# Recreational MLB 40' range

Discussion in 'Boat Design' started by Maverick510, Mar 12, 2008.

1. Joined: Mar 2008
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### Maverick510Junior Member

wow, great information this has been invaluable so thank you for your time. Got a few more quick questions, if I decide to move forward with a 34' to 36' version of the Swedish fiberglass boat what do you figure the approximate weight to be to get an idea of the cost? How much would a basic set of plans run to get an accurate estimate if you were to do it? Also what is the additional cost to have a project manager? I am very busy so I can't let this take over my life. I have a very good friend that builds high end powerboats in Kentucky so that might work out but I would like to know more about your South Africa yard.

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Quick scaling of weight can be done several ways, one is with a cubic number (length * beam * depth) or with scaling factors. Let's look at scaling factors. As boats are 3 dimensional objects and the scaling factor is different in each dimension they must be calculated and then combined for an overall weight scaling. The Swedish boat is 39.75' long and you want 35', scaling factor for length is .88. Beam of the SSRS is 13.8', to retain similar characteristics we scale the beam about 70% of the length factor, .916 is the beam factor for a new beam of 12'8". Depth we won't change because people don't get shorter and much of this boat is deckhouse. Scaling factor for depth is 1. Multiply the factors together for an overall factor of (.88 * .916 * 1 ) = .806. Lightship weight of the SSRS is 9.75 tonnes, approximately 21,500 pounds, 21,500 * .806 = 17,300 pounds. Thatâ€™s the approximate new weight.

Costs for a bid package can vary wildly, I would argue that it should be the most expensive part of the design as it will (or should ) lay everything out as to how the boat will be. The basic engineering (scantlings to ISO or ABS) must be done, hydrostatics, general styling, propulsion calculations, etc. If the boat is to meet ISO certification stability should be checked, if she's to be self rescuing a study of that must be done. The specifications can be simple (4-5 pages) or complex (30 pages). I would say a minimum of 4 full days would be required for a basic bid package.

Project management of small projects is tough to justify, as the savings may not be huge. Usually with small custom boats you are working with a small yard that "manages" each project themselves. Of course they are managing the project with their interests uppermost, but generally this works reasonably well if you are dealing with an honest builder. To be effective a project manager must be in the yard on a regular basis, probably at least once a week depending on his/her relationship with the yard. In many (most?) cases this will entail travel costs. It gets expensive....this is why most people just buy a boat off the shelf.

The South African yard is Moondance Yachts http://www.moondance.co.za/ A rather poor website, but I can put you in touch with the owners of the 48'.

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### BrasstomDedicated Boat Dreamer

an extra 2 cents

Are you looking to actually reproduce a CG boat, keeping the tradition of military spec you have now? If not, and you're just looking for a nice boat with a lot of the same abilities (etc) then check out George Buehler's "Diesel Ducks."

http://dieselducks.com/

I don't promise it'd be AS sturdy or AS fast (George might promise it, though!) but it'd be a heck of a lot easier to build, much cheaper (i'd think) and the plans are definitely much more readily available!

Of course, the Diesel Ducks are all fully displacement craft, so if it's speed you're looking for...disregard this entire post! haha

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### Maverick510Junior Member

Hey Tad, thanks for the breakdown great info. I have been reviewing the plans with my builder buddy, I will let you know more when I can work out more of the costs with him.

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