New hull design

[drhull]

I am a newbie here and am trying to get any information on what schools or colleges in the southeastern Wisconsin area (Milwaukee) have some sort of engineering or design classes that could run tests on a potential new hull with my rough drawn drafts for resistance / friction.This design would be mainly targeted at17-20+ ft. fiberglass power boats Thank you,ML

[kenJ]

Check the engineering departments of your local colleges. Its not close, but the U of Michigan has a great marine engineering/naval arch department.

[jehardiman]

As KenJ says UofM has a short tank (360'), but I'm not to sure the carriage speed (22 ft/sec) will get what you are looking for. There may also still be a commerical tank with wavemaking capability a Chicago Bridge and Iron in Plainfield Ill. but I haven't heard if it was still available in a decade or so. FWIW, for a boat that size it may be more cost effective to build a protoype full size than run a full model series.

[kenJ]

my limited experience has been on sailing displacement hulls. I was thinking perhaps there is also a planning VPP that might be used to back door the results.

[drhull]

Ken, way over my head what is "I was thinking perhaps there is also a planning VPP that might be used to back door the results".? Dont let my screenname fool you I have no experience at this. Thanks M.L.

[drhull]

This has probably been done before as I read on to further threads.the concept is almost the same as what the fish scale sounds like but only would be cavity tear dropped shaped^ flush with hull and air outlets to blow air from onboard blower(s) from midship aft. blowers would have auto shut-off once the boat is turned set amount of degrees to prevent skimming on water. This probably won't have any performance advantage at start but once on plane possibly?Blower intakes and sf/m blowers unsure about along with outlets on the hull. Ducting invovled but worth while not sure. Any ideas welcome or if this has been done before. I'm not trying to create a hover craft either just less friction. Thanks all for the info provided.M.L.

[drhull]

More info on this concept if at all new is for 12v.electric blowers to run through some type of smooth pvc plastic and lightest motors possible. Don't want to run exhaust because of heat and engine performance loss. Plus using fresh air won't have any EPA DNR issues. When boat is taken out of the water turn blowers on to blow out water and junk if inside. M.L.

[drhull]

This would not really be a new hull design, traditional V-hull or? With this incorporated into it.

[Myoung42]

If it's a planing boat, you can get some good idea of the resistance from the works of Dr. Savitsky. search his name on this forum and you'll come up with several papers dealing with smooth and rough water planing performance of flat bottom and V bottom hard chine hulls. If nothing else, it would help you size your engine and check for planing stability. Not exactly "light reading," but not all that complicated either.

Sounds like you're scheming to blow air under the hull to reduce resistance? So, the force of the air cushion pushing up = force of the boat dead weight which is a hovercraft. Either way, without some kind of skirt, the air would escape so fast that I doubt you'd see any resistance change, and the blowers would needlessly eat up power. So without a skirt, I don't see a blower making sense for a full air cushion.

It might be interesting to see what inducing a layer of individual bubbles against the hull does to resistance though. Maybe this could be done by running a series of open pipes along the buttocks of the hull with one end pointing backwards and the other open to atmosphere above the waterline (similar to an auto bailer for an RC boat). At high speed, maybe it would induce some bubbles. I don't know the effect of riding on bubbles would be, and when compared with the drag of the opening?

I hope some of this helps somehow. I apologize for getting long winded..

Good luck

[messabout]

Use the search function. The air entrainment,bubble generator/or whatever, idea has been the subject of numerous threads here. In fact the subject has been flogged mercilously over time. Hovercraft has also been discussed at length.

[J3]

A few threads on inducing air / ventilating the hull
The use of air
Air injection for planing hulls
Air Injection
Ram air stepped hull

http://www.bravamarine.com/docs/Cont...-Dampening.pdf

More common is passive air passages used to ventilate steps (Outerlimits, Hallett) - have not seen blowers pumping air under a hull yet.

[drhull]

Sorry guys/gals thought possibly it was a good idea. But has been researched thoroughly by others. The only thing I'd like to add is this would mainly work when on plane or at higher speeds that way the air cannot escape out the sides or front because of strake and chine design the craft would have to pass over the air because the strake and chines would be designed to keep it under until it the craft passes over it unless obviously going slower than planing speed. and again air would be emitted from midship to aft.On 17-20+ ft boats. Sorry for beating a dead horse! M.L.

[drhull]

Thanks for all the info, J3, Messabout,KenJ Jehardiman and Myoung,I should have checked into this more thoroughly before posting. Very informative. M.L.

[drhull]

Outlets would be pointing toward the stern in a teardrop concave/recessed area not to large staggered throughout hull between strakes and chines thus blowers wont have to force the air just lots of volume of air. Working somewhat like a drain plug but with air. Beating a dead horse again Sorry! M.L.