D&E Hoerner tips?

[whee]

My plane has the original NACA 4412 wing.

D&E Aircraft makes Hoerner wing tips for their Riblett GA30613.5 66” cord wings. I did a rough comparison and think I could make them work on my 4412 wing. They won’t be perfect but that’s ok; I’ve never seen tips on a production legacy plane that were perfect.

Has anyone looked into this?

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[whee]

I haven't pulled the trigger on this but am getting closer. D&E hasn't been responsive at all to my questions so I'm going off what I can figure on my own.

While it may not be exact; here is a plot of the two wing shapes. It looks like the D&E tip will be ~1/2" taller on the top of the wing. I think I can work with that. Still, $1000 is a fair bit to spend on a maybe.

Thoughts anyone?
image.png

[AKKen07]

Jon, if you aren’t in a hurry, I have a pair of stock carbon tips as well as Carbon Concepts that I will do a compare/contrast with. I’m getting closer to being able to do so but some engine puzzles have kept me from progressing to that stage. Hopefully by the end of September I’ll have some data to share.

[Utah-Jay]

I did a pretty deep dive on Carbon Concepts and D&E, CC make one that is a VERY good fit, cost is $900 plus $300 shipping from Alaska.

D&E told me they may be willing to make one for our (Bearhawk) airfoil.

To be honest, I am running out of money and just do not have $1000 to spend. I do believe they will add to slow flight in a very positive way. I am going with Hall Brothers VG’s and figure my 1200 +/- 25 pound plane will land slow and short enough. IF I had the money, I would 100% install Hoerner tips.

[whee]

My BH has the NACA wing. Plus I want as close to the ideal Hoerner shape as possible. I should probably just hire a local outfit to make me a set and be done with it.

[Nev]

If they are a good fit for the designed aerofoil shape then they probably won't fit initially on the BH riblett. However you should be able to split them along the aft edge, fit them, then epoxy the aft edge while they are in place to take the shape. When I made mine I kept the aft edge separated, then fitted them and epoxied as above to get an excellent fit.

Regarding the performance increase with a Hoerner wingtip, I was able to measure a very small improvement, but to be clear it was small and difficult to measure. It pales in comparison to the performance enhancement of adding well placed VG's for example. Some owners have gained a more measurable improvement by extending the wingtip length and thereby increasing the total wing area, but I wonder if the same improvement would have been observed if the wing length had been extended with a normal tip shape for example - i.e. perhaps the performance increase is being gained from increasing the wing area rather than the tip shape. Just some thoughts.

Would I do it again ? Absolutely. They have an excellent fit and more than anything I love the way they look !

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[whee]

I can’t recall for sure but Jono asked Bob how much we could extend the wings with longer tips. I think it was 15”. The tips I started building before I knew that were 18”; 10” of additional airfoil and 8” to get the Hoerner shape. Wish I had just built them the way I wanted instead of trying to make molds so I could build tips for other BHers. Sometimes it pays to be nice and other times it doesn’t. Haha

[Utah-Jay]

I think Nev most likely nailed it, 2-3’ extra wingspan is a lot of wing square footage, I am not saying the Hoerner tip shape does not help.

I am going with Chris Spira’s extensive testing data on the Hall Brothers VG’s for the best bang for my buck. IF I keep this up I will be down to dimes tho

[whee]

Why spend over twice the money on Hall Bros VGs vs Stolspeed VGs? If I ever install VGs I figured I’d just use the $97 Stolspeed ones.

[Utah-Jay]

whee

I like the metal rather that plastic, I like larger base and easier insulation/alignment of the HB design and the incredible results Chris got on his patrol

[Nev]

I think Nev most likely nailed it, 2-3’ extra wingspan is a lot of wing square footage, I am not saying the Hoerner tip shape does not help.

From memory I think the 4B wings are already longer than the 4A. Mark might be able to confirm. I probably wouldn't see any need to extend further on the 4B.

[fairchild1934]

I am not up to speed on the tips issue----- is there a droop type tip being tried ? (the kind that has the downward facing fin at the back...)
I really dont see where a mold would be that big a deal to make. You could make a model out of clay like the car body makers do. Maybe make
a left and right at the same time to make sure they are the same shape. Then lay up your mold on top of that. Could probably add a layer of thin shrink wrap plastic as a release layer. (maybe garbage bag ? nothing sticks to PE )
You could rough out the shape a bit underside from open cell white foam. Then add a layer of clay for the final contours. Use cross section templates at station points to get the shapes the same. The molds could be in two halves to make removal easier. Might even be a way to put in a couple of vertical ribs to make the shape less collapsible.

am I out in left field here ?

There might also be a way to vaccum form them in two pieces and glue the halves together. Maybe 1/16 lexan ?

[Nev]

You're right, it's pretty straight forward to make. I used polystyrene and a Hotwire to cut the shapes then covered them with packing tape.

[Hewko]

whee

I like the metal rather that plastic, I like larger base and easier insulation/alignment of the HB design and the incredible results Chris got on his patrol

What % of chord did Chris place his VG's at, and will you be doing the same?

[Utah-Jay]

What % of chord did Chris place his VG's at, and will you be doing the same?

7% after a lot of testing

Virgil went with 7% on his model 5 too

I’m going with 7%

[fairchild1934]

It appears that the VG's are just short pieces of aluminum extrusion. why not just make them...... ???

[Utah-Jay]

What’s your time worth? You can buy them for $185, how many hours would it take to make them? How much would you say the materials to make them would cost?

[Bcone1381]

Is Chris Spira's installation and testing data available for public viewing?

[Utah-Jay]

Is Chris Spira's installation and testing data available for public viewing?

I don’t believe so

[whee]

It would be appreciated if you fellas would take the VG chatter to a relevant VG thread. VGs are cool and all but they don’t have anything to do with Hoerner tips and the good information you are posting will get lost here.

I’m pretty sure these D&E tips will fit the NACA wing with minimal modification. However, another BHer has reached out and encouraged me to pursue getting some purpose built tips made. The idea is that sharing the cost of production may make it reasonably affordable. ie, if we are going to spend $1k on tips that mostly fit maybe we can pay the same for tips made for our planes. If anyone is interested in a set of tips for the original NACA 4412 winged Bearhawk send me a message. I’d guess the price will be about the same as the D&E tips, $1000.

[schu]

Count me in. I need wingtips and I want extended Hoerner tips.

That said, I suspect I’m part instigator.