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Old 12 April 2008, 08:49   #21
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Originally Posted by 9D280 View Post
As I said, if the speed limit is 10 knots...... I have a lot of open and speed limit free (well, most of it! ) water to play with. Time to plane & slow planing speed is irrelevant to me compared to the fuel consumption increase brought on by the drag. In Nick's case the fuel consumption will probably drop, as the hull drag not planing will be far geater than dragging the fins through the water at relatively low speed.
Dunno about all of that! Where did 10 knot speed limit begin to be a factor? Fins assist a 4.7 meter SeaRider hull in getting most of the way up on the step at 7-8 knots, and stay there. That speed is desirable for dragging baits. If I choose to haul ass, the difference between 29 and 31 knots does not ruin my Christmas.

I left my engineering calculator in the pub but....With the wetted surface of an average Rib combined with the leg of that noisy thing sticking down into the water, you're telling me that hydrodynamic fins of less total surface area than than a dinner plate are going to have a significant effect on my fuel economy? Were I so sensitive to be concerned about a rise of .002% in consumption, I'd get a row boat and be done.

I still don't get your "bow plunging precipitously" comment which has been posted before. I suppose with really evil trim, all my gold jewelry and a fat girl stashed in the bow I could induce a plunge as well but to blame it on the fins, I just don't agree. This is behavior that neither I nor anyone I have ever spoken with that used them on hard boats or ribs, has ever experienced.

I am not "anti" lifter. Fins however are not evil, don't cause the bow to plunge, don't negatively effect handling, don't ruin fuel economy which sucks to begin with, and are nice to use as a step to get one's ass back in the boat. If anyone wishes to select an alternative method to enhance trim on their boat, that is a fine decision in my book. Don't discourage use of fins though for reasons that just don't hold up to the vast experience of people that do use them. "I don't like fins because they refuse to speak Portuguese" uh well then I'll try something else
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Old 12 April 2008, 16:44   #22
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Originally Posted by SeaSkills View Post
Out of interest, what are they like when you go backwards?
Its crap it won't get on the plane going astern anymore ,
remember that bit in Jaws when the shark surfaces with all the barrels on and pulls the boat backwards thats how it feels
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Old 12 April 2008, 17:19   #23
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Fins or lifters.

Has anyone any experience of using doel fins on large power, heavy craft with drive legs? Say up to 300hp and approx 5 ton craft. Example Volvo duoprop, Bravo 3, etc. I would be interested to know if anyone has tried this and what, if any results, are there? Thank you.
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Old 12 April 2008, 23:40   #24
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Originally Posted by Matal Mickey View Post
Has anyone any experience of using doel fins on large power, heavy craft with drive legs? Say up to 300hp and approx 5 ton craft. Example Volvo duoprop, Bravo 3, etc. I would be interested to know if anyone has tried this and what, if any results, are there? Thank you.
The fat girl in the bow section got very wet!
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Old 13 April 2008, 17:08   #25
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Originally Posted by nickd View Post
1-Trim the engine so the anticavitation plate is 90 with respect of the rib bottom,
I don't think you mean that. I think you mean so the anti-ventilation plate is parallel to the bottom of the boat/surface of water (assuming flat calm)/direction of travel.

Quote:
usually second hole from transom.
not sure why it would be adjustable then. I think you will find it is dependent on the transom angle.

if you had to do everything else you suggested then the boat is way too sensitive to the balance etc and would benefit from some help anyway.
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Old 13 April 2008, 18:44   #26
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I am not "anti" lifter.
Glad to hear it, it's just not PC these days
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Old 13 April 2008, 18:53   #27
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Quote:
Originally Posted by Tomas

I am not "anti" lifter. Fins however are not evil, don't cause the bow to plunge, don't negatively effect handling, don't ruin fuel economy which sucks to begin with, and are nice to use as a step to get one's ass back in the boat. If anyone wishes to select an alternative method to enhance trim on their boat, that is a fine decision in my book. Don't discourage use of fins though for reasons that just don't hold up to the vast experience of people that do use them. "I don't like fins because they refuse to speak Portuguese" uh well then I'll try something else
If you troll a bait at 8 knots here you won't catch anything. When I had doelfins on a boat they made it bow steer uncontrollably. Don't forget they are also extra leverage to snap the ant-cav plate off when using it to climb back in
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Old 14 April 2008, 06:45   #28
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Quote:
Originally Posted by Tomas View Post
Dunno about all of that! Where did 10 knot speed limit begin to be a factor?
The original post- the limit that he wanted to be able to plane within........


Quote:
Originally Posted by Tomas View Post
I still don't get your "bow plunging precipitously" comment which has been posted before. I suppose .......... has ever experienced.
Engine on rear (outermost) pin Anything above 1/2 throttle and the bow went down. Fuel tanks at the transom, me on the jockey, anchor under the seat. . Al (motoring alongside) can verify.

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Originally Posted by Tomas View Post
I am not "anti" lifter. Fins however are not evil, don't cause the bow to plunge, don't negatively effect handling,......Don't discourage use of fins though for reasons that just don't hold up to the vast experience of people that do use them.
Once agian I quote myself:

As I've said before , one man's ideal is another's worst nightmare.

I have never "blanket slagged them off" I have just used my two experiences with two different boats to point out that they are not the "holy grail" that some make them out to be. In some cases they do adversley affect economy and handling. I also said that in Nicd's case they probably would be a valid solution for his low speed problem........
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