Please look at this set-up it's my first attempt - RC Groups
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Sep 16, 2009, 10:37 PM
Registered User

Please look at this set-up it's my first attempt

Hi to all, please look at this and let me know if it looks OK or I need to change something. I have never built a float plane or flown from water, but what the heck I will give it a try. Some info. on the plane and set-up...the plane is a Sig Seinor Kadet wing span is 80" Motor is a O.S .61FX Prop is a APC 13x5 Floats are balsa over foam that have been fiberglassed and painted. Prop to the top of the floats is about 4.50" From the bottom of the fuse. to the bottom of the floats is 11.50" Floats are level and elev. is level. The floats are on 24" from the center line of the floats and about 27" outside to outside ....I know that's a little wide but I thought it would make it a little more stable. PLEASE look at the bracing it is made from 5/32 music wire, I think that I need a "Z" brace in it. Also look at the C/G it's at the wing strut, I have it right over the step of the floats I hope that this is right. Please feel free to give any input.
Thanks, Eng30
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Sep 16, 2009, 11:10 PM
Registered User
The floats need to be rigidly mounted. A diagonal on each side and a fore and aft spreader bar would be ideal.
You are way over powered...not a bad thing
The step needs to be about an inch BEHIND the CG on a plane this size.
Balance it slightly nose low with a third of a tank of fuel.
Nice looking plane and floats.
Sep 17, 2009, 10:40 AM
Registered User
Hi Art, will put some more side bracing in . I also use this plane to piggy-back gliders on top of the wing with a mount then release them. Now with floats I thought the extra power might be needed, I can always pull the power back on the stick. I have moved the C/G 7/8" BACK from the step.
Why do I want to balance with 1/3 of a tank of fuel? Most of the time I balance with the tank empty. Also should I try to move the front brace closer to the front of the floats? ( the top of the brace would be leaning back to the tail of the plane)

Now for rudder control????? I was thinking of adding a servo just for the rudders and putting it on a switch on my radio, and mixing some rudder in....
The switch will let me turn it on while on the water and turn it off while in the air. this over kill?
Thanks , Eng30
Kenny Peek
Sep 17, 2009, 03:26 PM
Registered User
lake flyer's Avatar
The step should be 1/2-1" behind the CofG , not in front of it

The wings should have about 3 degrees of positive incidence , ( if the wing is a Clark Y , the "flat" part of the wing should be paralel with the top of the floats, that will give you about 2 1/2 degrees of positive incidence ) .

The prop should clear a line across the top of the floats by about 1", hard to tell from pic but yours looks higher than that , too high makes for tippy .

The "n" strut should run from the top of the front strut to the bottom of the rear strut.

Nice plane , have fun !
Sep 17, 2009, 08:36 PM
Got Water ?? Lets Fly !!

Welcome to the next level of our hobby... flyin off the WATER !!

First let me say your plane is a LOOKER !! Excellent job with your detailing.

I have taught several friends the art of waterflyin and it's a blast...

I fly a Sig Kadet Sr myself (on floats of course) and it's my favorite..

Couple of tips for your setup: As noted by lakeflyer it looks like you're a little high on prop clearance above your floats, this will make the float assembly a little more unstable in the water (think of standing up in a canoe) If you place a piece of tape across the top of the floats and measure the prop arc clearance you should be at about 1".

Your ARF Senior has a flat bottom airfoil, I would set your wing incidence at 2-1/2 to 3 degrees positive assuming you've already adjusted the step to the preferred location of BEHIND the wing CG.

A word about balance.... I have always balanced the waterplanes with a slightlly nose heavy attitude with an empty tank. Your palne is a floater and has a very wide stance, you will probably want to check the lateral balance as well, just remember to add the weight (if required) to the floats. You want to achieve the same balance characteristics that you had with the gear on for land flying.

If you want a tried and water tested rudder setup, give this some thought:
Sink a standard duty servo into the top of your float, coat the servo case and mounting with silicone sealer, generously grease the output shaft area with some EP grease and run the wiring up the strut to a Y harness connected to your air rudder channel. Then using a bellcrank (90 degree) arrangement connect the two water rudders to work in tandem.
Your weathervane effect is much less with two rudders. As an added bonus your float stance is wide enough to allow you to come in for a 1 float touch and go !! Very IMPRESSIVE with a big ride like your Senior !!

Last suggestion: from the pics it looks like your floats are quite tall, the concern here is the fusalage on the Kadet is large and has a lot of side area to it. Where we're going is directional stability with your vert stab and the possibility of the additional side area of your floats decreasing your handling in a negative way. Solution = dorsal fin below the vert stab.

You have done a great job with your setup and I'm confident with the talent here in the forums you'll get this ride dialed in in one flyin session.

See you at the lake !!

~doug @ lakesideranch
Sep 17, 2009, 10:00 PM
Registered User
Hi Lakesideranch, Thanks for the info. would you by chance have any pic s of your Sr Kadet? I would like to see them. I just feel like I have a lot of float out in front of the brace. Also I lowered the fuse to get about 2.0" of prop clarance but........then the floats looked way to wide. That's why some pic's would be great to look at.

Thanks, Eng30
Kenny Peek
Sep 18, 2009, 11:10 PM
Registered User
Kenny, airplanes have such a thing as "static margin' aerodynamic center and a weight center. ( look it up ) This is why a plane should be balanced slightly nose low. Balancing with a third of a tank will result in remaining nearer to the ideal CG for most of the duration of the flight.
Landing with a third of a tank will assure that the clunk remains submerged should the landing be rough.
The elevator becomes more sensitive as the plane burns off more fuel.
Just some things to consider along with the good advice from others. We all want the same thing for 'hook' you on water flying!
FWIW, art
Sep 19, 2009, 07:24 AM
Seaplane Nerd
JimCasey's Avatar
Hey, Kenny.
I finally found your thread.
All the "RULES" about float location are guidelines. You can be off some and it will still fly, just maybe it could be better.

Yours will most likely fly as it is.

If I were setting it up, I would not make the LG so tall. Same height as the "factory" landing gear. Actually, using the rear factory landing gear would provide a good basis for the assembly.

The front strut set looks a little far back. The rearward location gives the nose of the float a lot of leverage if you make a nose-down landing. That puts more load on the attachment points and can cause the wire to buckle, too.

I suggest, as others have, that you triangulate the gear legs with a drag link from the upper front to the lower rear. ALso you need a spreader bar between the rear float attachments as well as the front attachments. Float mounting should be completely rigid.

Make a fixture from a couple of boards. Assemble the landing gear to the fixture to the exact same dimensions as your plane. Get some sta-brite silver solder from the hobby shop or mailorder. Grind the drag-link so it fits against the gear legs. use your dremel tool. Don't grind the gear legs. Clean everything with steel wool and then preassemble and wrap with a single strand of fine copper wire. Use the flux with the sta-brite solder. Get the joints hot enough so that when you touch the solder to the joint it melts and wicks in to the joint. A bernzomatic works well for this. Dangerous if you try to do it on the plane but if you scorch an old board, -who cares. The solder joint should be wet and shiny looking, not just dull and blobby. Do it right and you will have a strut assembly that you can pick up and throw across the room without damage

here is a little diagram

Since you already have the nose gear in, remove the nose gear and replace it with a short piece of wire to keep the steering arm in. Run a straight-as-possible piece of gold'n'rod back from the steering arm to the water rudder. You only need one water rudder. Make sure you connect to the proper side so the WR goes the same way as the big rudder.
Last edited by JimCasey; Sep 19, 2009 at 07:31 AM.
Sep 19, 2009, 04:19 PM
Registered User
Jim, I have bolted the fuse to the 5/32 wire bracing it is Very strong front to back and back to for the bad news.....when I twist the engine clockwise and CCW I get torsional twist in the bracing. I am thinking of adding the "V" bracing (look at the pic's) Will this stop the twisting? Also I can pick up one float about 3.0" before to other one starts to come up. Or should I just start over because the braces are just to tall? I really like the plane being a little taller. Prop to float clearance is 4.0" I did move the front brace as far forward as poss. any more and I can not get under the fuel tank. Please take a look at all pic's and see what you think.
Thanks, Eng30
kenny Peek
Sep 19, 2009, 05:31 PM
Seaplane Nerd
JimCasey's Avatar
Diagonal bracing as you clamped up will probably not be necessary. If you want to stiffen it up, you could do an X between the spreaders. Use 1/16 wire. One wire will always be in tension and small wire has a LOT of tensile strength.

I still think that you will be happier if the plane does not sit so high above the floats.
Place a sheet of balsa across the tops of the floats, and set your nosewheel on it. That should be plenty high.

You did a nice job with the soldering.
Sep 19, 2009, 05:52 PM
Registered User
Jim, I will do that, and do I also need to bring the width of the floats in?
They are now 24" center to center, About 27" outside-outside. The joints are not soldered ,they are TIG welded and then a little blending.
Thanks, Eng30
Kenny Peek
Last edited by eng30; Sep 19, 2009 at 06:10 PM.
Sep 19, 2009, 06:28 PM
Registered User
It's probably just an illusion but are your floats toed out ?? ENJOY !!! RED
Sep 19, 2009, 06:47 PM
Registered User
Hi Redh, It's a illusion.....After talking to Jim, I think that I will lower the plane to the floats....4.0" is to high......but I liked the look, but having a good set up is more important.
Thanks for looking,
Kenny Peek
Sep 19, 2009, 08:17 PM
Seaplane Nerd
JimCasey's Avatar
common guideline for float spacing is 1/4 of the span. I don't think guys with clipped-wing cubs bring their floats closer together.
Sep 19, 2009, 08:28 PM
Registered User
Jim, The old wire is now gone .....bending new as I type.....After all of your help I know this is the way to go. Will post new wire pic's Monday night.
Will space floats at 20"......wing span is 80"

Thanks Again, Eng30
Kenny Peek

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