RE: [bolger] Re: Anyone work with "Hulls" program?

Frank,

Weston Farmer - I think - did a great article years ago on model powerboat hulls, including using wax (paraffin) as a standin for fuel.

The basic sneakeasy hardly needs a hulls program to modify. You just expand the lines in proportion. The displacement will vary in direct proportion to increases in beam, depth, or length, to the second power for any two, to the third power for all three.

If you wanted to double the displacement and modify all three in direct proportion, you would multiply the dimensions by the cube route of 2. Etc...

For any of those modifications your CB will remain in the same place. Where it gets tricky is if you double the displacement but use only 50% of the new displacement, then the CB will be different.

I have used plyboats a lot, and there is a new version coming out. I think it is a good thing, as long as you already know how to get there without the program... Making a model is a very sensible idea, you can make a model out of card or aircraft ply, in probably an hour. I use .6 aircraft ply and 1/8" for the bulkheads. You can then do real world test, and you will often see stuff you didn't anticipate from an on-screen model. That said, a sneakeasy is pretty simple.

--- Inbolger@yahoogroups.com, "f_swygert" <farna@...> wrote:
>
> I've been reading some about this program (http://www.carlsondesign.com/#Fun_Shareware,scroll down to find link). So it should give me center of bouyancy among other things. If I modified a Sneakeasy to take an inboard similar to the photo in my album, would the "Hulls" program tell me where the new CB would be? I'm thinking I would need to put a stock Sneakeasy hull in, then drop the motor where I would want it. Using the stock CB, the hull would then need to be modified to retain that CB, or get close to it. The CX500 motorcycle engine I have (water cooled) supposedly weighs ~220 lbs with radiator, carbs, exhaust, and air box. A Chevy Chevette 2.0L weighs ~302 lbs (cast iron block), a little Geo three cylinder ~150 lbs (both without cooling systems, 50-100 lbs more), Ford 2.3L ~300 lbs, and a Honda B18B 326 lbs. Add another 75 lbs for a small manual automotive transmission (for reverse). I find it hard to believe that the Metro (same as Chevy Sprint) engine is about the same weight as the MC engine, but the MC weight does include everything needed to run (subtract 100 lbs for everything but MC engine and it's down to 120 lbs).
>
> Keeping the weight around 400 lbs. just means two full grown adults. Moving the engine slightly forward of the front seating position and the front seating position slightly back should balance the hull back out without further modification. It would reduce the cockpit size, but should still be room for four adults.
>
> Someone mentioned looking at some Michalak designs for a shallow V bottom "Sneakeasier". I'll be doing that! I've had a similar idea -- make the box keel Sneakeasy but slant the bottom on each side of the 2" keel, and maybe reducing the keel max width to 18".
>

I've been reading some about this program (http://www.carlsondesign.com/#Fun_Shareware,scroll down to find link). So it should give me center of bouyancy among other things. If I modified a Sneakeasy to take an inboard similar to the photo in my album, would the "Hulls" program tell me where the new CB would be? I'm thinking I would need to put a stock Sneakeasy hull in, then drop the motor where I would want it. Using the stock CB, the hull would then need to be modified to retain that CB, or get close to it. The CX500 motorcycle engine I have (water cooled) supposedly weighs ~220 lbs with radiator, carbs, exhaust, and air box. A Chevy Chevette 2.0L weighs ~302 lbs (cast iron block), a little Geo three cylinder ~150 lbs (both without cooling systems, 50-100 lbs more), Ford 2.3L ~300 lbs, and a Honda B18B 326 lbs. Add another 75 lbs for a small manual automotive transmission (for reverse). I find it hard to believe that the Metro (same as Chevy Sprint) engine is about the same weight as the MC engine, but the MC weight does include everything needed to run (subtract 100 lbs for everything but MC engine and it's down to 120 lbs).

Keeping the weight around 400 lbs. just means two full grown adults. Moving the engine slightly forward of the front seating position and the front seating position slightly back should balance the hull back out without further modification. It would reduce the cockpit size, but should still be room for four adults.

Someone mentioned looking at some Michalak designs for a shallow V bottom "Sneakeasier". I'll be doing that! I've had a similar idea -- make the box keel Sneakeasy but slant the bottom on each side of the 2" keel, and maybe reducing the keel max width to 18".