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Old 12-29-2012, 11:14 AM   #61
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Marin any Beaver that "climbs like a rocket" must have a good prop on it.
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Old 12-29-2012, 02:29 PM   #62
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There were a few attempts in the 60's to get prop driven planes above supersonic. They were all abandoned because of the huge in inefficiencies they got when pushing them that fast.

I fly RC planes and some I've seen get into that situation and usually throw props at high speeds like that.

Boat props need to be able to get clean water on each bite. With a displacement boat like a trawler, you would have problems adding blades to get much smaller.

I have 4 bladed 26" x 18" props on mine and a spare set of 3 bladed 26" x 19" props as well.

Reducing the blades means trading diameter or pitch and you run out of pitch pretty quickly.
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Old 12-29-2012, 02:51 PM   #63
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Boat props need to be able to get clean water on each bite.
Really?
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Old 12-29-2012, 03:01 PM   #64
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Google "Howard Arneson"....
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Old 12-29-2012, 03:07 PM   #65
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I am most likely wrong but have been told in very basic layman's terms that the bottom third of a marine prop is the most efficient. Top 2 thirds not so much. Arneson surface drives where created to take advantage of that principal while reducing drag.


Can't wait to see Healhustler photo shop an Arneson drive onto Eric's Willard.
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Old 12-29-2012, 03:28 PM   #66
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Look at the tubes at the top, front of the props.
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Old 12-29-2012, 03:47 PM   #67
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CP,
Willy hits whales so I don't want to go any faster.

So Larry I'm look'in ...???

looks like ther'e there to pull in air.
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Old 12-29-2012, 03:54 PM   #68
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Howard Arneson shop is 20 minutes from where we live. I pass by often. In past years Iíve had the pleasure of meeting the fellow as well as being inside his shop. We see Arneson test boats on SF Bay and the pretty semi-rig that trailers them from shop to launch on tests. Howard is a genius - pure and simple. As most inventive geniuses will say - 90% sweat / !0% brains! He always worked hard.
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Old 12-29-2012, 04:08 PM   #69
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CP,
Willy hits whales so I don't want to go any faster.

So Larry I'm look'in ...???

looks like ther'e there to pull in air.
Yes, for better bite? I don't know. Way faster than we are though.
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Old 12-29-2012, 04:20 PM   #70
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I saw one in Alaska in 03 that had only one Arnason drive and went 70 knots.
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Old 12-29-2012, 05:16 PM   #71
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I watched one of Howard's boats "fly" through Raccoon Strait on the north side of Angel Island a couple of years ago. My rough timing and calculation had him pushing about 95 knots suckin' air the whole way!
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Old 12-29-2012, 05:27 PM   #72
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Yes, for better bite? I don't know. Way faster than we are though.
They are called vent tubes and are used to help get the boat on plane faster by ventilating the props so they work as designed rather than in "clean" water.
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Old 12-29-2012, 05:53 PM   #73
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Due to jet engine propulsion and/or type of fuel usage, some of Howardís speed boats were evidently registered with the FAA. Iíve heard stories there is basically no limit to the speed attainable so long as the boat can be kept on/in the water with the uniquely designed props still having water propulsion capabilities. Local rumor had it in the 90ís that 150 + mph was not unusual during some speed tests.

Personally, I like cruising in my pleasure boat at hull speed... etc, and, hanging on the hook to play with our tow behind runabout or go swimming deep inside SF Delta warm freshwater!
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Old 12-29-2012, 06:04 PM   #74
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Quote:
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Marin any Beaver that "climbs like a rocket" must have a good prop on it.
Been on a few beavers in my day, not fussy when they move too fast. I like enjoying all the ride and oh ya the scenery!

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Old 12-30-2012, 01:17 AM   #75
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Such boats (not trawlers) make "rooster tails" at speed.



Meanwhile, in an opposite view, Ray and I contemplate Sam's (in Tiburon, CA) menu:

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Old 12-30-2012, 03:05 AM   #76
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That was a great lunch. Where were all the folks?
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Old 12-30-2012, 10:54 AM   #77
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That was a great lunch. Where were all the folks?
Inside keeping warm!
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Old 12-30-2012, 11:18 AM   #78
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I like your pictures Mark and the humor that frequently tags along.

I get just about as excited about rooster tail boats.

The original poster only made one post after #1 and never did proclaim how the 3 blade prop was loaded. He says it "turns 2400 at speed". Is that w a 2500 rpm engine or perhaps a 2800 rpm engine. To your specific question I'd say yes it should be close. Two inches in dia is a lot but an extra blade is a lot too. The Michigan MP "workhorse" propeller is basically a commercial propeller for fish boats and such but it's very heavy duty and has lots of blade area. A possibility.

But I suspect that most likely there is nothing wrong w your 3 blade prop. Try to find other sources for your "problem" (the chop chop noise) unless the 4 blade is handy (as in don't have to buy it to try it) then just try it.

Most of us (at least lots of us) are running 2.57-1 BWVD gears so your gear ratio is'nt so deep as to be unusual. So there is an excellent chance your props are not overloaded and the 3 blade/4 blade issue is of very little importance.

If you can put your head right down near the bottom of the boat while running and if your boat is MUCH more noisier than others your prop to hull clearance is probably too close.

Perhaps your boat would benefit from a nice big fat overlay of matt right over your propeller on the hull inside the boat.
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Old 12-30-2012, 11:44 AM   #79
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I cruise at 1400 rpm with our 2500rpm FL 120s. To load the engine at this slow turn we have always over-propped and never had a problem. We put many hundreds, closer to a thousand hours a year on our engines. Works for us.
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Old 12-30-2012, 01:32 PM   #80
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Most of us (at least lots of us) are running 2.57-1 BWVD gears ....
The ratios of our Velvet Drives (and all the VDs used on GB36s) are 1.91:1 and 2.1:1.

And Eric, a piston Beaver with the so-called water prop on it does indeed get off the water much faster and climb like a rocket compared to the same plane with the three-baded prop most of them have today.

The Turbo Beaver, however, takes off and climbs like a rocket, period. Particularly Kenmore Air's two re-engined ones. Well, at least like a somewhat slow rocket.
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