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Author Topic: Mystery Boat  (Read 1376 times)

Nordsee

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Mystery Boat
« on: March 10, 2011, 04:47:59 PM »

I have just finished rebuilding this model. Someone did tell me her name, I have sadly forgotton it! It has a Speed 400 motor driving a Graupner P30 propellor, She is quite fast but does not plane, just pushes up a big bow wave. I have put 4ozs of lead right aft to get the stern down and the water line in a better position. Better but still no plane. Should I put sprayrails on her? It is years since I built her, so have forgotton. Should she plane or would that be incorrect for such a model? Perplexed, Germany.....

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John Mk2

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Re: Mystery Boat
« Reply #1 on: March 10, 2011, 05:18:26 PM »

Prop shaft angle to steep ? Just an idea  %)
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capterik

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Re: Mystery Boat
« Reply #2 on: March 24, 2011, 11:34:11 PM »

I have just finished rebuilding this model. Someone did tell me her name, I have sadly forgotton it! It has a Speed 400 motor driving a Graupner P30 propellor, She is quite fast but does not plane, just pushes up a big bow wave. I have put 4ozs of lead right aft to get the stern down and the water line in a better position. Better but still no plane. Should I put sprayrails on her? It is years since I built her, so have forgotton. Should she plane or would that be incorrect for such a model? Perplexed, Germany.....


That hull design is one that is meant to plane. If t it is going fast, then it is planing. A hull that is operating in displacement mode, is limited in speed by its length, and I doubt you would characterize that as fast. Does she sit on her water line? Maybe some pictures of her in the water, and maybe of her running gear would help. Spray rails wouldn't hurt and if its a wet boat, they would definitely help, and may actually act as lifting strips. Nice looking old boat.
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dodgy geezer

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Re: Mystery Boat
« Reply #3 on: March 25, 2011, 10:30:58 AM »

It is the NOR STAR 'OSPREY'.

The boat should plane in its current state, though properly designed spray rails will assist this. I suspect the boat either has:

1 - too little power
2 - too much weight

Small boats are harder to get to plane than larger boats, because the weight of the batteries starts to become a larger proportion of the boat. You need to build for lightness - shifting battery position, for instance, would be much better than adding more ballast! What kind of battery are you using - weight and voltage? You could try a lightweight NiMh, or even a Lipo.

Another issue which is less well appreciated is the propeller. It is surprising what difference changing this can cause. Often too large a propeller is used, which slows the motor down a lot and wastes power in drag. You might try a smaller propeller and see if that helps....
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Nordsee

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Re: Mystery Boat
« Reply #4 on: March 25, 2011, 03:49:59 PM »

Thanks for the replies. when she was first built she had a 2 channel radio, with the rudder servo and Rx battery pack under the rear decking, the on/off switch was also there. The speed control and Nicad pack was amidships. Motor was a Mabuchi 540 driving a Graupner P35.  Today she has an ESC and no Rx batteries. Mini Servo for rudder and a Nimh 2/3 C cells, 7.2 volt 1300 s. I sail alone so difficult to get a photo. Also our lake is covered with a fine brown scum, Pollen I believe. Where should the CofG be? How far from the Transom? It is annoying me, her not going as she should!
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