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Re: outboard




Bob Spencer wrote:

> Bob Schimmel wrote:
>
> >A displacement hull never gets up on the step as power is applied.
>
> >However, if you push the hull to its theoretical limits, 6 knots for a
> >SJ23....
> >...To push it faster than that
> >and it requires a significant amount of extra power...
>
> Yes, that's as I understand it. So, if it's true that a 5 hp outboard will
> push the SJ23 to 6 knots, its hull/maximum speed, then what reason is there
> to have more than that? I keep having the feeling that many people think
> they can overcome this handicap by adding more power, but that's not true,
> as I understand it.
>
> >Please keep in mind that this discussion centers around efficient speed
> >through
> >the water, NOT ground speed over the bottom.
>
> Yes, just as with an airplane. If you are making 6 knots/hull speed through
> the water, with a 7 knot current dead on the bow, you are going backward 1
> knot over the ground and being washed out to sea. It is my understanding
> that you can't solve this problem by adding horsepower, because you can go
> no faster than hull speed regardless of the size of your motor. So, the
> reason for my original question... how big an outboard does it take to
> drive the SJ23 to its hull speed? I don't ever want to get caught in a
> situation where a little more power would get me out of serious trouble,
> but I don't have it. How much do I really need, how much can I really use?
>
> How does the wind fit into this situation? If I'm on a lake with no
> current, but I need to drive straight into a hard wind using the outboard,
> will a bigger motor make that easier to do? A bigger motor can't overcome
> the water resistance which limits us to hull speed, but can it drive the
> boat into a strong wind where a smaller motor could not?
>
> Bob
>
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Have a look at Tech Tip D06.  I've summarized some comments from previous
emails.


--
Best Regards

Bob Schimmel
(Always stay curious)



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