnt want you to loose a beautiful plane if I knew a better way to do it and didnt offer some help. My heart was in the right place but my information was waaaay late.
Im really enjoying this thread and look forward to the completion and resulting flight report.
Enjoy,
Bob

[atjurhs]

Are there advantages/disadvantages to mounting the pivot point of the bellcrank forward or aft of the bellcrank's actuator leg?

I've always "heard" to place the pivot rod at the horizontal stab's 25% chord mark. So if you mount the bellcrank with the pivot point aft (as you have in the photos) then won't that break that "rule of thumb". Jim I'm not saying you're wrong. I'm just wanting to learn from your experience.

[jtlsf5]

Are there advantages/disadvantages to mounting the pivot point of the bellcrank forward or aft of the bellcrank's actuator leg?

I've always "heard" to place the pivot rod at the horizontal stab's 25% chord mark. So if you mount the bellcrank with the pivot point aft (as you have in the photos) then won't that break that "rule of thumb". Jim I'm not saying you're wrong. I'm just wanting to learn from your experience.

Todd,
This is the way it was designed. On just about everything else I've built/flown, it is as you mention, pivot forward, drive back. I have no idea why Bob did it this way, but it just goes to show, there are many ways to accomplish the same thing. I suspect Bob did this because the pivot is at the approximate center of mass of the stab, though not the aerodynamic center.

Also consider that this design was meant to soar, and was developed before overkill launches were the norm. A "zoom launch" 20 years ago meant pulsing the winch to get the plane to zenith, then a short bit of power to generate a little speed, followed by the application of down then up elevator to convert that bit of speed to altitude. The full pedal launches with camber to generate maximum tension (potential energy) really came of age due to the evolution of F3B and molded, high strength airframes.

An interesting side note. With the old style of drive system (the plumber's nightmare) and nylon clevises, an overzealous launch usually resulted in the elevator clevis popping off the servo arm (or transfer bar if using "Der Devastator", the mechanical flap-elevator compensation). The immediate result with this bellcrank setup was that the stab went full down as air load hit the stab. With a little presence of mind, the plane could be safely flown down inverted by doing very shallow turns, judicious application of flap, and just keeping the plane balanced while descending. I did this more times than I care to remember, never hurting the plane. On landing, the clevis was reconnected, back to the winch and in the air like nothing happened. Impressive to watch, but a bit nerve jangling the first time it happened. Fortunately this first time I was at max altitude and had time to sort things out and realized it was quite stable at full invert.

JT