lukemn

Ditto for both questions!

I'm looking to sell my avid amphib project (I'm open to offers & trades)  it will come with all associated parts and pieces I've collected & made for it.  Some of the highlights are a low time 80hp 912 with mount and exhaust that is fit to the amphib airframe, new IVO IFA 3 blade prop & new in box from avid flaparons.  The airframe is completely apart but in good shape the wings are in need of total overhaul straight but all the wood pieces should be replaced. A large amount of the "grunt" work is done with this project and the hard to find parts are included. Feel free to contact me with whatever questions or offers you have as I receive questions I'll update this post.

I seem to have forgotten where you are located.  Maybe some others would like to know?  EDMO

 I recall reading correspondence between Riblett and an avid owner, where Riblett discussed the modifications that might be made to the existing ribs, by applying material to modify the existing ribs.  Seems as though there was a flattening of the bottom, and a change and extension to the leading profile..?    I'm 99% certain that the "newer" kitfox ribs were the riblett design. The twist in the elevator on my cat is, as I recall, quite substantial.  I'm running a Hirth F30 swinging a three-blade warp drive prop, and I can really tell when I hit the drag curve-  more power==more noise, and not much else.  I can also tell when I'm even a half degree out of pitch on the prop- getting over the hump can get exciting. I can take off the water at 1250 lbs with my current setup.

I did use the plastic leading edges on my cat to reduce drag a bit.  I also have a pipe wall flange on the copilot side floor, pretty far forward. When I'm alone, I use a short pipe nipple and cap to secure a 25 pound barbell weight for ballast.  That way I can remove it when I'm flying pax, and they can sit up front.  I sat in the back once, and would never force anyone back there!  I also registered as a two-place, and placarded as such.  I'm 6' and 195, and even the front pax seat is cramped for me. And, since I fly sport...

I  changed to the full-lotus sponsons.  They saved me around 8 pounds, and I *think* they're a bit more aerodynamic.  I haven't finalized the mounts yet, as tufting indicated that they're still a bit high in the front.  I used a 1" diameter tube for the attach- I split it to form tabs for the sponson attach points, and stuffed a small "superball" in the ends. The pic earlier in this thread is the one I used as a template, and I've already extended about 2 inches down in the front, with probably another inch to go.  Here's a picture of that::

And yes, I still have fairing to do-  in this pic you can see an experiment, which I'm not quite happy with yet- monokote. .  I simply glued a paint stir stick to the back edge of the sponson support, and wrapped monokote around the lot and shrank it tight., just to see if it would hold up.  Thus far, it has, and I may do the rest of the unfaired tubes in the same manner.  I'd also used monokote to cover the strut fairings-  It was my first attempt using it, and I highly recommend buying a heat gun that has multiple temperature settings if you go that route, as quite a bit of shrinking needs to take place, and an iron just didn't work for me.  You might say working with monokote was a whole new wrinkle?  And- I struggled with where to and how to mount the transponder antenna-  this seems to work ok for me, and is easily serviced!

One more thing I did, and would probably not do again, is use the optional leading edge- a strip of thin material to better form the wing profile.  The manual called out aluminum, but to avoid oil-canning, I used plywood- it still oil-canned *after* I'd covered and rib-stictched, and done the second shrink.  I had to add additional finger ribs to strengthen the profile.  I *really* hated cutting off all that fabric, and in retrospect, while I probably gained lift, I probably increased drag at the same time.   If you fair out ( using epoxy and microballoons- slather the stuff on, then stretch saranwrap over it.  you can work out bubbles and voids with  your fingers (and a pin)  if need be, and it greatly reduces the sanding required.  This picture shows- the leading edge strip, the attached plastic leading edge and fairing in the gas tank (using saran wrap) before the pin was used to pop those bubbles.

Jack

Austin, TX

 

 

Luke and Don   Thought you might be interested in a project Dean W. Is doing now, he is modifying the original (proof of concept wheels only) Catilena. The original owner put over 2000 hrs on it with a 532, now the current owner wants to make it into an amfib. As well as changing engines, 85 cont. increasing GW, adding 12 inches on each side of the hull etc. Today it was upside down but I took some pictures anyway, you can see where he moved the dorsal tube over (at the "4") and on back,added a couple of vertical tubes, heated the vertical fin attach points to release stress etc. Anyway Dean said if he could be of any help, call him. Usually lunch time 12:20-1:00 pacific will catch him. 509-758-3269.

While you’re leveling off at cruise altitude, the forces of discharge air and P-factor still exist, but they are diminished because of reduced power. Here, the airplane designer  (which is you now) provides a corrective force: the left wing or right wing is rigged so that it develops slightly more lift at cruise speed than the other wing, offsetting the left or right-turning tendency. ( this can be adjusted with the left strut assembly) Now with an extreme condition you can add another strut assembly to the right side. The vertical fin is also slightly offset, so that at cruise speeds the push of discharge air on the left side or right side of the tail surfaces is corrected for. ( there are four aprox 40' angled supports for the stabilizer main tube that should be reversed or equaled to set correct fin angle which can be varied according to various drag problems that are unknown( exhaust, radiator location,etc.) This is why I went with straight for mine. These are just modifications to do flight tests and adjustments will likely have to be made after a few flight and taxi tests. Even a few static runup tests will show some adjustments needed to balance the aircraft.      These corrections are exactly effective at only one cruising airspeed: go faster or slower and aileron or rudder trim will be required. Engine adjustment may also be necessary so now is the time to add these features. Now to say that I know what I am doing is wrong and do not take anything I say as right. That is why I am here, To check what I have learned with others.

You have all got me to scratching my head and fingering out the P-factor:  I would think it would be less for a prop in mid-ship than on the nose, OR, would it take more rudder power to counteract since the prop is closer to the tail?  The right-turning Soob is just like all the old Conts and Lycs - right prop, right rudder.   The left-turners get left pedal.  A right-turner backward is really a left-turner, but looks like it will put more circular air on the VS and HS to bank left, but pressure under each wing should be the same, but the P-factor of the prop should still be right  .....Sooooo     Guess you just keep it straight with whatever pedal you need to use!    EDMO

Throw in the inverted "flying tail"  and I'm approaching being completly lost.  The elevator has some offset left to right that I'm guessing will need to be adjusted to deal with the reversed prop wash so it will trim out correctly. I need to move and reweld in the dorsal tube and that gets things in the correct places. (I think?) Some where on the site there's a link to a write up about optimizing the early avid tail desgine hopefuly I can find it againe just to help with getting the basics right.

Luke,  According to Kitfox, one side of the elevator trailing edge is fixed at 1/2" higher than the other side to prevent flutter - I cant remember which side is higher, but it probably don't make much difference.   EDMO

You have all got me to scratching my head and fingering out the P-factor:  I would think it would be less for a prop in mid-ship than on the nose, OR, would it take more rudder power to counteract since the prop is closer to the tail?  The right-turning Soob is just like all the old Conts and Lycs - right prop, right rudder.   The left-turners get left pedal.  A right-turner backward is really a left-turner, but looks like it will put more circular air on the VS and HS to bank left, but pressure under each wing should be the same, but the P-factor of the prop should still be right  .....Sooooo     Guess you just keep it straight with whatever pedal you need to use!    EDMO

I don't have an adjustable stabilizer on my craft. I was referring to The Lil Buzzard that has one on later models. They wanted an aircraft design that could be built for any engine. I wish I had taken the time and money to design one for a mine. At the time of recover I knew that I was going to change engines. I used the old fashioned method of grasping the tail and bending it forcibly to take out small amounts of deflection. The amphibs do not have as large of need for perfect vertical stabilizer as they are a pusher configuration and don't have the same P-factor as a tractor. I can't get to my aircraft at this time to figure out what tubes they had to lengthen and shorten but it was just a few of the ones that held the center tube going up to the main center tube that shapes the rudder and  stabilizer. I am already covered so it is difficult to see anything. A little adjustment did a lot. Now if you can get a picture on here of straight down to the rear from the center of the plane showing the tubes at the root.

Don't get to overly concerned. it is not very difficult at all to change the tail. I did not do it myself but it cost just a hundred dollars. I  watched the professional builder set it up and it looked very easy. Much easier than an engine mount. Run a string down the center line and extend or shorten tubes to get degree of incidence you want. Mine is straight now. I may change a little one way or another after first test flight if trim tab won;t be enough. This guy was the builder and designer for The Little Buzzard and they designed in  an adjustable Vertical stabilizer to fine tune handling. I just wanted everyone to remember the whole aircraft works as a unit when making modifications. Safety is control.

Just out of curisioty is the tail / vertical on other Avid or Kitfox modles diffrent 582 vs. 912?

I don't know about others, but I can tell you that my model C with the 582 has a very obvious amount of "left rudder" build in to the vertical fin. Where the forward tube of the fin intersects the cross tube it's definitely not in the middle. On my mark 4 I think it's pretty much neutral, but I could be remembering wrong on that one. I haven't looked at that one in a while.

Hello, just found this forum and I have an Avid Catalina conversion and now reconverting to subaru engine.

Don

If you really wanted drooped tips I have a set of brand new ones here still i two pieces so you could make them fit any profile $75 bucks and shipping and there yours.

 

The rib profile is a little different but you could make it work.  If I was to do I would just put tip plates on the end rib that were flat plates sticking up about 2" all the way around the rib. 

 

Sounds like a great idea sort of like the just aircraft wing tips.  So since I'm going to build all new ribs what profile undercamber? / speed? / other? For the little flying boat. 

If you are going to build all new ribs, I would be really tempted to go with the KF IV airfoil..

If you are going with KF4 airfoil, the drooped tips may not fit - So if you are going to use flat plates on the tips, I wont bother to dig out my tips for photos.   Let me know if otherwise.

EDMO

The rib profile is a little different but you could make it work.  If I was to do I would just put tip plates on the end rib that were flat plates sticking up about 2" all the way around the rib.