i have a Graupner ASW Electric Glider with a 103" Wing Span. Flies great and performs very well. Fiber Glass Fuselage and Tail is a very Lite Balsa material covered in Monokote...
Problem i'm having is that the T-Tail keeps breaking off when i land and my landings are reasonably Smooth..Nothing unusual. I epoxied it on very well with the help of a friend and this morning i flew it,,, and it flew very nice..Had a nice smooth landing and the slightest bump in the grass knocked the Tail right off again..it fell off sooooo easily as if it were never glued on...Just plopped right off......I DON"T GET THIS...3rd time this fell off..i now need to resolve this....i need some suggestions...Tail seems to be in Tac and ok....my only reasoning could be...
1. The Tail material which is Balsa is too week for the Fiberglass Fuse to stay on when there's a bump or pressure flying...? i don't know....i can't put my finger on it..Do i get a Fiberglass Tail? Do i put a Plastic Plate underneath Tail?
The original Design was not to be glued on..it was just a screw holding the tail on...so 1st time it broke off i was determined to keep it so glued it in...broke off again...my friend used Epoxy this time and now again...
Please help..

Try using a washer, for each bolt, placed on top of the tailplane. This will spread the load and, hopefully, stop the bolt head punching through the balsa.

That's the way to do it. You can make a plywood washer out of 1/32 ply to keep it light. Make it about an inch or so in diameter and you can cover it to match the colors of your plane.

When we were first starting back in the '80's, my friend got a Two-Tee and that dang tail broke off so many times it put a negative imagine in my head forever. I like the aesthetics of them, but can't get past my own prejudices.
My friend fixed it with different plane.

Glue it on with E-6000 or Goop. Those glues stay flexible for a couple of decades. Just make sure you keep it away from EPS foam, as it'll melt them.

Also, as you move up to bigger planes like this you have to adjust your landing style a bit. That last 6" above the ground are critical- try to land as smooth as possible, wings level, and let it sliiiiide.

I second E-6000.

A sidebar.... in 1994, my just-married wife and I bought a house in Henderson, NV. We didn't like the standard house numbers that came with the house, so we got this fancy metal frame thingy and nice ceramic tiles with numbers that fit inside the frame. problem was, there was no easy way to attach the frame to the stucco exterior.... so I used e-6000. As of last summer, we drove by, and it was still there....

Wow i appreciate the quick responses...lol....lot's of suggestions..i don't know where to start....i guess i have to find a way to get that blob of glue off the tip of the fiberglass where the elevator goes on.......
ok so let's start off with suggestions #1..
Using a Washer is something i didn't think about...but if i use a washer? what's stopping it from still coming off,,,,if i land again,,,and it comes off,,now i just damaged a bigger area the size of that washer.....i guess i'm being negative and quite nervous...That Glider is really big and it's quite dangerous if that elevator stab would have come off while in the air.....now i'm sort of afraid to fly unless i can be ABSOLUTELY sure of a fix....a Washer maybe a fix i am just not convinced..
i could be wrong and please correct me if i am....

ok suggestion #2... you said """"You can make a plywood washer out of 1/32 ply to keep it light. Make it about an inch or so in diameter and you can cover it to match the colors of your plane. """""
i'm not sure what you mean...are you basically saying to put something handmade and large enough between the screw and the Elevator Stab? i wish you can show me a photo of an example..i have an idea what your trying to say but not too sure....have look at photo..i made an example of what i think your saying in paint program...let me know if this is what your referring too..

Suggestion #3,,,let me research this on google...once i get everything cleaned up and i'm ready to attach elevator on again..i may use that E-6000 Glue.....

guys understand that i'm very very fortunate that this didnt happen in Mid Air so i'm really nervous now putting that Elevator Stab back on......i need to be Satisfied with possible results and only then will i tackle this problem....

let me ask,,is it possible to just get a Fiberglass Tail and sort of cut it to size and use that? therefore i use no Balsa and now material is all the same? i don't know,,just giving myself a suggestion...LOL...

You left a lot of balsa wood behind when the stab came off, so I don't think the glue is your problem, although a more flexible glue may absorb some of the shock.

The balsa wood is too soft to use just the screw by itself, so a washer has been suggested. Not a little washer, a big one. The larger the diameter, the less likely it'll pull through the stab. To save weight you can fashion your own washer out of lite ply. Along with the washer, you could also reinforce the top of the stab with a layer of fiberglass (after removing the covering in that area).

A plate that size in your picture would work, of course, but would be overkill. In fact, I'd even say it's orientation is 90° off too. Since the grain of the stab is lef-right, the plate should go front-back in order to capitalize on more grains of wood being retained. If 1/16" ply is used, I'd say a "looks right" width of 3/4" is what I'd do. Lots of room to do different stuff, but remember, the smaller and lighter, the better it is.

The 1/32" ply washer idea is an even better one with best compromise of strength-to-weight. You can use scissors to cut out a circle of an inch or so diameter, then use exacto knife to make a dead-center hole just big enough for the bolt to go through=a washer.

Originally Posted by GliderJim

You left a lot of balsa wood behind when the stab came off, so I don't think the glue is your problem, although a more flexible glue may absorb some of the shock.

The balsa wood is too soft to use just the screw by itself, so a washer has been suggested. Not a little washer, a big one. The larger the diameter, the less likely it'll pull through the stab. To save weight you can fashion your own washer out of lite ply. Along with the washer, you could also reinforce the top of the stab with a layer of fiberglass (after removing the covering in that area).

ok so i see a Big Washer of some kind is the best solution,....ok that's fine...i will try and Rig something up in my toolbox,,,but still one thing still puzzles me...we put a good amount of quality Epoxy on that Fiberglass and bottom of Elevator Stab before i screwed it on last night....so with the Epoxy alone,,shouldn't that have by itself keep that Stab on? i mean isn't that what Epoxy is for? why would it break off soooo easily...when that Eopxy settled in..even with force of me moving it, it wouldn't break off so i'm still puzzle why a landing would just make it plop off like that....

The glue is much stronger than the blsa. The balsa ripped, not the glue. Top reinforcement shoudl fix the problem.

If it were my plane I would do a plate as you have drawn on the top and bottom of the stab with 1/32".
If you have a dremel with a router attachment you could recess it, recover and have no unsightly bump from the plates.

Joe

Another look at the photos shows there appears to be very spotty application of epoxy? Almost like a large air gap was trying to be bridged with epoxy?

One single narrow plate along the span's length will receive the same leverage loads as without the plate, and will still be concentrated on a single point the diameter of the bolt head, which can still be pulled through the plate (depending on thickness) with a lot of extra weight with little strength gain.
If the plate were oriented for-aft, the load would be further spread across the stab right were it matters most, at the root.

Do NOT just add glue on top of glue again. Grind/sand off the top of that fin as flat/square as you can.

I think I would just make another elevator and glass it entirely. Then cover with what ever film you want to use. Could even glass the washers or one rectangular sheet as a brace onto the surface.

Here's a different thought process:

Why glue on the tail in the first place??
Why not build a new tail, use some basswood across the span at the back of the stab (a pseudo-spar), and a 2" wide band of 1/64" plywood on top of that.

Cover with your choice of covering, add your control horn, and then use some #12-24 nylon machine screws to anchor the tail on top of the fin on its seat???

Then, if you suffer a hard landing, you just replace the busted nylon screws.

I apologize if this post comes across as "doling of unwanted online advice" or "needless criticism" as is indicated by some other folks here at RCG (atmosteve)....
Its not, its just friendly, helpful advice designed to prevent you from having the same problem over and over.
Buy a couple handfuls of the nylon machine crews so you have spares if you do this.
They will need to be a bigger size than the metal ones that are there already to take the load, and to be safe, you should change them after every flying session.

Best of luck to you!

R,
Target