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#237328 - 09/08/11 05:51 PM Scaling up to 14 feet  
Joined: Aug 2011
Posts: 16
Dewey Offline
Dewey  Offline

Joined: Aug 2011
Posts: 16
What would be the downside,if any, of taking the DS12 plans and simply adding 16 percent to every dimension of every part? This should yield a boat that is 14'long with a 7'beam and all dimensions would be proportionate to the DS12.

Last edited by Dewey; 09/08/11 05:53 PM.
#237338 - 09/09/11 03:35 AM Re: Scaling up to 14 feet [Re: Dewey]  
Joined: May 2006
Posts: 1,333
JeffS Offline
JeffS  Offline

Joined: May 2006
Posts: 1,333
Kingston SE South Australia
I'm no boat designer but the stresses change a lot on a design when you add length to it, especially in front of the main beam. Darryl Barrett and Berny on the F14 forum have some great F14 designs and the hulls are the cheapest part by a long way.

Jeff Southall
Nacra 5.8 1667 Ram Raider
Nacra 18 Square
Taipan 5.7 134
Mosquito 404
Arrow 1576
#237339 - 09/09/11 04:28 AM Re: Scaling up to 14 feet [Re: JeffS]  


There is good news and bad here.

The bad is photocopier boat design doesn't work. The good is if it did I wouldn't have a job.

If you just scaled everything up equally the displacement would be wrong. For example if you make everything 10% bigger the boat's volume goes up by over 30%. You could just stretch the boat to 14ft but it probably still won't float right so you then need to scale beam and depth. Generally these need to kept in proportion to each other for the shape to work and now unless you have suitable software you can't use the existing geometry for hull sheets etc.

You 14ft boat will be faster than the ds12 so the foils can be reduced in size in proportion to the square of the increase in speed.

If you are using a trap and have more righting moment you'll need to scale the dagger boats up to tailor for the increase side force.

If your mast is taller you end up with a higher heeling moment for a given side force so you can scale the foils back down.

Unless you've scaled the rudders the same amount as the daggers your clr has now moved so you'll need to either resize them or move the daggers for or aft.

Etc etc. It is possible and may be an interesting project. But you might be better off starting from an existing design at the right size and tweaking instead of scaling.

#237341 - 09/09/11 05:27 AM Re: Scaling up to 14 feet [Re: ]  
Joined: Aug 2011
Posts: 16
Dewey Offline
Dewey  Offline

Joined: Aug 2011
Posts: 16
Thanks for the replies. There is quite a bit that goes into designing a boat that I am totally ignorant about, which is why I asked. I was just curious about the effects of scaling up a given design more than anything else.

Last edited by Dewey; 09/09/11 05:28 AM.
#239592 - 11/01/11 09:01 AM Re: Scaling up to 14 feet [Re: Dewey]  
Joined: Nov 2002
Posts: 465
sail7seas Offline
sail7seas  Offline

Joined: Nov 2002
Posts: 465
The length is linear, however:
The sail area is to the second power (squared)
The hull volume is to the third power (cubed)

An extreme example of this is Remote Control boats, they would not sail well if you scaled the depth of lead bulb (attachment)

Attached Files
hullport.jpg (203 downloads)
#240065 - 11/13/11 09:25 PM Re: Scaling up to 14 feet [Re: Dewey]  
Joined: Apr 2002
Posts: 695
Seeker Offline
Seeker  Offline

Joined: Apr 2002
Posts: 695
Ft. Pierce, Fl. USA
Since the F14 in its present form is the most wide open developmental class out there...and there is no F14 plans of contemporary designs available... at least modifying the plans of an F16 or F12 is somewhere to start... for those without any other option and a healthy dose of experimental spirit.
Two things come to mind when considering the option that make it more plausible...

The Viper F16 appears to be not too far from a compressed stationed (not a pure scale down)
F18...with a little tweaking, although the designer said that was not the case.

The "A" class is doing all kinds of radical experimentation, moving both rear and main beam locations, dagger board trunks, changing from straight boards to curved boards, even splitting the hulls wide open and changing the hull cross section...this on existing boats that were designed by seasoned professionals. With all the modification going on it appears that although number crunching is a necessary foundation. it no way is the end of the story.

Lets face it, the lion share of boat design is more about borrowing and applying a collection of proven attributes from proven designs...more so than starting from a completely blank piece of paper. More evolution than revolution.
Speaking about the hull here only not talking about the rig...not talking optimized....if there ever is such a thing...

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