I discovered something strange today during the maiden flight of my Sig Cap 231EX. The wing dowels actually charred slightly due to friction from the holes where they enter the fuse. Thought a Boy Scout was in there starting a fire. Never seen that before. A little lubrication solved the problem but there are still some small (black) channels on the dowels from the incident Has anyone else seen this before?

Mike

Mike,

The Hanger 9 Ultra Stick 40 is rather infamous for this problem. People have solved the "loose fit" in a multitude of ways from installing additional ply behind the mount to as simple as a rubber band around the dowels to snug them to the holes.
Not familiar with the Sig plane - sorry to hear of your problem.

Dave

Try a small piece of shrink tubing on the dowel. Replace it when worn. Cheap fix. Worked great on my US 40. Jt

I actually heard of a fire starting in a model from this. Tim.

I use a piece of brass tubing slipped over the wood dowel. But the heat shrink idea sounds good.LOL the oil sounds like it would make more smoke?

Doug

I have heard of using brass tubing around the down to reduce wear and improve fit but I have never heard a plane with enough vibration to char the wood. Wonders never cease!

I had this problem some years ago with a Wot 4 (high wing sports Type), never did find a cure but I wish I had, in the end the fittings got so loose I had to retire the model.

I would strongly recommend that you implement a 'fix' other than lubrication, remember that as the dowels are worn down, so the holes will be reamed out, simply replacing the dowels will not work long term.

Simon.

Yup, trust him guys, wing dowls CAN char! I've had a couple of different models do it over the years. I just used brass tubing that was a slip-fit over the dowls, glued it in place with epoxy onto the dowels, and then opened up the holes accordingly in the fuse former to accept the dowels with brass sleaves.

Lee

On my US 60 the dowels darn near burned all the way through! Like the others, I glued a brass sleeve over the dowels. No problems since.

On my US 60 this happened as well as the leading edge of the wing. I think one of the problems is that the wing does not really have a good snug fit. I solved my problems in several ways. Not only did I cover the mounting dowels with pieces of aluminum arrow shafts but I also lined the wing saddle with, 1st contact cement and rubber bands (lasted a little while), 2nd I picked up some door insulation strips from Lowe's and lined the wing saddle with that. Finally, I also placed a little insulation between the wing mount holes and the leading edge of the wing. I haven't had any more problems.

Hey Ground Zero, glad I'm not the only one that has seen this problem, I recently inserted two new wooden dowels to compensate, The old ones are nearly cut 1/2 in two...Kneesaknock'n

I had the same plane, same problem. I fixed it by replacing the wood dowels with aluminum dowels and brass tubing inserts. Then I made a nice silicone wing saddle seat and never had a problem again. I sold it and missed it when it was gone.

I had this happen once also. Put some heat shrink tubing around the dowels and foam tape on the wing saddle. Problem gone.

Mark

This get's me a little worried for my 4*60's wing dowels, still in the building process. I wonder if coating the dowel with thin ca does the job ? Anyone tried this ?

Not a problem on my two and a half year old four star sixty with hundreds of flights on her. This is usually a problem with heavier planes, but you should allways look at the dowels during your preflight checks!

Doug

Sounds good. Thanks Stomper

These dowels are charring because they are moving or vibrating at a high rate.

(I have a remarkable grasp of the obvious )

I would first try to cure the problem rather than protect the dowel.

Thanks for the input guys. I ended up putting a copper sleeve over the dowels, securing them with epoxy and making sure the receiving holes on the fuse were snug with the sleeves. I also put some saddle tape on to snug the wing. The trailing edge of the wing sits about 1/8 in above the saddle allowing the bolts to pull the wing firmly against the saddle. The sad thing was that I really didn't have to open the holes in the fuse much to fit the larger dowel/sleeve. Thanks again, hope this cures the problem.

Mike

Quote:

The sad thing was that I really didn't have to open the holes in the fuse much to fit the larger dowel/sleeve.

That sure could have been the problem. The fix sounds good.

My US 1000 has this condition and I hadn't a clue what was going on. The dowel fitment is not tight, I'll have to rework that now that I have a grasp of the obvious.

I had this problem too. Mine was not on a dowl but on a ply pin. Apparently there was some slop side to side causing the issue. Made it nice and black. Also cut into it causing even more slop. A simple shim made out of brass fixed the problem

Phil (Mesa, AZ)

Built stock, the Sig Cap wing has short legnths of dowel glued only into the lite ply at the front of the wing. I have built 2 of these and in both cases, after a few flights the dowels got loose and wiggly. Another one at the field had the same problem.
The fix is to get 5/16" dowel and cut pieces long enough to extend back to the ply joiner. I cut out some squares of 1/4" ply, drilled in the center for the dowel, and glued the dowels into the ply and the ply onto the forward face of the wing joiner. You have to cut out 2 small access holes in the top of the wing to do this. It's easy and once patched, doesnt show since the patched area is inside the wing saddle. I also reinforced the dowel holes in the fuse, gluing predrilled plywood squares on the forward side of the former. Again, it is easier to do by cutting out the ultracote from the front of the fuse. This area is easily patched and covered by the cowl. I dont think this is your problem now, just a heads up to a potential problem.

Peter