Where do we Go From Here?

[Tim_Duggan]

My son (Eric) did some CFD markups and modelling of some of the SAW sponson and boat designs that we had seen at Flint, and a set of M Nowicki 21 SAW sponsons that I have. (Eric is currently working on his Masters at the University of Michigan in Aerospace Engineering). The results were very interesting and a lot of the shapes that we thought would be aero slick had a lot of room for improvement. It was really pretty interesting stuff but he is so busy with full time work and full time at the U of M that the project has been filed for the future. He is convinced that there are aero opportunitys out there for our boats... . Tony J

TJ, Your son Eric must be one very smart cookie - a Masters in Aerospace Engineering - WOW!

The stuff revealed for our application from CFD research would be invaluable. The jump in performance could be huge. F1 teams spend serious bucks on this plus wind tunnel testing in very sophisticated tunnels for very good reasons. Wings in ground effect are very tricky things.

 

[moparbarn]

google switzercraft flying wing. remember, these boats were raced in the mid to later 60's. wings & aero considerations are not new in boats. probably one of the first sucessful applications of these concepts. i grew up watching these boats race. they could run with just the props in the water for the entire straightaway.

 

[tobbec]

The secret to what this wing does is in its shape top and bottom reverse aero foil section. You wont find a single modern competitive tether hydro any where in the world that does not use these wings. Regards Martin.

Hi Martin,

Do you run a particular wing profile and width, or is it more of a "trial and error" approach?

Tim.

Surely there will be a certain profile thats the best one for our purpose but the way to find that out can be long

My dad where in rc flying also and build lots of different sailplanes i remeber and there was way over 100 different profiles.. I had to help him then with the computer to fit the program and so. Thats why i remember this.. But it seems to me it should be an upside down profile of some kind ?

 

[Jorgen Andersson]

Hello

In tether racing I see little use for a fin, but in RC it could be a good help on certain designs.

As Charlie pointed out the straight line stability gets affected when you go from a "box" tube and sponsons design to a more streamlined. I have my stabilitzer tests and I will add a small fin, I will let you know my findings.

When it comes to the stabilitzer profile I think a typical Clark-Y will work great to start with. This is a flat bottom profile you use on airplanes that are designed to be stable and not aerobatic.

In heatracing, could it be an idea to see if you could steer with the turnfin instead of the rudder? Or both?

Jorgen

 

[Martin Hamilton]

Hi Tim the wing shape we use is reverse aero foil, Basically an aeroplane wing in reverse. The top surface of the wing is not flat but a gentle even convex curve from front to back on the wing, Under side is curved from front to back but instead of an even curve it starts off from the front with a steeper curve an reaches maximum thickness around 1/3rd of the wings width in from the front of the wing and then a more reduced curve the other 2/3rd. Bearing in mind this is for tetherd boats as i dont run rc hydros. Size wise we know more or less what works for us depending on size & class of boat but some times you find you might need to on a new boat to use a smaller or larger wing. Regards Martin.

 

[Jorgen Andersson]

Hello Tim

That airfoil is the classic design you have used on race cars since the 50´s.

Both fullsize and RC cars have used this type for a long time.

One of the first attemps was a Swiss guy in a Porsche 550 that used a piece of a crashed airplane wing, mounted upside down in the middle of the car and mounted on steel tubes.

If someone wants to do initial tests on the RC hydros, I do not think that the airfoil is very critical in order to see how it performs in respect, wing, no wing.

Jorgen

 

[Archie Stanton]

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[Jorgen Andersson]

Kevin

Just make it easy to start with.

There are several good mounting points on the back of the boat.

I have made my stabilitzer and fin in Divinycell and the covered in one layer CF.

The mount to the boat with nylon screws. The idea is that screw can break off in a potential crash in order to save the parts.

When I did my first tests 3 years ago I made the stabilitzers i balsa and/or light plywood and the covered with Monocote, just like RC planes have.

Jorgen

 

[Archie Stanton]

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[Jorgen Andersson]

Hello

Yes, many ways of making one off parts.

I try to make a few versions of each new parts to be tested, and to make the first ones VERY simple, in order to get an idea of how it workes.

Many times it comes out very different from the first design or idea......

Jorgen

 

[Archie Stanton]

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[Jorgen Andersson]

Looks good, that will work.

What do you plan to cover the stabilitzer with?

The only potential "problem" I foresee, is that it will be sensitive in a crash, but no real issue at this point.

Jorgen

 

[Archie Stanton]

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[Jorgen Andersson]

Plywood will work fine, but must be epoxied or something similar.

To improve the strenght and ridgidty, may I suggest that you incorporate the airfoil section on the mounting/centre pieces?

Jorgen

 

[Archie Stanton]

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[lohring]

As I said, the pitch on available propellers isn't enough at existing engine rpm limits except for 3.5 engines that turn over 30,000 rpm. Mark Grim got the first G1 hydro record over 100 mph with a custom prop. We beat that record with another custom prop. Before that the best G1 boats ran in the high 90 mph area with pitched up 2170s. The difference between that speed and our 109+ GX1 record was mostly engine rpm.

When we were going after the GX2 record, we built a custom pipe that gave away nearly 2 hp to be able to turn 25,000 rpm. Unfortunately, that was beyond the mechanical limit of the engine and we limited the rpm to 23,000. Don Maher and others have experimented with gear boxes. Considering the rpm the electric boats turn, that seems to be promising.

Lohring Miller

 

[Charles Perdue]

That would work with grinding an angle on the vertical fin, but any change that you make at the back like that is very sensitive. May be better by making it straight to the centerline and shimming the yaw in the rudder.

One trick that I do is offset the nose of the boat slightly to the left to trim the boat, this accomplishes the same thing. Then you can finish "tuning" the boat with a sanding block at the lake to make it run neutral.

 

[Chris Wood]

one thing i would suggest maybe.. if your boat is going to have a bait box.. till you get things set.. try dbl stick tapeing it to the bait box lid.. that way if you do flip. it will pull the lid off that is taped to the boat.

chris

 

[Martin Hamilton]

Archie that is the reverse aero foil shape that we us on the tether boats, Much simpler looking at a drawing than me trying to explane the shape we use. Regards Martin.

 

[Charles Perdue]

This is the 40 version of the new Boss rigger design.

Marty Davis, you should like the rooster tail behind this boat.