Propeller and power from human
I'm working on a schoolproject. We are designing a human powered boat. We're supposed to use Wageningers B-series propellers. The problem is that the BP value I find (to use in the Bp-delta diagram) is to low for the diagram. Of course I can tune the RPM so the Bp value fits into the diagram. But I wonder if there can be any better solution. Anyone who can give me a suggestion?
We tested power on a excercise bicycle, and we got 450 W out.. The boat shall be built for an competion. The boat shall go 200 m. So we count around 1 min time from start to goal.
We hope to get a speed up to 9 knots. Someone told us that CRP propellers can give us better effect... Is this true??
Hope anyone can give me something..
Greetings from Norway
Get a copy of Principles of Naval Architecture (the current 3 vol set - you need Vol 2) through SNAME, probably by interlibrary loan. It has the algorithm to develop Kt, Kq vs J directly for B-series props.
A CPP prop probably won't help, since you are only interested in one speed point.
Wageningen B series propeller
Send me some data of the boat:
Lwl, Bwl, T, T-transom, Cb, LCB.
Hull shape (V, U ) = ?
P= 450 W,
Distance of center of propeller to water line = ?
Send me this data and I will let you know what can be done.
First, the Wageningen B series propeller is a pretty poor prop for human propulsion as the blade area distribution is all wrong. If you have to, use a B2-20 or so, pitch it well up, lower the RPM (about 200 max) to reduce losses, maximize the diameter, and DO use counter-rotating because it will get you better initial performance (I assume the 200m is from a standing start) from the human power so the added complexity is worth it. See if you can "bend" the rules and use the base Wageningen series to develop a better prop that the "standard" ones.
When designing a HPV prop it is important to remember that the torque curve of a human turning a crank is basically flat until you reach about 40-60 RPM and falls off rapidly to 0 at about 90-120 RPM. This is due to the energy expended in just moving the mass of the legs so get your propulsor into training now. Also make the prolulsor recumbent with a backboard and handgrips to allow him to overpush his weight. A gear shift is also helpful once the vessel is moving well to recover torque on the curve.
Try www.ihpva.org or www.foils.org for more on human powered vessels
Edited to add www.waterbiking.org
Last edited by jehardiman : 03-15-2005 at 03:14 PM. Reason: added ref
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