This is more for curiosity. I searched and it seems that many say it is sharpening the strakes and making sure the bottom is symmetrical. And if there is any UNINTENTIONAL hook or rocker removing it.

My question is, how do you sharpen the strakes without breaking through the gel? Or do you have to and then re-gel?

I'm curious also in this particular process. What are the methods to arrive at a blue printed hull with sharpened strakes?

If you are going to be changing the shape at all, you are automatically having to sand and true the bottom up, and then re-gel it. The right way to do this job is to de-rig the boat and flip it over so it can really be worked. Some areas may just need to be scuffed.

+1
It's ALOT of work!!!

I actually did my hull bottom with Interlux Perfection (2-part Polyurethane), and it seems to be holding up well. I wouldn't use this on a boat that was to be left in the water a lot, but it is a very tough paint that is almost impossible to scratch, but maintains some flexibility. I have some leftover pucks from the bottom of mixing cups that are from projects three years ago, and you can still bend them in half without breaking, or whack it with a hammer, and it remains resilient.

Anyway, I digress. The bottom of my boat had already been painted with something, so I sanded (DA and hand, 80 grit to get going and knock the old stuff down, and 220 to smooth it out) and made up some epoxy filler to fill rock chips, and in places the edges of the strakes and chines needed to be built up. For the most part, sharpening them consisted of block sanding them flat so you get a nice edge. I grew up as a ski racer, so this was very natural for me, like sharpening ski edges. Take more from the sides to sharpen, and file on the base only as necessary so as to bevel away the deadrise. You can get them rediculously sharp, but that's not necessarily good, as they won't hold paint, nor be strong, so you want to just slightly break the edge so that its not a razor.

If you have to focus your energy in one particular area, you are best served working from about midships at the keel, in a "V" shape back to the chines maybe 3' aft of amidships, and working aft for about 5' on the keel, and all the way aft to the end of the chines. This is where the stagnation zone is going to be at high speed, and where most of the lift and drag get created. If you want to get serious, start making templates every few feet, and transferring the template from one side to the other to ensure the shapes are the same. Also a good time to make sure your boat hasn't developed any "hook" from sitting on the trailer. Nothing will kill your top speed faster. One thing about the old Cigarette Mistress hulls that is immediately apparent, is gobs of rocker built in.

Then it was epoxy primekote (I think I did two coats with sanding in between), and then three coats of Perfection using roll-and-tip.

I did all this with the boat jacked up and blocked about 1' off the trailer. I did this right before repainting and re-covering the trailer bunks, so I didn't care what got on the trailer. As you can imagine, working alone, this was a lot of hours of low-crawling, sanding and painting in rediculous positions. My trailer is built like a brick ****house with transverses every couple feet too. I got to where I could apply a coat in about 3 hours, and it took just over two quarts per coat. Rolling and tipping by yourself takes a lot of time. Hmm, maybe I need to get some friends...

I didn't have the means to flip the boat over at the time, but if I had to do it again, I would build a second gantry and roll it over for sure.

In almost every case, you'll need to add material to sharpen lifting strakes. Yes, it would be nice to just block sand them to sharpen them, but there just isn't enough material there. So you end up scuffing the surface to get some bite, adding material, sharpening that material, then re-gelling for protection. Depending on how "round" your strakes are, it can make a hell of a difference in how well the hull bites in turns.

I'd love to take advantage right now while my hull is still bare (flip it) then start the blueprinting while working on my feet. Couldn't imagine creeping under the boat working over my head. As it is now I'm completely sore just from climbing in and out while my boat is right side up

Yes, it was a very crappy job. I destroyed two sets of coveralls. The increase in productivity should easily offset the time to flip. Just make sure you support it correctly during the flip and while upsidedown. Get some big hunks of styrofoam, and keep them out in line with the hillsides, preferably at the transom, and near any bulkheads.

For the best and safest way to flip a hull go to (my winter project) post #25-#27

I've seen many different ways to flip a hull, by far that has to be the most efficient!