iam trying to understand propellers tell me if i have this right 4 blades more torque than 3 at given rpm the higher the number the greater the pitch ie 40 more pitch than 25 more pitch moves the boat further per rotation blade diameter should be the size of the rudder to give best turning radius
Its like starting in a higher gear your motor has to work harder to get it up to speed since it has to go through more.
i see so less pitch and a high rpm is the sweet spot how many rpm is safe before cavitation or is that trial and error
Once you have decided on what ship you are building. There has already been "trial and error" Ask what others are using for a drive train. You will want to match the motor gear box or direct drive with prop.
well actually thats what i was doing maxspin i am building a cleveland class cruiser i have gotten suggested motor ad prop sizes but something i read made me think a different approach could work better the recomendation was 3 blade 25 pitch 1.25 props on 380 motors but the prop will be slightly taller than the rudder i was considering a 1 inch prop and widening the rudder under the 50 percent rule for boats over599 foot instead of making it taller i could lengthen the rudder giving better coverage to the twin props
Just remember that once everything is glued in place it is difficult to move them. The problem being out by your self is that it is difficult to compare setups. I would imagine that for a Cleveland the difference would not be all that substantial either way. I would say that you would do better with the 1.25 prop. For a cruiser you want to line up your shot, then be able to accelerate quickly to get out of danger before someone can get their sidmounts on you.
Cruiser should be speed, not turning. You want to back down on your enemy and shoot, then accelerate and get the heck out of dodge. You have 50 bb's to shoot, take your time the battle lasts longer than you think. Go with the 3 blade 25 pitch 1.25 props on 380 motors. You can always change it out later after you battle it. How far are you into your Cleveland build?
well i would be further but work weather and a broken scroll saw blade have conspired to slow me down i have the front part of the keel and the front half of the ribs cut out and some are sanded the back ribs are still together i was cutting them out when i broke the blade in the scroll saw i had bought spares which turned out to be too long i bought some and a hand held saw tonight on the way home from work also i have most of the deck outline cut for the piece the deck gets screwed down to i will post pictures in a little while i should be ready for a dryfit saturday late i have brass tube to make stuffing tubes from but i may just buy some i was ready to order motors props and tubes thats why i was asking also i need to make a decision on rudder shape as i said 1,25 props are taller than the rudder and the rudder doesnt cover the props sideways either so i was thinking change the pitch a bit and go with 1 inch props get a wider rudder and i would get better prop coverage and i do understand the strategy but from what i was told originally a boats dont want to chase a boat with sterns and if they do its good for you and i will have to turn sometime if someone is chasing me that would be the most vulnerable time for my billboard cruiser also wont the smaller boat take off faster due to the mass difference
