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Hal-i-chopter
07-09-2007, 10:01 PM
I have posted on the Scale E-Powered about my Eflight J3 Cub with pontoons. The one remaining problem I was having was the splashing from the pontoons hitting the prop.

I tried going to a smaller, higher pitch prop and it was a disaster. I crashed 2 out of 3 take offs. It just doesn't have the power to get off the water. And it didn't even reduce the blade splashing (prop is now in trash).

I think the only solution is to put a splash guard on the pontoon inner edges towards the front. I have resisted because the pontoons look so nice right now. Has anyone tried this and if so, can you describe what you did, how it worked and pictures if possible?

Jim Casey
07-10-2007, 02:48 AM
It's pretty easy just to glue a piece of balsa triangle stock to the bottom of the floats in the area where the splash originates.

Jim Casey
07-10-2007, 02:50 AM
It's pretty easy just to glue a piece of balsa triangle stock to the bottom of the floats in the area where the splash originates. Waterproof the balsa with Superglue. Paint it to match your float. And it only needs to be on the inside for splash deflection, but inside and outside will help with getting the plane up on step.

Quinn
07-20-2007, 05:44 PM
It's pretty easy just to glue a piece of balsa triangle stock to the bottom of the floats in the area where the splash originates. Waterproof the balsa with Superglue. Paint it to match your float. And it only needs to be on the inside for splash deflection, but inside and outside will help with getting the plane up on step.

Jim's right. In almost all flying boat designs since 1930's, the hull edge was flared to throw water out & down. Many float/pontoon designs do not have this architectural feature. The balsa strips should do the trick.

Quinn

Hal-i-chopter
07-20-2007, 06:28 PM
I don't like the idea of balsa wood in the water all the time, covered with superglue or not. Maybe I can find some plastic that is the same color.

Not sure I understand how the triangle balsa is supposed to attach. A triangle will not deflect the water down unless the bottom edge extends below the bottom edge of the pontoon. If I extend the triangle below the bottom edge then only a small portion of the 'attachment' edge overlaps the pontoon, thereby reducing the surface to glue.

I am thinking if this is simply an edge to extend below the bottom of the pontoon, then wouldn't a flat piece of material be easier to cut, easier to form to the curved pontoon surface and lighter?

Jim Casey
07-21-2007, 04:27 AM
Not sure I understand how the triangle balsa is supposed to attach.

I seem to have failed in the picture I drew. I have no more communication skills.

BradT
07-21-2007, 07:37 AM
Jim's drawing above is how most chine rails are done. However, if your floats are set up correctly, you should only be getting a little bit of spray into the prop at initial acceleration, before you get on step, and virtually none after that. The floats must be far enough apart - 1/4 span minimum, but 1/3 span is better; they must be long enough in front of the prop, 1/3 of prop dia. is good here; the lowest point of the prop disc should be at least 1" above the top of the floats; and the step must be very close to the c.g. of the model. Wing incedence must also be a few degrees positive to the float tops. Set up like this, you should get only a few drops of spray into the prop as you throttle up, before getting on step, then no water at all as you accelerate to lift off while on step. If there's enough chop on the water to splash the prop while the model is at rest, then it's probably too windy to fly.
Brad.

Hal-i-chopter
07-23-2007, 07:06 PM
Not sure I understand how the triangle balsa is supposed to attach.

I seem to have failed in the picture I drew. I have no more communication skills.
You didn't fail, I just didn't see the picture. Your second post was just text and that is the one I saw. Now I get it. I didn't envision them attaching to the bottom.

Hal-i-chopter
07-23-2007, 07:09 PM
Set up like this, you should get only a few drops of spray into the prop as you throttle up, before getting on step, then no water at all as you accelerate to lift off while on step. If there's enough chop on the water to splash the prop while the model is at rest, then it's probably too windy to fly.
Brad.I don't get spray once I'm on step. However even at full throttle it is quite a spray (not just drops) to get on step, even though it only takes about 2 seconds to get on step. However at full throttle it doesn't look 'scale'.

As far as the distance between pontoons and length etc, it is pure out-of-the-box E-Flight pontoons for the J3.

I will try something like Jim's drawing.

Jim Casey
07-27-2007, 03:02 AM
When you first goose it you should hold full UP elevator.
As soon as it pops up on step, neutralize the elevator to let it build speed.
Then eeeeeease back stick to let it take off gently.

Hal-i-chopter
07-27-2007, 05:18 PM
When you first goose it you should hold full UP elevator.
As soon as it pops up on step, neutralize the elevator to let it build speed.
Then eeeeeease back stick to let it take off gently.Jim, interesting. I have not been doing that. I will try it and see if it helps. Will this eliminate splashing to the prop without the triangular rail?

If not, I was thinking of covering the trianglular balsa rails with monokote instead of painting them.

Jim Casey
07-29-2007, 04:04 AM
It should help with the water in the prop problem.

Monokote will work, but the sharp edges of the tri-stock are prone to damage, so it's best to seal the wood anyway.

Hal-i-chopter
07-29-2007, 06:48 AM
I tried the method of pulling back on the elevator until getting up on steps and that reduced the prop splashing by about 1/2. :-)

brnyrbbl
07-29-2007, 06:54 AM
I wonder if you could make splash guards like they sell for hobie cat boats. They look like small airfoils that extend horizontally off the top nose of the pontoons. Sort of a flat one piece V that wraps around the nose.

pd1
07-29-2007, 11:41 PM
Hal-i-chopter, Jim Casey gave you excellent advice about the takeoff procedure.

Full sized seaplane use spray rails, flat aluminum sheet that is attached to the edge of the float and extends horizontally or vertically to block the spray.

I have not tried all methods of stopping the spray, but here is what I have tried.

1. Moving the floats forward. You can only move them a little, and sometimes it can cause other problems.
The rear of the plane should not "sink" if it does you're too far forward.

If the step is too far forward the plane will not rise and attain a high speed planing attitude.

2. Enlarging the elevator, more up elevator will help in keeping the tail low until the plane rises up unto the step.

When you first start to move the spray comes off the front of the floats.
As the plane gains speed and reaches the step position, the spray will move rearward until it comes off a point at or close to the step.

At this point the plane can be put in a high speed or nearly level position.
Since the spray is so far back it shouldn't hit the prop.

3. New floats with more width forward of the step. More volume ahead of the step will make the plane less likely to drag the front and throw excess spray.

4. Sometimes as a last resort, moving the floats closer together.
This doesn't always work.
This just changes the pattern of the spray. Sometimes it helps.

First picture Lake Amphibian with horizontal spray rails.
Second picture Cessna 150 with vertical spray rails on inside of floats only.

Vertical spray rails can be made out of thin sheets of plastic.
If vertical doesn't help then try horizontal same material.

Jim Casey
07-30-2007, 02:11 AM
Ok, the spray rails don't have to be balsa. You can make them out of thin ply, aluminum, revoked credit cards (don't use the numbers) , Or leftover windshield stock from a BTE flyin' King. But they should be angled downward. What that does is to catch the spray that is squirting up essentially parallel to the surface of the float, and to turn it down. There is a lot of force generated in turning a jet of water, and that goes into lifting your plane.

But the triangle stock ones I showed earlier are easier to make.

Hal-i-chopter
07-30-2007, 04:26 PM
Or leftover windshield stock from a BTE flyin' King. Hey, I like that idea! Transparent rails, that way I don't have to try and match the grey fiberglass. Easy to try too.

Jim Casey
08-01-2007, 02:27 AM
Not that easy. It's necessary to cut a groove into the float to stick the deflector into. Epoxy it into place. The triangle stock thing is the mostest easiest :-/

Hal-i-chopter
09-11-2007, 10:20 PM
I did the transparent plexi splash guards and they work great! I didn't need to cut a groove but just double sticky taped them to the inside edges of the pontoons. They look good too. I've was thinking the double stick tape was temporary and was going to screw them instead but this way they allow drainage and they are holding up well so, if it ain't broke don't fix it.

I will post photos when I get a chance.

Hal-i-chopter
09-30-2007, 06:06 PM
Here are the promised photos. I think I should have made them a little longer. There is no spray on the prop but the rails shoot a spray underneath the fuse and get the bottom wet.