Sign in to follow this  
Followers 0

looking for a speedwing rib


12 posts in this topic

Posted

I am looking building a set of speed wings for my Avid Mk IV s/n 1492.  In 94 I built my heavy hauler wings with the fiberglass tanks that came apart and contaminated my fuel, then I went to the poly tanks but there is a lot of unuseable fuel etc. etc.

Does anybody have a speedwing rib I can trace or can somebody do a full wing trace?  My plan was to draw the airfoil on CAD and waterjet cut the rib centers, make a wing jig and glue up the cap strips.

Anybody help?

 

Tim Morris

tjmorris@mossvale.com

 

Share this post


Link to post
Share on other sites

Posted (edited)

Why not use Kitfox 4 or later ribs?  Much better than Speedwing or undercambered ribs in most opinions.  There is a drawing in Files and Forms or Kitfox IV ribs that you can enlarge and copy to size with the yardstick pictured, making sure that the enlargement is proper size to fit your spars.  I made modified KF4 ribs from my undercambered ribs with tails to fit my old flaperons.  Jim Chuk, "1AVIDFLYER" or Doug Holly "A+" might be able to help you.  Doug used a transitional Wing with both undercambered and speedwing ribs on one bird.  I have a KF4 rib too, if Akflyer don't want it, OR, Kitfox will maybe sell you one rib?   EDMO

Edited by EDMO

Share this post


Link to post
Share on other sites

Posted

I second what ED says copy the kitfox 4 rib. If you are making them from scratch you could easily build them with a wood flaperon hanger off the back of the rib. Unless you want to go the extra mile and and make different hangers as well either way use the ribs that work.

Share this post


Link to post
Share on other sites

Posted

Might as well use a Kitfox mixer and flapperons and you'd really have something...

Share this post


Link to post
Share on other sites

Posted

Might as well use a Kitfox mixer and flapperons and you'd really have something...

Much cheaper to just switch Avid controls to F7A modifications.   Still, Kitfox 4 ribs would be better, IMO.  EDMO

Share this post


Link to post
Share on other sites

Posted

I wonder how the Kitfox 4 flaperon hinge location verses the Avid Flyer (or pre Kitfox 4 models) would line up.  Might have to change the location of the flaperon bearing on the side of the turtle deck??? Not sure, just wondering.  Also, a Kitfox 4 does not use long ribtails to hang the flaperons, but aluminum brackets riveted to the rib.  The Kitfox 4 is probably a better airfoil though.  Just might run into other problems you didn't think of to start with.    JImChuk

Share this post


Link to post
Share on other sites

Posted (edited)

I wonder why he don't use his original ribs?  Were they undercambered?  If so, then they could be easily modified like the KF4 bottoms the way I did mine using original ribtails.  If he has Speedwing tanks, then modify the Speedwing rib bottoms like KF4 or the modified KF4 ribs should also work with them.  Being "creative" is my word for building cheaper and easier!   EDMO

Edited by EDMO

Share this post


Link to post
Share on other sites

Posted

EDMO,

Modifying the originals is not off the table by any means.  I am approaching this with caution because airfoils can be tricky. (i.e. pitching moment, center of lift, controllability).  There is plenty of experience out there with the existing speedwing and KF airfoils.  I was not aware of the files in the forms section.  They were of great help.

So my question is how did the airplane fly with the undercamber heavy hauler rib modified with to mimick the Riblett with the flatter slightly curved bottom and leading edge extension?

Did it change the pitch?  Stall speeds ok and controllability ok?

Thanks

Tim

Share this post


Link to post
Share on other sites

Posted (edited)

EDMO,

Modifying the originals is not off the table by any means.  I am approaching this with caution because airfoils can be tricky. (i.e. pitching moment, center of lift, controllability).  There is plenty of experience out there with the existing speedwing and KF airfoils.  I was not aware of the files in the forms section.  They were of great help.

So my question is how did the airplane fly with the undercamber heavy hauler rib modified with to mimick the Riblett with the flatter slightly curved bottom and leading edge extension?

Did it change the pitch?  Stall speeds ok and controllability ok?

Thanks

Tim

Tim,  My plane has not flown - unable to finish because of illness.  Kitfox 4 ribs fly better than any of the others according to users - About same TO & LDG and lots faster cruise reported.  They don't hit 90 mph wall like undercambered, caused by a bubble forming there as described in the letter from Harry Riblett, and better TO, LDG & cruise than Speedwing ribs.  One KF4 pilot posted that if landing speeds are same as undercambered the KF4 will float more and not drop in as fast.  If you follow the KF4 rib pattern, the modified ribs should fly about the same.   EDMO

Edited by EDMO

Share this post


Link to post
Share on other sites

Posted (edited)

I can trace a new Avid speed rib if you decide to pursue. If you construct a new Avid speed wing you will also need to make the special transitional root ribs that mate the speed rib wing profile to your existing undercamber HH/STOL rib profile butt ribs. If you add (2) 5gal. Ridge Runner poly wing tanks to the wing (they seem to be the easiest poly tanks to source these days), I suggest you also use the special transitional ribs to replace rib #3 (if using 18" o.c. speed wing specs) or rib #4 (if using 12" o.c. HH wing specs) outboard of the tanks, along with another in between the two tanks. This will provide structural strength and a little more cavity space between top/bottom fabric for the tanks and associated supports. I can trace one of these for you as well. 

That said, if I were building new wings from scratch, I would personally use the KF 4-7 rib profile and flaperons. You will need to modify the Avid mixer and flaperon push/pull tubes (or remove and replace it with the KF 4-7 control system) as well. However, having owned and flown both KF3 (very, very similar to the Avid under camber wing) and KF4 models, there is a night and day difference and it would be well worth the added effort IMHO.

[edit] Ed- I can confirm the sink rate of my KF4 increased dramatically below 60mph, but it also had a greater tendency to float than the KF3. Go figure.

Edited by dholly
2 people like this

Share this post


Link to post
Share on other sites

Posted

I have access to ribs as well. What is your mission with this plane? 

EF74F018-9F6A-43C7-A7BB-3EF5F9DEEE87.jpeg

Share this post


Link to post
Share on other sites

Posted

I have access to ribs as well. What is your mission with this plane? 

EF74F018-9F6A-43C7-A7BB-3EF5F9DEEE87.jpeg

Adding too, that Kitfox is now selling Ethenol Resistant Tanks for both undercambered and KF4 rib patterns.  EDMO

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
Sign in to follow this  
Followers 0