Wingtip Fit

[alaskabearhawk]

I'm not entirely thrilled with the fit of these wingtips. I have to extend the tail about 1/2in so the aileron lines up. That's a pain, but relatively easy to fix. I do have a "pooch" near the tip though. It measures about 1/4 inch. I can slit it and patch it, but I'm not sure what would look worse...the pooch or the patch. I suppose if I go out far enough it would feather out. Any creative ideas on how to fix it?

[jaredyates]

I fiddled with the tips for too long before giving up and just going with them. If I had done that sooner, they would have looked the same but I would have been flying a few weeks earlier. In the years years since, I may or may not have hit the hangar door with one, providing further relief that I had not strived for perfection.

[PaulSA]

It looks like your screw spacing is on the long side. I actually modified to make a flush fit but my spacing was around 3". Even then, I got a little pillowing.

[alaskabearhawk]

I drilled out every third rivet and replaced it with a nutplate. The fiberglass is just the wrong shape for the airfoil.

[zkelley2]

I had the same issue. The fiberglass wingtips just don't really fit the airfoil. I've got the same "pooch" as you and just went with it until I get around to making a pair of my own.

[svyolo]

I don't grind fiberglass indoors so I would leave it until it is outdoors/already flying.

When i did fix it I would slide some sheetmetal under the affected area to protect the wing sking, leave all fasteners in place, and I would grind all the affected area away, plus put a bevel in the adjoining fiberglass that is remaining, probably at least a 3/4" wide bevel. I would then remove the sheet metal, replace it with waxed paper, and apply new fiberglass. Fair the new glass in.

I think if you remove the tip to fix the problem, you will never get the shape correct. The fasteners are stressing the tip into place, I would grind away the offending material, in place, and re-glass in place.

[whee]

Every BH I’ve seen in person has that same fit of the tips. Most older certified planes do too. I’m not sayil Sds ng you should leave it but I do agree with Jared.

[James]

I've never seen another bearhawk out and about flying, but when I did my wingtips, they were too short. I slotted them up the trailing edge, made up a template of MDF based on drawing #7, and gave the whole lot to a boat builder with some money. The wingtips came back the right length. Keep in mind when drilling out the rivets for the nutplates that you can obtain more even a spacing by aligning the existing rivet hole with either the centre hole or the leg holes of the nutplate. Also, use mini-pitch nutplates if you get cramped near the wing spars. I used NAS1169-6L countersunk washers, and there's hardly any pillowing. Countersink the fibreglass after installing the nutplate with a #30 100degree countersink bit mounted in a drill - it auto-centres in the nutplate and won't bottom out! :-)

Because they are so heavy and easy to take off, the wingtips might be part of the aircraft I look at modding down the track, maybe some of those fancy carbon fibre stol wing tips :-)

[PaulSA]

I took the time to make a flush fit by adding a strip of 025 under the skin on the outboard rib. Got a nice fit. Probably a day's work but well worth it. Bit late now for you as you've already fitted the nutplates to the rib but I would recommend it to other builders.

https://bearhawkforums.com/forum/too...lush-wing-tips

[svyolo]

I wanted to try to get my wingtips to fit a bit better, so I spent a little extra time. I drill out every third rivet which is a little over 4" centers. I wanted to try transferring the holes to a straight edge, and then using that straight edge to transfer the holes to the tips. I thought using a strap hole duplicator would cause more billowing between screws. I sacrificed a couple of strips I had cut and set aside for lower wing root fairings.

It came out OK, but not perfect. The top shape is OK. The bottom, the amount of billowing is minimal, but it had the effect of pushing all the extra material aft to the aileron leading edge. So I have a ridge I need to get rid of. I will cut along the spine of the ridge, and cut out a small slice and repair it from the inside to get the shape right.

The amount of billowing between holes on the bottom is probably 1/16" or a little less. The top is 1/16-1/8". If I rivet the tips on, and add another rivet between the current holes, it would lie pretty flat top and bottom.