I have a KMP Beaver setup on Sea Commander Floats. Unfortunately, I did not build it.

Upon further review of what I've purchased, I have noticed that the builder installed the floats with the step over 3 inches behind the CG.

The floats still extend 5 to 6 inches in front of the propeller, but I'm very concerned about what is going to happen with the step that far back.

I imagine that the airplane is going to want to nose over in the water when the floats dig in, but I just don't know.

I've never tried to fly one with this setup and, of course, I don't want to damage the airplane.

The other problem is that it would be a major amount of work to get the floats moved forward, so I'm trying to avoid that if at all possible.

So, please let me know about your experiences with this sort of a setup...

I believe it may be squirrelly on takeoff and you may not get it off the water. There may be a lack of directional control.
With that much float out front it may not dig in at all since normal would be less float out front.
A lot will depend on total size of the floats and the flotation capability. I believe the actual answer is "try it".

The way I understand it, and I may be incorrect, the step is like the main gear. Too far back and the nose acts heavy where it takes a lot of elevator to get off the water, just like with a land plane that is really heavy on the nose gear, it takes a lot of up elevator to take off.

That being said, I have a Fazer on floats and originally the step was 3 inches or so behind the CG. It took off fine, but I was using a Tower .46 and had plenty of power and I also had 3D control throws. I would hold full up elevator and give full power and it jumped on the step. If I tried to stay down too long it would skip so now I take off quickly.

Now, I'm running a Saito .72 since I added dual water rudders and this moved the CG back more than I thought so I went to a slightly heavier engine. It still jumps off the water quickly.

I don't know how you are going to nose over if you are "flying" the plane on the water. I always (and was told to) hold full up elevator and add power. When the plane rides up on the step, I release about half the up and "fly" it on the water. It's not much longer after that the plane wants to lift off. Even with a scale plane, you have plenty of lift and some nice floats. I would give it a try.

How long are the floats in relation to the fuselage... from the info you have given us, they sound like they are too long......

I think the only critical issue will be at high speed on the water..If it rides too far on the front part of the floats, it will probably water-loop....it would be directionally unstable until the flying surfaces took over ( like a cub with a full swivelling tailwheel...)

I really appreciate all of the responses so far. I figured there would be some helpful folks who are familiar with a situation like this before. That's one of the great things about these forums, so thanks!

In light of what has been said, (and unless other opinions sway my decision and in consideration of all the work it would take to fix it), I've decided to give it a try as it is to see what happens.

I'll have the recovery boat waiting nearby and ready-to-go. [sm=drowning.gif]

If this float step placement doesn't work then I'll just have to take my time and repair it, so I may be looking for ideas on how to move a set of floats forward!

Another important facet that hasn't been mentioned is the incidence between the wing and the floats. If you have a couple (1 - 2) degrees of positive incidence - wing angled up more than the floats - the misplacement of the step will be reduced significanlty as the plane will want to gently lift off instead of rotating aroung the step.

Yes, the wing / float incidence is fine, probably 2 to 3 degress positive

You'll be OK. Although there are "rules" ( Punctuation markes are to mimic when Dr. Evil said "Lasers") , the step placement is not vastly critical and having it too far back will only make the plane want to run truer on takeoff and possibly be sluggish on the elevator. When you land ( water?) it will probably rock forward and kill all the lift, But I can't imagine the plane nosing over with all that buoyancy in front of the prop.

Still, I think back to the post where the suggestion was offered that your floats are too long.

Ideally (there's the "rule") the step of the float should be under a point corresponding to 40% of the wing chord.
Then the Nose of the float should be about 20% of the prop diameter in front of the prop.
And the overall length of the float is 75-80% of the distance from the prop washer to the rudder hinge line. That SHOULD be double the distance of the nose to the step. Betcha your floats are bigger than that.

I have been fantasizing about building another Mud Duck for floats. I had one of the originals from the MA plans, and I LOVED it. That one was balsa and ply, and flew with authority on a .25 HB. I tried a Crikit, and it wouldn't fly at all. I think I'd like to scale up a Mud Duck to about 70" WS, and use a .70 4-stroke. Whatever happened to the designer, Tom Chipley, anyhow??

I've got a Mud Duck MKII, sadly my first duck was 'shot' out of the sky by a radio malfunction. My Dad built both of them and I've often thought about installing floats on the big duck (120" span), but I'm afraid the paperboard probably isn't the best material for a float plane, especially if it were to flip or get blown over on the water. I have the giant inner-tube tires on the duck, perhaps I could find a floating "tailwheel" (like a 1/3rd scale inflatable tire) and just forget the floats altogether as it would be amphibious, like a real duck!

It appears that Mud Duck Aviation is trying to make a comeback (http://www.mudduckaviation.com), but I haven't heard much about the revival or seen any ads, but their website has been updated as of April 2007. Sorry (and glad) to hear about the Cricket because I was thinking of building an electric version of one, but if it doesn't fly, I won't bother.

Thanks again for the comments about the Beaver. I've decided to go ahead and give it a try after I get it properly balanced. Possibly this weekend if it stops raining in Missouri and gives us a descent flying day. I don't believe the floats are too big, they were made by Sea Commander specifically for this airplane. They certainly cost enough that they ought to fly!!

I'll let you all know how it turns out, with photos!

You may want to take a look at this thread http://www.rcgroups.com/forums/showt...=4#post7103455

I would suggest making sure you keep some up elevator and dont let it rock forward too far on your takeoff runs and stay one stp ahead of it on the rudder. It will try and water loop if you let it rock to far forward if you floats are even slightly out of alignment (I know this first hand, atleast with the KMP floats). You will also probably benifit from adding an additional venteral fin. It made a huge difference in mine.

Akflyer, thanks for the suggestion, I appreciate it very much. Is there any way you can post a picture of your additional venteral fin on here for us to see?

http://www.rcuniverse.com/forum/m_34...tm.htm#3405414

towards the bottom of the page are some pics of the fin.