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Larry,

     He is trying to match the Zero degrees of wing incidence that the later Kitfoxes have with the Riblett wing.  I'm not convinced that it is necessary yet - I just read a chapter in my aircraft design book, and it says that most planes have about a positive 3 degrees of incidence???

     I am going to chew on this bit of jerky a while longer before making up my mind on the change of incidence - Thinking right now that with my heavy Soob and nosegear that maybe I need a little more up-force on the nose, so why lessen it by going to zero incidence - I think the original Avid/Fox incidence might just be OK with the new wings.

EDMO

I have to ask, what is the design goal of raising the front carry through tube?

Larry, thanks for the details on Dave's plane. I wish I could have talked to him. I considered leaving off the wing fold capability, but I'm kind of convinced I should keep it now. I'm still thinking through my options. Right  now I'm still leaning toward raising the front tube. It seems like it would solve my problems, and not create any new ones (at least not many). It will probably cause issues with the struts, but they are an issue I have to deal with already.

Here is my current  plan in a nut shell:

1. Remove some of the front structure (those front uprights need to be extended).

2. Make some particle board jigs using Solidworks to get the new structure true and square (also note the clamp on collars that would have temp tubes welded to them to hold the rear tube in place during welding).

3. Here is what I would hope to end up with.

4. Another view with all of the tubes in.

Luke - I wish you could have met Dave, he was only at OSH for Tuesday.  He's a wealth of practical knowledge about aircraft building.

He chose to completely convert his Avid C.  He retrofitted the Kitfox IV control mixer system along with the airfoil and symmetrical flapperons.  He didn't set his up to fold so that was not an issue for him, but the incidence and other wing settings were not changed either.  He built the wings right from the Kitfox IV builders instructions for washout and dihedral.

He did not raise the overhead, with all of the complications associated with that, but chose instead to lower and extend the footwell in order to make the cabin human sized.  

IMO, raising and changing the overhead is opening a pandora's box of issues that will effect the handling and flying characteristics of a great, proven aircraft design.

I don't really know a lot about the airfoil characteristics Ed. I'm sure what you said is correct. I didn't really want to take the time to dig into all that. I figured if I imitate the KF configuration as far as angle of attack and HS angle, it should get me pretty close.

I've decided to go with the second option you mentioned, and raise the front spar carry through tube. The only problem is that when you tilt the airfoil up more in the front, it makes the flaperon clearance worse for folding. To counteract that, I'm going to change the way the rear spar attaches to the rear carry through tube to raise the rear spar as high as I can. It looks like that will give my flaperons about 1/2" of clearance over the turtle deck.

While I'm  at it, I'm going to change the front diagonal brace tubes that go behind the windshield. Because raising the front tube would make those brace tubes even more upright (looking from the side) than they already were, I'm going to change to the Kitfox style of "X" brace. Because they go right to the top motor mount bolts, it will give them quite a bit more "rake". I'll post some pictures of my computer models when I get a chance.

I see someone has a 3 blade new  IVO 72" left hand with opening bid of $450 on ebay as well.  They are way more than that now.  I got a RH one about 4 years ago for $458 from ACS and the price  went up right after I got it. It's still hanging on the wall but maybe I'll get a chance to use it some day soon.  Jim Chuk

Mine is about 1"+ higher on the rear spar mount, like yours - Since I have now modified my ribs to the Riblett type, I was wondering if it was worth the trouble to cut and reweld the top - 1"+ on 2 feet chord would give roughly 6" from cabin to tail, and I have increased the height of my Rudder about 10 inches.

     Since the Riblett airfoil has less downforce on the nose than the Eppler ribs, the incidence could be changed as you stated to give a higher tail position - but it might be easier to raise the front mount rather than to lower the rear mount and have problems with flaperon clearances.  You could put a filler strip at the top of the windshield.

     You need to make all the changes on the wing mounting before you put the threaded inserts in the top of the struts, so the struts are the right length to fit.  I made my inserts with 7/16 - 20 threads to fit my rod ends which are stronger than the 5/16 diameter originals.

Luke - Did you give the incidence of your horizontal stabilizer of the Avid?

EDMO

Yeah, I've pretty much decided I just need to bite the bullet and make some pretty big changes to make it work. I will actually be solving a few problems at once, but it will add a bit more time to the project.

I measured the incidence on two late model kitfoxes (5 or 6 can't remember). They both have the same airfoil that I'm using, and both had the airfoil at about 0° of incidence. It's probably not really 0° (I know angle of attack is usually measured through the cord line). The way I measured should serve my purposes though. I just put a straight edge on the bottom of the wing (on the first rib next to the fuselage), and measured the angle. I compared that to the bottom of the door opening. They were almost exactly the same angle. I used a very sensitive digital level to do this.

Both planes also have the movable HS, and I asked the owners to set the trim for cruise. When I measured the angle it was about 0° also. That's pretty close to where my Avid HS is. I figure I'll be happier in the end if I get this right. I'm not very tall, so I don't want to sacrifice any visibility over the nose.

Whoops!  I am talking and thinking 4-strokes again!  I thought a 912, especially the 100, could swing a 70 inch prop?

EDMO

Luke,

    The Kitfox incidence was changed to make the tail higher in flight - You can cut and adjust your spar attach points to make it match the Kitfox as long as your struts fit.    There seems to be a lot of engineering done to change the wings, but anything is possible - just more headaches to go along with it.  I believe the rear spar on the Kitfox 4 wings sets differently in the rib - this has to also be considered.

    such is the nature of "true experimental" building.

Keep us posted.

EDMO

Well, when I bought my Avid MKIV, the wings were built wrong, but I figured  for the price I paid, I could afford to buy some Kitfox parts and build KF wings to fit it. I've found that there are several issues that need to be addressed to make this work though.

The first issues were pretty easy to deal with:

Lift strut attachment - The KF spar brackets are all made to accept rod end bearings instead of the wider end of the strut tubing that the Avid has. I figured that the easiest solution is to just weld threaded fittings into the ends of the struts.

Flaperon location - Because the flaperons hang on the KF wings differently, they end up in a different spot relative to the support bearing on the fuselage. No problem, just modify the support bearing and linkages as needed.

Then the bigger issues:

Wing incidence and wing folding - Because of the differences in the KF airfoil and the Avid, the mounting points at the fuselage position the spars differently between the two planes. On the avid, the front spar carry through is about 1.4" lower than the rear (using the lower longeron as a reference for level). You could adjust the angle quite a bit by modifying the height of the tubes that the spar pins go through. Even if you do that though, the best I can get is about 1.7° more negative than what the KF has. Also, it appears that the flaperons will just barely clear the turtle deck when folding the wings. You could adjust it to get more clearance for the flaperons to be safe, but this would make the incidence angle even worse.

Has anyone dealt with this before? Larry, I know you had a friend that did this. Any info on what he did?

I'm thinking the only way to do this right is some pretty extensive cutting and welding...

Thanks,

Luke D.

ChrisB,

      I am trying to catch up with you on the nose gear.  Here is a photo I took today of my idea of a castoring, 600x6 nose wheel - I could always convert it to be steerable if I am not happy with it.

- I don't have the bushings installed, and need to hang about 250 pounds of concrete blocks on the nose to know where to cut the pivot tube and spring - or get different spring.  Plane is now sitting on 3 legs - I have about 51 inches between main and nose wheel axles - If I have to turn my offset Grove main gear around for balance I will have more distance to nose gear.  When I get my wing struts tacked, the plane goes back to the welder to add side braces from nose outer pivot tube to outside lower corners under edge of firewall, sort of like Tri-Pacer.

Added:  Forgot that later I will add the nosewheel fender off of a Tri-Pacer, to keep mud and dirt off of plane and maybe belly radiator.   The fork I am using was sold as "homemade", but looks more like a 200 series Cessna.

It is not a Tri-Pacer fork - I have a Tri-Pacer gear and mount or two stored away.

Do you think that if I tell the inspector that the modified streamline tubing strut and mounting are mountain bike frame parts I got out of the trash dumpster, that he will count it as "homemade"? 

It sure beats the Kitfox price of $1500 by a lot.

EdMO

Ron,

     now I am curious about a cross tube at the bottom of the strut - can you post a photo?  Does it really need a tube there?

Thanks,

EDMO

I have only found a little info in Wicks catalog on the white Superflight Primer coat for fabric - It says it is epoxy and the same material as the fabric, and "encapsulates" the threads of the fabric - BUT it says nothing about UV protection.    The FAA approved the process for certified planes. 

I still plan to use the Stewarts glue, but don't like their primer because it is not gas proof, so considering other primers / paints.

Can anyone tell me more about Superflight Primer?

Thanks,

EDMO

Ed, the cross tubes at the top and bottom of the struts are 1/2" tubing.

See ya,

Ron

Ed,

My Magnum struts are 1" in diameter. They also have the wooden speed fairings glued to them, I'm sure that adds some strength too.

Ron

I had a neighbor that was a truck driver and he thought Mystik was the only grease to use! He said he was driving and got caught in some flood waters on the road that came up to his axles at times. When he got home he pulled all of the wheels and took a look. Not only was the Mystik grease still there but it repelled the water too! Ever since he told me that I grease my Jeeps and my tractor (before I sold it) with Mystik.

So Doug I think you are spot on!

Ron

FYI - There is a 66" prop with (120 ?) hours listed EBAY in AVIATION PARTS PROPELLERS for a 912 for $795 - Owner says he paid $1100 for it - No Nickel edges on tapered blades.

Is this a little short for a 912?  Maybe OK blades for a 582/503?

EDMO

Thanks - The big sign says "BENDIX" - I think they were in Ohio too?

EDMO

Probably the Cleveland Air Races.

Looks like a Packard to me, too...

Thx for all the reply's

             Marv

Ed, That is where the brace is meant to be bolted, and where the float N strut would bolt to on the I and II.

Robert on my KF 1 & 2 there is an angle sticking down under the fuselage strut attach fitting - I could drill a hole in it and bolt the brace to it.

EDMO

959- if you have one of the older airframes it will not have the tab welded on the lower end to bolt the front brace to. If this is he case you can have the tube go below the lift strut attach point and come back up just inside of the lift strut attach point and have a small tube welded on to the brace that points fore and aft that a bolt can go through. Hope this makes since. I will be down to the airport in the next couple days and try to get a picture of what I'm talking about. hopefully this drawing will make some since in the meantime  

Sorry for the camera glare - Can anyone identify the 1932 Car?  Packard V8?

Also guessing about "Reno"  The car has Ohio plates on it.  This was a little before I started flying!

Maybe this should be labeled "Cleveland Air Races 1932"?

EDMO