Rendegade

Hey all, I'm getting ready to knock out a Mach none, and I want to keep it light and stiff.

Also because I'm a tight fisted #@*#, I've got a lot of 1/32" sheet left over from sheeting my cores.

I'm thinking of laminating the tail surfaces, possibly with either 3 laminates of 1/32" or a stack of 1/32 -1/16 lightened-1/32.

I know this will give be a stiffer structure less prone to warping due to it's stucture being like ply, but will I see any weight benefits ?

Is it worth doing or should I cut up another sheet of 1/8"?

combatpigg

My Feedback: (3)

By the time you dispense enough glue to bond the plys it's debatable if you've improved on Mother Nature or not. Making some balsa ply from 1/32" sheet sounds like a worthwhile thing to do though for some parts. The plys can be bonded with spray contact glue without picking up much weight, but the glue isn't sandable so you can't have exposed edges that will show. Cutting hinge slots in balsa plywood might be a challenge.......
I used firm 1/8" sheet for tails for years but have switched to using light 3/16" and airfoiling it.
If you assembled your balsa sandwich with a bare scraping of laminating resin and vaccuum bagged it, the results of that would be interesting...for strength VS weight

Rendegade

I was considering bagging them with polyurethane, in the same fashion as my wings.

I might give it a whirl anyway. If it's light enough (even if it's the same) I'd propbably go with it just to allow me some extra stiffness.

Hinge slotting becomes easy with laminated parts, just cut the shape of your hinge out of the centre part then glue it all together! voila!

flyinrog

My Feedback: (1)

I have laminated 1/16 balsa to make 1/8th , you cut out the part you need evelator or whatever then use the spray glue or white if you have time for it to dry, and then cut and sand to the original piece size and as you say "voila"...have done this several times..Rog

gkamysz

My Feedback: (19)

I used to make tail surfaces for 400 racers with 1/16 balsa - glass - 1/16 balsa sandwich. I don't remember how much glass I was using, but 1-2 layers of 4oz sounds right. It made stiff surfaces, that could be sanded to very nice sharp edges. I covered with film and used film hinges on the top side.

RocketRob

My Feedback: (1)

Why not make tail feathers out of both and weigh and then apply a highly scientific twist test and report back......

Depending on your planned cg/engine weights a bit of weight aft may not hurt for the increased strength/

KidEpoxy

Any time I tried to lam some 1/16 with white or yellow glue, I get warpage out the kazoo.

What do you guys do to keep things flat?

combatpigg

My Feedback: (3)

The way to keep things flat is to not use water based glue for laminating!
I've heard about applying a bare scraping of Elmers to both sides, let it dry, then iron the sheets together.
I'm usually too busy using techniques that I know will get planes done to try out new ones.

Jim Thomerson

I've been building tails with 1/32 on either side of a built up center, however thick. They are very stiff. Not sure they weigh less. I build the center section on the bottom 1/32 sheet and then glue on the top 1/32 sheet. Put a piece of plate glass on top and weight it down.

Andrew

Anytime I need a stab or fin that is 3/16 or 1/4, it's always laminated like Jim's post above. There is no reason that 1/32" sheeting could not be used over a 1/16" frame. I lay out the framework over the bottom sheet and attach with CA. When the top sheet is glued on, I use Poly-urethane. The framework get an almost dry film of PU and the top sheet is misted with a spritzer before being laid on. I use finished plywood plates on the top and bottom and weight with about 30 pounds for 24 hours.

For 3/16" thickness, all parts are 1/16". For 1/4", the framing is 1/8" with 1/16" sheeting.

If you keep the inner frame small, you get a light, stiff stab. The attached drawing is not too good, but you get the idea.

andrew

KidEpoxy

Thanks for the input guys.
Guess I'll have to switch from Happy Cow white glue to Mean Bull foamy glue
and get a press way more substantial than 'a few books on top' [&:]

combatpigg

My Feedback: (3)

KE, scrape most of the PU glue off after you apply it, then fog the air with a water mister, then assemble the parts. On a 70-80 degree day Gorilla glue is bone dry in just a few hours.

For years I was on a quest to build the ultimate AMA C/L combat plane, taking the best looking ideas from every plane I ever saw that was a winner. I spent many hours fiddling with all the bits and pieces to build built up stabilators and after seeing the results of these heroic efforts came to the conclusion that you can't improve on the correct weight of solid sheet. Unless the part in question is to have enough volume to make using solid balsa not pratical from a weight, strength or cost perspective, I don't think you can do much better than solid sheet.
Much easier to repair, also.....[as long as you don't punch a bunch of those lightening holes in it just to save 1/10th of an ounce].....

vicman

My Feedback: (10)

If you haven't tried Gorrilla glue you will love this stuff!
We are messing around with some .75oz fiberglass over blue foam this winter. But for the most part I use .25 sheet with .016 ply spliced into the edges and glassed then bagged for my quickies. In fact now I use kevlar for the hinges...man what an improvement over using the covering!

KidEpoxy

Vic-
Yeah, I use PU for the blue FFF electrics I've been building for past couple years.
With FFF I combo'ed PU joints with HotGlueGun spot tacks, to make quick builds with slow glue.

I was referring to the Elmers PU with the really grumpy looking bull on the bottle vs the happy cartoony cow on elmers white school bottles. The laid back monkey on the GorrillaGlue bottle just doesnt look like he is that committed to the cause... while the bull is ready to get it on!

Yeah, PU is not just gap filling,
it spans joint chasms, forms its own fillets, and dont let go

Andrew

KE -

I use the Elmer's brand of PU too. It seems like it's a little thinner than Gorilla Glue and spreads more easily.

CP -

Like you, I use a mister rather than wiping down the wood. With less moisture, the PU doesn't seem to kick off as quickly and doesn't foam as much. I like the skinned stabs and fins. With sparing use of PU, I think there is some weight saving, but the final product seems to be a lot stiffer and less prone to warping than a solid sheet. The downside is that you don't have much wood left for airfoiling.

Vic -

I tried some wing skinning experiments using beaded foam. I skinned a test core about 3" square using PU and 1/16" sheet. The PU on the balsa was squeeged off until it was barely tacky and the core was just passed thru a water mist in the air, then stuck and weighted. I could peel the skin, but not without pulling out chunks of foam. I then melted the remainder of the foam away with acetone to see how the glue performed. It looked like lichen growing on the balsa where it had penetrated the spaces between the beads. It needs to be weighted well or bagged, but I think PU with foam is the way to go.

I didn't have access to a couple of pics this morning when I added the drawing - here's a couple.

andrew

flyinrog

My Feedback: (1)

About 40 years ago my mother bought a piano, they were packed in mahogany crates,, my dad asked if he could have the crate, guy said sure...came back from a long weekend in the mountains to find 12 mahogany crates in the back yard...dad and I got to work stripping them (right after he called to stop any more from coming)...long story short we built a solid mahogany bar in the basement,,,with clamps and snoopy school glue,,its still standing and still flat...Rog

KidEpoxy

Andrew
But that can be taken care of by using 'airfoiled' rib style cross pieces... right?
Its just a 8" span, 6rib, 10% Symetric foil sparless wing [8D]

Yuu

Andrew... Good info in your post #15. Your description of the process and the results were great, IMO. The 'mister' idea was good, too, because I use too much PU glue and get big lumps. I will scrape and mist from now on.

Jim Thomerson

Might mention that when starting a new airplane, I build the tail bits first. That gets something finished and encourages me to press on.

vicman

My Feedback: (10)

I use an old windex bottle to mist anything I use G-glue on. I used Elemers PU glue for a while early on but it just wouldn't keep long enough and after tossing two of the large bottles when I had just gotten going in them I changed to G-glue and have a lot less waste from it curing in the bottle. Just my $0.02
I have also begun experimenting with the new quickset G-glue. Nothing to brag about yet.

mikegordon10

On the horiz and vert stabs for my 1/2A Pylon Racers I trace out the outside pattern on a piece of 16th contest balsa. Then I cut strips of 64th ply maybe 3/8" wide, glue these onto the 16th balsa following the traced out pattern. I'll leave gaps in the ply strips wide enough where ca hinges are to be installed.
I'll glue this down one strip at a time with thin ca pushing down on the strips with the edge of a metal ruler against my glass table top. This keeps everything perfectly flat.
I'll also put a few small pieces of 64th inside the framework in a spot or two and solid 64th where it will be glued to the fuse.
Then I sand down the 16th balsa with the 64th framework glued to it until the bench sander just touches the 64th ply.
Then using medium ca I glue this down on another piece of oversized 16th contest grade balsa and then finally trim that down to the 64th.
When I shape the LE and TE down to the 64th ply it leaves a razor sharp edge.
The hinge slots are now already in place.
Sometimes I'll do the horiz stab and the elevator at the same time, shape them both together and then cut the ele off and sand the bevel into the LE of the ele.
I don't think this is any lighter or heavier than just a piece of 1/8" but it does make a nice sharp edge and as said the hing slots are already done.
This is a lot easier to do than it is to describe and it comes out strong, stiff and flat.
My 1/2 a horiz stabs are 10" X 3" including the Elevator and they all seem to weigh in at 0.3 oz.

combatpigg

My Feedback: (3)

That's pretty slick Mike! You could apply the same idea to larger scale planes I'll bet.
You rolled out a new design this year, didn't you?

mikegordon10

As near as I can determine every racer I've ever built is a new design. I don't think I've ever built two that were twins. There are similarity's to all of them but they are not totally the same. That would be way too easy.