HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Nov 20, 2010, 08:05 PM
Master of the Wind
G Norsworthy's Avatar
United States, CA, San Jose
Joined Sep 2008
1,177 Posts
Here it is all laid out. Took the afternoon and made an Ed Berton style bow with turnbuckles. This one pulls really tight, and you can further tighten it after heating. Trying to minimize wire sag to keep down the rework before bagging.
G Norsworthy is offline Find More Posts by G Norsworthy
Reply With Quote
Sign up now
to remove ads between posts
Old Nov 21, 2010, 02:23 PM
Master of the Wind
G Norsworthy's Avatar
United States, CA, San Jose
Joined Sep 2008
1,177 Posts
wing hinges

Spent a few hours on the wing details. Part numbers all picked out for the RDS from IFR. Looks like nice stuff, one size bigger than the Supra plans, reasonable. Stared at the Icon and PP hinges for a bit, studied the Supra drawings, and sketched out the details of the hinge. I'll steal Dominic's idea of embedding the glass facing in the aileron slightly back from the hinge line. This way there is no wrap facing and no tape covered triangle. It all gets glued back together before bagging, and the facing never sees daylight again except where you scrape it back to bond the wiper. Makes the bagging easier with no cut parts flopping. The disadvantage is that you have to cut out the relief for the wiper on the wing side and hand lay it up as the last step. Should not be so hard after just facing a DLG wing. It also relies on a bond between the glass facing and the carbon skin. Standard 1.7 kevlar hinge under the skin, filed out after bagging. This scheme leaves only a 0.030 slice in the top skin between the wing and the surface, and no tape. A straight cut up and down seemed to have the least interference between the up aileron and the top skin on the wing.
G Norsworthy is offline Find More Posts by G Norsworthy
Reply With Quote
Old Nov 21, 2010, 11:44 PM
Master of the Wind
G Norsworthy's Avatar
United States, CA, San Jose
Joined Sep 2008
1,177 Posts
Busy day waiting for the mail. A bit out of order but I moved on to the fuse internals. Nice thing about drawing out the design is you can put the pieces in the fuse and expect with reasonable certainty the holes to line up during the wing installation.

Found a MPX Royal in the bottom of the servo bin for the rudder. Had previously done flap duty so it had the lugs cut off, will be a goop installation. Planning on using the Airtronics 94820 for the remainder of the surfaces.

Next step is to work the fuse seam so I don't cut my hand carrying this thing around. Daunting amount of work left but my employer and their funders were kind enough to throw us all out for the whole week so I should make a lot of progress.
G Norsworthy is offline Find More Posts by G Norsworthy
Reply With Quote
Old Nov 22, 2010, 12:41 PM
yyz
Registered User
yyz's Avatar
USA, CA, Paso Robles
Joined Dec 2004
2,405 Posts
Quote:
Originally Posted by G Norsworthy View Post
Spent a few hours on the wing details. Part numbers all picked out for the RDS from IFR. Looks like nice stuff, one size bigger than the Supra plans, reasonable. Stared at the Icon and PP hinges for a bit, studied the Supra drawings, and sketched out the details of the hinge. I'll steal Dominic's idea of embedding the glass facing in the aileron slightly back from the hinge line. This way there is no wrap facing and no tape covered triangle. It all gets glued back together before bagging, and the facing never sees daylight again except where you scrape it back to bond the wiper. Makes the bagging easier with no cut parts flopping. The disadvantage is that you have to cut out the relief for the wiper on the wing side and hand lay it up as the last step. Should not be so hard after just facing a DLG wing. It also relies on a bond between the glass facing and the carbon skin. Standard 1.7 kevlar hinge under the skin, filed out after bagging. This scheme leaves only a 0.030 slice in the top skin between the wing and the surface, and no tape. A straight cut up and down seemed to have the least interference between the up aileron and the top skin on the wing.
Greg,

I've very interesting in seeing how you pull off this hinge arrangement, specifically the wiper on the control surface.

Mike
yyz is offline Find More Posts by yyz
Reply With Quote
Old Nov 23, 2010, 12:42 AM
Master of the Wind
G Norsworthy's Avatar
United States, CA, San Jose
Joined Sep 2008
1,177 Posts
I've very interesting in seeing how you pull off this hinge arrangement, specifically the wiper on the control surface.

So am I. Just because you can draw it does not mean you can make it.

Waited all day for the mail. It was worth it. JuzWuz does better work than I could ever hope for. No reason to ever cut my own again. I continued with Anker's process which does not take off anything for the skins. These skins will be pretty thin and taking out the thickness in the past has left a pinch at the trailing edge.

Wasn't happy with the Ikea table so I went out and bought the flattest piece of ply I could find. Might even allow me to do some bagging here in the comfort of my own home.

Started with the hardest part, the stab tips. 68% ratio with just over 2" chord. Burned a few before I figured out what was going on, but they are small. Will leave the bigger pieces to last. Tomorrow starts the cutting in earnest.
G Norsworthy is offline Find More Posts by G Norsworthy
Reply With Quote
Old Nov 23, 2010, 06:23 PM
"Flying is my life!"
FlyVA's Avatar
United States, VA, Salem
Joined Oct 2002
295 Posts
What is flat?

Fellows...with respect...there is no such thing as a "flat" piece of wood...every piece will have some measurement of cup or twist.

The "flatest" thing shy of a machinest's plate is piece of pool table slate. High end pool table shops will have pieces of slate that have chipped corners and are happy to sell them. The best tables use slate about 1" thick. It is best to get a 4" thick piece of foam rubber to rest the slate on so it will protect the slate from any pressure point. If the slate is too big, just cut it down using a masonry saw.
FlyVA is offline Find More Posts by FlyVA
Reply With Quote
Old Nov 23, 2010, 07:37 PM
Registered User
dbaya's Avatar
United States, CA, Union City
Joined Mar 2004
403 Posts
That some pretty good progress on the tips. Mine usually come out with some serious ripples. From here all I can recommend is adding 3 piece of making tape to the trailing edge airfoil template to prop it off the table to make the trialing edge thicker.

I think a granite flat surface would be great. That would take it to the next level. Right now my shimmed up table seens to be okay for now.
dbaya is online now Find More Posts by dbaya
Reply With Quote
Old Nov 23, 2010, 08:05 PM
Master of the Wind
G Norsworthy's Avatar
United States, CA, San Jose
Joined Sep 2008
1,177 Posts
If you had told me it would take a whole day to finish this I would have said you are crazy, but here it is dinner time and I still have a lot to go. The little tips were difficult until I added a wheel to the bow and did it all hands off except for the start. I cut them cold and slow and they came out perfect. The bigger panels I am finding need to be hotter and faster or there is too much lag on the short side. I suppose it was unrealistic to believe I could pull off this whole job without any spackle. Two biggest inner panels left.

The table is flatter than the foam, which is all I ask. I did have to shave a few pieces in order to get the bottom I was satisfied with. I considered stone but I am a bit transient and don't want to own anything that heavy at the moment.
G Norsworthy is offline Find More Posts by G Norsworthy
Reply With Quote
Old Nov 26, 2010, 12:28 AM
Master of the Wind
G Norsworthy's Avatar
United States, CA, San Jose
Joined Sep 2008
1,177 Posts
Not been idle, just not much to show, though I could not resist the stab drying in the window. Note the lineage, I traced the PP for the very tip. Apt is starting to look scary. Got a couple opportunities to fly but should be back at it hard Saturday. Plan is to have the tails ready to bag this weekend, and the last wing panels cut if I can find another pair of hands.
G Norsworthy is offline Find More Posts by G Norsworthy
Reply With Quote
Old Nov 28, 2010, 01:02 AM
Master of the Wind
G Norsworthy's Avatar
United States, CA, San Jose
Joined Sep 2008
1,177 Posts
Never get as much done as I think but I have one more day of freedom left. Got the center panels cut out and the tips and tails spackled and defuzzed. Always more spackle than I would like but these panels have minimum wire sag from the bow and otherwise look pretty good. Pretty much follows Anker's thread up to here. There are two new items in this build I have not tried before, the full depth spar and the wipers. Dreading both. Once we are through these the rest will go very quickly.
G Norsworthy is offline Find More Posts by G Norsworthy
Reply With Quote
Old Dec 01, 2010, 12:20 AM
Master of the Wind
G Norsworthy's Avatar
United States, CA, San Jose
Joined Sep 2008
1,177 Posts
shear webs

Shear webs started as a sheet of marine balsa sliced and mounted on scrim. I peeled it off and glued the slices back together oversize for the shear web. Next I cut a carrier of wood from the ever present shipping crates and squared it up in the table saw. The fence was locked down in one position for all the remaining steps. The balsa was fixed on the carrier using double stick tape, the one with actual tape in it, not the 924 that we will use later to attach the LE and facing cloth. First the curves and bumps were trued, and then the opposite side was cut for the correct thickness. The angled cut was done by drawing the final size on the carrier, mounting the balsa with the edge hanging over, and cutting off the excess. End result was sized perfectly.

Next the shear webs were mounted on the bottom half of the spar caps. The first one was 30 minute epoxy with microballoons and the second one with fairing compound. The fairing compound spreads better but takes longer to dry, the price of the nice working time. The bond was cured in the same Al channel fixture used to make the caps. The assembly comes out perfectly straight, no choice really clamped down like that. Next is to fill in the ends with dummy foam where the joiner boxes and center joiner will go. Then that sickening feeling of slicing the gap in the wing.
G Norsworthy is offline Find More Posts by G Norsworthy
Reply With Quote
Old Dec 01, 2010, 03:05 PM
Registered User
Cambridge, MA USA
Joined May 2001
1,742 Posts
Quote:
Originally Posted by G Norsworthy View Post
Shear webs started as a sheet of marine balsa sliced and mounted on scrim.
Looks good. If you're careful about the structural details, this spar will be able to bend into almost a U-shape before it fails, since theoretically the carbon can deform that much (I've seen this on my Supra in a really violent zoom). You then should have an essentially unbreakable-in-the-air XC airplane.

One key piece is to size the shear wrap adequately, since if the shear wrap fails the spar will crumple. The attached PDF shows the shear wrap loads caused by a central load F. Normally this F would be the half of the winch load (front and back shear skins share the load). On an XC airplane a reasonable number is
F = 0.5*(max_fuse_weight + 0.3*wing_weight) * design_G_factor

The more conservative tension-only calculation is more prudent:
(sigma*t) = F / h
where h is the spar height. Sample calculation for 50 g's:

F = 0.5* (10 lb ) * 50 = 250 lb
h = 1"
(sigma*t) = 250lb/1" = 250 lb/in

Aircraft Spruce gives glass cloth breaking strengths:
https://www.aircraftspruce.com/menus...ass_cloth.html
It looks like 6.0 oz cloth or equivalent (2 layers 3oz or 3layers 2oz) will be about right. This is in the center -- the thickness ideally wants to taper roughly linearly to zero at the tip.

It's also essential to generously round off the corners of the sparcaps, otherwise the glass will fracture at the corners far below its normal max load. I know this from testing spar samples.
markdrela is offline Find More Posts by markdrela
Reply With Quote
Old Dec 01, 2010, 10:34 PM
Master of the Wind
G Norsworthy's Avatar
United States, CA, San Jose
Joined Sep 2008
1,177 Posts
Mark,

Thanks for chiming in. I was not sure about this but now I feel really good. The center section spars and the tips for a bit past the joiner will be wrapped with 8 oz carbon sock, which by simple scaling should be over 400 lbs/in. For the same reason the spar is oversized to fit the joiner box tooling we have, I went for overkill on the design and ease of construction on the build. It worked really well on the last one. The remainder of the tip spar where there is shear web will be wrapped with 2k carbon tow, tighter at the center and wider towards the tip. The graphlite sticks are round but I will be sure to knock the edge off the tip spars before wrapping. It may look different but most of the construction of this plane borrows heavily from the Supra plans.

If all goes well we will also be chopping up my temporary foam cutting surface into a hinged bagging table, meaning that the center will be bagged in one piece with two pieces of 5.7 carbon cloth overlapping in the center. This means the center skins have no center joint and all the bonds are primary.

All this is driven by having the luxury of a 5 kilo budget to play with and trying to get it at least ready for assembly by mid Jan.

Indeed I am looking for something that is unbreakable in the air, and one must be aware of all the weak points, like the fuse/fin joint, stab mount, hinges, pushrods, etc. The sparless #8 has taken a 2 second push forward and yank with no damage, which is more than anyone should ask of a plane, though it happens more often than we would like.

Interesting that the Pike Perfect spar, which I had the misfortune to have to work on, has no wrap, though the spar is quite wide. This plane is not much bigger than the PP and will be built quite a bit sturdier.

Back to work!
G Norsworthy is offline Find More Posts by G Norsworthy
Reply With Quote
Old Dec 01, 2010, 11:36 PM
Registered User
Cambridge, MA USA
Joined May 2001
1,742 Posts
Quote:
Originally Posted by G Norsworthy View Post
The center section spars and the tips for a bit past the joiner will be wrapped with 8 oz carbon sock, which by simple scaling should be over 400 lbs/in.
OK. I forgot to mention that the joiner box needs extra shear strength, typically even more than the wing center. My Supra has 1.5x thicker wrap over the joiners than the center. I think the single 8oz sock should be enough, but that's a guess. I'd also use the sock over the joiner on the outer panel for this reason. Typically you also need a tow wrap over the last 1/4" at the very end of each spar to prevent a burst failure caused by the ~500 lb prying load of the joiner rod. I sand down the sparcaps enough to make room for the tow wraps so they don't protrude out of the airfoil contour.

Quote:
The remainder of the tip spar where there is shear web will be wrapped with 2k carbon tow, tighter at the center and wider towards the tip.
I wouldn't do this. A simple tow wrap does not increase shear strength. Only +/-45 degree fibers do that properly. I'd use one layer of 3oz glass, and then also the sock over the joiner. Stick it on with 3M with the seam on a sparcap, and then saturate with epoxy.

Quote:
If all goes well we will also be chopping up my temporary foam cutting surface into a hinged bagging table, meaning that the center will be bagged in one piece with two pieces of 5.7 carbon cloth overlapping in the center. This means the center skins have no center joint and all the bonds are primary.
I stuck down a 3/8" wide strip of the skin fabric along the center core joint with 3M, so the mylars and their skins could simply butt together over this strip. Essentially it had the same function as the usual LE wrap, but along the center seam. This was a lot easier than trying to overlap the skins somehow -- not easy with the mylars there.

Quote:
Interesting that the Pike Perfect spar, which I had the misfortune to have to work on, has no wrap, though the spar is quite wide. This plane is not much bigger than the PP and will be built quite a bit sturdier.
F3J spars are sized for stiffness. But since they are typically not shear-wrapped (tow wraps don't count), such spars have only a small fraction of the potential strength of their sparcaps. Like I said, your spar should be able to bend into almost a U. No unwrapped-spar glider can come close to that without splintering.
markdrela is offline Find More Posts by markdrela
Reply With Quote
Old Dec 02, 2010, 12:14 AM
launch low, fly high
New Zealand, Hawke's Bay, Havelock North
Joined Dec 2004
1,854 Posts
Quote:
Originally Posted by G Norsworthy View Post
Indeed I am looking for something that is unbreakable in the air, and one must be aware of all the weak points, like the fuse/fin joint, stab mount, hinges, pushrods, etc. The sparless #8 has taken a 2 second push forward and yank with no damage, which is more than anyone should ask of a plane, though it happens more often than we would like.
Greg,

First, I'd like to say that I applaud your dedicated work on XC design and manufacture!

That out of the way, I have to disagree with the 2nd sentence above. I'd suggest a more stringent qualification for XC planes, maybe something like a 5 second or more vertical dive followed by a full up elevator pull... Where this requirement comes from is in a final glide with lotsa lift in the last few miles, and the pilot loses sight of the plane when it is going at high speed (trim close to neutral or tuck speeds). Sometimes the plane ends up doing a nose down after loss of sight, and due to the already high airspeeds the few seconds of lost visuals has the potential to get the plane up to 150 mph or so. The unfortunate natural reaction when reacquiring the plane visually in a vertical attitude is to *pull* on the elevator. Seen more than a few planes go poof in this manner... Wile E was designed, built, and tested to this criterion. A graphic demonstration of its durability occurred when I got jammed by a repeater on my 72 freq back in the AM days (late '80s, gawd I'm getting old!) and the plane lost maybe 1k ft in a vertical dive. I ended up trying to bend the elevator stick in hopes of some form of recovery. Finally the radio won over the interference, and the plane responded to my full up command. A whole buncha "g"s, but nothing failed... I like robust XC ships!
Joe W is offline Find More Posts by Joe W
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion XC racer #8 in a series G Norsworthy Cross Country Soaring 185 Oct 01, 2014 01:52 AM
Discussion XC#9 in a series, Giant Supra and other possible wings G Norsworthy Cross Country Soaring 96 Apr 23, 2011 07:14 PM
Discussion Getting Started in XC - Planes, tips, advice aeajr Cross Country Soaring 42 Sep 02, 2010 06:45 AM
Discussion Giant RC DC-10 Turbine Powered Crash trev0006 Fuel Plane Talk 2 May 01, 2010 07:42 PM
FS: Giant WOODIE. Saggitta XC ronrange Aircraft - Sailplanes (FS/W) 5 May 17, 2005 12:17 PM