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[petermun]

A friend has asked me to refurbish a 48 inch Perkasa.   At the moment it is only fitted with two shafts, two 50 mm props and two rudders.   Can anyone advise, please, on the size of motors and props I should install.   Many thanks,  Pete

[Shipmate60]

How do you want her to perform, fast or daft fast?

Bob

[petermun]

Bob,  Just fast.  Pete

[Shipmate60]

2 x Graupner 700BB turbos. 9.6 volt motors on about 12 volts.
But with MiNim battery or batteries.

Bob

[petermun]

Bob,  thanks for that, should I keep the same props?  Pete

[Stavros]

You want PROPER fast then fit a pair of 900 series motros....get them off ebay fit them with 55mm 2 blade props use on 24v ACTion speed controllers and run on stick packs you should get around 45 mins on the plane.I have one with a single 900 motor in it and it just flies.The 700 motor are far to power thirsty in My opinion
 
 
Dave

[petermun]

Dave, thanks.   I now have to make the choice between your and Bob`s suggestions.   Pete

[Shipmate60]

Dave,
The cheap ones from Lukethemonkey are no longer available.

Bob

[Mrs Stav]

Ok But thye are still available form Steve Modle boat bits at £26 ea
 
 
Dave...using kellys lap top

[petermun]

One final question:  The boat is 48 inches in length, needs ballast so I will use a 12v 9Ah for ballast and power.  The overall weight will be around 7Kg.   With two motors and 50mm props, what sort of revs should I aim for at 12v?  Thanks to you both for your help.

[malcolmfrary]

The boat is 48 inches in length, needs ballast so I will use a 12v 9Ah for ballast and power

The last thing wanted in a performance boat is ballast.  In the early days of Perkasa models, lead acid was what was available, there are much better alternatives today.  Almost any technology, NiCad, NiMH, anything with Lithium in it, will do a better job of holding a charge and delivering the current needed with a much lower weight penalty per unit of power stored.

[petermun]

Thanks Malcolm, I am aware of the battery technology, what I should have done before deciding on battery type is to put it in the bath and check its flotation.   The other point is that the boat will normally be sailed on a relatively small water, about 60 metres in length, and so duration is more important than very high speed.   Thanks anyway, Pete.
 
 
 

[Stavros]

You dont need ballast and if what you say about the length of the lake then a pair of mfa 800 and use a batt as you said but if it is speed and duration you want then go 24v per motor witu either nimh or lipo batts


Dave

[petermun]

Dave, I think you are right, the answer is to keep it simple. Thanks to all for your help,  Pete.