Start to plane

Brooksie · Oct 15, 2013

Does anyone know of any information concerning sharpening the corner of the hull between bottom and transom and if it can lower the speed at which the vessel begins to plane. As an example, sharpening the corners of spray rails keeps the water from running around the corners increasing their effectivness.

I like to run my downeast style boat at the speed at which the wake just cleans up. Lowering this, even a 1/2k would be a help.

Phil Fill · Oct 15, 2013

Not sure I understand you question? Are you thinking about adding hard chimes?

Since your boat is a round full displacement hull it should not put out that big of a wake to begin with. The Eagle if we push above hull speed will start to climb out of the water, which creates an even bigger wake. We run at 1500 rpm which is between 6 to 9 knots and the wake is maybe a foot tall.

Ron T · Oct 15, 2013

I know there is a company that makes a spray rail that gules on to clean fiberglass. Owners have added them down low on the turn of the bilge. It acts as a gate holding water on the bottom of the hull longer giving a little lift to the stern. The water flow tries to move outward from the keel. It hits the rail and some of water flow moves aft giving lift to stern. May be worth looking into.

DavidM · Oct 15, 2013

I think that anything that you can do to increase planning area such as sharpening corners will improve things. There is even a new downeast hull that incorporates a squared off corner in the middle of a soft chine. Sort of a bastardized solution, but it probably works.

David

Brooksie · Oct 16, 2013

Thanks all.
No, not talking about my troller but a traditional downeast lobster boat no chines. Sorry for confusion not talking about chines, altho some DE boats like the Dyer do have sprayrails which continue to the transom at the WL and do add to their speed.

What I was talking about was sharpening the corner between the bottom and the transom (which is now radiused like all FG boats) to lower the speed at which the water breaks away and the boat begins to plane.

FF · Oct 16, 2013

>What I was talking about was sharpening the corner between the bottom and the transom (which is now radiused like all FG boats) to lower the speed at which the water breaks away and the boat begins to plane.<

In theory building a sharp edge with Bondo might make the boat drag less water behind , but the small , few sq inches of added plaining surface would be hard to measure a plaining difference.

The boat only plains when the lifting force is sufficient .

Probably a smooth bottom and clean prop would do more.

Brooksie · Oct 16, 2013

FF Roger that. Squaring the corner would only add 1/2" to length so nothing. However, the water might break away sooner and not drag up the transom. Just a thought...

psneeld · Oct 16, 2013

Brooksie said:
FF Roger that. Squaring the corner would only add 1/2" to length so nothing. However, the water might break away sooner and not drag up the transom. Just a thought...

trim tabs maybe? they work well on the Shamrock 26' I run....

Nomad Willy · Oct 17, 2013

I think so. And I wouldn't be surprised if it amounted to a fairly significant reduction in drag. I've thought about that for years and considered doing it but never got around to it or the particular boat didn't need it much ... like my powered canoe w small transom that gets regular beach use.

Ideally the bottom should go straight back w no hook unless the hull is begging for it. I think the only 2 reasons why all boats don't come that way is the difficulty making the edge sharp edge and the potential for damage. A 45 degree flat (like a 2 chine hull) would probably make a good compromise.

Making them would present a significant challenge. Any ideas?

Brooksie · Oct 21, 2013

manyboats said:
I think so. And I wouldn't be surprised if it amounted to a fairly significant reduction in drag. I've thought about that for years and considered doing it but never got around to it or the particular boat didn't need it much ... like my powered canoe w small transom that gets regular beach use.

Ideally the bottom should go straight back w no hook unless the hull is begging for it. I think the only 2 reasons why all boats don't come that way is the difficulty making the edge sharp edge and the potential for damage. A 45 degree flat (like a 2 chine hull) would probably make a good compromise.

Making them would present a significant challenge. Any ideas?

Yes, I think I'll try it. I'll clean off the bottom paint, rough the gelcoat, put a couple layers of duct tape on the bottom hanging over as a mold and fill with epoxy to a square corner. I know right where this boat goes on plane (wake cleans up) now, so in the spring I'll have some result. Maybe it will be at a lower speed which is what I am looking for.

Start to plane

Brooksie

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Ron T

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DavidM

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