Wing tips

[Bradrock]

Is there anyone on here that has made their own wingtips? I gather most people buy them, but hopefully someone can suggest some guidance on the profile.

I am making up the mold and have just made the curves from the outer edge to the rib as flowing as possible without applying any science to it. Nothing specific is mentioned in Beartracks.

[jaredyates]

Rex Ervin wrote about how he did it in 2009 Q1. Let me know if you don't have that handy and I'll send the text. The consensus that I've gathered from smart-sounding people is that tip shape has as much to do with personal taste and marketing as it does aerodynamics in our application.

[Bradrock]

Got it. Thanks Jared.

[EricP]

We are doing ours out of sheet aluminum but that probably doesn't help. Pretty heavy duty metal working skills needed plus welding. Brent is doing all that work!

[whee]

Wish somebody would build some droopies for the BH. I don't really care about functionality, I've always just really likes the look of drooped tips.

[Battson]

Brad - if you want to collaborate on some longer semi-drooped wing-tips which extend the wing span a little, I'd be happy to help.

If you are going to the trouble of making moulds anyway, might as well make awesome tips!

The ones you buy are really tidy, light, and smooth - but don't add very much to the aircraft other than a cap to the end of the wing.

[Bradrock]

I had some spare time while I waited for some parts, so I started tinkering. Partway through mould already, but haven't started with the laborious filling process yet.
Let me know the dimensions you're thinking of.

[Bcone1381]

If the wing tip has nil effect on performance, a Mooney style tip would save weight and simplify things

[Battson]

Having done research on this recently, I've read that those tips are the best solution for smaller lighter planes like LSAs. The study went on to say that a profiled tip has the advantage for larger, faster, heavier planes.

[epapa]

Here is what was in my old RV-4 plans. I don't know if making a drawing similar to this would be helpful or not.

[Baloo]

Rex's Bearhawk is now Roy's Bearhawk and lives up here in Canada. Here are photos of the Tips described above. I had the pleasure of flying her today and compared to my "Standard" rounded tips (Yellow Bird) I found that this aircraft was remarkably stable on the lateral axis. I wonder how much these tips would contribute to said stability. I was thinking of making a mould of them and building a set. Do you think this design might add to lateral stability given its profile and what I would assume would be an upwards and inwards lift vector at the tip?

[Battson]

By saying lateral axis, are you talking about roll, pitch, or yaw?

[Glenn Patterson]

I did a lot of research on this, bought the parts to make a foam cutter & the epoxy with cloth. I squirrel everything in directories and will pass this. Here are two videos of a really slick method of cutting the foam shapes that I was going to follow.

https://www.youtube.com/watch?v=ULhZchv7ito

https://www.youtube.com/watch?v=RoOh-fgI8oU

I have on the other computer Langford's detailed info on glassing a set of Hoerner wing tips over foam core for a KR2S. We considered adding about 4" of the wing profile before cutting the taper to extend the wing. If the Hoerner end is baisically square then there is enough topside lift that in effect lifts the wings. A longer taper would extend the lift side of the wing.

I am capable of building a set but decided otherwise for the short term & took my own advise. Shortest path to get this in the air & bought a set. We bought the BH wingtips and they are quality pieces. The wingtips were nicely done & other than the modifications to our needs were perfect. I have bought fiberglass parts for cars & the MC3A nosebowl that need a lot of love to make them the way they should have been built. Not the case with the BH wing tips.

It still takes glass & work to get them paint ready. The trailing edge is long to accommodate everyone & they needed to be modified to line up with our wing profile. We also built the bump outs for the lights. The glass work still takes time but a lot less than what I had intended with the Hoerner wingtips. The BH wingtips finished out nicely & will get us in the air quicker.

We have been 10 years and it is time to wrap this puppy up & make some noise. I spent a lot of time building the trim around the windshield with epoxy & glass. It takes time to do quality work.

A too much time was spent modifying the MC3A & creating the nose bowl to fit with our Continental I0-360. Discovered in the process that the nosebowl was not symmetrical across the top & it took a lot of pie cuts with templating to make it the profile that I paid for. Less than happy with the quality across the top. Spent a lot of time making a nose bowl that no one will appreciate as at first glance it looks like every other BH. I became weary of glass work & lost my appetite to make a run at Hoerner wingtips.

The BH wing tips will make for a great looking airplane, shaved tons of hours off & will get us flying sooner. The Hoerner wingtips can be built in the future & sell someone a nice set.

Glenn
BH727

[Battson]

Brad - I am making some plugs to make some proper Hoerner tips following the process like Glenn describes above.

If you wanted to collaborate on a set, we could turn those plugs into a pair of moulds. I haven't looked into that step, I was going to make mine based on the plugs alone. But of course, moulds make more sense once you start making any volume of parts. Otherwise I'll have the plugs spare at some stage, but it's a spare time project for this winter - so is going slowly.

[Mark Goldberg]

Bob Barrows has described WITTMAN style wingtips which he feels might give some slow speed improvement. Not Hoerner type wingtips. Not that I know anything about it. BUt Bob was considering Wittman type wingtips for his 540 powered BH, but then decided it already landed short enough and he didn't want to spend the time. Mark

[lsa140]

Steve really enhanced the performance of the Tailwind when those tips were added, that would have been really interesting to see them on a Bearhawk.

[DRLPatrol]

Mark do you have a picture or link to a picture of WITTMAN style wingtips? Doug

[Mark Goldberg]

No I don't. I looked for them to understand what Bob was talking about and saw a few pictures. But none that gave me a very good understanding. Mark

[marcusofcotton]

Mark do you have a picture or link to a picture of WITTMAN style wingtips? Doug

Google has several good links with ease.

[Glenn Patterson]

For now we are considering installing vortex generators as they seem to give the benefits of a lower stall & better climb. Ron Jones used the Hall Bros which are not a huge investment & brought his stall speeds down. He has a good description of the installation on his Kitlog. Somewhere we read that some put them on the horizontal stab and would like to see the results of that.

The hoerner wing tip is supposed to lower the stall speed & increase top speed. From my reading of the vendors that sell the hoerners as certified up grades they do lower stall but not as much as vortex generators. They offer a couple more knots less stall but there is very little solid info on testing an aircraft before & after. They definitely do clean up air flow. We were going to build our wingtips & if going that route then hoerner had benefits & perhaps the easiest glass over foam core to build as symmetry is easy.

Years ago I saw a University of Maryland students windtunnel experiment that demonstrated the difference between a plain end wing & the hoerner. There is quite a swirling eddy off the standard wingtip but the air flows clean off the hoerner tip with no turbulence. That is the significant difference is that the hoerners do make the wingtip more aerodynamic. There was a more detailed article with these photos but these photos were the heart of the article. http://www.jefflewis.net/aircraft_images_alpha13.html.

This is an old youtube that shows a hoerner wingtip in a smoke test that also demonstrates clean air off the wingtip. https://www.youtube.com/watch?v=TZ7ECKGcnZg

The zenairs use an aluminum hoerner wing tip & have a write up somewhere on their site. The Zenair hoerner on their STOLs is an all aluminum angled miter.

If BH'rs are looking for vendors to see more there is
Lo Presti speed mods
Metcoaire
Knots2u

The subject of VG's and hoerner wing tips debate has been going on forever & will continue.

If a BH builder swaps out the std for a nice set of hoerners there is an opportunity to learn the differences & benefit. Share the lessons learned for others.
Glenn
BH727

[Chris In Milwaukee]

I stumbled across a YouTube video today that's about an hour long. A fella outlined the entire process of how he made his Hoerner-inspired wing tips for his Sonerai. Pretty cool stuff.

[lsa140]

Nice, thanks for posting. Good stuff.