Building materials, covering

[Greg Doe]

StampingKid,
Use of carbon fiber has been discussed on this forum! My kids airplanes have a strip of carbon fiber composit sheet glued to the top of the motor stick to make the motor stick stiffer. The stuff were using is about .007" thick, and seams to add less than 1/10 of a gram including glue.
Most people believe the use of carbon fiber won't contribute any advantage since our airplanes
can be built to the 7 gram minimum fairly easily. I have not seen or read of anyone else using it.
Greg Doe
Smyrna, TN

[StampingKid]

I have read about how it might be used here but had been wonderin if anyone had seen an innovative use. I had thought about using it as you had but just made a new heavier motorstick. Does it work better to fight high torque arching? And is on the top better than the bottom?

[Greg Doe]

StampingKid
My post said "it's glued to the TOP of the motor stick". That way the carbon is put in tension, instead of compression.
Greg Doe
Smyrna, TN

[StampingKid]

Thanks. I noted in your post that you had it on top but had not thought out the significance of using it in tension as opposed to compression. And I guess that is especially true since you were using a sheet of the composite material which I take means it was more like carbon fiber tow as opposed to carbon fiber rods which would be more rigid though I guess both technically all would be carbon fiber composite.

[Greg Doe]

StampingKid
Yes, it's sheet material made out of carbon tow. The carbon is bonded with some form of resin,
and formed into a sheet .007" thick. The strip is about 1/8" wide.
Greg Doe
Smyrna, TN

[blue cobra]

I just covered my stab with mylar, but it's too lose. Should I pull the covering off, or burn it off, or cut it off and recover? Or would it be best to just let it be? I need this for tomorrow, by the way.

[jander14indoor]

How loose is too loose? If you adjust trim appropriately, covering is fairly forgiving on these models.

If you choose to recover, I'd try carefully pulling off first. If not too much glue, it might work. Then I'd use a small brush loaded with dope thinner (in a well ventilated space of course) brush it along the frame outline to soften glue and pull off. It shouldn't take much.

Jeff Anderson
Livonia, MI

[smartkid222]

it might actually just be easier to make another one.

[jgan96]

I have got a question about the material used to adhere the covering to the wing. My old coach used some sort of mix of Naphtha/lighter fluid and Super 77, but I can't seem to be able to figure out the correct ratio of each. He would mix the two together in a shot glass and then use a paint brush to paint the mixture onto the ribs. Then he would drop the ribs onto the mylar which was laid out on a frame, and it had EXTREMELY sticky, light, and great results. Has anybody ever done this and know what the ratio is?

Also, has anybody tried using an undiluted glue stick? I find it easier, cheaper, and less messy than spraying on Super 77. Just rub the glue stick onto the ribs and drop it onto the mylar. I don't know if this adds a ton of excess weight... Does it?

Thanks,
Jason

[jander14indoor]

I've done it several ways.

Quickest is to simply spray a light mist of 3M77 over the frame, flip it over and drop on covering.

If you prefer a brush, thin it somewhere between 1 to 1 to as much as 3 to one, thinner to glue. How much depends on how heavy the covering is. Heavier coverings need more glue than lighter coverings. Then follow one of two paths.
- Brush a coat onto the ribs where it will contact the covering, let dry a little and then flip over and drop on covering.
- Alternatively, make a frame to hold the covering between two sticks so it droops to match your ribs. Drop the frame on the covering, brush the glue around the frame allowing it to wick between the frame and covering. Don't use much, works better with higher dilutions of thinner to glue.

Glue sticks work OK, but does tend to be heavy. If you plan ahead, you can keep it within your 7.0 gm weight budget for a WS plane. If you want to build the real light stuff, its hard to keep the weight down low enough. Plus on real light planes, hard to apply the glue stick direct without breaking things.

You can brush on glue sticks and keep things about as light as 3M77. Use rubbing alcohol or water and follow either of the brush techniques above.

Note, I don't like glue stick as I find it less stick for same weight. And seems to get weaker as time moves on. Don't have that problem with 3M77.

Jeff Anderson
Livonia, MI