|
design by Jim Michalak - Lebanon, Illinois - USA |
Dani Jay, Low Power Launch, 20' x 6', 500 POUNDS EMPTY
Dani Jay is the chosen name of the project I called Bobsboat in last year's essays. The idea behind it was to have an easily driven seaworthy launch that would take a bunch of adults around in a laid back style. It was not to be a planing boat so big horsepower and speed were not an issue.
I went with a multichine hull since it is efficient and good in rough water. Big benches on the cockpit sides as I have used in a lot of my designs. They are a full 10' long with a 2' wide walkway between - lots of room. (I have never met a boater who had so many friends that he would fill this boat.) The benches are also 2' wide at maximum and some of you would be able to sleep on them. I would expect the empty hull to weigh about 500 pounds and maybe 700 pounds for the boat with motor and gear. It will take about 2200 pounds to push the boat down so that its chines touch the water so that is about another 1500 pounds of people.
Dani Jay has its motor in a slot in the stern, almost an inboard well. I've drawn such a thing before but that boat was never built. I have stayed away from inboard wells mostly because Phil Bolger, who knows all, hates them so much after having used such boats. Well, I just don't know about that but i do know the Dani Jay man wanted the well very much. It puts the motor right at hand at the back of the cockpit. The well takes up a lot more room than you might expect and Dani Jay is in some respects a 16' boat with a couple of narrow 4' sponsons on her stern. I measured up a few of my own motors and saw the motor slot needs to be a full 2' wide to allow for a full turn and of course nothing can be behind it if you hope to raise it up in the usual way. Phil's argument is that also you have noise, smoke and water surge to deal with. Having the slot open in the stern will keep the water from "pumping up" inside the well. And the motor must be a long shaft to keep waves from surging up into the well and over the "transom' which in this case is an interior bulkhead slanted 15 degrees. I don't think noise will be an issue at all - the only motor to use with something like this is a 5 hp job, 4 stroke if you can afford it. That should push it at full speed at about half throttle. If you use a smaller motor you will be tempted to run it at full bore a lot, and if you use more you will be tempted to overspeed the boat a lot. But a hull like this will not be oversped. It will just dig a deeper hole in the water and make a bigger wake. Last summer I was lucky enough to get a long ride on Paul Effrit's very modified Selway boat which was set up like Dani Jay. As he motored along I lifted the hood and saw there was no evidence of water pumping up or surging inside his well which was also an open slot to the stern. The noise and smoke of his modern 4 stroke was nothing. And full throttle just gave us a huge wake. I am quite confident it will work well if the power is just right. It won't work well if the power is wrong.
Although sailing was not part of the original idea, it was clear that this shape of hull will sail quite well if it were a pure sailing boat. I gave it a simple and cheap and effective balanced lug right with my usual pivoting leeboard. How will the motor well affect sailing? It isn't going to help. You could build it as a sailer only and omit the well. The thing is that if I don't draw the sail rig I will forever be answering requests about sailing it. So there you are - the sail rig.
Taped seam construction from nine sheets of 3/8" plywood and three sheets of 1/2" plywood.
Read Jim Michalak's Newsletter
|
