Dollar Tree Foam Decathlon

[Hutch Bunch Rc]

Who would like if I designed a 48” foam board decathlon? I would probably make a simple boxy fuselage and I would be willing to try doing a “balsa style” wing with ribs and I take the paper off of one side of the foam and wrap it around, that would be a smoother wing over the ft style, but the ft style would be simpler in my opinion. Let me know what you think, I persionally like the idea

 

[Grifflyer]

That'd be awesome!!

 

[Ketchup]

I think that a nerdnic speedwing style would keep things smooth while also keeping them kinda simple. It is similar to an FT style wing, but a lot of paper is removed and it is much smoother all over.

 

[Hutch Bunch Rc]

I think that a nerdnic speedwing style would keep things smooth while also keeping them kinda simple. It is similar to an FT style wing, but a lot of paper is removed and it is much smoother all over.

Yeah I’ll either do something like that or just do a ft wing 🤷‍♂️

 

[Tench745]

At 48" you could probably do a fuselage with some of the shape of the Decathalon fuse' it's pretty angular already. An armin style wing would probably be easy enough to maintain those curves without doing ribs and all.

 

[danskis]

Yeh You don't need ribs for a smooth wing...just take the paper off the top inside wing ahead of the spar. Put packing tape on the leading edge before folding. If you want to you can form It on the table edge like master series

 

[TheFlyingBrit]

View attachment 184450 Who would like if I designed a 48” foam board decathlon? I would probably make a simple boxy fuselage and I would be willing to try doing a “balsa style” wing with ribs and I take the paper off of one side of the foam and wrap it around, that would be a smoother wing over the ft style, but the ft style would be simpler in my opinion. Let me know what you think, I persionally like the idea

I saw a built up wing made from foam once the ribs wher individually cut from foam and it had twin spars (which where double thickness for improved rigidity) running down the wing, in the top top and bottom of the ribs as in a conventional balsa build. the weight was kept down because there was no paper on the foam. Maybe you could use the same principle inside the wings and internal formers etc, but leave the paper on the outer surfaces to improve rigidity ?

 

[Hutch Bunch Rc]

I saw a built up wing made from foam once the ribs wher individually cut from foam and it had twin spars (which where double thickness for improved rigidity) running down the wing, in the top top and bottom of the ribs as in a conventional balsa build. the weight was kept down because there was no paper on the foam. Maybe you could use the same principle inside the wings and internal formers etc, but leave the paper on the outer surfaces to improve rigidity ?

I’ve seen the same video, it think I could do that style of wing

 

[Hutch Bunch Rc]

Well I may or may not have done this today

I may have pulled too tight of a loop on my ugly stick (my design) and folded the wing, all of the electronics are fine except for a wing servo and the leds I had in the wing ripped in half! 🤣 I started out with 3ft of led and now I have 1 ft. 🤣 The reason I’m talking about this is now I have space, and a really good spare motor, for the decathlon

Its a turnigy sk3 3536 1400kv motor, it’s very efficient and doesn’t use a lot of power, I really like it and have had it for a coupe of years, it’s also been on a cub I designed, that cub had the same fate, I pulled a loop and *loud crack* 🤣

So if I do a 4ft wingspan decathlon, this motor should suit it pretty well eh? Paired with a 4s battery.

 

[Hutch Bunch Rc]

I saw a built up wing made from foam once the ribs wher individually cut from foam and it had twin spars (which where double thickness for improved rigidity) running down the wing, in the top top and bottom of the ribs as in a conventional balsa build. the weight was kept down because there was no paper on the foam. Maybe you could use the same principle inside the wings and internal formers etc, but leave the paper on the outer surfaces to improve rigidity ?

I’m thinking I’ll just do an armin wing for simplicity, I’ve never built an armin wing so it will be a learning experience, even though it looks pretty simple.

 

[TheFlyingBrit]

To be honest the Flite Test wings are based on the Armin wing design, so not to dissimilarin principle.
If your planning on pulling some high G manouvers, might I suggest some plywood bracing in your wings and/or some carbon fibre spars.
If you laminate the ply either side of your foamboard spars you can get away with pretty thin stuff like 1/16" ply. However, if you want to go single ply spars for some real strenth then I suggest a min of 1/8".
My other advice would be take the bracing to the win tips, seen a few instances where failure of a wing occurs where the bracing stops. The fracture always happens at the weakest point where there is the least bracing.

 

[Hutch Bunch Rc]

To be honest the Flite Test wings are based on the Armin wing design, so not to dissimilarin principle.
If your planning on pulling some high G manouvers, might I suggest some plywood bracing in your wings and/or some carbon fibre spars.
If you laminate the ply either side of your foamboard spars you can get away with pretty thin stuff like 1/16" ply. However, if you want to go single ply spars for some real strenth then I suggest a min of 1/8".
My other advice would be take the bracing to the win tips, seen a few instances where failure of a wing occurs where the bracing stops. The fracture always happens at the weakest point where there is the least bracing.

I’m thinking about using the same 3/8 hardwood square dowel that I used in the big guinea for a wood spar in the armin wing.

 

[TheFlyingBrit]

3mm solid carbon rods provide a lot of structural strength yet keep the weight down, its more expensive than dowel I accept but there is a big weight saving even with x2 carbon spars.
I fitted some in my Tiny trainer 4ch wing and my sons too following some fractures around the wing joints. Never had an issue since and we both flown those planes within an inch of there lives. Tight full power loops, barrel rolls, inverted stall turns etc
For bigger planes like the Simple stick, I would add a plywood brace for the centre section, plus 2 carbon rods front edge and trailing edge just to make sure.
I normally cut a V notch in the foamboard deep enough to bury the CF rod, then glue it in place with Gorilla glue. I then cover the area with reinforced tape to give it a smooth appearance and hide the bracing. I only needed 1 CF brace for the Tiny Trainer, but I would use more rods for a bigger model.

 

[Hutch Bunch Rc]

3mm solid carbon rods provide a lot of structural strength yet keep the weight down, its more expensive than dowel I accept but there is a big weight saving even with x2 carbon spars.
I fitted some in my Tiny trainer 4ch wing and my sons too following some fractures around the wing joints. Never had an issue since and we both flown those planes within an inch of there lives. Tight full power loops, barrel rolls, inverted stall turns etc
For bigger planes like the Simple stick, I would add a plywood brace for the centre section, plus 2 carbon rods front edge and trailing edge just to make sure.
I normally cut a V notch in the foamboard deep enough to bury the CF rod, then glue it in place with Gorilla glue. I then cover the area with reinforced tape to give it a smooth appearance and hide the bracing. I only needed 1 CF brace for the Tiny Trainer, but I would use more rods for a bigger model.

I’m going to start working on the decathlon very soon, I’m not 100% worried about weight so I’ll use two pieces of the square dowel stack on top of each other, then on either side I’ll do the plywood for sheer webbing. I’m not sure what I’ll do for the outside parts of the wing, I have 1/8 CF. The dowels are 3’ long each, so I could cut them a little bit and put a few together and have a wood spar running all the way through the wing? I don’t know for sure yet.

 

[Hutch Bunch Rc]

3mm solid carbon rods provide a lot of structural strength yet keep the weight down, its more expensive than dowel I accept but there is a big weight saving even with x2 carbon spars.
I fitted some in my Tiny trainer 4ch wing and my sons too following some fractures around the wing joints. Never had an issue since and we both flown those planes within an inch of there lives. Tight full power loops, barrel rolls, inverted stall turns etc
For bigger planes like the Simple stick, I would add a plywood brace for the centre section, plus 2 carbon rods front edge and trailing edge just to make sure.
I normally cut a V notch in the foamboard deep enough to bury the CF rod, then glue it in place with Gorilla glue. I then cover the area with reinforced tape to give it a smooth appearance and hide the bracing. I only needed 1 CF brace for the Tiny Trainer, but I would use more rods for a bigger model.

Almost forgot! I also plan on having the 4 wing struts like the real thing has, I’ll make them out of aluminum.

 

[joelspangler]

I use a lot of 1mm x 5mm (I think they are 750mm or 1meter) spars in my builds. I use them on the leading edge of the wing inside the paper, which helps protect the wings, or on double layer spars (again inside the paper). Whenever I order anything from Hobbyking I buy another set of 5, because I find all sorts of uses for them.

 

[Hutch Bunch Rc]

I use a lot of 1mm x 5mm (I think they are 750mm or 1meter) spars in my builds. I use them on the leading edge of the wing inside the paper, which helps protect the wings, or on double layer spars (again inside the paper). Whenever I order anything from Hobbyking I buy another set of 5, because I find all sorts of uses for them.

Your talking about carbon fiber?

 

[joelspangler]

yes - and sorry for not being more clear. I also found they are 1x6x750 and called carbon fiber strips. Here's a link - Carbon Strip 1x6x750mm (5pcs/set) (hobbyking.com). Being so thin, they only strengthen in one direction, but the wing is only thin in one direction. I've also used the 1x3 ones Carbon Strip 1x3x750mm (5pcs/set) (hobbyking.com) embedded in a sheet of foam (cut slot, add superglue to slot, push in, make pretty by covering with "wing tape"). I also get my wing tape (colored packaging tape that's thin/light) from hobbyking.

 

[Hutch Bunch Rc]

yes - and sorry for not being more clear. I also found they are 1x6x750 and called carbon fiber strips. Here's a link - Carbon Strip 1x6x750mm (5pcs/set) (hobbyking.com). Being so thin, they only strengthen in one direction, but the wing is only thin in one direction. I've also used the 1x3 ones Carbon Strip 1x3x750mm (5pcs/set) (hobbyking.com) embedded in a sheet of foam (cut slot, add superglue to slot, push in, make pretty by covering with "wing tape"). I also get my wing tape (colored packaging tape that's thin/light) from hobbyking.

Thanks for the clarification

 

[Hutch Bunch Rc]