Am thinking of changing from my 2 blade prop to a 3 blade. A 12" 5P 3 blade is the what I was told to use. What has been the thoughs on this change.
Thanks David
Why would you change if the two blade prop was 'sucking' up all the available hp that your engine has?
Wouldn't a three blade just have less pitch in order to keep the rpm of the engine in the same range as the two blade?
I can never figure this stuff out.
Anyone know why an automatic transmission that can shift through the gears are not used on any boats?
I mean as the hull through the water increases in speed why not shift gears to reduce engine rpm's...?
I remember one of my dad's houseboats having twin Chrysler 383 V-8's with Velvet drives and 4 blade props that would stand both Carter four barrels carburetors butterflies wide open and engines would turn maybe 3200 rpm, but we were on a plane and could go skiing quite well.
skip.
Hello David,
As there is a two blade prop on the boat I just made an offer on I thought I'd do a little reading about it. I may wish to replace the prop while she is still on the hard... As you might expect, there are advantages and disadvantages both ways. Either way, I always think it best to make informed decisions if possible.
http://www.sailnet.com/forums/general-discussion-sailing-related/4205-three-blade-prop.html
http://www.cruisersforum.com/forums/f114/two-blade-vs-three-blade-prop-24747.html
http://www.rhkyc.org.hk/files/Marine%20Article/Props.pdf
http://www.boatfix.com/how/props.html
http://archives.sailboatowners.com/pviewarch.htm?fno=0&sku=2002273163242.53&browse=T&g=%5Bg%5D&ptl=Prop%3A%202%20Blade%20or%203%20Blade
There is a lot more information out there. Just Google two blade vs three blade prop if you have time on your hands. By the way: Welcome to the forum!
Quote from: txsurbrook on March 16, 2010, 08:38:08 AM
Am thinking of changing from my 2 blade prop to a 3 blade. A 12" 5P 3 blade is the what I was told to use. What has been the thoughs on this change.
Thanks David
Quote from: txsurbrook on March 16, 2010, 08:38:08 AM
Am thinking of changing from my 2 blade prop to a 3 blade. A 12" 5P 3 blade is the what I was told to use. What has been the thoughs on this change.
Thanks David
David,
I recently attended the Central NY boat show and was talking with Schyler Barnes from 'The Sailboat Shop" (www.thesailboatshop.com) who mentioned that they sold a new 27 last year and ended up replacing the 2 blade prop with a 3 blade prop in order to get rid of a vibration problem. You may want to contact them & "pick their brains" so to speak.
Bill E
In general, two blade props are more efficient but three blades run more smoothly and may require less diameter. I have a two blade on my CP-27 and the small Universal 10 hp engine. Vibration is not much of an issue, but efficiency is, so I plan on keeping it.
There is some good reading on propeller selection (which gets very technical very quickly). A good, accessible discussion is in the "Dummies Guide to Boating" (which I found in my local library) but many yacht design books will cover it too, if perhaps with more maths. I'd recommend reading up on it a little before deciding to switch the prop.