hey, i am building a Great planes piper cub 40 ARF... There is quite a bit of play in the wing joiner/wing joiner slot, is this ok? or, what should i do?

Use LOTS of epoxy.

Jim

Ditto that, Make some functional struts as well. They look cool.

Actually, that's fine. I have seen some tight fits that I had to sand a bit, to allow the wing halves to align correctly. You won't have that problem.

Follow the directions, make sure you know in advance how to align the wing halves and clamp them in place, and - as jrf says - fill the void completely with epoxy. Wipe off what drips out with a towel soaked in alcohol, clamp the wing halves in place (remember, you practiced earlier) and wait the required time for the epoxy to set up. You will have a strong, correctly aligned wing.

Good luck,
Dave Olson

This is from GP Shoestring manual for joining the wings together. It should work for your Piper Cub also. Mixing microballons to the epoxy makes it thicker so it stays in place and fills the gaps around the wing joiner. Use epoxy without the microballons for actually joining the wing together. Hope this helps.

�3. Prepare 1/2 oz. of 30-minute epoxy. Add 1/2 oz. of
microballoons. Working quickly, thoroughly coat the inside of
both wing halves where the joiner fits and one half of the
joiner with the epoxy and microballoons mixture. Making
certain the joiner is upright, insert the coated end into one of
the wing halves. Coat the other end of the joiner with the
remainder of the epoxy and microballoons mixture. Proceed
immediately to the next step.

�4. Prepare an additional 1/4 oz. of 30-minute epoxy only
(no microballoons). Coat the ribs on both ends of the wing
with the epoxy. Join the wing halves tightly, holding them
together. Use a paper towel to wipe away excess epoxy that
comes out of the wing. Tightly hold the wing together with
masking tape, making certain both halves are in full contact
and that the leading edges and trailing edges align. Wipe
away excess epoxy and do not disturb the wing until the epoxy
has fully hardened.


You can find the Shoestring manual at this site for more info on how to join your wing. Takes awhile to load so be patient .http://www.greatplanes.com/parts/

Hi,

I am also assembling this plane and I just went through this step the other day. For what it's worth... I always replace the ply wing joiners with a piece of solid maple that I cut to size with my table saw. I have had wings fold at the joint in the past and noticed that the ply wing joiner had broken at that point - I am sure that a great many folks probably have not had a problem with this (maybe I fly too hard). I took notice of how sloppy the fit of the supplied J3 joiner is and I made the new one a bit tighter. I agree with the other responses that using alot of epoxy will allow you to use the supplied "sloppy" joiner. Good Luck!

Steve

Dan I'm building one too! Maybe we can trade some ideas, tonight? At work now. My home email is [email protected] Bill

Use a heavy coat of polyurethane adhesive, polyurethane is a one part epoxy that is activated by the presence of moisture. I have joined the wings and tail feathers of my last few arf kits using gorilla glue. Also using Deft Lacquer based polyurethane works great alone or with fiber mat for glassing any surface and it can be applied so thin that there is almost no weight gain. You can have almost an 1/8 of an inch or slightly more of play and a thin coat inside slot and on the jointer stab of epoxy. The joint should be stong enough, if you're doing hard g aerobatics then you should glass the joint. or double jointer the wings, with a long dowl pin further back on the wing halves. Have Fun!!!!!!!

Will

Should I just cut off some covering and glass the underside along the seam?

Dan,

Once again I do not know if this is even necessary for scale flying , but I will tell you what I did. I removed about 1 1/2" of covering from the top and bottom of each wing half prior to joining. After joining (and curing) with the new maple wing joiner and 30 min epoxy, I used SIG SH226 pinked glass tape and more 30 min epoxy on both the top and bottom of the wing. After curing, I applied a very thin additional coat of 30 min epoxy for final smoothing. Once this cured, I sanded the joint and recovered the center with a 5" wide piece of coverite fabric (same stuff that the plane is covered with). I looks pretty good and now I am not worried about wing fold. The next area of concern are the strut ends. I am hearing that they (the hinge material) will tear after some number of flights. All in all I think this is a pretty nice ARF - especially for $179 (Tower sale price). With a few mods it should be a pretty nice plane.

Steve

To each his own !! I have to agree with cstevenpeterson, I want my wing joiner snug.
Epoxy does not have the shear strength of plywood or maple. If you compare the
ARF to a build it yourself kit nowhere in the instructions will it say to leave the
dihedral brace loose and just fill the void with epoxy.

tommy s

For what it's worth.....

Maybe I should expand a bit more on what I have done and why, relating to wing joiners. Everyone has their own experiences that drive their decisions and this is mine...

I had an instance where I probably got a bit too agressive with my trainer a couple of years ago and the wings folded cleanly at the center joint. After looking at how it failed I came to the conclusion that the joiner was a definite weak link and I decided to look for an alternative. After looking at engineered materials and wood, I decided to stick with wood for convenience and fabricated some joiners out of aircraft ply, oak and maple. Wood properties vary with respect to type, variable quality, moisture content and grain, however, maple is the strongest with oak closely behind (per my engineering handbook). I conducted non scientific break tests without measuring moisture content or forces and it was clear that the maple I was using was supereior. Oak is also superior, however it has a much coarser and variable grain when compared to maple. I feel that this coarse grain could also allow many starting points for crack propagation to begin. The ply joiner was weaker and the strength of ply is very dependent upon the quality of the laminating adhesive and the quality of the wood "fillers" in the laminate. There may also be voids inside. So, now I make my own maple joiners for all of the ARF's that I assemble. In my opinion this makes the center joint the strongest part of the wing structure - especially if you add glass. The result may be that some other unknown part of the ARF wing may fail before the center joint, but I have had no other problems to this point. I stress ARF's here because when you build your own kit, you know how well the structure is asembled and you can ensure that it is robust right from the start.

Steve