Are you building a ship, if so whats your propulsion system, otherwise you might have to correct your figures. I learnt the hard way, when I launched off my local jetty, I got about 30m up before the glue got wet and the cardboard panels came apart, my $ 12 cyclic fan didnt work to good for propulsion either, and nearly electrocuted my self in the splash down. My vehicle weighed 10kg, not including my 5 kg fan and my 20 kg batteries, and last of all my 100kg body weight, as you can see from my experience in the space race, its very important to know and understand your own math, Asking someone else can lead to all sorts of problems, not to mention the $100 dollars I lost in seeking engineering advice from the local Country Womens Cooking Association. They all looked wise being old and grey and very patient,( now that I think of it they were probaly dozing) but anyway be wary of advice you believe is coming from an authentic source, those old ladies stitched me right up, and ive never really fully recovered. Now that Ive learnt from my experience, I realise now plastic is far more durable than cardboard, next time you see me, I will be on the cover of time magazine, getting the nobel prize for inventive engineering. you can tell every body when you join the race, "that man gave me some great advice and I wouldnt be where Iam today without his words of wisdom."<br /><br />Cheers<br /><br />Sponge. <div class="Discussion_UserSignature"> <p><em><u>SPONGE</u></em></p> </div>