sponson tubes

[Chris Wood]

I seen some pictures recently of some boats running and seen some things i didn't like with round sponson tubes. Over the yrs all boats or 99% of boats have round tubes.

Has anyone tried or seen anything in a shape oh say eliptical?

I realize round is the easy choice for our application but i want to try something. I thought at one time i seen some carbon fiber or fiber glass ELPTICAL tubes? I remember YRS ago on some of the old huey boats they had square tubes but that was out of really heavy alum.

Please realize i am looking at this as a builders side of things.. if i can make whatever work i want it to be repeatable and not overly complicated.

thanks

chris

 

[Duck899]

I would think that anything other than round gets complicated.....

 

[Jay Skutle]

I seen some pictures recently of some boats running and seen some things i didn't like with round sponson tubes. Over the yrs all boats or 99% of boats have round tubes.

Has anyone tried or seen anything in a shape oh say eliptical?

I realize round is the easy choice for our application but i want to try something. I thought at one time i seen some carbon fiber or fiber glass ELPTICAL tubes? I remember YRS ago on some of the old huey boats they had square tubes but that was out of really heavy alum.

Please realize i am looking at this as a builders side of things.. if i can make whatever work i want it to be repeatable and not overly complicated.

thanks

chris

all I can think of is the Octura Wing Ding boats from years ago, they had solid aluminum square booms, looked cool but heavy

Jay

 

[Duck899]

I built 3 or 4 gators in the 80's that had hardwood booms with angle pieces of wood then shaped into a wedge on all 4 for downforce.....looked nice.

 

[P THOMAS]

K&S tubing makes some airfoil shape tubes in sizes. this could slip over the round tubes. K&S web page say streamline tube is available 1/4 to 3/4 size.

I have used it for wing struts on scale hydros

http://www.ksmetals.com/retail.html

 

[Glenn Quarles]

Chris, I used to run 1/8" X 1/2" flat booms in some of my .21 SAW stuff...infact the first .21 hydro to ever go over 80 mph had them. They worked good, were very nice and stiff, and I don't remember ever breaking one,

Glenn

 

[dwilfong]

K&S tubing makes some airfoil shape tubes in sizes. this could slip over the round tubes. K&S web page say streamline tube is available 1/4 to 3/4 size.

I have used it for wing struts on scale hydros

http://www.ksmetals.com/retail.html

This is the stuff you are talking about.

David

 

[Chris Wood]

ya david.

only i want the WHOLE TUBE to be that stuff out of carbon fiber or fiberglass if possible. that would replace the round tube all together.

i am probably wasting my time on this but after see some pics it is stuck in my head

chris

 

[shoboat]

Chris,

Not as critical as one may think, we have tested many different set ups.

Smaller diameter tubing will work just fine. I think a lot of people are

caught up in the aero-profiling of their boats, but I know most still need

a better pipe and motor combination with better fuel. RPM = SPEED

Most still are not producing enough RPM and so now they are looking at the

profile of the boat. A lighter boat will help most go faster, but you still

need to find away to make more RPM. Testing different combinations is the only

way that you will find a better set up. Like Roger Penske says "Effort Equals Results"

Just My Observation Currently,

Mark Sholund

 

[mtruex]

ya david.

only i want the WHOLE TUBE to be that stuff out of carbon fiber or fiberglass if possible. that would replace the round tube all together.

i am probably wasting my time on this but after see some pics it is stuck in my head

chris

chris,

i have looked for some of that stuff too with no luck..not only are they less drag, but i was more interested in torsinal stiffness to control the turn fin sponson better.

 

[lohring]

I won a free lunch from Mike Bontoft over round sponson tubes. He did his usual careful testing and found that the drag of a streamlined tube was much less than a round tube. I bet that we couldn't measure any difference in speed at around 100 mph that our gas rigger was running. The point is that air drag is tiny compared to water drag. Anything you can do with air lift to lower water drag will help despite an increased drag penalty. We ended up angling the airfoil on the front sponson tube up to help hold the front down. The boat was able to go faster.

Lohring Miller

 

[Rudy Formanek]

If you really wanted solid carbon rod in an airfoil shape, you could make it yourself. Some of the competitive R/C glider guys have made custom CF wing joining round rods with a dihedral bend in the middle so they can take the stress of super powerful winch launches and high "G" turns. They make a mold with open ends and use carbon tow saturated in epoxy, they cut it a little over twice the length of the mold, tie it in the middle to a STRONG twine then drag it into the mold from the end. There have been a couple threads on some of the glider forums. Maybe you can find them with a google search. The type of epoxy that you use will be important to the final product. Some epoxies are rubbery and are great for wood assembly, but not so good for laminate lay-up. Rudy

 

[dwilfong]

ya david.

only i want the WHOLE TUBE to be that stuff out of carbon fiber or fiberglass if possible. that would replace the round tube all together.

i am probably wasting my time on this but after see some pics it is stuck in my head

chris

Chris

The LHS has this in different sizes. It is quite stiff and light. I will see if the one size will slide in to the next size up. If I remember it will.

As for the airo effect, It will make the boat handle different. The AOA of the foil will change the ride of the boat. Took it of my boat, made the set up real hard for me. Too many variables to control,for me at least. I think it would work good for a SAW boat running on calm water. On a heat race boat Don't think so. Not for me any way.

David

 

[Chris Wood]

cool david

let me know what you find out.

thanks for the info lorhring.

chris

 

[dave roach]

The only way to fined out with set up that Chris is talking about on the tubes is to have a wind tunnel to do testing.

Dave Roach

 

[Tom Foley]

I know I'm old and conventional in thought patterns ...but thrashability between rounds and quick cheap replacement is where it's at for me . Also when your boat reaches for the sky and you lift to bring it back down ..more positive AOA from eliptical tubing won't help you much I wouldn't think !

 

[misshydro]

Chris,

Not as critical as one may think, we have tested many different set ups.

Smaller diameter tubing will work just fine. I think a lot of people are

caught up in the aero-profiling of their boats, but I know most still need

a better pipe and motor combination with better fuel. RPM = SPEED

Most still are not producing enough RPM and so now they are looking at the

profile of the boat. A lighter boat will help most go faster, but you still

need to find away to make more RPM. Testing different combinations is the only

way that you will find a better set up. Like Roger Penske says "Effort Equals Results"

Just My Observation Currently,

Mark Sholund

So you rather go for speed then looks/aroprofile/aerodynamic? I would do both to get the fastest speed out of it.Ya you can get a brick to go fast,but how fast? There alimmit a rigger can do without aroprofiling it. With making them aerodynamic like cowls to the tube widht at the front to sponson design. I bet most of those fast riggers at saw trials have aeroprofiles to them..I've kind of like chris's idea about those boom tubes. The ones that Dave posted could acted like spoiler to maybe help keep the front end planted down at hight speeds?

 

[Ian Webster]

Not seen any in glass or carbon but the you can find aerofoil masts in aluminium for sail boats:

Aerofoil spars

 

[Charles Perdue]

I seen some pictures recently of some boats running and seen some things i didn't like with round sponson tubes. Over the yrs all boats or 99% of boats have round tubes.

Has anyone tried or seen anything in a shape oh say eliptical?

I realize round is the easy choice for our application but i want to try something. I thought at one time i seen some carbon fiber or fiber glass ELPTICAL tubes? I remember YRS ago on some of the old huey boats they had square tubes but that was out of really heavy alum.

Please realize i am looking at this as a builders side of things.. if i can make whatever work i want it to be repeatable and not overly complicated.

thanks

chris

Hello Chris, did not get to see you in Hobart, things did not go as planned.

Use the size of K&S steamlined tubing that satisfies you, find the size of CF rods that will fill it tight (usually 4 peices of different sizes), mix up chopped CF with some good epoxy (I use West Systems), generously coat the rods and slide them into to tubing. This works great. Use the next size up of tubing, cut short lenghts to go into the sponsons, stand them on the edge and very gently tap them (this will make them thicker) until the sponson tube will fit. Mount these into the sponsons and leave about 1 1/2 inches sticking out and put a 4-40 screw into them to hold in place.

One of the other advantages of this system is the aluminum tubing will show if an impact hard enought has happened to crack the CF rods, it will wrinkle.

Have been using this setup for quite a few years and no problems.

This is like the old woman whizzing in the ocean, every little bit helps.

Charles

 

[lohring]

Our record holding 110 mph rigger is "streamlined". It is more to look good and have controlled lift than to reduce drag. Running an exposed pipe as well as adding various blisters and imperfections didn't change the speed. Changing the rudder design added 6 mph at 100 mph. Changing the sponson design added 3 mph. Shortening the rudder 1/8 inch got the peak speed from 108 to 110 mph. Water drag is the problem, not air drag.

Lohring Miller