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Old 10-15-2015, 01:10 PM   #51
Lynn Matteson
 
Join Date: Dec 2008
Location: Grass Lake, Michigan
Posts: 48
Default Re: I still need float-rigging info

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
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Old 10-15-2015, 04:03 PM   #52
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Default Re: I still need float-rigging info

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.
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Old 10-15-2015, 09:50 PM   #53
av8rps
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Default Re: I still need float-rigging info

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...

Last edited by av8rps; 10-15-2015 at 10:36 PM.
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Old 10-18-2015, 06:18 AM   #54
Lynn Matteson
 
Join Date: Dec 2008
Location: Grass Lake, Michigan
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Default Re: I still need float-rigging info

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!

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Old 10-19-2015, 03:34 AM   #55
Lynn Matteson
 
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Default Re: I still need float-rigging info

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???
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Old 10-19-2015, 06:50 AM   #56
Lynn Matteson
 
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Default Re: I still need float-rigging info

I just had a good look at the damaged #2 bulkhead on my Zenair floats. It looks like the crack at the top of this bulkhead....it's the bulkhead that carries the entire front wheel retracting mechanism...had started way before I made my landing at Coldwater (KOEB). In looking further at that crack, it is not a new crack, but shows aging...blackness from probably being rubbed back and forth in the time prior to the hard landing at OEB. In studying this area further, it is obvious that the upper flange on this bulkhead, and the bend that forms this flange is the weak link in the front gear layout. This bend is what cracked. It is (now) obvious that this area must be reinforced, as it is this area that ultimately takes the shock of landing and of all bumps on rough surfaces. The bulkhead itself is well "armored" but there is no reinforcing at the upper flange and here is where it is weak, and subsequently failed. I can't wait to check the other float to see if it too, is cracked.

Lynn
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Old 10-20-2015, 09:31 AM   #57
av8rps
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Default Re: I still need float-rigging info

Lynn,

I am really sorry to hear you are having so much trouble with your Zenair floats. It shouldn't have to be this difficult. I've flown those floats on different aircraft over the years, and honestly I have to say they are overall a very good performing float both on water and at the airport.

As an example I've flown a set on a Rans S7 with a 912s on it for about 30 hours, and even loaded with passengers as big as 375 lbs off the water it still did well. Here's a video of that same Rans loaded with 2 adults doing a water takeoff https://www.youtube.com/watch?v=mzHPDLfsOEI and this is their landing showing both guys in plane https://www.youtube.com/watch?v=DQJ4cPhVhFg . You will notice the takeoff run wasn't very long at all, and the water handling is indicating nothing unusual. It is a very good flying LSA amphib overall. That is the Czech built version of the Zenair float. So the design is the same, with the exception of some gear strengthening improvements. Btw, that particular Rans has been landed on grass lots of times, and as far as I know the gear is still holding up ok. And one strip it occasionally goes into is pretty rough, far rougher than I like to go into with an amphib.

For water performance of the Zenair, that same basic Zenair float design is the same on all their smaller floats, and it has been used on some super high performance floatplanes. Take John Knapp (aka Snaps) and his Zenair 750 straight float equipped Avid Flyer with a Rotax 583 2 stroke that no one at Greenville Maine's seaplane take off contest can beat. Solo he can get off the water in under 3 seconds. Here's a video showing performance https://www.youtube.com/watch?v=qjDSatUSoCY . I also have a video from OSH showing him taking a 385+ lb passenger off the water in only 10 seconds. And he was grossly underfloated, as his Zenairs were only 750 lbs of buoyancy (a more appropriately sized float would have done better). So with all that said, I don't believe the float design for water performance is poor. There are just too many cases where it has proven itself to work well.

I do agree that the stock Zenair gear could stand to be a bit stronger. But it sounds like you may have figured out how to improve that part? I also agree that it would be nice to add some suspension to the nosewheel area, as that would reduce stress on the float itself. I have always found when landing an amphib floatplane that if I can do all I can to land on the mains (tail low) and then do all I can to keep the nosewheel off until as slow as possible that I can reduce a lot of stress on the nosewheels. In my Kitfox I can keep the nosewheels off until I get into the low to mid 20 mph range. You can also do the reverse to takeoff, getting the nosewheels off as soon as possible to reduce nosewheel stress. I like to think of all operations on amphib floats like doing "soft field" operations with a tri-gear land plane.

Next installment to this thread I will address the gear position strategy I've used since 1993 when I first started flying my Lake Amphibian (which if you mistakenly land in the water with the gear down is almost always fatal... so Lake instructors drill you VERY hard on proper technique for gear position).

Later...
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Old 10-20-2015, 12:48 PM   #58
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Default Re: I still need float-rigging info

I just couldn't resist after stumbling on this old 1979 magazine last night...
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Old 10-20-2015, 04:11 PM   #59
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Default Re: I still need float-rigging info

Ok, now that I'm done screwing around I will get serious...

In 1993 when I was trained to fly my Lake Amphibian, I was taught to always say out loud my landing intention and the landing gear position at least two or three times during the landing phase. This training is critical in any amphib, but ultra critical in a Lake because most gear down water landings result in fatalities. I paid special attention to that part of my training after I saw a picture of a Lake that landed in the water gear down. Everything forward of the wing was gone - it looked as if a bomb had gone off in the cabin! (for anyone that doesn't know what a Lake Amphib is, this link will not only show you what a Lake is, but also how the gear goes up and down for land and water ops https://www.youtube.com/watch?v=2Hxh_8EEohc [see if you notice a little dog while you're at it] )

So getting back to my procedures for proper gear position, here is an example of what I do when flying my Lake Amphibian that can be applied to most any amphib;

At an airport landing on pavement, my first effort to check my gear position is when I initially enter the downwind for the landing pattern. Once I have all normal traffic duties accomplished I say out loud to myself "This is an airport landing, and the landing gear is going down" while reaching over and putting the gear handle into the down position. A few seconds later I look into the mirrors that are attached to the wing floats so I can look to see that the nose gear is actually in the down position, followed by a visual on each main gear (mains are easy to see on a Lake as they are right next to the cabin when down) and that my hydraulic pressure is up. Last, I verify the landing gear position by lightly touching the "Gear down" lights as well as the gear handle to make sure they indicate the gear is down and locked.

Then when I make my downwind to base turn, during the bank I again call out my gear position. But this time I also look into the mirror that is on the lowest wing so I can see the nosegear hanging down against the nice blue sky / horizon (much easier to see against a one color background than when the aircraft is level), while again checking my main gear visually, double checking that my hydraulic pressure is holding, then again verifying and touching my "gear down" indicator lights, and also lightly touching (but not grabbing) the gear down handle to verify its position.

Last, right after making my base to final turn, and once happy with my stabilized approach to the runway, I make a last landing gear check. Again I say out loud "This is an airport landing, and the landing gear is down", followed by one last visual check to make sure the gear is down, my hydraulic pressure is good, the gear down indicator lights are on, and the handle is down, all indicating the landing gear is in the down position and locked, ready for an airport landing.

For water landings, well before my approach to the water surface (when I still have plenty of time and space) I will call out loud "This is a water landing, the landing gear is up, I'm now a boat", while looking in my mirrors and banking to verify the nose gear position is "up" against the sky, then verifying visually the mains are up, hydraulic pressure is good, followed by a visual and touch verification of the "gear up" lights, and touching (but not grabbing) the gear handle to verify it is in the up position.

Then when I am on my final approach to the water landing, early in the approach I say one more time "This is a water landing, the gear is up, I'm now a boat", while again making a last visual check of the gear position, hydraulic pressure, and the gear up indicator lights, along with the gear handle.

As a personal rule, I always verify gear position before any landing. Even if I just took off from the water and plan to do a landing right after takeoff (also known as a "splash and dash"). Most seaplanes do not have an "Uplock" on their gear mechanism, so just imagine what might happen if on that last bouce off a wave that made you airborn, the gear unlocked for some odd reason? (... a hydraulic line that came undone, a gear link broke, etc.) You'd unknowingly splash down right after your takeoff with the gear down, spoiling a lot more than just your day!

So even though the Lake Amphib has a really nice uplock in its gear design, and so do my Aerocet floats on my Kitfox, what if for some reason or other it stopped working that day? Plus, because I often am flying other amphibs, I just make it a point to never assume the gear stayed up just because I thought it should. So again, I verify visually the actual gear position, even for splash and dashes.

Also, if you have a passenger with you don't be afraid to task them with making sure you are doing the right thing with the gear. I've found they like to know about that when explained to them, and that they like to help you keep an eye on it too (self preservation is a really strong instict apparently ). Just include it in your passenger pre-flight seaplane safety briefing (which you should always be doing anyhow).

And as far as using lights and hydraulic pressure, that is fine. But more importantly is actual visual verification of the landing gear position. My Kitfox amphib only has mirrors, no lights, and no hydraulics, being that it is a manual system operated mechanically by a Johnson bar. So I rely entirely on my mirrors. Many would say the Johnson bar is all you need, but what if a cable or a pulley inside the float that actuates the gear broke? My handle would show the gear up, but part of it could be down. So again, I trust my mirrors to visually show me where exactly my wheels are before any landing. Indicator lights and switches are prone to failing in a water environment, so I only consider them an additional, or backup to visually verifying gear position. The same goes for voice warning systems. They are only as good as the switches that actuate the gear lights - which is poor at best in my opinion.

Call me old fashioned, but I prefer to trust my eyes for knowing exactly where the gear is when flying an amphib. And if it just wasn't possible to do it effectively with mirrors, you'd be seeing me installing a small camera and video screen system in my plane so I could use that to visually verify my gear. They can be had for under a hundred bucks these days, and could be used for some cool seaplane video stuff as well (like this https://www.youtube.com/watch?v=j3kO2nZoSDA ). In fact I have thought about doing a camera system for a few years now, after installing a cheap backup camera on a camper a while ago and seeing how well it worked. But for now my mirrors still do a good job, so I'll keep what I have. But my next amphib (a new Highlander) will definitely incorporate mirrors AND a camera system.

Ok enough rambling. I sure hope those of you that hope to one day fly floats don't get discouraged by all this discussion about issues related to amphibs. Once you get your plane set up properly, and you get the proper training and get used to your new amphib, you will have an absolute blast being able to fly from land to water and back. It's like having your own magic carpet. I've always said that amphib floats is the best accessory you can add to an airplane. It in fact will make your airplane an amazing machine that will take you to places you probably otherwise would never experience. So don't let any of this discourage you. I can't imagine not being able to fly my Kitfox off water...it works so well.

Lynn knew going into this that turning a Jabiru powered Kitfox Speedster into an amphib might be a really challenging task. We had talked previously. And it certainly has been from all he describes. I'm almost embarassed how easy mine was to make work after reading of his struggles. But I have to say that it still looks like Lynn is going to pull off what many of us wouldn't believe was even possible with the Jabiru powerplant. So more power to him (no pun intended...really). I'm confident he is close to success, and will one day soon succeed in his mission. It might even be a bit selfish on my part, but I have this vision that one day soon I will see him land at the EAA Oshkosh Seaplane Base in his cool Kitfox amphib, and will have the time of his life in his new adventure machine

Last edited by av8rps; 10-20-2015 at 04:33 PM.
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Old 10-20-2015, 11:09 PM   #60
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Default Re: I still need float-rigging info

I feel as though I could almost take my seaplane check ride after following this thread. Thanks for all the good reading guys. Something about float flying appeals to me like no other kind of aviation even though I have only some experience as a passenger and zero time on the controls of a web-footed aircraft.

Now , back to more float talk.
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