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Material for Covering Lightening Holes?

I received a good suggestion that I might want to close up the lightening holes in each outer rib of my horizontal stabilizer. The idea is just to improve the drag/air disturbance factor in the area between the elevator horn and the end of the H/S. Got time on my hands waiting for my wing kit, so what the heck...

I've seen some good durable lightweight fabric used on the inside panels of the inner gear doors of my Bonanza, but I don't know what it's called or how to find it. Looking for light weight, durable, preferably self-adhesive fabric to seal over the holes that, I'm guessing, are no more than 3" in diameter. Even if not self adhesive then a good bonding adhesive to the zinc chromated rib will be needed.
Any suggestions?
 
Filling hole s

If you really want to do a great job filling the holes, you could glue in some foam into the gap, coat the foam with micro ballons then lay up a layer or two of fiberglass and sand it all nice and flush.
 
is it really worth it?

I doubt that covering over those lightening holes will make any noticeable difference to performance, otherwise why would Vans make them that way? Most of the time when flying, the elevator will be neutral and aligned with the HS. But if an aerodynamic expert has the data to back up the suggestion, or you just want to do it anyway, then what the heck!:)

I think that there is actually an advantage in having them open as it allows for easy internal inspection if needed. And if the gap seal material that is bonded to the zinc chromate comes loose and jams the elevator? Really don't wanna think about that!
 
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I doubt that covering over those lightening holes will make any noticeable difference to performance, otherwise why would Vans make them that way? Most of the time when flying, the elevator will be neutral and aligned with the HS. But if an aerodynamic expert has the data to back up the suggestion, or you just want to do it anyway, then what the heck!:)

I think that there is actually an advantage in having them open as it allows for easy internal inspection if needed. And if the gap seal material that is bonded to the zinc chromate comes loose and jams the elevator? Really don't wanna think about that!

And the openings allow ventilation of the structure - less moisture, less corrosion.
 
Besides the foam/glass idea, you could use aircraft covering fabric or Mylar drafting film. On my C180's aileron spar holes, I used the Mylar drafting film (I have a bunch of it on hand) and attached it with Pliobond, with the drawing side to the airframe. The individual holes remain covered now, after around a quarter century and around 1,200 or 1,500 hours.

For other C180 owners, this slightly but noticeably reduced the aileron forces. I suspect that it contributed to the slight speed increase that I got at the same time, but as I included a few other minor changes at the same time, I can't be sure. I used individual circles of the Mylar, overlapping the holes by 1/4" radius.

Dave
 
I plugged mine. It's parked outside and those openings seem to attract spiders and other denizens who tend to leave droppings. Like Paul said, a concern would be something coming loose and jamming the elevator. I made circular plugs out of thin Al, slightly larger than the hole, and cut a slit on the edge to allow them to be inserted through the hole, then pro-sealed them in place on the inside. They've held up fine for 400 hrs.

(the install can be messy trying to apply the pro-seal and position the plugs. Just drill a small hole in the center of the plug and insert a cleco to hold on to, then later plug the hole with pro-seal)
 
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How about find some piper cub guys on the field and have them help you. They could probably cut some dacron fabric, glue it on with Stewart's or Poly tack, shrink it with an iron and maybe even paint it.
 
Good plan!

I have seen production aircraft with std a/c fabric glued in place, shrunk, and painted the same color as the rest of the ship. My take on this is it helps keep the bugs etc out - tho it might restrict the exit air as the holes in the empennage are covered.

I had a chance to get a cockpit tour of the amazing restoration of the A-20 at OSH. Amazing technology on that ship. The ‘fairing’ around the empennage was all fabric glued and shrunk in place, then painted. The lower sfc of the H Stab had a nicely shaped fabric seal, with the fabric cut with pinking shears along its edges. The same process was used on the upper sfcs, and on some other places on the ship. It looked like a very quick process to reduce excretion drag too.

A simple bluff body exit under the H Stab would make a nice exit for ‘pilot cooling air’...
 
Tip seal

Someone made a video a while back on enclosing the tips. Can't find it now but it was pretty good.
 
Why not aluminum HVAC tape? It sticks well, but if it fails, the tape is thin enough you'll be able to tear through it without undue stick forces.
 
If you really want to do a great job filling the holes, you could glue in some foam into the gap, coat the foam with micro ballons then lay up a layer or two of fiberglass and sand it all nice and flush.

I did it.
Excellent visual result. I left a little hole in the lowest corner for water or moisture.
 
I made some circles out of aluminum scraps from the kit. Make them just a bit smaller than the lightening holes on the aft spar of the HS.
Put some of your favorite adhesive (I used proseal) on the edges of the small circles then put them inside the aft HS holes. The lightening holes on the side ribs are smaller in diameter, so the circles will fully cover them.

I used a sharpie to mark the center and edges, then used a magnet on a stick along with some steel washers to be able to sandwich them and hold them inside the HS. Then some painter's tape to hold them while the proseal cures.

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They are solidly in there and haven't moved or come loose in 6 years.
 
I’m sorry, but I have to admit, I don’t understand the reason for this. If you are parked outside and worried about bugs or rodents finding a home inside your control surface, then that makes sense, and anything more than a taped covering seems like overkill to me. Confession - I actually did a glass-over on my first RV, and the reason was totally cosmetic. That turned out to be a waste of time, material, and weight, because nobody ever noticed. If the reason is aerodynamic, then it seems to me, you would actually doing the opposite. Reducing drag, thereby increasing airflow through this gap, is actually detrimental. This goes for filling/smoothing aileron, flap, and wingtip rib cavities. It seems to me that you would want to restrict airflow between these gaps, so greater drag is a good thing. After all, aren’t these lifting surfaces? High pressure on one side, low pressure on the other (wing and tail being opposite). The more air that leaks through this gap is just spilling lift created (either up or down), and to compensate, just requires more angle of attack to counteract - either up or down (HS). The amount of lost lift is probably infinitesimal, but why waste time on this if the result is negative? NOBODY will see it but you, and it will not wear the same as your metal surfaces.

Keeping the bugs, etc out, is probably a good idea, if you have a problem with that. Other than that, I don’t understand the reason. Edumacate me.....
 
Yep. Nice video. Pretty much what I did on my first RV (RV6). It looks cool. Looks slippery - but it isn’t. Well, actually, it is. But it isn’t something you want in this location if your goal is speed. It may slow you down 1/10th of a knot, because it will not decrease overall drag when you consider induced drag. This is a teny-tiny amount of difference. But it takes extra effort to achieve a tiny bit of decreased performance. If looks is you goal, this is a good mod. Makes your metal airplane to look a little more like a composite airplane. Go for it.
 
why not 3M 1080 or 2080 vinyl? lots of colors. I put vinyl over those areas and then proceeded to cut out the holes. There is no reason that the holes can't be left closed up after applying the vinyl.
 
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