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post #1 of 8 Old 07-22-2007 Thread Starter
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swallowtail sugar scoop

hi, i bought a boat that has had a swallowtail scoop stern extension modification done on it, i m guessing to increase speed by lengthening the lwl. after some thought and observations, i m thinking that the swallowtail design is actually creating drag on my boat rather than increasing the speed due to a longer water line . does that make sense and is it possible? any guess at what sort of hit i may be taking in as far as speed? more importantly, how can i fix it - do i have to take of the extension or do i just fill in the V? also its a transom hung rudder, i guess that needs to be moved back also? maybe too big of a hassle?
thanks and cheers
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post #2 of 8 Old 07-22-2007
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Telling us what boat/size and a pic of the transom mods would help a lot here.

Most times, if properly executed, such transom extensions have the potential of added speed due to additional LWL, but more often simply provide easier access to dinghies, stern moorings and swimming. Not to mention trying to update to today's common open transom designs.
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post #3 of 8 Old 07-22-2007 Thread Starter
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its a 39ft boat that was extended w/ the scoop. australian made

here is a picture of a similar backend. i don't have a picture of my boat but its pretty much identical w/ this one, although mine is a bit longer cuz its a bigger boat (i think its about 2 feet long). fyi the rudder hangs down thru the split
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post #4 of 8 Old 07-22-2007
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Do you have a side profile photo of the boat? That would tell us a bit more about the hull shape and whether the swallowtail might be helping or hurting your speed.

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post #5 of 8 Old 07-22-2007 Thread Starter
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swallowtail sugar scoop-hull1.jpg

sure, here you go, excuse my stupidity but what are you looking for? fyi, it all sits in the water, ie no flare out of the water
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post #6 of 8 Old 07-22-2007
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Since it has a submerged end (i.e. the counter does not clear the surface) it probably is a drag producing feature. However the original transom would have had the same effect so there's likely no disadvantage to leaving it alone.

Getting on and off the boat at the stern is greatly enhanced with this modification - probably the reason for it in the first place along with a little more LWL.

The restriction to the rudder swing may be the biggest downside although even then it prevents you from "putting on the brakes".

I think I'd leave it be. btw- neat looking boat!
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post #7 of 8 Old 07-22-2007
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I'd leave it as well. It should help the resale value having a swim platform. Would be great for coastal cruising.
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post #8 of 8 Old 07-23-2007 Thread Starter
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thanks for that. the scoop is nice for standing, fishing, and climbing back on board on. i never much thought about the negatives it until i thought about getting an irc rating and then the possible drag it may create. also i m wondering if it would be considered to increase my waterline even though the scoop isnt clean across, meaning there is a big 'hole' in the scoop. have no idea how to figure out how much drag it would create either......
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