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Old 18 July 2015, 10:15   #11
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bag of sand /container of water in the bow?
I wish there was room!
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Old 18 July 2015, 10:16   #12
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All being said...this is the most fun I've had with the kids all year!
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Old 18 July 2015, 15:27   #13
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Bag of sand in the bow will have a lot more adverse effects at other speeds/conditions than the fins will. I've found that the effect of "Doel Fins" is marginal but definitely marginally better for getting "out of the hole" and at speed they have absolutely no effect one way or the other as they aren't even touching the water.
Compared to the mass and thrust of the engine hanging on the back of a boat bouncing in and out of the water the additional loads imposed by the "lift" from a pair fins is trivial and IMO would not generate any significant additional stress on engine mounts or pivot.
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Old 18 July 2015, 15:31   #14
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4 blade prop maybe worth a looksy rather than fins.

cheers
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Old 18 July 2015, 19:17   #15
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Do you have propeller dealers like solas props over there ? After talking with solas out here they told me of many people who had had issues with foils on engines and strongly recommended not using them.

One particular boat I was wanting to use for towing the kids in donuts etc as well as offshore game fishing with slow to midrange trolling they recommended a smaller pitch 4 blade stainless prop (expensive) but it did make the boat handle way better. We have an extremely dangerous bar crossing where the extra grip from the 4 blade meant getting through way easier.

I would put the smart tabs on my 550 pro but unfortunately theres not enough room on the transom after fitting two transducers and a live well pick-up. When I was mentioning the cost being about the same I was talking about the se sport fin not the dolphin cheapy.

Jon

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Old 18 July 2015, 20:14   #16
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Compared to the mass and thrust of the engine hanging on the back of a boat bouncing in and out of the water the additional loads imposed by the "lift" from a pair fins is trivial and IMO would not generate any significant additional stress on engine mounts or pivot.
Hydrodynamics are a powerful thing, relatively small foils create a lot of lift. the effect of a wing is more pronounced in water than air.
Check out the size of the foils on an AC45 or a Waterskipper.
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Old 19 July 2015, 02:08   #17
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"Hydrodynamics are a powerful thing, relatively small foils create a lot of lift. the effect of a wing is more pronounced in water than air.
Check out the size of the foils on an AC45"

Without actual figures it is difficult, so I'm not going to stand on a soap box to get shot down but.......
I figure the "effect" is roughly equivalent to about 50Kg sitting in the bow and if we assume the effective centre of gravity to be about a third of the way down the length from the stern then, the "lift" force required to produce the same effect would be 1000N. As the engine probably already weighs around 100Kg, 1000N is simply supporting the engine's own weight leaving the imposition on the bracket at zero. Ask yourself...would I lift the engine by these plastic fins, how much more weight would they lift before they broke.
IMO they would 'fail' long before the engine mountings would.
As I say, all sort of guess work and I'm not advocating that they're the solution to his problem.............the 4 blade prop sounds interesting.
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Old 19 July 2015, 02:58   #18
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Still doesn't answer the question if manufacturers still give full warranty if they are fitted and whether they recommend them. We can all have our opinions and personal experiences with them but none of us are experts in the field where Yamaha, Suzuki, solas etc are.
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Old 19 July 2015, 05:26   #19
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Still doesn't answer the question if manufacturers still give full warranty if they are fitted and whether they recommend them. We can all have our opinions and personal experiences with them but none of us are experts in the field where Yamaha, Suzuki, solas etc are.
Given that the involve drilling holes in the anti ventilation plate no manufacturer is going to warrant them. I've never seen any official guidance from a manufacturer suggesting bearing issues, have you? Can you share it with us?

If they were universally great then manufacturers would offer different leg designs with bigger plates built in. That they don't tells me that they arent needed by a big part of the market.
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Old 19 July 2015, 05:51   #20
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You don't need to drill for fins if you don't want to-

You have a couple of options, couple are below depending on the mounting method you want.

Force 4 Marine Dynamics Stingray Starfire Hydrofoil

http://www.force4.co.uk/force-4-stin...B#.Vat0EShwbMI

https://youtu.be/AoDFQwyRSxY

Cheers
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