lift strakes.... how?

[woodrat]

So I recently got a partly completed 24' hankinson designed planing hull, built in plywood. It has one layer of glass on the outside, and no lift strakes installed yet. How exactly does one go about laying these out? There isn't any lofting information with the plans, just drawings of where they go and what width they are. Do I just fasten on 1x4 stock with countersunk screws and then plane off the excess to make it fit right? Any help with this would be very appreciated. Getting these on and the outside of the hull finished, sanded and painted is the next step I need to take.

[lazeyjack]

i would do this

With a batten say 3/4 square, draw the strake line, you will either need a few pairs of hands OR hold it in place with car jacks
The make a msmalll pattern every couple of feet, the vertical edge will be , vertical ,(smart eh) the edge to the hull will be taken from the hull and the downwards edge can sloping up 3 degress, the other way is to lift the shape off the body plan , if you have it?
Be careful dont over strake often they are not needed for lift but to help make the boat track, in which case two short 8 footers about a foot up from the keel works
Strakes make a boat ride HARD, so take it easy)

[lazeyjack]

here is a rough sketch

[PAR]

Lazy, has made a good point here. Many designs don't need lifting strakes and haven't incorporated them into the bottom. Often you'll see some "rubs" that are mis-represented as lifting strakes, but they'll real use is, to protect the bottom of the boat in groundings and during launch and recovery at the ramp.

Typical designs not requiring these strakes will have flatter aft sections in the hull shape. Hulls having a substantial skeg(s) also would generally not use lift strakes.

Check the plans carefully, to insure you're not about to install something, that the boat doesn't need, because number, location and shape (of the strakes) can dramatically affect the performance of the boat.

[woodrat]

the plan shows three per side, the ones closest to the keel being shorter than the outside ones, not running all the way to the stern. It is not a particularly flat bottom design, I think it would be called a semi deep V.

http://glen-l.com/designs/hankinson/cuddysport.html

[lazeyjack]

my advice, try just the short ones, then add only if necessary, I have had designed many power boats and built many I use a wide chine and only when absolutely needed a strake But then now you are on your own, I donrt look for thanks here, but some sort of acknowledgment is appreciated

[ucb4ume]

Hey Woodrat,

I am also building a modified deep-v (16 degree deadrise) boat that calls for 3 sets of lift strakes on each side. The instructions say to take a 2x4 and rip it on the diagnal and then to taper one end.



The designer indicates that the lift strakes are not only to help the boat plane better and to give directional stability, but they also are a critical structural part of the hull.

Go here for pictures

Pictures of my current project

[woodrat]

mine wouldn't be a critical part of hull strength. the hull is 3/4 thick ply on the sides and 1' on the bottom. I notice when I look at newer aluminum boats they never have lift strakes, yet most older glass boats do have them. Anyone know why the difference?