I still need float-rigging info

[Lynn Matteson]

Thanks VERY much for that info, Paul. Just to give you a bit of feedback, I had set my floats up exactly to the 6-foot centerline separation that you suggested, and because my floats are 24" wide, the max of 8 foot that you mention is adhered to. I went with the 6-foot centerline wheel separation that my Grove landing gear gave me, as that looked "about right for float separation." (solid engineering presumption on my part, eh?)

Next, I had rigged up a mock Kitfox lower longeron "frame" and had this spaced 18 inches above the float walkway. I had originally figured that I had to keep the overall height of the tail fin under 120" due to the height of my hangar door. Your dimensions will fit within this parameter. I'll just raise the lower longeron on my mockup. This mockup is just to give me an idea of what the struts and diagonals will look like and allow me start some of the cutting on those parts without having to actually ground the plane so soon. I wouldn't actually build to this mockup, I will just use it for getting the bottoms of the struts and diagonals cut to shape, leaving adequate length for the tops to be cut when the plane is actually hanging over the floats.

Lynn

[av8rps]

Thanks VERY much for that info, Paul. Just to give you a bit of feedback, I had set my floats up exactly to the 6-foot centerline separation that you suggested, and because my floats are 24" wide, the max of 8 foot that you mention is adhered to...

Lynn,

I had a computer crash (and a brain crash ) after a bunch of interruptions while trying to put this whole thing together for you. So please make sure to go back and read all that I just reposted. It will probably make more sense than the earlier gobbledy gook I wrote.

I like the idea of your rigging mock up. I'm not that smart, I just crawl around under the airplane while it hangs mid air from a chain while I cut struts and cables (see pic below and note wife's comment "Are you sure this is safe?)

Your 18 inch spacing between the fuselage and top of float would probably be ok because you aren't running a long prop.

But also remember that whatever throat angle you use will lower or raise the tail accordingly. And it's amazing what an inch or two off a strut can do to tail height. The original rigging I got with my used Aerocets were modified for a VW powered Kitfox , so it had a HUGE throat angle. After I figured out what I needed for struts and I got them installed the tail came up a about a foot and a half! I'm lucky I have a tall hangar...

(of course a guy can always build a cart or two to go under the nosewheels to keep the tail down when in the hangar)

[av8rps]

I put at the end of this post a random bunch of old photos I had saved of Kitfoxes with Zenair or Czech floats installed. I thought if you hadn't already seen them you might like to. As we all know when it comes to building things, sometimes a picture can be worth a thousand words...

(Incidentally, the blue, red, and white Kitfox IV on white Czech amphibs is a short wing Speedster version as I recall...FYI )

In addition, just below this post you should find a mechanical drawing of my Aerocet float details with dimensions. But more importantly it shows my full scale drawing of the fuselage attach brackets you will probably need for installing your floats on your Kitfox. You might still be able to buy those fittings from John or Deb at Kitfox? But if not you can hopefully make your own from the drawings on that sheet. I traced them full scale and then scanned them into digital, so I'm thinking if you print that page on an 8 1/2 x 11 piece of paper, you should probably end up with a full size template. And if not at least the fuselage attach fitting concept is there for you.

But if you do end up making your own, I would recommend making the fittings longer (per the hashed lines I added). That way if you need to you can adjust your float rigging up or down without having to buy all new (expensive) strut material.

Paul

[Lynn Matteson]

I put at the end of this post a random bunch of old photos I had saved of Kitfoxes with Zenair or Czech floats installed....Paul

Thanks for the updates, Paul. I haven't re-read the original posting (with edits) nor all of the latest, but just skimmed it enough to make a reply. The one thing about rigging that Zenair DOES make available are machined fittings that fit the Kitfox IV factory-welded brackets. I already have these fittings and all the strut and diagonal brace material, and of course the plane has the 4-on-each-side float/ski brackets. Yesterday morning, after thinking of how to make the rigging somewhat adjustable, I laid an aluminum bar across the pickup tubes on one of my floats...fore and aft...to check on the feasibility of making the throat adjustable. I leveled the float so this bar was reading "zero" on a digital level. Then I placed a 1/2" shim under one end of the bar....the dig. scale read 0.5 deg. Then I removed the 1/2" shim and used a 1.5" shim (2x4) and the reading was 1.5 degrees. Swapping the shims to the other end, one at a time, and the reading were the same. In short, as luck would have it, whatever the thickness of the shim is in inches, adjusts the reading a similar number of degrees. So if I were to use, say, a 1" shim under each of the four rigging blocks that bolt to the spreader bars, then set the plane-to-float (throat angle) angle at say, 4 degrees, fly it, and if an adjustment were necessary, I could remove the front 1" shims, and the throat would close up 1 degree to 3 degrees, or remove just the rear shims, and the throat angle would open to become 5 degrees. Or, if the plane flew well at the original setting, I could remove all four shims, and still be at the 4 degrees of the original setup. Now, is this what others have done to have some adjustability, or am I all wet (no pun intended) on this theory? Using shims judiciously under what Zenair calls the "pickup fitting" which is shaped like a pillow block and to which all the fittings are attached, raises or lowers the entire rigging package...struts, diagonals, x-wires, and airplane....at once, and no changing of the struts or diagonals is needed. So, in my thinking, I can easily change the throat angle, but it's the placemant of the step in regards to the C of G that would involve drastic changes of strut/diagonal tubing length if that original step/CG placement were not made right to begin with.
Your thoughts?

Lynn

[av8rps]

Lynn,

Typically people use extended float fittings at both ends (float and fuselage) so that you can move it up and down in the other bolt holes to adjust it wherever needed. But the way you are describing yours with using shims, I can't see why that wouldn't work just as well.

And yes, I agree it is much more difficult to be able to adjust the step location. I've seen people use a c-channel mounted upside down to the top of the float (usually attached to the area where the spreader bars are) so the struts could be moved to different bolt holes in the c-channel, allowing the float to be moved fore and aft by just moving the strut fittings in the bolt holes. If you can figure out a way to do that even temporarily until you are ok with how your airplane performs, that could save you a lot of time and frustration (and probably money because you won't need to cut up so much strut material). Once you know you are happy with how the floats perform, you can always make a permanent fitting for attachment.

Half the battle with installing floats is understanding what you are trying to actually accomplish. And from what I'm hearing from you, you are most definitely on the right track

Paul

[Lynn Matteson]

Lynn,

Typically people use extended float fittings at both ends (float and fuselage) so that you can move it up and down in the other bolt holes to adjust it wherever needed...

Thank, Paul....I hadn't thought of the C-channel idea for fore-to-aft placement, but that's a good idea. I might even be able to incorporate the shimming-for-throat-angle method into the C-channel idea, and have a more or less universal temporary flyable mount. This is getting exciting!

Lynn

[Lynn Matteson]

Paul-
I have a question regarding that blue, red, and white Kitfox IV....it is the only one of the planes pictured that has the diagonal brace starting from the rear fuselage bracket and going forward and down. I have been told that the diagonal brace (on float-equipped planes)will start at the fuselage directly above where the original landing gear was mounted...or near where the original main wheel was. So, if that is true, that would make all the other pictures of Kitfoxes (that you posted) appear to have been originally tailwheel planes, and the blue, red, and white one would have been a tricycle gear plane originally? Just curious...

Lynn

[av8rps]

Lynn,

I don't think that installation has anything to do with being a taildragger or a trike gear setup.

I'm guessing the reason for that is because those floats have the spreader bars closer together than most floats. A lot of builders as well as manufacturers don't really know what they are doing when putting floats together, so they put spreader bars too far back, too far forward, too close together, etc, etc.. if you compare the blue airplane to the others, you will notice there is a lot more float forward of the the front speader bar, besides the rear spreader attach being moved forward causing that rear strut to be more vertical. So something is different with those floats than most. At one point I do know the Czech's were building a 1250 that moved the step 6 or 8 inches back to offer more forward buoyancy for the Rans S7 guys, and I know the first sets did not have the spreader bars moved ahead to match the new step location. So I'm guessing those might be a set of those floats?

The Czechs did the same thing on their first set of their CZ 1300 amphibs. They made them initially for a specific airplane that had really closely spaced attach fittings that also were way far forward. They essentially couldn't give those floats away for install on other airplanes until Ken from Harbor sport aviation modified them and redesigned the landing gear so they could easily be mounted and used on other airplanes like the Rans, Kitfox, Highlander, etc. Ironically, after the spreaders and gear were fixed, they became one of the nicest floats out there.

[av8rps]

Hey Lynn, are you out there?

I never heard back to see how your float installation turned out? I figured by now (knowing how commited you were to making a Jab powered Speedster work on floats) that you must have it all figured out or you would have recontacted me.

Hopefully you are having so much fun on your floats that you didn't have time to write but now that float season is ending I'm hoping you may have some time to let us know your results.

Paul

[DesertFox4]

Lynn hasn't logged in since 2-1-15. Hope he is ok.