Removable wings on foamboard builds, best method?

[Kartman24]

On my latest foamboard build the wing will have to be removable due to the bulk of the model, my only other foam build had the wings glued on so i am looking for suggestions from those that have done it for putting in mounts that will keep strength in the wing. I am planning on using two dowels at the front and have the front spar to mount a block to so am happy with the strength in that area but at the rear it is just an expanse of top and bottom sheeting with no structure to attach to. If i cut the top and bottom skins and glue the balsa block the bolts go through to the skins would this provide enough strength using gorilla glue or do i need to add more structure/some sort of spreader/spar to add more strength in? If you have done something similar can you describe what you did or add pictures, it would be most appreciated.

 

[RossFPV]

Depending on the size, You could try something similar to what someone did on this thread.

 

[Piotrsko]

Traditionally people use a second piece of material known as a doubler either inside or scabbed on the outside. Grain orientation is immaterial

 

[tamuct01]

A lot depends on the type of build you're doing. Is it a high-wing, low-wing, or mid-wing? What connection mechanism do you want to use? How much strength is needed, etc? I've done this a few ways. For high-wing trainers, the tried and true rubber-band attachment to dowels works well. Usually, you beef up the fuselage a little around the dowels and where the wing saddle meets the wing. This can also be done for low-wing designs. If you decide on the dowel peg leading edge and bolt-on trailing edge you will need to secure the mounting points in the fuselage. I've done this with a low-wing design and used a small plywood plate at the trailing edge and a nylon bolt to attach them. If you cut threads into the wood, you should soak the thread with thin CA glue to make it very hard and keep it from stripping out easily.

 

[The Fopster]

I did my P47 with a Velcro strap to retain it. Works brilliantly. I stole the idea from Ben Harber - he did it on his monster sized B52. If you find that on YouTube he showed how he assembled it on site for the maiden - think that’s where I saw it.

 

[Tench745]

It's a little difficult to advise more than generally without seeing what you're working on.
Presumably you have side skins and a top or bottom skin you can tie into somehow. Maybe add a foam block or wood plate you can put a screw or other attachment into.

 

[Kartman24]

Sorted it now thanks, holes have to be drilled for the dowls i have fitted to the front of the wing and for T nuts at the rear. Wing has been strengthened where the bolts pass through it.

 

[danskis]

@Kartman24 - I've done several "screw on" wings. I find that its way easier to make/use one dowel instead of two. I've also used both square and round dowels (pegs). Your off to a good start with balsa reinforcement on the sides of the fuselage, which I've found absolutely necessary. Just a suggestion based on your second picture. To secure the piece of wood going across the fuselage I would have left a little more space between the wing and the cross piece to glue a small bit of wood on each side between the wing and the attachment as that end glue joint might not be sufficient by itself to resist a vertical pull. The best option at this point would be to put that reinforcement on the other side of the crosspiece so your not relying solely on the end glue joint.

I put a piece of 1/32 plywood on the outside of the wing to reinforce where the vertical screws go through the wing to hold it onto the plane. This is easy to cut with a scissors.

Referring to your first pic, I use 1/8 plywood as the vertical crosspiece between the fuselage sides to insure that a hard landing doesn't destroy the mount. Again, I would reinforce the vertical piece from behind to keep it being pushed forward in a hard landing (which you may have already done but of course I wouldn't see it).

Keep in mind these are hard stress points and this is probably not the place to try and save weight unless this is a very slow flyer which will not crash.

 

[danskis]

Pics of my swappable Spitfire. I find that each plane is somewhat unique and presents different opportunities for wing mounting. The Spitfire fuselage has some flat horizontal pieces on either side of the wing - so I took advantage of that.

First pic shows the front of the wing which doesn't have a dowel but a painter stir stick which was attached to the wing. The Spitfire has a very convenient flat slot there once you cut the wing out of the fuselage. The foam on the wing was reinforced with 1/32 ply.

This is the inside of the fuselage. The vertical uprights are stir stick with holes drilled in them. They are attached to the fuselage with Gorilla glue. The glue has expanded through the holes.



I really liked this square peg mount. Easy and it works well.

 

[danskis]

@Kartman24 - rubber bands? Nothing wrong with rubber bands.

Also, 5minute JB Weld is your friend when working with wood.