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Old 09 September 2010, 17:22   #11
Country: USA
Length: 4m +
Join Date: Aug 2010
Posts: 9
Still stand by what I said. The amount of drag can make a huge difference in accelleration.

I get down to Monterey usually a couple of times a month (and some of my dive buddies have been talking about diving around SC anyway.) Maybe we can set up a meet-and-demo sometime (though I'm heading north this weekend, so that's out...) Might be able to come up with some ideas.

jky [/QUOTE]


It does feel like it's drag related, that's why I was thinking it could be from the foil. just looking at the foil, it looks badly designed from a hydrodynamic point of view.. and the feeling when the boat takes off is of coming "unstuck". I'm thinking that the water may be maintaining attached flow on the foil most of the time, but then aerating when I come off a wave, dropping a bunch of drag for a couple of seconds.

I probably won't have the boat back in the water for a few weeks as I'm out of town for a while. Are you tank diving or freediving? I'm a freediver myself.


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Old 20 September 2010, 14:23   #12
Country: UK - Wales
Town: west wales
Make: humber destroyer 5m
Length: 5m +
Engine: 90 yamaha
Join Date: Apr 2010
Posts: 202
I'm the guy ed dash mentioned with the 70 evinrude and 5m humber,I've done loads of playing around with props on my boat and from what you say I'd guess you need to junk the fins and put a 17'' prop on it,then do the trimming out 'till it looses grip as suggested to work out your trim angle. My engine is set up with the cavitation plate an inch and a half above the bottom of the boat which is probably too much for most situations (only did it to try and outrun eds boat !) rule of thumb is level with the bottom of the hull I think.
I've got a tacho on mine and it tops out at just under 6000rpm but will happily rev to 6500 with a shorter prop (don't know how long it would last tho')
I think you need to aim for 5750rpm at WOT?

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