Air Foil VS Foam Filled Rudders

A general, non-powerplant specific, discussion on airboat technology, ie., hulls, rigging, polymer, etc..
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JMOE
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Air Foil VS Foam Filled Rudders

Post by JMOE » Mon Jan 12, 2009 7:41 am

Could someone help me out with the advatages (if any) of air foil vs foam filled rudders. I know that they are lighter, but a rudder is a rudder right? as long as it directs the air as you steer they all do the same thing.

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Whitebear
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Re: Air Foil VS Foam Filled Rudders

Post by Whitebear » Mon Jan 12, 2009 7:58 am

Ok, both are airfoils just air filled or foam filled. I have used airfoil foam filled and never had any issues. My kids boat long time ago had a huge single rudder that had no fillig. It was an excellent performer. I "think" the foam filled thing got started from using a thinner skin and they filled it with foam to help it keep its shape. Not at all sure its necessary but never built one that was air filled only. Built right you wont see any difference except that the foam filleds might flex less under hard rudder shaking with max throttle. Heck we used to use flat rudders made from street signs and they worked. Its the airfoil shape that makes them work better than flat rudders not the foam filling.

Scotty
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Waterthunder
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Re: Air Foil VS Foam Filled Rudders

Post by Waterthunder » Mon Jan 12, 2009 9:15 am

The foam rudders put a bunch of weight in the last place you want it. If you have a heavy boat it doen't matter but if you have a standard sportsman airboat go with those super light none foam filled!
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Re: Air Foil VS Foam Filled Rudders

Post by ZoomZoom » Mon Jan 12, 2009 3:02 pm

Foam filled or not I don't think it makes much differance. The rudders that I run on my boat are not foam filled but they do have 3 foam ribs and the skin is only .025" thick (2024-T4) and they have held up quit well for the better part of 8 yrs., their size is normal 4' by 22", weight is 9 lbs.each. Zoom Zoom.

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Waterthunder
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Re: Air Foil VS Foam Filled Rudders

Post by Waterthunder » Mon Jan 12, 2009 6:47 pm

I have seen several Foam rudders hold water to! It all add's up if you can get a set for nothing that's one thing but if your buying new I would go Foil all the way!
THE PROOF IS IN THE PROP!

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Re: Air Foil VS Foam Filled Rudders

Post by goldhunter_2 » Mon Jan 12, 2009 8:10 pm

I agree with waterthunder if your buying new differently get a airfoil not a foam filled rudder :!:

I have had and seen others with foam filled and they hold lots of water. and as someone who like to build/fabricate stuff the foam filled is the "economy" version where the old say "you get what you pay for " comes to mind the foam actual is providing some of the structural strength instead of proper design IMHO
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Re: Air Foil VS Foam Filled Rudders

Post by Whitebear » Mon Jan 12, 2009 11:30 pm

I must be wacco or something. I have never seen a foam filled rudder that wasn't an airfoil rudder. Is there something new I am missing?

Scotty
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Re: Air Foil VS Foam Filled Rudders

Post by R L Williams » Mon Jan 12, 2009 11:57 pm

Yes Whitebear, we must be missing out, every rudder I've ever seen had an airfoil shape to some degree, except the flat ones that had yield on them.
Closed cell foam is light and adds a lot of strength.

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Re: Air Foil VS Foam Filled Rudders

Post by Whitebear » Tue Jan 13, 2009 12:10 am

My flat rudders had a big turn arrow on them. Shhhhh

Yes closed cell foam is strong and light. However I have seen rudders that were some kind of suspect foam filled that would wick a good 30 pounds of water in them. No clue what they were filled with, but it was the wrong stuff.

I'm thinking what were running into here is something like a trade name or a colloquial name not a scientific descriptive name. Thats all I can figure until somebody replies to this.

Scotty
"The Constitution is not so the government can restrain the people, it is so the people can restrain the government." Patrick Henry
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Re: Air Foil VS Foam Filled Rudders

Post by Waterthunder » Tue Jan 13, 2009 8:28 am

Your right White bear most people call the rudders that are 3'' or wider Air foils and do not consider the narrow foam filled ones 2'' or less as air foils! I ran a boat of mine for awhile with foam filled rudders then they came to be 50 or so pounds from holding water so I switched to wide air foils I noticed a few things I liked about the lighter wider rudders right away! Once again it's preferance but you should try both and talk to people who have ran both before you make your choice!
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Re: Air Foil VS Foam Filled Rudders

Post by Whitebear » Tue Jan 13, 2009 9:38 am

Thanks Dave, I kinda figgered thats where it was going. Back in the day before the new hollow rudders were popular here we called the foam filled ones airfoil rudders. We also called the big single glades rudder an airfoil. Ok, now I got it. I have run both and don't see a huge difference except the old rudders with more front to back area might have a bit more authority. I'd run either without too much concern.

Going a bit further, Im thinking the red foam we used to see is not the closed cell foam. We filled ours with the airconditioner gap foam and they did not wick water that I ever knew of but they werent open anywhere. We sealed the fill hole and the air vent hole after the foam had expanded. We used a 1/4" hole and a piece of steel brake tubing to inject the foam then threaded a 1/4-20 bolt in the end plates with some JB Weld and that was that. We shot the foam with the rudder rods in place. Just the old way of doing it but it worked for a lot of years.

Scotty
"The Constitution is not so the government can restrain the people, it is so the people can restrain the government." Patrick Henry
The government cannot give anything --
that they have not first taken from someone else.

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Re: Air Foil VS Foam Filled Rudders

Post by czech » Sun Jun 22, 2014 4:57 pm

I may be a little slow on this subject. I have hollow rudders and I noticed yesterday when I gave it the gas from a stand still while my rudders were turn. Look like walls were pushing inward.
When it gets to tough for everybody else,that's when its just right for me.15 X 7.5 Duckmaster,330 hp 350,79 3 bld whisper tip....and that's enough for me.

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Re: Air Foil VS Foam Filled Rudders

Post by bonecollector » Sun Jun 22, 2014 7:55 pm

doesn't someone make carbon fiber rudders?
Sensenich, Ox Drive gear box dealer 386-279-3712

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RJ
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Re: Air Foil VS Foam Filled Rudders

Post by RJ » Sun Jun 22, 2014 8:22 pm

I think Sensenich???

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Re: Air Foil VS Foam Filled Rudders

Post by boatair » Sun Jun 22, 2014 8:33 pm

I have run both. 2 sets of the hollow air foil rudders both developed cracks after several hundred hours of run time. The only thing on the foam filled rudders I have had has been rudder bushings [ after more hours than the others] I did notice a difference in steering when I changed rudders on my last boat but the hollow ones were 40" and the foam filled that I changed to were 48".

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Re: Air Foil VS Foam Filled Rudders

Post by ptillman » Sun Jun 22, 2014 10:28 pm

Where is Wade when you need him. I am on my second set of Hamant rudders (foam filled) and have had zero problems with them.
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Re: Air Foil VS Foam Filled Rudders

Post by happy harold » Mon Jun 23, 2014 7:44 am

foam filled are stronger with thinner metals. they are difficult if not impossible to repair. without the foam - repair is easy, but being hollow they pick up a lot of gearbox and engine noise.

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Re: Air Foil VS Foam Filled Rudders

Post by DannySauls » Mon Jun 23, 2014 7:59 am

A company called hammerhead aviation makes a set of carbon rudders there out of California, b-white has em on his boats

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Re: Air Foil VS Foam Filled Rudders

Post by rhodes » Mon Jun 23, 2014 1:23 pm

I believe the biggest reason they quit using foam,was the foam would expand when they were put in a powder coat oven. This would cause rudder to split at seam.

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