Cfm

[Jayhawk]

No nothing about mini-airboats. Do you go by CFM for prop size and speed?

[Duane Scarborough]

Jayhawk,

Welcome to the Mini Airboat forum.

Many of us may not know what CFM means.

No, we do NOT judge a Mini by CFM.

There used to be a definition of "What is a Mini" on the log on page. I notice that it's no longer there.

I can't remember exactly what it said, but basicly a Mini is a small airboat that uses a small engine. They are usually non-automotive engines. Though we do welcome those that build boats with SMALL automotive engines. There's not many, but there are a couple.

MY boat uses an ex-military 4A084 generator engine. That's a 4 cylinder horizontally opposed 45 HP, 84 cubic inch air cooled engine. It stretches the limit a bit, but is still acceptable.

Look around a bit, and you'll get a feel for us.

Duane

[buster]

Jayhawk,

Welcome to the Mini forum. If you are interested in airboats, especially smaller ones, you're in the right place. Some of us didn't know much about them when we found this site, but you can't help but learn fast.

Ask any questions you can think of, and someone will be glad to supply the answer.

BTW, it sometimes helps to know what part of the country you are in?

Dave

[Jayhawk]

S.W. Kansas--Have never seen an airboat in my area. We do have a little bit of water.
Was just going to try and play around with something before i put much money in an engine and prop.

[Wildfowl]

Hey Jayhawk,

Back to your question CFM in itself is not a good measure for indicating prop size. There is some great prop information all over the site but if you go to Mini Tech and then Props that is a good start.

Lots of opinions there and at a given time all of them correct... well most all of them. In a nut shell you want to run your engine at the rpm where it makes maximum horse power. Then you weigh your prop options from there. If your motor makes maximum rpm at over the max rpm's for a particular prop style you'll want to use a reduction unit (thread for those too) that lets your motor run at higher rps then is recommended for the tip speed of the prop. The reduction unit spins the prop slower than your engine

Reduction unit or not you want to pick a prop that will get the most push and still allow your engine to make maximum HP. Too much prop and the engine will bog down and you loose push. Too little prop and you over rev, burn more fuel, go slower, and make a lot more noise. Oops... sorry, make more sound. We try not to use the n_ _ _ _e word around here.

[buster]

Hey Wildfowl,

First, glad to hear from you again.

Second, I don't think us airboaters need to avoid the n----e word, Just do like the guys that play musical instruments do, call it a "joyful" noise (That could also be interchanged by any number of adjectives...cool, neat, powerful, awesome, etc.

Dave

P.S. In case you are still looking to buy a boat, the Aircat 084 is up for sale, I just relisted it on ebay.

[Duane Scarborough]

Hey Jayhawk,

Back to your question CFM in itself is not a good measure for indicating prop size. There is some great prop information all over the site but if you go to Mini Tech and then Props that is a good start.

Lots of opinions there and at a given time all of them correct... well most all of them. In a nut shell you want to run your engine at the rpm where it makes maximum horse power. Then you weigh your prop options from there. If your motor makes maximum rpm at over the max rpm's for a particular prop style you'll want to use a reduction unit (thread for those too) that lets your motor run at higher rps then is recommended for the tip speed of the prop. The reduction unit spins the prop slower than your engine

Reduction unit or not you want to pick a prop that will get the most push and still allow your engine to make maximum HP. Too much prop and the engine will bog down and you loose push. Too little prop and you over rev, burn more fuel, go slower, and make a lot more noise. Oops... sorry, make more sound. We try not to use the n_ _ _ _e word around here.

Mike,

Good answer. I wish I'd said that.

Glad to hear from you again. I was beginning to wonder if you'd been flung off of the rock.

But the "N" word doesn't need to be whispered though. We ALL need to be conscious of "N", and do what we can to reduce it. There is no way to make a stealth airboat, but we do all need to keep the "N" as low as is reasonable. That'll help keep the anti's at bay.

Another thought that I've had: We need to invite our closest neighbors, (the ones that may object most to the "N") for a ride. They may be a bit more tolerant of the test and tune "N", if they've had a ride or two. Just sayin'

Duane