Long wing Bearhawk

[Battson]

Very helpful food for thought - thanks.

I was always expecting a maximum tolerable G-force reduction would be required with such a mod, to avoid putting excessive bending stress on the wing (or are you talking about distributed load per chance?).

[Chris In Milwaukee]

I came up with that with distributed load calcs, and then those loads become additive as you move inboard. But that also assumed a cantilevered wing, so the bending force may develop at a different rate with a strut-braced wing. But that far out, it may be negligible.

[Battson]

The load distribution is quite different in a strut braced wing, at least in some areas. Apparently it may not effect the outboard sections - but I am not an expert. At least at a macroscopic level, the analysis is quite easy.
http://soaringcafe.com/wp-content/up...ilsafefa10.png
In that regard, lengthening the wing only adds a small force to all the inboard sections, relative to their maximum design load. That is what leads to the small reduction in maximum G-force, assuming you want to maintain the original safety factors.

[Peter Bishton]

Jonathon one way fwd would be to build yourself a new set of wings and make all the changes integral rather than a tack on. Also that would give you a chance to use a riblett airfoil and move the ailerons outboard the extra bay and increase the flap length the same amount which is all increasing the effective CL over a longer length of the wing span wise. There was some good info in Pazmanny's design book on it i.e. calculating the effect of longer flaps span wise on slower landing speed. It would only be an incremental increase but it's all working in the right direction so to speak.
Once you had them completed and fitted you could sell the existing wings.

[jaredyates]

I like this plan. You should be able to knock it out this winter. Take some pictures for a Beartracks article please!

[Battson]

Hahaha - yes, of course, it's just that easy!

[Peter Bishton]

Guys I tried to write a comment today and saved it in the wrong place. I will try and get some numbers for you on the W8 work my dad did with the Riblett airfoil. Dad is in New Zealand at the Hastings fly in with John Corby his mare of Corby Starlet fame. From memory the Riblett airfoil to approximate similar characteristics to the modified 4309 section on the W8 was a GA35 (or 37) Ax12 with the x I am not sure of the value and the 12 may have been a 13. The upshot was several knots more speed at cruise and substantial improved slow speed. Peter

[Peter Bishton]

Photo of Riblett wings on W8 with Hoener wing tips.

[whee]

When I was looking a wingtip designs I thought I read somewhere that the Hoerner tip added 4-6" of effective wing length which is why I wanted to use that style. My thinking was to eventually make a fiberglass tip that extended the airfoil 12" then transitioned into the Hoerner tip. That would increase the effective span by 2.5-3 feet. The WingX increases the Cessna span by something like 4' and on some airplanes requires a aluminum and stainless steel reinforcing straps added to the main spar in the lift strut area. Someone should perform the calculations on the BH wing to determine if similar reinforcement would be required; that way I can add them before I close up my wings

[kestrel]

Wing-x adds 3 feet.

[Battson]

Jon, if you are serious about making some longer Hoerner tips like that, please consider me as a potential "customer" for your work on the moulds.
If you made some moulds, I would certainly be prepared to pay you a premium to lay up a second set of fibreglass tips.

As I said before, I would go ahead and do it myself, except for NZ is so very far away from 95% of the Bearhawk world - the effort of making the moulds seems to be a waste of time, as they wouldn't be able to be shared with the community. I don't think its worth making moulds just for one plane. Plus I have never made a set of moulds before on that scale, I bet they would be expensive, and you would want to recoup some cost by selling a few extra sets of tips to others.

I am sure such a product (extended fibreglass Hoerner wing tips) would be a great seller. In fact - maybe that's a market Mark G. or Bob B. should consider tapping into?

[whee]

My dad is set on making our own tips so I'd say the probability is pretty high that they will also add some span. I'll have a bunch of studying to do to figure out the right shape.

It shouldn't be too difficult to make the molds. Back in the early days my dad used to make molds for kayaks. As long as we get the design right I'm sure he can make them.

[whee]

I found the following information about the Isham Piper PA28 wingtips interesting. Their Hoerner tips add 2' 2.5" of span but don't decrease ground roll or stall speed.

[Battson]

​I would say there could be certification / POH related reasons why they don't claim higher performance.

[Chris In Milwaukee]

Wow, you have a Commander? Drooool. It's one of my favorite GA airplanes. I've never been in one, but I remember reading an article in P&P a number of years ago that a guy restored a 112 to beautiful condition. They certainly have managed to keep their value over the years, too.

[JimParker256]

Not meaning to hijack the thread, but yeah, the Commander is very cool. Largest cabin interior among all 4-place GA aircraft (by far!), two doors for easy entry/exit, built like a tank, and trailing-link landing gear that turns every landing into a squeaker... And the ramp-appeal is second to none, though some V-tail Bonanza owners will argue that point.

I'm selling it (contract pending) to fund the Patrol build, because the Patrol better suits my post-retirement flight mission statement. I'm having a lot of fun building, and can't wait to start flying it. My demo flight at OSH was absolutely amazing! Bob designed an awesome airplane, and Mark puts out a great kit.

[Battson]

Thanks Jim - that's some very interesting information you provided!

[Battson]

By the by, I spoke to Bob about lengthening the Bearhawk wing. He was not keen on the idea, which is not surprising.

He cited a number of factors which would need to be considered regarding the strength of the spars and a few other factors. He didn't think there was any "fat" in the design, any room to increase the design loads without reducing safety factor below the stated limits. He thought the wing would need extra cap strip material at the strut attach point, if I recall correctly.

He notes the Patrol wing, which is longer, has a deeper profile and this considerably increases the 4th moment of area - which means the wing would be stiffer and stronger if the spars were exactly the same on both models. Of course that's not the case in reality, both wings are probably about the same strength.

[whee]

Battson, Didn't Bob reluctantly agree that 15" extensions probably wouldn't hurt anything? I thought you were perusing the idea of 15" long Hoerner tips.

[Battson]

Battson, Didn't Bob reluctantly agree that 15" extensions probably wouldn't hurt anything? I thought you were perusing the idea of 15" long Hoerner tips.

He agreed to a 15" full-chord lift generating wingtip, which he said was the longest he could approve at full chord. He said a Wittman W10 style wingtip would be acceptable with a longer span, because of their much shorter average chord length.

He wasn't prepared to approve any extension of the wing structure itself.

[tailwind]

Has anyone done a tailwind style wing tip on a Bearhawk. The wing tip makes a lot of difference in the performance of a tailwind.

[Battson]

Has anyone done a tailwind style wing tip on a Bearhawk. The wing tip makes a lot of difference in the performance of a tailwind.

Mark told me that Bob originally intended to use a Tailwind style wingtip on the Bearhawk, but it never happened for some reason.

[Bcone1381]

I may have shared this before...someday I hope to factually discover the advantages of different wing tip desings...using a different and peculiar way. I plan to get the aircraft rigged so that it flies straight, then install one of the subjects to be test on one of the wing tips. Then flown in cruise flight, the wing tip with the lower drag will induce a measurable yaw force. We can test a Standard tip, Hoerner tip, Tailwind Tip, Round/Square, then the Mooney "Cut off" tip...which is best? Do they really make a difference? No question if the power was set differently that day, or if the atmosphere's vitals were measured accurately to determine density altitude. We get simple, raw, side by side comparisons, kind of like a drag race with one wing tip compared against the other.

I also sense the tailwind tip may be least draggy....kind of ugly/boxey/trapazoidie, but it looks like it minimizes tip losses to me.

[Westward_Flyer]

Sorry to resurrect an old thread but I have a burning question. If Bob approved a 15" full-chord lift generating wingtip, how long of a hoerner tip does that equate to?