Streamlining sponson tubes

[Preston_Hall]

First of all, this calculation is flawed. It is a static measurement, not a dynamic one. The air is moving across the surface instead of the surface moving through the air. Potato -Potatoe, It doesn't matter.Was lateral loading of the bearing surface calculated?Why? What was the bearing surface? If a better bearing were used then you would see increased diffrences.Was the surface of the raw tube the same as the streamlined one? If the numbers are right then I will use whatever surface he had. But I am sure that is miniscule.Even if all of this was considered the rear tubes will not see the same air pressure as the front ones, because they are in turbulent air. Ok, so instead of a 1lb gain you get a .5lb gain, agreed?Also this calculation would only be correct in a straight line. So I go faster in the straights, great!In a turn the resultant vectors would give a significantly different result. Again, miniscule in the grand scheme of things but since we are getting picky.

I would be interested in seeing the equation that was used to determine this.

F=ma

I think it was a 7lb boat, 2 second interval, 30-100mph that we assumed. This would be a typical 100mph straightaway pass.

Found the thread Calculation

Is Ben Stein wrong also? Don Ferrette said it sounded good to him as well.

Basically, all we are asking here is if the collected data at the beginning of this is correct or not. It was measured and agreed upon. It was down and dirty but good enough to prove a theory. Nobody says it will go directly on a boat and provide an instant gain. That is like saying, "Here is a prop that will go 150mph. Put it on your boat and you will go 150mph." That would be silly.

 

[rhomodel]

Guys I think Mike has already done a lot to his gas rigger ( e.g. a 3,5 inch tub, aircraft fuselage formed tub) to reduce drag and make thge frontal area smaller. Now he's on to the boms trying to reduce those as well. Only making the booms a different form wouldn't help but if the rigger design is different from the start all the little bits will help. I would not be surprised to see his rigger break the 100 mph barrier in a week

julius

 

[Preston_Hall]

The value of C[SIZE=8pt]D[/SIZE] (Drag Coefficient) for the drag on a smooth sphere moving through air with a Reynolds number of approximately 10^5 is 0.5. A highly steamlined shape like that used in most airships(blimps) has a C[SIZE=8pt]D[/SIZE] of approximately 0.04, a reduction by more than a factor of 10. ( I said that before)

Drag coefficient of a cylinder is 1.2. For a navy strut (airfoil shape) .1.

Courtesy of

Applied Fluid Dynamics, Fourth Edition

If you drive your car 100 miles and use 5 gallons of gas then you got 20 miles/gallon. No matter what math there is to figure out burn rates, friction, port area timing, gas velocities.......blah, blah...............if you get some other answer other than 20 mpg then you are wrong. The guy stuck a boom tube to a scale in front of a leaf blower!

Mike,

I hope you break 100! And when you do I'll sit back and watch every gas rigger get fitted with these tubes.

I bet if AB used them we wouldn't even be having this discussion.

 

[Ron Olson]

Charley, I understand that his calculations might be flawed. Who's to know if the Leafblower really was putting out 100 MPH speed? This wasn't done in a Laboratory but probably in his garage. He did what he could with what he had to do some experimenting so these numbers aren't hard and fast or etched in stone but interesting anyway. He has piqued some interest with 4 pages now of responses!

 

[TimD]

I bet if AB used them we wouldn't even be having this discussion.

Exactly. I still think discussing this issue is worth persuing regardless of how small the gains may be - why? Because we can apply similar techniques to other areas also. I would think sponsons and transoms on a rigger could definately benefit from more research into aero. Remember 2 bicycle repairmen revolutionised the world as we know it by trying things just like this!!!

 

[Don Ferrette]

"I bet if AB used them we wouldn't even be having this discussion."

Actually, Andy has played with this though his approach is a little different. He went for a reduction in cross section of tube rather than risk possibly inducing lift with the airfoil shaped boom tube..........

 

[ClayGlover]

Hey Don, does that boat's sponson have a dip in the crown near the front 1/3, or is that just an illusion in the pic? Also, that strut bearing extends back about an inch and a half longer than mine. I think all of the newer cmd struts are like that. Do you feel it's worth replacing the "flat-backed" one I have for the extra leverage on a 45sg?

 

[Don Ferrette]

It's an illusion, look at the other side & you'll see it's not there. I thought the same thing at first glance....... :huh:

 

[ClayGlover]

woops, dang you ARE fast Don. You drive as fast as you type?

I edited in a second question and you had already answered my first before I could hit enter...lol

Hey, I think we met a few years ago at the 2000 nats. Were you set up just to the right of the pits? Could be wrong.... that's my brains on nitro :lol:

 

[Mike Bontoft]

I have been busy finishing boats, I have to leave on thursday morning. In boat testing the foils they did not seem to have any adverse effects. I was very carefull to get a neutral angle of attack. I expect them to yeild about 1 mph at 100, and it is true the reduction in drag compared to other forces is miniscule, I would be very supprised to see any more than this. But right now I will take every MPH I can get.

Mike

 

[TimD]

Good luck at SAW trials Mike!

 

[Mike Bontoft]

Thanks

If everything holds up and the weather co-operates you will see some big numbers!

Mike

 

[Don Ferrette]

woops, dang you ARE fast Don. You drive as fast as you type?
I edited in a second question and you had already answered my first before I could hit enter...lol

Hey, I think we met a few years ago at the 2000 nats. Were you set up just to the right of the pits? Could be wrong.... that's my brains on nitro :lol:

'99 in Huntsville was my last Internats

 

[PHM Racing]

Have any of you guy's considred putting an APPLICATION in to NASA :lol: :lol: :lol:

Keep up the good work guy's and remember we do this for fun not to hang out with of wives not that i don't love mine

Mike