I still need float-rigging info

[Lynn Matteson]

The mirrors have been suggested, but when you get them mounted far enough out that they can be seen, most of them....wide angle...are pretty much useless in trying to determine whether the wheel is really all the way down. My over-center indicator won't indicate until the mechanism is over center and the wheel is locked in place. With a mirror system, the wheel shows up so small that it is impossible to tell if it's REALLY all the way down or not. On the Republic Seabee that we have been working on...ahem, Oshkosh Seaplane Grand Champion, 2014, Sport Aviation, Oct.2014, p.82, thank you very much... the mirror for the tailwheel is out on the tip float, and when you try to see if the tailwheel is down, it is SO small as to be useless. He has a light that indicates position, and the mirror is only to verify.
When I came up with the mechanical indicators, it was, in my mind, the easiest solution that was pretty much foolproof, and didn't involve lights, wires, etc.

Now to fixing the Oshkosh damage...

I left Oshkosh two days after getting there...my usuall stay...and flew home
to fix the floats.

After it slid on the belly of the right-side float, there was grinding damage to the keel for about 13" but very little damage to the skin...only about 2" of the skin was ground away. I made an overlapping scarf-type repair to the keel, and overlapped the skin and the step bulkhead with new material.
There was room to reach inside the float to buck rivets, because I had built the floats with pump-out openings in the walkways. I had cut six 3.5" openings into the walkways of each float and installed pumpout cups in the areas of the separate compartments. But I felt more comfortable being able to get both arms inside, so I cut an additional 3.5" x 6" opening into the walkway, and later added a flange and a hinged access cover. Maybe I'll line that compartment with styrofoam and be able to carry ice and beer, eh?

I had taken the floats off the plane to repair the damage, and had the plane flyable the next day after returning fron Osh. Brian called me and I told him I had the floats off and was flying the plane, and he suggested that I come back up to Osh..."you'd probably be the first guy who came in on floats, left and returned to Osh on wheels" I doubted that and opted to not go through the effort...if I had been assured of setting some kind of Guinness Record, I probably would have though.

Anyway, got the damage all fixed, and reinstalled the floats 4 weeks later. It was during this time that I devised the main wheel position indicators, built them and had them in place when the floats went back on. It was also during this time that Brian suggested that the step needed to go further back in relation to the plane. That would have involved making new struts and I was reluctant to just start making new struts, cutting the longer ones down, making new ones, etc., on the notion that this would help the plane off the water. Instead, I decided to build a new set of brackets to allow the plane to move forward...floats back...and these would allow for a movement of 2.75", and if the brackets were flip-flopped, another 2.75" in the same direction. It took almost another 4 weeks of designing and building and installing to get these in place, and in the meantime, I got a few more hours training in the Cub on floats.

While training in the Cub, Brian would have me call out all the moves that I was doing, but as they related to flying the Kitfox. It would go something like: "Kitfox downwind for lake landing....carb heat on...water rudders up...engine speed set...mixture set (Rotec throttle body)...operating gear switch (actually pretending to reach for the switch)...pause...pressure building....pressure maxed out...left float wheels indicate up, right float wheels both up...configured for water landing...."

We would do this time after time, landing on the water, having read the wind direction, and landing accordingly. He would have me do high-speed taxiing, which was ok, but I was not so comfortable doing high-speed turns on the step...it just didn't feel right to me. Also, the Cub tach is a counterclockwise rotation for increasing rpms, and that was WAY different than the digital tach that I ws used to seeing in the 'fox...GRT EIS. The carb heat is located where I couldn't see it, so it was "out of sight, out of mind", as well as the location of the water rudder pull-up handle. All of these little things have a way of frustrating this 78-(79 by the time I get this documented) year-old brain. Along with the little details of flying the Cub dual was the problem of getting the plane into the water and getting ready for a lesson. Brian has a small pond in his backyard which is long enough for the Cub to take off one-up. But because it is a straight-float plane, he has to fly it to a local lake, I drive the car there, wade out, get in, get an hour's worth of work in or so,(about all the stress this old-timer can handle) wade back to the car, while Brian takes the plane home. We then back the tractor and trailer into the water, load the plane aboard, and put the combo into the hangar. Because I don't like to be a burden on others, all this effort to get such short flying time in wears on me....frustrating.

By now, I had the floats moved back the 2.75" and ready for the next lesson. It is amazing how much different it is to get training in ones' own plane, or in any amphib for that matter. I called Brian to meet me at the local turf airport...3NP, Napoleon, MI. He climbs aboard, we lift off the ground...feet are dry, thank you...we make a few landing and takeoffs at a local lake, and he says "It didn't help....move it back to where it was." Thank God I hadn't cut up a bunch of strut material only to have the move negated! In retrospect, whether it was working with strut material or chunks of aluminum, it was a lot of work for naught.

A day later I had the adapter brackets removed, the floats back to where they were originally, and flying again. I still wasn't cleared to land on water, but at least we had determined that the step-to-airplane position was more or less correct. Three days later, I made a decision while flying that would require the removal of the floats and a BUNCH more work than the earlier keel damage...stay tuned.

Lynn

[Lynn Matteson]

Paul-
I should point out that the floats were originally set up with the step at 5" behind the c-of-g, so the moving back of the floats had it to about 7 3/4 inches or so.

Lynn

[av8rps]

Paul-
I should point out that the floats were originally set up with the step at 5" behind the c-of-g, so the moving back of the floats had it to about 7 3/4 inches or so.

Lynn

I'm thinking if you stop posting the rest of the story here on Teamkitfox, that maybe I can work a publishing deal with you for the book rights? Then all those in suspense will HAVE TO buy the book to know the end of the story...

Yeah, I was surprised that 5 inches didn't work originally. A really good test for identifying if you have the step in the best location is to step taxi at about 35 to 45 mph to see how stable it is and if it will easily porpoise , or if it will fall off the step. Properly set as on my Model 4 you can hold full forward elevator at 35 mph and only develop a mild, very gentle porpoise that is easily stopped by reducing the down elevator just a bit. So I'm glad to know the original number wasn't way off. But I guess I wasn't sure what your instructor meant about the rear of the float being snatched down on landing?

Aw hell with it....finish your story here. We can get together later to write a book (once you have yours working like they should). We'll call it "How to fly floats". Oh that's right, J. Frey has already written that one. Maybe a bit more specific like "How to fly floats, with a Kitfox attached".

[Lynn Matteson]

Or "Flying floats with a lack of power and too many people aboard" ?

Now the big one...

Three days after I had set the plane back to its' original location relative to the floats, and flying it off the ground only, I made a spur of the moment decision to fly to Coldwater (KOEB) airport for lunch with 4 other planes. I was the last one to get there, and I had heard all the others calling for landing on 07. The wind was 150 at about 14 knots, as I recall. That made for an 80 degree crosswind landing if you took 07, or a 10 degree slight headwind if I took 16, which is turf, but crosses both 7-25 and 4-22. Thinking I'd be better off dealing with the turf-to-hard stuff transition than the 80 degree crosswing, I opted for the 16 turf runway. Making sure the wheels were down and locked, I called for the landing and eased it down, cruising over 7-25, and touching down just after that runway, and getting on the brakes hoping to get slowed before I crossed 4-22. Well, I didn't, and the transition was not as smooth as I would've liked. The plane bounced a bit, crossed 4-22 and I got slowed down and made the turn-around and taxied back to the restaurant, which is near 7-25 mid-field. Had a nice lunch of French Onion soup, swapped lies with the rest of the gang, told them of my decision process that had me coming in like I did, posed with them for pictures by my plane, and we all headed out. By this time, the wind had shifted to better favor an 07 midfield departure, and off we went. I retracted the wheels, everything seemed ok, and I flew home. Got home, called out...to myself...all the usual landing tasks, wheels down especially, and landed without incident. Taxied to the hangar, pushed it back inside and was feeling pretty smug until I noticed that the right front wheel was sitting kinda offset. The front fork had a couple of about 10 degree bends in it. It is made of two 3/16" aluminum plates, parallel to each other, but now bent like a jog in the road. The fork would still retract, but it was offset, and would require replaceing. Then I looked further into the mountings, and saw that the upper part of the bulkhead was ripped right at the flange where it was riveted to the outer skin. There are two plates that are supposed to be braces, but they both broke off during the landing, one was missing, and the other was hanging by a thread, I easily pulled it off. The welds were very poorly made (factory), not penetrating nearly enough for the job. When I get a replacement part, you can bet that I'll do a much better job of making those welds secure!

So now I've removed the floats, I'm back flying on wheels, and I have the one float home in my shop and I'm currently designing a suspension system for the front of these floats which will absorb any future landings like the one I have described. Harking back to what my CFI told me: "Make all landings on pavement whenever you have a choice, and if your destination is turf, go somewhere else for breakfast" That's a little harsh, I think, but after the landing that I made, it's probably better to have listened to him than not.

I had thought of running low pressure in the tires to help absorb shocks, but the tiny little...2.80/2.50-4's...don't carry enough air to allow for such a practice. The mains are 4.00-6's, so I can run them a bit on the soft side which will help, but making a spring suspension for the fronts is definitely the way to go, I think.

I've tried to straighten the bulkhead where it is bent, but to no avail, so I've cut the upper part of the bulkhead out and will replace it and strengthen it in the process, as well as design and build the aforementioned suspension system, using a small coil spring....at least that's the plan for now.

My home field is turf, so I'm stuck with at least one takeoff and one landing on turf, and so I have to have something that will hold up to these conditions if I'm to fly with the floats at all. Making the floats stronger and capable of handling rough field conditions through the addition of some sort of suspension system will be top priority on my calendar, for sure. Then I can get back to seeing if it will make a worthy seaplane.



Back to what you said, Paul, about the rears being snatched down....Brian says he has worked on large seaplanes...Widgeons, etc...that would demonstrate this phenomenon of "snatching". He says he felt the tails of my floats being sucked down during landing...(my ass is too old to feel anything anymore)...and he calls this being snatched down. What they did to improve this condition was to make a hole in the bottom of the area back behind the step, and run a vent tube up from there, exiting out the upper side of the float skin. This vent, he said, breaks the suction that occurs from the water passing under the step, and affecting the bottom of the rear portion of the float....I hope I'm explaining this right. He showed me a fuselage that is in one of his hangars that is a Widgeon that has this vent. It is just a box-shaped tube that connects the upper side of the float to the bottom of the float, which allows air to enter from the top and out the bottom, and supposedly breaks the vacuum in that behind-the-step area. He also said that he's never seen this on a set of floats, but has seen it and done it on hull-type floats.

Part of the reason for his feeling so strongly about this tentative modification is that the "sweet spot" is very hard to achieve....it's either on the step, or the tails are in the water when "on the step" is being sought.

He had me measure the Edo floats on the Cub, and on my floats, comparing the angle behind the step on both makes. I found that the Edo's had 0.8 degrees greater angle than the Zenith's, measured from the horizontal to the rear keel. I didn't think that less than a degree would make much of a difference in finding the sweet spot, but I could be wrong. In any event, I won't be cutting these vent holes until I repair the floats, and have weighed all the input that I can gather concerning this theory. Whatcha think?

Lynn

[DesertFox4]

Great read Lynn. "It's not easy flying floats, the first time" might be the title of the book. I've seen this syndrome before while watching a couple friends attempt water flight. Just more to it than meets the eye.

[av8rps]

Lynn, and everyone else following this thread,

This might take me a few posts to answer all the various things I've picked up on from Lynn's experience. And I might be all over the place with the order of how I adress things I picked up on, but here goes.

Let's start with the floats;

Zenair probably doesn't want to hear this, but I really think they should pay closer attention to not only the strengthening improvements the Czechs applied to their floats, but also to the quality of how the Czechs built their floats. A float takes a huge pounding across the water, as well as when operated off turf runways, so quality is equally important to design.

I'm sorry if I sound like I'm bashing the Zenair float, because I actually like the float (for the money). But I've looked closely at the Zenair compared to the Czech produced versions, and there is a huge difference in my opinion. Especially in the nosewheel and gear mechanism and overall construction quality. At least that's my opinion.

So with that said, and having confidence in Lynn's building abilities (have you seen his Fox? It's a beauty...), I don't think Lynn built the floats poorly. Rather he is dealing with a product that while it works in its original form, it only does so marginally. It is likely that had Lynn stayed on pavement, and did all super-nice gentle landings, he probably wouldn't have these tales to tell.

Now in defense of the Zenair float, pretty much all amphib float gear mechanisms are weak. My Aerocet amphibs on my Kitfox are probably even more delicate than the standard Zenair, so I avoid turf runways like the plague. Now if I know it is a super smooth grass strip, I may go in, but I will do everything I can to grease it on as smooth as I can while also minimizing taxi and takeoff.time. Sadly, that is generally the price to be paid for having an airplane that can land on water as well as land. Spend big bucks (35 to 55k) and you are more likely to have an amphib float that will do better on grass. But it likely will be heavier, and still not guaranteed to be any more sturdy. Again, that's the price you pay to be able to operate on land and water...

I would like to hear more from Lynn so I could adress water performance. So while I adress other things, maybe Lynn can fill us all in better regarding water performance.

On that comparison of the float angle being off compared to the Cub, while 1 degree doesn't sound like much, the best way to get an underpowered airplane off the water better (aside from more HP) is to make the wing do more of the work sooner by increasing the throat angle, or angle of incidence of the wing in relationship to the floats. Not sure if you remember, but I believe I suggested making adjustable length fuselage float attach brackets so you could easily change as needed. I think you will be amazed if you increase the throat angle by a few degrees. Downside is your cruise will be a bit slower, but you will also be able to land a bit slower with more positive wing to float incidence.

Oh, and about that vent tube for the step...other than the old Avid fibreglass float designed by Dean Wilson, I have never seen a float with a ventilated step like Grumman used on their flying boats. I also own a Lake Amphibian (4 seat production flying boat designed by two Grumman engineers) and it does not have a ventilated step. So I believe it is overkill on anything but a real heavy and fast amphib (like the Grummans) that develops a lot of speed (and suction) on the step to takeoff. I could be wrong, but I'm willing to bet if you do that to your Zenair equipped Kitfox, you won't notice any improvement. You'd probably get better results if you put anti hydrophobic paint on the bottom of your float. But hey, if it's easy to ventilate the step, go for it. Dean ventilated the step on his float with a simple horizontal hole drilled on the back side of the step, and then ran a tube into the top side of the open storage compartment. Even better would be to use a ram air scoop into the airstream that would actually pressurize air into the area behind the step, making air bubbles. But again, that is all in my opinion overkill, which is why I believe you never see it done on floats.

And for the record, I'd be amazed if ventilating the step will do anything to keep the airplane on the step, or "the sweet spot" better. That is more a function of float placement and location of the step relative to center of gravity, and the pilot getting used to the airplane when on the step. High speedwater taxiing is the best way to get the feel for that in my opinion, as when you're in takeoff mode, you're usually focused on getting it to fly. High speed step taxiing allows you to "play with it" on the water to leisurely get the best feel for it. I always step taxi a new to me airplane first before flying it, as that gives me a really good feel for the airplane before having to actually fly it. However, please note that a lot of seaplane accidents are related to high speed water taxiing. You have to gradually work your way up to that, and try to limit yourself to great water conditions with little or no waves and /or boat wakes. I have to compliment you Lynn about your comment about feeling uneasy doing step turns as that tells me you probably already have a good feel for step taxiing. Sharp turns on the step should rightfully bother anyone that has a good feel for the airplane, as the physics and inertia of that step turn are working against you, and have in fact wrecked a lot of seaplanes. So whether just on the step, or while doing a step turn, always be on top of your game. But learn it well and you will have a blast doing it. I swear I step taxi as much as I fly when wind and water conditions are good.

More later...

[Lynn Matteson]

Thanks for the input, Paul. I tried to reply yesterday, and spent nearly 2 hrs thinking and typing, and while correcting something I'd written, it all went away....never to be found. So I'll respond later, but I'm heading out for a flight to get chili....and the weather is chilly!

Lynn

[Lynn Matteson]

Apparenatly I need to add something up here to satisfy an error message that says I need to lengthen my message to at least 10 characters...eh???

[Clark in AZ]

WOW! What a story. Waiting for the next installment...