1st Build

[chris holley]

hello i have had boats before but this is my 1st build an its a diffrent hull and size. I have a cheap hull, (cheap as there is a good chance it will get damaged during racing) its 930mm long, 230 wide and 100mm tall. I will be running a graupner 700bb motor, along with 16 nimh cells (old school i know) an i wont be changing so please do not say try this brushless or lipo route.

I wont to no how to work out twhere the motor should sit, shaft length where to put the servo so its not to heavy at the back, things like that? is this something someone can help me with any advice would be great. thanks chris

[dana]

put the motor where it fits best. you can always move batteries forward if its too heavy in the rear. or try a float test with the motor in different spots

[chris holley]

love to try float test but there is a holey bottom, lol. i have been told that the cog is 30% from transom, so tried that method cog is 279mm (930/100x30) which is what you once told me the boat ballanced with motor at the 279 mark with battries in (graupner 700 16nimh cells),

shaft length out off transom is 10% so tried that at 930+10%=930.1 or 1inch going down that route? but seems to close to the transom with length at 10inch shaft? does this seem right to you?


chris

[dana]

huh? too many numbers and *!***!***!***!** man. getting a little overly complex are we? geez lol

[chris holley]

sorry, the cog is 279mm from transom, so with motor an batts the boat is leval.

shaft length is 25mm from the back off transom? seems short!!

[dana]

you know you dont have to figure motor placement based on mathematics? you can put it where it fits nicely

[chris holley]

oh ok, but is does not look right

[Rich]

put the motor where it fits best. you can always move batteries forward if its too heavy in the rear. or try a float test with the motor in different spots

That's the way most of us would start out. The batteries are the majority of the weight.

[chris holley]

ok well its all in then, all bar the shaft. But how far should the shaft extend the back off the boat.

thansk

[Rich]

Are you using a flex shaft or a solid shaft?

[chris holley]

no it will be a solid straight out the back

[Rich]

That depends on the rudder. The rudder's leading edge should be where the prop starts, if memory serves me right.

[chris holley]

ok well iam running a double rudder.from transom to start off rudder is 85mm which would me i need a shaft off at least 385mm

[Rich]

That sounds about right. Pics of what you have done?

[chris holley]

yea will get them up in a bit doing a bit off sanding down at the moment. thats a long old shaft then?