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49" Perkasa MTB - Which motor do I need?

madwelshmanmadwelshman Club Members Posts: 2

Hi folks, I have a 49 inch Perkasa motor torpedo boat that I would like to convert from a 25cc petrol engine to brushless instead.
After much searching and reading, I'm now totally confused.
I believe the kit was originally designed for a .60ic engine and if I'm not mistaken 0.60x1200= 1200w
I have seen calculations based upon scale and the power of 1:1 scale version, so in this case, 10500hp total (3x gas turbines), the kit is 1:24 scale, so 24 cubed = 13824. 10500/13824= 0.7596. 1hp= 746w, so 746x 0.7596= 566.662w. Adding between 25 and 50% onto that for efficiency and I have ended up with a motor of between 707 to 849w

Does ANY of that sound remotely correct?
The boat is 49 inches long, mono hull, single shaft drive.

ANY advice you can give me will be much appreciated.

Thanks in advance
Will

Comments

  • WTWUKWTWUK CornwallClub Members Posts: 13,469 ✭✭✭

    Yep. 1200W or even 1500W. Lovely hull on it - friend of mine had one, and I had the 32nd scale version years ago - but the kits were crap!

  • madwelshmanmadwelshman Club Members Posts: 2

    Thanks for the reply WTWUK.
    Yeah, I do like the hull shape and agree, the kit isn't the best quality or fit. lol
    So you agree with my figures then, that's good to know that what I have read has made some sort of sense to me.
    I'm guessing a large diameter outrunner is the way to go and maybe 4s or 5s lipo?

    Will

  • WTWUKWTWUK CornwallClub Members Posts: 13,469 ✭✭✭

    6S would be better still. Plenty of weight needed in it or it will porpoise like crazy.

    The one my friend had was fitted with an OPS90 and it was quite astounding, but did require a serious amount of weight to get it to the waterline, and both his and mine benefitted from servo controlled trim tabs.

  • canabuscanabus Club Members Posts: 39

    Hi
    A G60 brushless (1500Watts)is equal to .60 IC motor runs on 4 to 6S Lipo's.
    My mate Has a Fantome cabin cruiser which is about size and is fast.
    I have two of the smaller ones with 35mm 1100kv motor and only use 60% throttle.
    Check out you tube under bjsteveg.

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