Model Boat Mayhem
Technical, Techniques, Hints, and Tips => Other Technical Questions... => Topic started by: iDENTITi on August 09, 2010, 11:28:05 pm
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I'm scaling up existing plans I have of a power boat for a 30cc motor and 50mm water jet drive.
It's going to be 100% bigger (48" vs 24").
Just wondering how much bigger I have to go up in material sizes, and wether its prudent to add more frames and/or stringers to the hull design? Original is made in 3mm lite ply and, I think, 1/16th ply sheeting. All fibreglassed outside.
It's a MMI "voodoo" if anyone is interested.
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Hi Identiti, The accurate curve of the hull lines may be easily 'lost' or straightened and not maintained with the increased spacing/distances between frames which were adequate for the smaller hull size as originally drawn. Additional stingers may also be required to support the much larger area of ply skin required for the hull sides, especially where the sheets are flat rather than curved.The 1/16 ply should be fine for the larger hull's sides. Many modellers avoid liteply for frames on larger hulls and use standard ply for increased rigidity and reduce weight by profiling/removing void areas and this practice also enables free/open access through most of the hull frames/bulkheads for easier placement of running gear, batteries etc. The internal fitting out and running trim of the hull is best thoroughly sorted and undertood before final deck openings limit access. ........................(A few general observations off the top of me head. Voodoo ??????? %)
Much detail depends on the specific model you choose to enlarge, but the enlarged plan views will supply the exact size, position and shape of any additional hull support structure which may be needed. :-)
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I'm going to model it up on solidworks first to see how it all works (and because I don't fancy redrawing all the frames by hand!)
A thought did cross my mind to get a local engineering company to cut it out of blue foam on their CNC mill and just make a mould from it. It would simplify the construction immensely. But I'm still deciding on that..
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Hi Identiti, just take your original plan to a copyshop and have it enlarged/doubled........... quick and easy , but check they have correctly sized the scale % increase you wanted. :}
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Hi Identiti, just take your original plan to a copyshop and have it enlarged/doubled........... quick and easy , but check they have correctly sized the scale % increase you wanted. :}
CAD means I can input the sizes of the jet drive + motor and see how they fit... Otherwise I'd avoid the headache and just get them enlarged! I'm trained in CAD though so it isnt a massive pain, also means I can have fun stress testing it! (without breaking anything.. )
I think I'll double the amount of frames and stringers, and also look into just getting it cut into something I can use to mould from.
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Your 8) plan sounds good. :-)) ............. <:( I have to stick with my half remembered, geriatric GCE Tech Drawing skills and lay running gear on the plan views and sharpen my very blunt pencil. :} )
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I'm trained in CAD though so it isnt a massive pain, also means I can have fun stress testing it! (without breaking anything.. )
So why the original Question?? Surely the stress testing ability on screen without having to chop and waste wood should answer this?
Regards Ian.
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Original is made in 3mm lite ply and, I think, 1/16th ply sheeting. All fibreglassed outside.
Forget the LITE ply and use ply.Take a look at this plan for material http://www.latua.com/RC/rcveneita/WASABI1300F.pdf (http://www.latua.com/RC/rcveneita/WASABI1300F.pdf). The frames in this boat are 6mm ply
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So why the original Question?? Surely the stress testing ability on screen without having to chop and waste wood should answer this?
Regards Ian.
It's not massively accurate for testing hulls, only really designed for normal engineering uses. I figured I'd just ASK, kind of quicker since I dont have access to my CAD computer at this point. It's not a question of strength as such as the fibreglass should handle that, it was more ease of construction, something I cannot test until it comes to it so was calling on others experiences before making costly mistakes. Hope it clears it up for you.
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Looking at your proposed plan there seems to be little between Voodoo and Wasabi.
Wasabi 900E (http://www.latua.com/RC/rcveneita/WASABI900E.pdf (http://www.latua.com/RC/rcveneita/WASABI900E.pdf)) - the plan for the small electric version with a 25 as power source goes like stink on nitro - see attached jpeg. Both plans are "free" off the web as PDF files so you only need to get them printed. The difference is just the 900E is modified to take a 21/25 engine instead of the cells.
For a free CAD package see http://www.mydigitallife.info/2009/08/26/turbocad-deluxe-12-5-free-download-with-serial-number-for-activation-key-code/ (http://www.mydigitallife.info/2009/08/26/turbocad-deluxe-12-5-free-download-with-serial-number-for-activation-key-code/)