heavythumbs

I am finishing up putting together a tower hobbies .40 ARF and am wondering what rout to take with holding on the wing. It is designed for rubber bands but I really like the idea of nylon bolts w/ 1" washers holding on the wing instead. It seems easy enough to drill 2 holes in the trailing portion of the wing and epoxying some plywood inside the fuse with nuts in place. The leading wing is a bit trickier. What is the best method for securing the dowels in place? Also, because most of the force on a bolted wing would be from the underside as opposed to the top from the rubber bands is the wing going to be able to handle the different stresses?
Thanks, Heavythumbs

burndred

hey , im going to give my opionion on this , but maybe im wrong..


the forces will still be on the top of the wing ,- the washers pushing down onto the wing .. only concentrated in the area of the washers

you need to make sure that there is enough material in the trailing edge to take the sqaushing force of the washers , best way would be to cut an opening and fill the wing with balsa so its solid in the area where the bolts are . as for the leading edge a similar thing , cut an opening in the sheeting and fill it in with solid balsa . only wide enough to go from one dowel to the other and high enough so that it fills the wing top to bottom then drill into that and ca the dowels in . maybe even make a plywood filler peice inside the wing spanning the top and bottom spars that you can drill thru the leading edge and into the ply to glue the dowels into


Rick

burndred

oh , and depending how far it is from the leading edge to the plywood filler peice on the spars , you might need to strengthen that area or it could just rip the leading edge of the wing apart because thats weak compared to the spars , i would fill it with balsa like the trailing edge and then drill thru all that


Rick

raideron

My Feedback: (1)

heavythumbs... Wing bolts are nice..., As said, you have to
strenghten the area for the bolts and dowel/s..... So it's not
a lot of work, but some extra stuff to do....
That said.... The rubber bands will have you more "give" in
a crash which could lessen some damage... Use the required
amount of good rubber bands and the wing will stay on...
Just something to think about....

carrellh

Download the manual to the Great Planes PT-60 Kit from www.greatplanes.com
This kit provides for bolts or bands. I built mine with bolts.
There are photos and text for a "center rib" that the dowel glues into.
You'll also see how they designed the bolt block in the rear.
You will probably want to glue a doubler to the fuselage former where the dowel goes.

If I were assembling an ARF trainer I'd probably just stick with the rubber bands rather than doing these modifications.

DaveB

Although I am in favor of bolts over rubber bands, I would exercise caution in converting a plane designed for the rubber bands to the bolts. The problem I see is making sure the leading edge dowel(s) pass through plywood or similar back at the main spar. If you are confident there is some support aft of the leading edge you can glue to, then I would say go for it. Otherwise, stick to the rubber bands and go for bolts on your next plane.

DaveB

MikeEast

My Feedback: (3)

What is being discussed is called a "hardpoint." Any time you run a bolt of any kind through any surface on your plane that is bearing a significant load like a control horn, wingbolt etc.., you do not want to run it through balsa only. So you cut out an area, replace it with a bit of hardwood and secure it to the balsa with a slow drying epoxy like 15 or 30 minute at least. A small circle or square that is a little larger than the OD of the washer you intend to use is what you need. Its not hard to drill out a hole with the bit the OD of the hardpoint and then fashion a hardpoint with that OD on your belt sander or scroll saw. Make it slightly large so that you can trim sand it down so that it fits tightly into the hole you drilled for it. It will never come out if you make it a nice clean, snug fit.

As far as rubber bands or bolts, I like bolts. But rubber bands are more forgiving. The main thing is keep a box full of fresh rubber bands and use new ones every outing of posible. If you get any fuel or oil on the bands whatsoever they become mushy and break easily. Kindof like a plastic worm that sits on the bottom of your tackle box too long.

britbrat

I suggest you examine your flying skills first. If you are still banging the planes around, then stay with the rubber bands. If you are past that stuff, then bolt it.

piper_chuck

My Feedback: (12)

Complete agreement with this. Wing bolts are certainly neater, but for a beginner, it's better to wait till you are past the cartwheels due to botched landings and takeoffs before you consider wing bolts. The beauty of rubber bands is they provide some shock absorption during mishaps. Wing bolts tend to result in greater damage.

Scar

My Feedback: (3)

The biggest problem I have seen with installing wing bolts in a trainer designed for rubber bands is interference with the aileron torque rod linkage. In four instances I have seen hardwood blocks installed which provided plenty of support for the bolts - and then the blocks were ground very thin, close to the threads, in order to clear the aileron linkages. I have seen three such conversions fail in the air.

I recommend you stick with the rubber bands. If, instead, you feel you must convert to bolts, I suggest you look into the DuBro wing bolt kit. It mounts a plastic threaded block to the outside of the fuselage, leaving plenty of room for reinforcement inside the fuselage next to the aileron linkages.

Good luck,
Dave Olson

Flak

My Feedback: (1)

Heavythumbs,
Leave your trainer the way she is and fly the covering off of her! The rubber bands allow for cushioning and a good possibility the wing will "Pop Off" if you strike a wing tip on the ground when landing. The bolts are almost guaranteed to add more serious damage to the air frame in the same condition. Your next plane can be a bolt on wing, as you will, (hopefully) be an accomplished aviator by then and beginner screw ups won't be happening. Trust me, I know what I'm talking about. I have been R/Cing for a long time. There is no shame with rubber bands. Good luck.

"Keep 'Em Flying!"
Flak

heavythumbs

Thanks for all the input guys!!!! Rubber bands it is... I feel right now it is just too much fuss and effort for the result. I also really don't think that this wing is structurally designed for putting dowels in the leading edge without sacrificing some wing integrity. I have two bags of rubber bands so I can use new rubber bands the rest of the summer for each time I fly. Thanks for all the input!!!

Rodney

With a little forethought, you can get as good a crash protection from nylon bolts as you do rubber bands. The secret, use the proper size bolts. For a 40 size plane, 6-32 nylon are more than enough, 8-32 for up to 120 size and #10 for quarter scale. 1/4-20 are usually a poor choice for any plane as they will not shear easily enough, in fact their sheer strength is greater than the tensile strength; just the opposite of what you want. You want the bolts to have adequate tensile strength but a lower shear strength. Then, to be effective, you must have no slop between the wing surface and the fuselage surface where the bolts go through. This creates a scissors action on shear loads like when you land on a wing tip that lets the nylon bolts shear without tearing up structure in the process.

ICE_MAN

Instead of the washers like you stated.. Make one big spacer from a tin piece of ply wood...

Look at the pic of my Ultra Stick Lite where the wingbolts are.. Make sure you line everything up.. then epoxy it to your wing then either soak the piece in Thin CA or cover it with thinned epoxy or even just monokote to fuel proof it.. This way the load is spread over a wider area.. And no washers to loose!