I've put the sheeting on the wing. On Friday, I'll cut the wing in half and trim it for dihedral.
The problem is that neither the plans nor the instructions from this late '70's kit tell me how
much dihedral there should be.

Wingspan is 50". It's the Flight Dynamics, Inc. (FDI) kit.

If you'll tell me the wingspan of your plane and how much each tip is up, I can figure the
dihedral for my plane.

Thanks!
Mike

I just checked the plans on my kit, and they are dated Nov. 77. On my plans, it calls for 1" at each stab tip and 1" at each wing tip. Looks about right based on the side view in a Squadron/Signal book.
Randy

Randy,
I see it now. Those figures are written between the two views of the fuselage!? Why there?

Regardless, I see it now.
Thanks!
Mike

Please don't take this as criticism, but I was just looking at your post on dihedral, & saw the pix of the wing. Is the wing sheeting designed that way from the plans? Normally on all full sheeted wings, the wing skins cover each half of the wing, meet in the middle, and are supported by spar joiners/fiberglass reinforcement so as to creat a continuous load path along the wing.

Just curious.

RCS

The foam is actually three pieces. I though about sheeting other ways but didn't think it would make much difference. I hope it doesn't. I'll cut the wing in half later today with my circular saw
Mike

Also...,

The plan shows 1/4" square balsa along the trailing edge. I did that.

I then deviated from the plan by trimming the foam and installing a balsa leading edge before the sheeting. Given that and that the Jack Stafford B-24's foam wing has the same balsa leading and trailing edges and then wing sheeting that is many pieces, do you think I'll be okay?

I base my work only on the B-24 kit as I've done nothing else like this.
Mike

b-24 nut:

Your plans show the joints fiberglassed and hidden inside the nacelles. Your joint appears to be outside the necelle. Don't skip the fiberglass even though it will leave a bump. The butt joint in the sheeting has no strength and the wing will fail at that point unless it is fiberglassed.

Jim

Thanks Jim,
The foam joints are glassed under the sheeting and will be under the nacelles like you wrote. The leading, trailing and tip balsa really did make for a strong box without the sheeting. That's why I didn't worry about where the sheeting joints are. I hope and think all will be okay.
Mike

Here's the three pieces of foam before I glued and glassed. I then
put leading, trailing and tip balsa before I sheeted it. I felt that if
it was good enough for a 90" wing and four engines, it should be
good enough for this one. My B-24 wing plan shows many pieces
of sheeting including some that do not reach the center.

The advice about fiberglassing the skin joint on the outside is really a good one. The foam under the sheeting (skin) has zilch tensional strength. It does good in compression, but where the failure will occur will be where the weakest skin is. All of the flight loads on the wing will try to stretch the lower skin and compress the upper skin (positive g). The reverse will occur in a negative g situation.

If it was my plane, I would not merely trust the fiberglass on the foam to provide the necessary joint strength. Whenever I was racing, I would always add a strip of CF along the max thickness point of the airfoil under the skin, but firmly adhered to it, as well as a wrap around the center section on the outside in order to provide a continuous load path from tip to tip. It didn't add enough weight to make any difference, as I always had to ballast the plane anyway to get it to min flying weight. My pattern planes basically were the same, except I put the CF strips on both the upper and lower skins, since they pulled negative Gs.

Except for one incident where my son closed the wing in the garage door, none ever had a flight problem.

Good luck and good flyin.[sm=tongue.gif]

BTW, I am new to this forum with all the smiley faces. They are kinda neet.

RCS

B-24:

The foam cores add virtually zero strength to the wing. Glassing the foam core joints therefore adds zero also. If you glassed the entire core you would be doing something useful. Byron kits used to be done that way. In most kits though, like yours, the balsa sheeting provides the strength. I can't speak for the B-24 kit you are referring to, but I suspect that there are some mitigating circumstances that add strength in other ways.

By the way, the leading and trailing edges add very little strength in the vertical direction (flight and landing loads). These loads are carried by the spars. The spars in a foam core wing are the top and bottom sheeting. What you have done is add an unreinforced butt joint in the spars of your left wing outside the nacelle. The only thing you can do now is try to reinforce it with a fiberglass doubler.

Or start over, sheet the foam cores individually with full length balsa, join them and then fiberglass the joints.

Oh, and I suspect the dihedral is supposed to be built in at the core joints, after sheeting but before joining, not at the center.

Jim

The leading, trailing and tips balsa added a lot of strength.

The edges of the sheeting are epoxied to each other, the leading and trailing balsa and the tips.

Per the instructions, the three pieces of foam were to be glued, glassed then the wing cut in half. I
just sheeted before cutting. Instructions also say that no sheeting and no leading edge balsa are
needed if the engines are to be .049.

Pressing down on the wing shows that the weakest point is the center, not where my sheeting
joint is. I had my son do it with his eyes closed so he didn't see the sheeting joint. I agree with
what he felt.

I just think it's gonna be fine this time. I won't do it again though.
Thanks!
Mike

One other thing. If you glass the skin joint with (with light wt cloth if nothing else) it will help hide the seam.

RCS

Well, with small engines and a light touch on the sticks, you might get away with it. I certainly hope so. But I would definately, as you say, try a more conventional approach next time.

Jim

Welp, I guess that all planes with a wing that's larger than a piece of balsa are gonna break.

Okay, I glassed the offending sheeting joint with 6 oz cloth and 30 minute epoxy. I cut the
wing in half and there is one layer of 6 oz in the middle, so far. I'll do a second.

I'll glass the entire plane with .75 oz cloth.

It'll have two OS .10 LA engines. I wish I could find more powerful .10's. Any ideas?

Thanks for the advice on the wing. I know that all are trying only to help me. I appreciate it!
Mike

Balsa comes in 4 ft. lengths. That gives you 8 ft (plus tips) with only a center dihedral joint and that's about as big as sheeted foam wings go. Center dihedral joints are universal, and on sheeted foam wings they are always glassed on the outside of the sheeting. The glassing is then hidden by the fuselage.

Jim

PS: One layer of 6oz glass is more than adequate for your airplane.

Thanks for the tip about the one layer of 6 oz glass being enough. I'm glad that I'm finished there.

Again, my B-24 has sheeting over the foam that is in multiple pieces and not all of them go from
root to tip. I've heard no complaints from others about wings breaking.

Some people just like to have the best, I guess. That's fine. But when the best is not needed,
I feel that some people are maybe upset about the time and money that they spend to achieve
the same results as "lesser" builders.

This reminds me of all of the people that told me that I needed major fuel system modifications
to achieve what my car was already doing, over 400 bhp. The "advisor's" cars were doing much
less. They still don't have as much power as me and yet they criticize my car.

It always seems to be the guys that do only as much as is needed that outrun me. The "Fluff"
guys seem always to be slow.

I think that my plane will do just fine.
Mike

Here's the plane today...

I was just trying to tell you what the conventional construction technique is. Now that you've glassed the joint, I wouldn't expect it to fail.

Be sure to post some in-flight shots after you're done. Then you can say "I told you so" to all of us who "have to have the best".

Jim

Looking good so far!

Listen, I want you to know that I was not in any way trying to be snobbish or anything related with regards to the posts I made. I've been doing this hobby/sport for about 40 years now (sure hate to date myself) & I, like others who posted on this thread, saw & heard something that was not not conventional in the photos of the wing.

You are right in that some personalities just have the best/most complex systems in their endeavors, but here, it is just not the case. I don't know how long you have been building, but my feelings are, that in this hobby, if I see something that can potentially cause someone a problem and do or say nothing about it, then I feel I am being remiss. This hobby in particular is fraught with enough problems as it is, particularly when our creations are airborne. Any time we do not have full control of our plane, there is potential for someone to get hurt or property to be damaged. A wing failure puts our plane in an uncontrollable situation, particularly one that has an assymetrical failure.

This same idea is why most clubs have a requirement that new planes be thoroughly checked out by experienced members.


Good luck and good flyin.

RCS