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Thread: SSM gearcase design philosophy
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07-20-2021, 03:15 PM #1
SSM gearcase design philosophy
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07-22-2021, 10:17 AM #2
The SSM was never intended to be below the surface except when sitting at the dock or punching thru a waver here and there. Sportmasters were made for both worlds so you can cruise around at lower speeds with it deep and the more rounded nose will keep the water flowing clean around the case or you can completely surface it like an ssm with basically only the skeg in the water. Any bass boat (allison) out doing an F1 may look like a bass boat but no ones really fishing with it. Just my thoughts since nobody seemed to bite...
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07-22-2021, 07:38 PM #3Screaming And Flying!
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07-23-2021, 08:01 PM #4Screaming And Flying!
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Can’t compare a one off run of an XB2002 setup for a kilo run to what an F1 boat runs in a normal race. Put a big prop on an F1 and string it out it’ll run 160 mph or more
Erik Kiser
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08-03-2021, 02:22 PM #5
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08-03-2021, 03:47 PM #6The Historic Photo Master
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08-03-2021, 08:34 PM #7Screaming And Flying!
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08-04-2021, 03:10 PM #8
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08-05-2021, 01:42 PM #9
I may have found a good enough answer on my shelf. Jim Russell's Tunnel Boat Design book has a part on gearcase design. Seems like the Sportmaster gearcase is pushed to it's hydrodynamic limit at speeds around 110 or 120, can't remember what it said. Beyond the limit, blowout occurs from the water separating from the surface of the bullet. The way to fix it is to lengthen the bullet (higher L/D ratio) to accelerate the water around the bullet at a slower rate. Hence pointy is good.
Another feature of the SSM gearcase is the on the backside of the pinion back to the prop shaft. It helps offset the stern lift generated by the from the front of the bullet.
Although the course speeds in an F1 track aren't wildly higher than an Allison with a sportmaster, I suspect the turning action of the F1's would push the water separation phenomenon to occur at a comparatively slower speed than if they were running in a straight line.
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08-05-2021, 02:11 PM #10
Narrow is better!
https://aeromarineresearch.com/drive_unit.html
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08-05-2021, 06:48 PM #11The Historic Photo Master
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...this drive was designed by the same braintrust as the aftermentioned. it has a cleaver propeller too. how come its not as pointy?...
Last edited by FUJIMO; 08-05-2021 at 06:56 PM.
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08-05-2021, 07:07 PM #12Screaming And Flying!
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The chains and wood shed.......Must be from a horror movie......
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powerabout liked this post
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08-05-2021, 07:43 PM #13The Historic Photo Master
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...nope. see that wood garage door waaaay down there. its in front of that garage door...
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08-05-2021, 08:16 PM #14Screaming And Flying!
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HeeHee.......Ya peekin'.........into windows........
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08-05-2021, 08:23 PM #15The Historic Photo Master
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...you think i'm kid'n don't you? i'm not. thats where the photo was taken...
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