Wing tips

13 posts in this topic

Posted

Doug,

Describe the removable wing tips you are going to use: What lengths does that give you? GW with and w/o tips? How are they taken on and off? Are these offered by Airdale?

Thanks,

Randy

Randy -

As you know, the wing tips supplied with the Avid+ kit are attached to a spar extension and, therefore, permanently fixed. I prefer removable tips for inspection and quick repair if necessary so I took a look around to see what might work. At the moment, I'm leaning towards a set of Hoerner-style 'Speedster' tips sourced from www.KitfoxAircraft.com. You can see from the following pics, the Kitfox 4-7 'laminar flow' rib profile designed by Harry Riblett is very close to Avid's flat-bottom 'speed wing' rib profile. Using the tips full width will only give me another couple/few inches per wing but I'm hoping the Hoerner style and shape will provide a bit more lift and speed than the oem Avid tips. Who knows, the big thing is removability and I prefer the looks over the Avid tips.

Here is one of my Avid speed ribs next to the Hoerner style tip supplied with a friend's Kitfox 4-1200 kit.

post-53-12687729199751_thumb.jpg

Top curve looks good.

post-53-12687729574193_thumb.jpg

Bottom looks good too.

post-53-12687729804428_thumb.jpg

Leading edge cuff is easily integrated.

post-53-12687730248995_thumb.jpg

Only issue we found was length, but the good news is that Kitfox tips are supplied over-size and open at the trailing edge to allow custom fit by each builder.

post-53-12687730499373_thumb.jpg

These tips were trimmed approx. 3" in length and 2" in width (to fit in his barn with wings folded), then trailing edge sealed.

post-53-1268773106166_thumb.jpg

I think the extra trailing edge material will allow the KF tips to be fitted to the longer Avid speed ribs with very little modification.

post-53-12687731561126_thumb.jpg

Now the issue becomes how to attach the tips. I have seen the tips attached directly to either the inboard or outboard cap strip of the tip rib with self-tapping screws. This typically requires the addition of an epoxy bead buildup along the cap strip/rib web junction to give additional material for the screws to grip into. I have eliminated this for aesthetic reasons, I simply think the tip sitting on top of and higher than the fabric as opposed to flush with the top wing surface looks like ass, especially if it's wavy. Some folks even put nutplates in the capstrip and it still looks like ass, IMHO. Not to mention a lot of work but to each his own I guess.

post-53-1268773632522_thumb.jpg

Couple of comments on the KF list about attaching with invisible piano hinge. Yeah, it looks great but since I'm not looking for a Grand Champion trophy here the extra trouble to cover a bazillion rivets isn't worth it to me. Right now I'm thinking I'll probably just glue and rivet a strip of aluminum to the underside of the outboard tip rib cap strip to receive either self-tapping screws or floating nutplates like this.

post-53-12687739364506_thumb.jpg

I would add a stiffener strip along the inside of the wing tip edge to strengthen and help make sure it lays tight along the edge rather than waving or oil canning. Maybe even glass in a couple foam ribs in the tip. Hopefully that will help minimize a couple of what sound like common problems when using screw heads directly on the f/g, ie. vibration causing paint chipping, hole elongation, etc. I was going to continue the fabric and tape past the rib and over the strip riveted to the rib, being careful to get a nice sharp edge at the 'step' between cap strip and backer strip. To keep it all flush, I just need to figure the correct thickness of the aluminum strip in the tip and install it after covering the wing because the thickness of the tip strip and the tip material must be equal to the cap strip thickness less whatever thickness the fabric + reinforcing tape + paint layer ends up being.

Open to any alternatives, trying to K.I.S.S. to keep things moving.

Share this post


Link to post
Share on other sites

Posted (edited)

BTW... stating the obvious, these tips won't work with Avid's Hauler/STOL under camber rib. However, the Just Aircraft Escapade and Highlander use a very similar airfoil profile and are supplied with Horner style wing tips that are fixed or removable by builder choice. Also, if you can find them, the old Kitfox droop tips were supplied in two pieces which would make adapting them to an Avid wing a piece of cake. You can see from the following pics the Avid HH (blue tape) and KF 1-3 ribs are almost identical, just a tad more under camber in the Avid rib.

post-53-12688433692141_thumb.jpg

post-53-12688433834786_thumb.jpg

post-53-12688433939695_thumb.jpg

post-53-12688434147267_thumb.jpg

post-53-12688434361595_thumb.jpg

post-53-12688436046095_thumb.jpg

post-53-12688436525845_thumb.jpg

post-53-12688438723611_thumb.jpg

post-53-12688440911313_thumb.jpg

post-53-12688441362556_thumb.jpg

Edited by dholly

Share this post


Link to post
Share on other sites

Posted (edited)

Thanks for all the information Doug. I agree with you that screwing the tips on top of the rib just doesn't look very finished, and I have yet to see one that isn't wavey. That is one of the reasons I like the look of the stock Avid tip. May not be the best for lift though. If you are calculating your backing strip thickness down to the paint thickness it should be very nice!

I'm still kind of hung upon building a longer set of wings for the Avid+ sometime in the future but will put on my HH wings initially to get it flying. I fabricated a new set of flaperon horns the other day since they have to be about 1" longer to extend into the Avid + fuselage. I am hoping that I can mark the riet holes in the flaperons on an index tape and transfer that to the new flaperon horns. If I can accurately locate the rivets I should be able to reuse my old ones back on the Avid if I build new wings in the future.

A couple of years ago I saw an add for an Airdale project that came with a set of Magnum wings. I was wondering about he chord of the Magnum wings but Leni thought they were wider chord than the Flyer wings. I'm still thinking about how to get a wing that is about 2' longer per side and built to around 1400 GW. Haven't talked to Brett about what he offers yet though. What length wing did you end up building for your Avid+? Since you used the speedwing rib did you space them like the speedwing or the HH wing?

Randy

Edited by SuberAvid

Share this post


Link to post
Share on other sites

Posted

hello,

the wing tip at trailing edge shows what i was wondering about ribs modification to get more lift on speedwing, what is airfoil of KF? and where can i have numbers to draw and specs of it?

manu. :beerchug:

Share this post


Link to post
Share on other sites

Posted

I realize this is an old post but I'm wondering if anything was ever done with installing hoerner style tips? I built and installed some on my current plane and the difference was so worth the 40 hours I spent building them. Now that I know what I'm doing (at least better) I'm sure my construction time would be about half that.

Share this post


Link to post
Share on other sites

Posted

I've got them on my Kitfoxes. Nothing new there. The Avids didn't use a bolt on tip, so you are a little limited unless you go custom.

Share this post


Link to post
Share on other sites

Posted

Have you flown your Kitfox with and without the tips? Just curious if you noted a big enough change to warrant the work to adapt something like that on an Avid. I don't mind doing the work to make it custom!

Share this post


Link to post
Share on other sites

Posted (edited)

I don't see much "work" - just leave off the end and put on Kitfox tips - either permanent or removable - I like Hoerner tips, and have them for mine - Otherwise, you could just leave flat ends on wings.

EDMO

Edited by Ed In Missouri

Share this post


Link to post
Share on other sites

Posted (edited)

My buddy has the round "Avid" or "Cub" style tips on his hybrid.  (He prefers the look of it.)  My plane is faster, but there is little if any difference in takeoff or climb.

 

With the speed and power to weight profile of these planes, I seriously doubt weather there will be any more than a marginal difference.

Edited by Av8r3400

Share this post


Link to post
Share on other sites

Posted

Guess we're back to the issue of where to put the VG's on the tips to disrupt the flow of the wingtip vortices then. I've seen the pictures on here, but does anyone know of where they are located?

Share this post


Link to post
Share on other sites

Posted

The Hoerner tips were tested and found to be more efficient at reducing drag when the trailing edge is more than 6 degrees farther out than the nose.

The Finch tips are supposed to be more efficient at shedding vortices if angled up a few degrees.  But they are eye-pokers!

The vertical winglets act to lengthen the wingspan and add to the aspect ratio, reducing drag.  

A more efficient winglet was tested which mimicked the end feathers of a bird's wing - I have photo, but no data on the design.

EDMO

Share this post


Link to post
Share on other sites

Posted

Ed was the bird type wing tip actually several extensions going out span wise? That's an interesting concept I hadn't considered.

Share this post


Link to post
Share on other sites

Posted (edited)

Yes, but the engineering is far beyond my feeble mind - I have an engineering design book that shows them, but they also had a wind tunnel to test them in.  Some of them are wild and complicated.

If anyone wants an engineering book that most people can understand - It is called "Design of the Aeroplane" by Darrol Stinton, a test pilot and engineer in England.  (May be out of print now?)  Lots of good design info.

His other book, "Anatomy of the Aeroplane" is practically useless for us, and I have it too.

EDMO

Edited by Ed In Missouri

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now