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Blocking off ends of horizontal stab.

DMFenster

Well Known Member
Those of you that sealed off the ends of the horizontal stab, do you think it's worth the extra work? And did you use the same method as the fiberglass tips? I used glassed-in 1/4" balsa on my first build, and plan to do the same on this build. I saw a beautiful 14 at Front Royal airport in Virginia that had these areas filled and it does look better. Really got nuthin to do until the wings get here. Already polished the tail... :)
Dave
 
I didn't do it, mainly because of the fear of fiberglass that I had when I built my empennage. I have not yet found any birds or insects in there. I'd probably fill it in on my next build, since I'm much more comfortable with fiberglass. I've seen some people install cameras and such on the top of the v-stab, so having that open might provide me some benefit down the road. Dan57 installed a 360 degree camera there and the videos are awesome.
 
Tip tips

I used closed cell foam about 1" thick. Cut to fit. Applied a layer of light fiberglass to make it solid then floxed it in place.
 
I cut out some circles of aluminum scrap and used proseal to hold them in place. The lightening holes on the aft spar of the HS are larger than the lightening holes in the ribs, so it was easy to get the circles inside. I used a magnet on a stick with a piece of steel to sandwich the circles for easy placement. Blue tape to hold it in place while the sealant set up.

IMG_2262-M.jpg


They have held up fine over 8 years and 1000 hours.
 
Those of you that sealed off the ends of the horizontal stab, do you think it's worth the extra work? And did you use the same method as the fiberglass tips?

"Worth" is a tricky word ;)

I think the community already established there is no speed increase. Done wrong it's a potential control jam. Not worth it to me.
 
Where's a wind tunnel when I need it?

Dan, I will defer to you on the "no speed increase" consensus. I did the work to enclose the ends of all the control surfaces. Lots of work. Correct about the possibility of a control jam if not done with proper care (and who knows what that is).

I cannot wrap my head around the lack of speed increase, as there is no way the open-cup exposed rib configuration has less drag. Perhaps just not enough delta to measure.

Given the above, I would _not_ do the extra work again. But I would be tempted on my next build to try gluing elevator end-ribs, flanges-out, all over the landing gear instead of installing the usual gear leg fairings - to see whether there was a speed loss. If the conventional wisdom is true, these complex end-rib shapes are amazingly lacking in drag - and aerodynamics is at least partly magic.

Could the drag secret here be the ol' golf ball dimple trick, scaled-up to the size of an aileron? Stick a half-inch deep, sharp-edged cup sideways into the slipstream and it has the same drag as a 90-degree flat surface?
 
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I did this on all three builds. There is no drag reduction, it is purely cosmetic. I like it as open ribs at the end ribs looks "undone" to me.

Worth it? Depends on the builder.

Carl
 
"Worth" is a tricky word ;)

I think the community already established there is no speed increase. Done wrong it's a potential control jam. Not worth it to me.

I agree.
Along with it closing off future inspection openings...something that builders often don't have forward thinking about.

Some might say "inspection opening?, I never inspect inside there".

And I would say, "Why not?"
 
just me

I plan to block mine off with metalized or Kapton tape. Once it is painted, then the tape color will match the paint. QED
 
I did mine for the clean look of it. It cost me nothing but time. Check out my website on how I did it. Did not use any wood. Did not want anything that can rot on my metal aircraft.
 
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