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  1. #1
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    SSM gearcase design philosophy

    Does anyone know why the SSM is so sharp?

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    Maybe the relatively blunt nose of a sportmaster would result in too much sternlift? Aren't there some bass boats that rival top speeds of Formula F1 hulls?

  2. #2
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    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...

  3. #3
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    Quote Originally Posted by slowJEEP View Post
    Does anyone know why the SSM is so sharp?

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    Maybe the relatively blunt nose of a sportmaster would result in too much sternlift? Aren't there some bass boats that rival top speeds of Formula F1 hulls?
    How fast is your torpedo going?

  4. #4
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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

  5. #5
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    Quote Originally Posted by powerabout View Post
    How fast is your torpedo going?

    I was surprised to see how slowly those torpedoes run. I think that paper said something about 30 knots.

  6. #6
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    Quote Originally Posted by slowJEEP View Post
    Does anyone know why the SSM is so sharp?
    ...hydrodynamics...

  7. #7
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    Quote Originally Posted by slowJEEP View Post
    I was surprised to see how slowly those torpedoes run. I think that paper said something about 30 knots.
    yes, a 747 versus a 104

  8. #8
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    Quote Originally Posted by FUJIMO View Post
    ...hydrodynamics...

    I assume so too. Getting past that into a why, is where I've struggled. Maybe it just looked faster...

  9. #9
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    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.

  10. #10
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  11. #11
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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.

  12. #12
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    The chains and wood shed.......Must be from a horror movie......

  13. Likes powerabout liked this post
  14. #13
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    ...nope. see that wood garage door waaaay down there. its in front of that garage door...

  15. #14
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    HeeHee.......Ya peekin'.........into windows........

  16. #15
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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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