Purpose Of Strakes

[SuperPiper]

The photo below shows the hull a Sandpiper 565 being pulled from its mold (circa 1974). The Sandpiper is a 18'6" trailerable sloop with a retractable daggerboard keel. The keel includes 300 lbs of lead ballast.

You can see in the photo that there is a strake on either side of the keel trunk (or are they called keelsons?). What is their purpose? Do they somehow affect the flow around the keel? Do they provide some amount of lift? Or, are they just there to stiffen the hull until the liner and deck are installed?

I don't see strakes on more modern hulls.

[Pericles]

How far do they protrude beyond the hull?

Pericles

[GuestR01312011]

The just look like seats on the inside of the hull for seating probably the keel & mast support super structure... I dont think they would protrude on the exterior of the hull, if so they'd be very very small bilge fin keels, but I doubt it...

[sharpii2]

They look like 'beaching strakes' to me. These were added to the hulls of wooden centerboarders that were to dragged up the beach (which wasn't necessarily sand) after use. They were expendable planks to protect the hull.

That's my guess.

Bob

[SuperPiper]

Sharpii2, beaching strakes sounds the most logical. These do protrude to the outside of the hull. They are about 1" x 1" x 3ft long on the hull's exterior. Unlike the wooden beaching strakes, these cannot be removed or renewed.

My guess is that they provide rigidity to the hull. Even with the liner and the deck installed, there is no structure to give the hull stiffness in that 3rd dimension.

Do they improve the performance of the boat? I can't believe that these irregularities can allow smooth flow around the boat's bottom.

[Omeron]

To me they do not look deep and wide enough to protrude outside of the hull.
To me they look like a kind of foot hold to bond internal members more strongly and cleanly, without adding several extra layers to the floor.
Quite likely that standing headroom is very limited and every cm counts.

[SuperPiper]

Yes, these do protrude beyond the hull. As mentioned above, they are about 1" square x about 36" long outside the hull. No, nothing keys into them inside the boat. They are hiding in the lockers under the side berths.

This is what one of these boats looks like:

[alan white]

They appear to be there to both protect the case opening and to assist holding the boat upright. Not all ideas are good ones, and the boating industry is rife with examples of design features that never caught on. Often protrustions like that wear through and water gets in, so the boat taks on water and gradually suffers structurally.
Canoes have been built that way, usually in order to track easier for inexperienced paddlers. When they wear through, it's less of a problem. Just glass them over again.

Alan

[the1much]

i wonder if they're for keeping the boat from turning to quickly,,,the hinckley jet boats had a set of 2 little "fins" on the very end to keep the boat from turning so fast it "hurled" the first 58 year old owners "crew"(3 old ladies and a dude that couldnt walk),,,,the "fins" kept the lawsuits "at bay"
it suks when the world stops spinnin and you dont ;(