Question on Tornado hull side plan

[mystrwizard]

I am looking to build some hulls from a Tornado plan I downloaded. On the side panel dimensions, there looks like two numbers for offsets on the upper side of the Datum line (See red arrow)? one looks like the original ones but there have been a 2nd set of dimensions added. anyone know why the second and which one I should use?

Thanks

Reese

 

[rwatson]

Still trying to figure them out.

I presume you got them from http://www.thebeachcats.com/pictures?g2_itemId=11057

I found another source with step by step instructions, and it had those 2nd set of numbers too. It seems to be a bit more detailed, with other datum lines that look usefull
http://www.instructables.com/id/Tornado-Catamaran-Building-Instructions--79/

Do you think you will actually build one ?

 

[mystrwizard]

Im planning on building a Strike 18 or 20 Trimaran and one option I was thinking if I scaled these down to either 19' or 17' I could use them as the outriggers/ama's for either of those two trimarans.

 

[Tom.151]

The duplicated dimensions seem to be different by exactly 6 mm

That would be one way to get added free-board very easily.

 

[rwatson]

I put some of those offsets into Rhino, to see what they looked like.

I have attached the illustration.

The curves from those two sets of dimensions were really fair - no errors in the 4 frames I did.

I think that you would be safer to use the taller dimensions, as the difference is quit small, and you can always reduce it later.

Maybe the second set was the distance after the ply was bent and fastened ?

 

[rwatson]

The duplicated dimensions seem to be different by exactly 6 inches

That would be one way to get added free-board very easily.

Um - they are in Millimeters Tom. 6 mm.

446 inches would make a very tall Tornado.

 

[Corley]

If you had concerns you could always just draw them out on some ply (doesn't have to be marine grade) and run a fairing batten over them, if in doubt the fair shape would be what you would go with.

 

[rwatson]

Im planning on building a Strike 18 or 20 Trimaran and one option I was thinking if I scaled these down to either 19' or 17' I could use them as the outriggers/ama's for either of those two trimarans.

Yes, that would work.

Why wouldnt you use the ama designs for the Strike ?

 

[Mr Efficiency]

The duplicated dimensions seem to be different by exactly 6 mm

That would be one way to get added free-board very easily.

A quarter inch of extra freeboard, do you think

 

[Tom.151]

Um - they are in Millimeters Tom. 6 mm.
446 inches would make a very tall Tornado.

Damn, no wonder my last set of amas came out a 'little' off.

 

[redreuben]

Im planning on building a Strike 18 or 20 Trimaran and one option I was thinking if I scaled these down to either 19' or 17' I could use them as the outriggers/ama's for either of those two trimarans.

Or you could stretch the Strike ?

 

[patzefran]

I built the first Strike 20 using Nacra 5.8 hulls. They are very well suited but a lot heavier than Tornado one (62 kg instead of 45 kg for ply or sandwich Tornado hulls). Richard Woods say Tornado hulls can be used for Strike 20, so you don't need to scale them down. I plan to build new ply outrigger.......sometime !

https://www.dropbox.com/s/6uk10p6q6jx85qn/VIRB0082.MP4?dl=0

Patrick

 

[patzefran]

Another problem is when you scale down a Tortured ply hull , you also scale down the radius of curvature of the ply, so you may exceed his bending capability !

 

[Tom.151]

I built the first Strike 20 using Nacra 5.8 hulls. They are very well suited but a lot heavier than Tornado one (62 kg instead of 45 kg for ply or sandwich Tornado hulls). Richard Woods say Tornado hulls can be used for Strike 20, so you don't need to scale them down. I plan to build new ply outrigger.......sometime !
https://www.dropbox.com/s/6uk10p6q6jx85qn/VIRB0082.MP4?dl=0
Patrick

Patrick, very nice indeed.

Since you're the one with a built and sailing Stike20, have to be curious what's your choice for your planned replacement outriggers for the Strike20? ...and why?

Thanks,

 

[upchurchmr]

You should be very concerned with succeeding if you scale down the shape of the panels.
Tortured ply is very different from any other method and the Tornado panels are very close to breaking when they are first built. Changing the shape could push it over the limit.

No way that I know how to check before building, unless you did the process shown in the Gougeon Brothers Boatbuilding book.
Here is a free download.
http://www.westsystem.com/ss/assets/HowTo-Publications/GougeonBook 061205.pdf