What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Wing tip help

skyking902001

Well Known Member
Need some wing tip advice from the collective brain trust. I wanted to stiffen the wing tips, but the law of unintended consequences bit me. Several mistakes--I used 3/8" dowel rod--1/4" would have been sufficient. Also used 2 layers of glass over the rods--1 layer would have been enough. And the real problem--I clamped the rods in while glue was drying and it left a depression on the outside of the tip. My question--should I just fill the depression with micro to regain shape or should I attempt to remove the dowel and try again. The pics show where the depression is on the exterior and approximate location on the inside. Thanks in advance.


t54ye8.jpg
,
2uhwwsj.jpg
 
Steve - although the wing tips seem flimsy, they are more than adequate when installed. I would leave what you did well enough alone and fill for cosmetic reasons, as long as the indentation is reasonably thin. I wouldn't invest anymore time on it than that. Removing the rod might not get rid of the depression anyway as the fiberglass layers might keep that shape.
 
For future, it is best to use foam for shape and fiberglass around it. The shape of the F/G reinforcement does all the work and it keeps the weight down.

If it were me, I would just fill the depression with bondo or epoxy/micro. It really depends how good you are at sanding / shaping. If you have no experience with this, you may not like the results. It's very hard to see when you have it right until the paint goes on, but there are some tricks to help. That said, your painter can quickly clean it up and make it right.

Larry
 
Stiffeners

I did not stiffen the tips but thought some really soft triangle balsa stock might make a good former. If your not happy with your outcome couldn't you just cut off the stiffeners and do it over? Just a thought.
 
Blue/pink foam.

Cut into 2" square strips. Glue using West across as ribs every 2' or so. Slash to enable them to conform.

Cover with 3/4 oz deck cloth.

Really helps out..
 
Easy fix

Here's how I would do it. Dremel out the dowel in the area of the depression. It should relieve the pressure allowing the depression to pop out. Cut a few layers of glass cloth that extend an inch or so around where the depression was and epoxy in place on the inside of the tip. This will strengthen the area.

Fill and sand any remaining depression on the outside.

Before you do that, you might be able to reshape the depression with a heat gun. If this works you'll at least reduce the depression and have less to fill without messing with the dowel.
 
Thanks

Thanks everyone for the replies. The depression is very shallow-only visible if the tip is held at just the right angle, but you can feel it. I think I'll try a little heat, then fill with micro. Thanks again.
 
Steve,
Thanks for posting! I'm actually right where you are and thought of the dowel rod install instead of the foam due to an Archer Nav antenna installed in the left tip. I don't know how the foam would interfere with the signal if it were placed over or around the antenna. The dowel seems like a good compromise for interference. This build-log has a good write up on the foam that may help.

http://www.rvplane.com/?categoryid=7&dayid=965

I would be concerned about blocking out the localizer on an approach with all that foam in there.

In your case I would just fill and file with micro balloons.
 
Trying to smooth wing tips is like chasing a ghost the more filler you put on the more depressions you create, the curing process of fillers especially bonds cause more problems the only way I have been successful is to rivet stiffness on the inside and then use filler sparingly
 
Steve - although the wing tips seem flimsy, they are more than adequate when installed. I would leave what you did well enough alone and fill for cosmetic reasons, as long as the indentation is reasonably thin. I wouldn't invest anymore time on it than that.

JonJay's advice is good. I've not seen reinforcement added to wingtips in the past. Once all those screws hold the tip in place, it's plenty rigid.
 
Trying to smooth wing tips is like chasing a ghost the more filler you put on the more depressions you create, the curing process of fillers especially bonds cause more problems the only way I have been successful is to rivet stiffness on the inside and then use filler sparingly

I agree with Jerry.
If the depression is nothing more than very slight, adding any type of filler other than high build spray primer will be inducing a bunch of additional work and problems.

Personally if I was working on it, I would cut away any portion of the dowel that is distorting the tip from its original molded shape.
 
I agree with Jerry.
If the depression is nothing more than very slight, adding any type of filler other than high build spray primer will be inducing a bunch of additional work and problems.

Personally if I was working on it, I would cut away any portion of the dowel that is distorting the tip from its original molded shape.

It is certainly worth a try. My concern would be the sheets holding it down are part of the issue. Anyway, yes, chasing filler is a moving target. Without a good picture, I assumed it was a small depression, not warping.
 
The deformation is likely being cause by using an object (dowel) that wants to be (relatively) straight and forcing it to match the curve of the wing tip.
This will impart some of that bending force (the result of the dowel wanting to go back to its original shape) back into the wing tip.

The proper way to stiffen a fiberglass structure such as this is to lay in some thin foam or honey comb which will freely conform to the shape, and then cover it with another layer or two of glass cloth. This imposes no additional stress that will being trying to change the shape, but will make it very stiff.
The pre-preg cowl is a perfect example. It is two thin layers of glass with a core material between.
 
The fix!

Ok, I was about to sand the outside and mix some micro, then decided to see if I could remove part of the end of the dowel. I sanded the new glass down to the wing tip then worked and sawed with a hack saw blade along the edges on each side of the dowel until it was loose for about 6". I cut off about 3" and the depression is gone! I still have a couple of inches of dowel that is not glued down, so I think I'll add some flox to make a fillet along the sides to stabilize the forward end of the dowel. Thanks again for all of the advice.:D

2vt5nx0.jpg
[/IMG]
 
Back
Top