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[Shipwreck1963]

Hi
I have an 88cm Vantex Budweiser Select Catamaran which I have modified with a Leopard 36 series 1900Kv motor on up to six cell. Should the COG be central on the length of the boat and if not where should it be? Is the answer to this the true for all catamarans?
 
Thanks

[big bill]

gday , i don't really know the answer to your question , but it seems most don't either ?
my limited experience w cat/tri hulls in sail mode ,was the CG was well aft , w a foil,large , fitted to the bottom of the rudder , to create more stern down thrust at speeds , as they tend to trip ,and nose over .
 are you sailing it or powering it ??
w electric power , CG would be approx. centre of hull
really need more details , but most cat hulls aren't good to sail , very fast , but prone to trip and nose overs , you may need a dingy ??
good luck , i only through this in , because no else had a go , yrs ago , i almost built one , even brough the hulls
bill s

[w3bby]

30 -33% of the length (around 27cm) from the transom would be my starting point. Adjust from there depending on how the hull behaves.

[Martin (Admin)]

From the transom or propeller?

[w3bby]

Thought I was clear  .... 30-33% of the length of the boat (88 x 30/100= 26,4) round to 27cm from the transom.

[Martin (Admin)]

Not disagreeing with you, it's just I read somewhere that for an offshore racer etc. the dynamic length of the hull should include the 'strudder' that's where fulcrum point is.....

[w3bby]

I have always measured from transom forward and used the actual hull length not the l.o.a.

[big bill]

gday folks ,
 it seems clear to me , w the mearsurement approx. 33% from the transom, it puts the CofG, well to the rear of the hull , were it is harder for the sail to force the bow down and under , tripping the hull , same as what i thought was the case , BUt
 the original post still hasnt stated what  the hull will be doing ?? sail or power ??
it would also be nice to hear form some-one who knows about it (w3bby) , if we should measure from transom or prop , not a lot too ask , is it ??
it is only a difference of no more than 100 mm, as some stern drives now hang well back from transome , but it could be all the difference in performance
keep up the good work , food for thought
bill s

[w3bby]

Big Bill, read the op... It is powered, here is the hull.



http://www.rchighperformancehobbies.com.au/buy/vantex-fiberglass-electric-artr-rc-brushless-victory-trailblazer-2.4ghz-jet-boat/BM041EP

[Martin (Admin)]

 
Found this:

http://zenoahmodifiedengines.com/rc-boat-tuning-tips.php

[big bill]

gday w3bby , well it is obviously powered !! i dont see any sails !!! LOL on me !!!
out of my area , but you can see why i asked was it powered or sail +also these often use transom off stern drives
i run mainly scale these days+sailed yachts for over 10+ yrs , still do , but im only a sunday sailor , never will win a race , nor do i need to .
im following these brushless money pits , last motor i brought cost $12- so a bit of a shock when i buy brushless for $60- then another $100+ for controller !!
i would like to know what s/control works well w tugs ?? good slow speed control -any advice ?? i intend to run t/belt g/box .
 regards and good luck , going to look at a glen guest boat , more my speed LOL
bill