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"Tuning" props for salt vs. fresh water.

Discussion in 'Props, Shafts & Seals' started by Capt Bill11, Oct 7, 2014.

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  1. Capt Bill11

    Capt Bill11 Senior Member

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    Anybody ever heard of having two sets of props, one set "tuned" for fresh and another set "tuned" for salt?
  2. captholli

    captholli Senior Member

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    When I worked for Circus Circus in the mid eighties I had the opportunity to work with Bill Bennett's unlimited Hydrofoil team "Miss Circus Circus" for two seasons as a telemetry technician and the race team did have sets of cleaver props that were pitched and tuned for water density's i.e. Salt vs Fresh. They were always dealing in fractions of speed increases but I can't see a motor yacht or S/F going to these extreme's. I'm sure if you drill down enough on the web there's going to be some viable information in regard to this topic and how it would apply to yachts.
  3. Capt Ralph

    Capt Ralph Senior Member

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    I was at Mission Bay watching her race side by side with Pay n Pak late 8os. Both boats came up and flew over backwards. You there? Awesome sight.
    Last edited: Oct 7, 2014
  4. Capt Ralph

    Capt Ralph Senior Member

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    May have a font problem there. I was hitting the zero key and it types lower o.

    Zero 000000
    lc o oooooo
    uc o OOOOO

    It's just the font on zeros makes it look like a lc o.
  5. captholli

    captholli Senior Member

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    I believe your talking about the spectacular double flip by the then two side by side Hydro's Miss Madison & Miss Circus Circus in San Diego 1988 ? I think that piece of video received more air time on ESPN and in the previews of any unlimited race after that. Bill Muncy threw in the towel after that experience. I don't want to get to far off topic of the thread but if your interested I have some stories of the egos and $$ involved between all those teams. Drivers, Crew chiefs and designers jobs were never safe and you lasted only as long as you won. Mr. Bennett was an interesting gentleman and I got involved with the Unlimited team after completing the build of his De Vries 42 meter Feadship in '83 / I'm told that a PM is now a conversation? still exploring the new site...
  6. Capt Ralph

    Capt Ralph Senior Member

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    Darn slow brain cells, the second boat was Miss Madison. Somewhere around here I have a picture from the east (island) beach. Was watching both of them thru my big camera lens when they flew up, startled me and as I raised up I did push the shutter button. Did'nt realize I had a picture until I returned to Jax.
    Thx for the correction and video lead.
    Shush, only 26 years ago and not thought of in over 20.

    Oh, Back to the OP;
    If your flying inches over the water and thousands of horsepower is screaming behind you, It can make a difference. The weight of the air makes a difference on those turbines.
    I don't think Fresh/Salt water tuned props will offer you anything on a stock boat.

    High altitude lake operation IS a consideration for wheel changing.
  7. Capt J

    Capt J Senior Member

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    Different props for fresh or salt, not usually. However, the boat will sit lower in fresh water and also not be quite as fast. So if you're overpropped for Salt water, you'll be even more overpropped in freshwater.
  8. Wl3175

    Wl3175 Member

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    On a huckins I ran we had fresh and salt props .helped with her speed as she floated differently
  9. Capt Ralph

    Capt Ralph Senior Member

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    Can you offer some specs please? Power, weight, differance in props, differences in speed and rpm?

    From FL coast to coast thru da lake, I've never noticed anything in many different sized boats.
    But we are eager to learn something new, soundly.

    If you can offer the ships delivery name or hull number, I can have the office look up the original specs.
    I'm tied to their (Huckins) dock currently.
  10. Capt J

    Capt J Senior Member

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    I'll usually see a yacht sit about an 1" lower on the water line than in salt water. I have noticed most 20+ knot yachts will lose about a knot in freshwater at cruise.
  11. Capt Ralph

    Capt Ralph Senior Member

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    Would Lake Okeechobee be considered pure fresh water? Never noticed any change. Except sucking the bottom in some places.
  12. Capt J

    Capt J Senior Member

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    Yes, but with the shallow water you get some lift running so you don't notice it.....if you really look at the waterline, it's easy to tell, but you're losing weight as you go across......(fuel)
  13. Wl3175

    Wl3175 Member

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    Left you a message
  14. Marmot

    Marmot Senior Member

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    If the boat is in displacement mode in shallow water the draft will increase due to "squat." It will also require more power to achieve the same speed.

    Both of those factors so far outweigh any difference due to water density effect on a small boat as to make the whole issue moot - in shallow water at least.
  15. Capt J

    Capt J Senior Member

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    By running, I meant on plane. On Plane in shallow water you tend to gain a little speed. It is true with displacement speed that you will lose a little speed in shallow water, also they will handle very weird in shallow water and like to make 60 degree turns sometimes without any predictability.
  16. Marmot

    Marmot Senior Member

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    That is called "bank effect" and is also related to bottom profile. While the extent is not very predictable, the effect is to be expected. I see it has not been mentioned yet but I suspect that may be one of the underlying causes of the recent Suez Canal collision.
  17. Capt Ralph

    Capt Ralph Senior Member

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    So if the canal had some irregularities, say from a side channel joining, sudden direction may change? I need to copy this to that thread.
  18. Capt J

    Capt J Senior Member

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    No, if it gets shallow on one side of the hull at displacement speeds, the propellor on the shallow side will have a tendancy sometimes to suck the whole boat towards that side.....
  19. Capt Bill11

    Capt Bill11 Senior Member

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    Hmmm.... I always felt the cushion of water on the bank side of a vessel moving at displacement speeds push the boat away from the bank not suck it towards the bank.
  20. Marmot

    Marmot Senior Member

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