Sarik model ballast

[Tim MoodyParticipant @timmoody76107]

I am currently building my first model which is the Sarik Vosper Whaleback. Would I be right in assuming I do not need to worry about ballast in this model?

[Tim MoodyParticipant @timmoody76107]

[Richard SimpsonParticipant @richardsimpson88330]

I would say Tim that you should at least consider the ballast in any model. My own process is to put the bare hull in the bath and add weights until it is down to the designed waterline. Remove the weights and accurately weigh them.

You then need to weigh all the components you intend putting in the model such as the structure and fittings, motor, shaft, rudder, RC gear, battery etc..etc.. Hopefully the weight of all this is less than the weight required you get the hull to its waterline. Assuming it is less the amount of difference is the additional ballast that you might need to add. If it is very close you might decide not to bother, if there is a big difference you might decide to add a percentage of the difference as permanent ballast and use the remaining to adjust trim and handling.

The big problem is when all the model components weigh more than the weight required to push the hull down to the waterline. Then it could either sit too low, be unstable or even sink! It does pay to do some trials in the bath.

[Charles OatesParticipant @charlesoates31738]

With a slow running or displacement model I do things exactly as Richard said, with a fast scale model I take a different approach. Any added weight only slows the model, and effects the handling so I don't worry about the waterline, if there is one. I just do a flotation test to be sure of the best place for the battery.

The Whaleback is a very nice running model and easy to set up, so you shouldn't have any problems.

[ashley needhamParticipant @ashleyneedham69188]

Whereas I would agree totally and absolutely with Richard regarding ballast in anything but a fast planing hull (essentially your whaleback) I am not sure you need to worry about ballast unless you have managed to build an absurdly light hull and are using very lightweight components.

Things like power boats or torpedo boats don’t really need ballast unless they float really high. You may need ballast to trim it though, and of course a pond first test MAY show a need for ballast, especially if it appears to be unstable (!) so I wouldn’t rule it out completely

As Richard says, a bath test is the way to go initially, but adding weight slows a fast hull down remember.

Ashley

[Tim MoodyParticipant @timmoody76107]

Thanks for your help much appreciated.

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