Prather 40? deep conversion

[rick h]

Hey folks!
1st post to the forum but I have been searching for some answers on weight for a few weeks. All is I can find is answers about weight distribution. I have a grasp on that. But I was wondering what is considered a heavy boat for a 40?. I know it?s archaic and I might just move the power train and hardware to another boat in the end, but the hull seems to be only a little more than half a pound heavier than the OSE 38? delta force mkII. 4.2 lbs for the Prather and 3.58 lbs for the mkII.

The parts I have are, leopard 5692 1340kv, a castle hydra ice 240. Prather props s230 and s235. Was going to run it on 2 6s 5000mah batts in parallel.

I am in the process of converting it to surface drive. It weighs about 8.8lbs without batteries and the batteries are 3.75lbs combined. So I?m looking at about 13lbs running weight. Is that way too much?

here are som pics of current progress

[rick h]

Thank you for your help! Some more pics

[rick h]

I’m not sure why all the ? Marks got added for punctuation

[srislash]

I would not worry about that weight. The only places that a boat suffers from weight is takeoff and powering out of corners. And by that I mean when speeding up thru the corner. Once a boat is on plane weight actually helps make it more stable. Good to see another oldie make it back to water.
Shawn

[rick h]

Cool thanks for the reply Shawn. I’ll just have to see how it works out.

[Panchothedog]

Prather was once one of the most popular nitro powered hulls out there. At least in California where you and I are from. They were competitive boats in their day. All of the parts you have seem right on for successful conversion.
Everything stated by Shawn in post #4 absolutely correct.

[Bande1]

Id start with the S230 and monitor temps.

[Alex.v.Schie]

I think you are better off going with 12s .
The amp draw on 6s is way more than at 12s.

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[Peter A]

Weight is not a major issue in monos. I ran a HK Osprey (43") with 5 kg of batteries in it for offshore endurance. Testing showed that top speed was not affected by the extra weight. In rough water it will be more stable. It is more important to get the boats balance (CG etc) right. The motor etc you have will work ok I think. If you were going to buy a motor I would suggest around 600-650 kv and run 12s. Higher voltage gives you lower current draw and temps, but start with what you have.
In the Osprey I ran a TP 4070 440 kv on 12s and a Prather 240 detongued, it was set up for endurance running so top speed was only around 70 kph but I could run for 20 min on 20,000 mah packs. It was only pulling 55-60A.
On 6s 2P you can get a reasonable run time, you will have to test and check temps, power used etc. I would suggest to start with set the lvc at the highest voltage and adjust down when you know how much you are drawing out of the battery packs. This will save you bruning up packs.

[rick h]

Thanks for the info and help folks. I was thinking of going 8s because that?s all the esc will handle. I have had these parts for this project for quite a while. I will see how it works on 6s then take from there. I live in the desert so there?s no lakes close by. But I go up to big bear lake in the mountains once a year for vacation. That?s why started this project after someone gave me the boat. I have a gas boat a 40 inch enforcer that I mess around with so far but it only gets used once a year. I like building rc stuff so this boat has been a learning experience for me.

[rick h]

Wow Peter, that?s 11 lbs of batteries alone. But it?s also 50+ volts. I think my kv rating is too high for 8s but I see how it does on 6s. Knowing what I know now, I would have went with a lower kv motor than I did at the time.

[rick h]

Prather conversion complete.

Finally finished this. Not sure when I?ll get to test it. Hopefully it will run decent. Here are some pics:

[srislash]

She looks good. Nice work