HiTec Sea Nymph

[meechingman]

Don't know if this should go here or in 'fast electric', but my better half wanted a faster boat than her 'toy' RNLI Severn. Spotted a Hi Tec Sea Nymph on Ebay for a cheapo price. It arrived today, and works as advertised. A bit plasticky, perhaps, but rather better than the current cheapo chinese toys, with a proper Futaba/Hi Tec r/c system, at least!

Anyone have any knowledge, experience, tips etc. According to the box, the motor is a Mabuchi 550, driving a 35mm {quote} Pitch 35.5mm [1:40"] {unquote} prop. Anyone know how good/bad that is? It looks like I could replace the 3-step mechanical speed controller with an ESC and go from the plastic prop to a brass one with no problem, but would it be worth it? At the moment I've borrowed an 1800maH 7.2v Tamiya pack from my son's car to power it. Any idea how long that might last on the water?

Cheers
Andy

[Ghost 2501]

pic please :)

[meechingman]

2 pix of Sea Nymph

[Ghost 2501]

plastiky maybe but convertable to regular rc, shouldnt be a problem :) with a better esc and motor it may actually achieve the first part of its description of fast electric

[Rex R]

one thing you'll need to know before you get too far with your plans; is what size dia. is the prop shaft(motor shaft as well but isn't quite as immediate a need). then find out whether the the prop threads on or slides onto the shaft. looks like 35mm is about as big as will fit the space. at a guess I'd say 5-6 minutes on a 1700mah batt pack. then let the motor cool while the pack is recharging. a 600 series motor would prolly run cooler.

[Kmot]

It appears to have hobby grade electronics already. If it is indeed a Hitec product then it has a Hitec radio and esc. Nothing to worry about Hitec stuff.

[meechingman]

Thanks so far. 5-6 minutes. Hmmm, I think I'll get a couple of 3700 maH packs - they're pretty cheap from Modelpower here in the UK. The r/c is good quality, just the speed controller I might change to ESC.

[meechingman]

My son and I took her down to the lake today, perfect conditions, almost like glass.

She runs well and turns pretty sharply. She's quite wide at the stern and stays pretty flat.

She took on a little water, either through the rudder tube or more likely the stuffing tube, so a little remedial action is needed before her next trip. For what I paid (£25) I'm pleased. I could have spent more on a bit of junk that conked out whenever anyone else had a TX switched on nearby!

Forgot to take the camera, darn it.

Andy

PS My son now wants a boat for himself that goes faster - another convert to our hobby!

[pompebled]

Thanks so far. 5-6 minutes. Hmmm, I think I'll get a couple of 3700 maH packs - they're pretty cheap from Modelpower here in the UK. The r/c is good quality, just the speed controller I might change to ESC.

Remember to watercool your motor, before running 3700mAh packs, the increased runtime will heat up the motor to destructive temperatures...

A little(!) thin grease in the stuffing tube should remedy the leaking, don't stuff it completely, this will add drag and slow the boat down.

Keep us posted.

Regards, Jan.

[Kmot]

Jan is so right! Most people do no equate run time with destructive heat! The longer you run, the more heat is generated! That is what water cooling is for. To allow extended run times without damaging components from heat.

[meechingman]

Thanks for the advice. With the shaft out and prop off, I can check out how easy it is to replace with a brass prop. If it can be done, it would make sense to do it then before reassembling.

I ran her for a few minutes, then brought her in and checked the motor temp. Surprisingly cool, but the box does point out that she has a shaped air duct behind the 'driver' that forces air over the motor.

The idea behind the battery upgrade is to give me several sessions, I can run the tugs in between.

Thanks
Andy

[pompebled]

The idea behind the battery upgrade is to give me several sessions, I can run the tugs in between.
Thanks
Andy

As long as there is an outlet for the warm air, the duct should work up to a certain point, I've tried something similar in an Academy cat.
The motors still would be very (too) hot after a run, so I converted to watercooling, no heat issues ever since.

From the battery lifespan point of view, discharging a NiMH in several short sessions is not a good thing. These cells are rather sensitive to false treatment.
NiMH cells perform at their best when warm from the charger, ran cold, the performance drops sharply and the cells may even take damage.

For this reason, race boaters have several packs, which are 're-peaked' (warmed up) shortly before running them in the boat.
Also don't run them until the battery goes flat, when the speed starts to drop off, bring the boat in and allow the battery to cool down for several hours.
Don't (charge and) run a NiMH pack more than three times a day.

If you don't want the hassle to take a charger, car battery etc. to the water, you're better off using the best Nicads around; Sanyo 2400 Nicads, which don't mind being run cold.

Regards, Jan.