Question about temperature?

[mikeochs]

Hi guys, quick question concerning temps of water? Today I was running my boat at the lake, very nice and cold though. Water must have only been just above freezing because far end of pond was frozen. Im assuming where I was running must have been around 35-40 degrees. What I am trying to figure out is the other day at a different lake I was able to hit 55 pretty easily and today the highest I could hit was 52.6. Now the other day I was running a x442 on 6s and Today I was running a even more aggressive prop the x642. Same diameter but more pitch. The batteries were cold the motor was not even over 75 nor the esc. Is it possible for the cold weather and the cold water keeping from reaching full power, I know this is true with planes but was wondering if this will apply to boats aswell. I should easily be able to attain 60 with that setup. Leopard 4074 1400kv, seaking 180, octura x642 6s 40c 4400. here is a video of it, the lvc actually shut down for a second then reset. I am assuming the batteries couldnt provide the amps needed. Ran these before never hit the cutoff. The packs read 11.75 each after a 1.54 minutes run.

http://www.youtube.com/watch?v=udvB4S21458&feature=email

[egneg]

It could be that the 442 is a more efficient prop.

[RaceMechaniX]

Different lakes and specifically the viscosity, dissolved particulates, salinity, etc will affect the speed of boats. With those cold temps it can also easily be your batteries are too cold. Lipos perform much better when warmed between 80-100F. If you ran the packs near ambient conditions they probably were not putting out the amperage they do when warmer.

TG

[sundog]

With those cold temps it can also easily be your batteries are too cold. Lipos perform much better when warmed between 80-100F. If you ran the packs near ambient conditions they probably were not putting out the amperage they do when warmer. TG

[LarrysDrifter]

Warm your batteries, hull and tape. Youll be good to go.

[stadiumyamaha]

may be the water was colder an therefor more dense. Just a thought

[mikeochs]

Ya that all sounds logical, Im sure it is a factor with the cold batteries and water

[CornelP]

Water at 40F is about twice as viscous as water at 70. Theory says drag is directly proportional with viscosity (through the Reynolds number) and inversely proportional with density. If you do the math, with all other conditions equal, you can see a decrease in speed of about 11%.
Combine it with the Lipo temperature and you ca see a drastic difference.
Add this to the fact that a cold tape on a cold hull will never stick properly and you can almost lose a boat (ask me how I know....).

[siberianhusky]

If you just swapped props and made no other changes perhaps the boat wasn't set up as well for the 642? COmbined with the cold batteries...
Use good tape and you have no problems with cold weather, I run my boats until water is freezing on the decks and have never lost any tape.
3m hockey shinpad tape, way way better than the Renfrew stuff, thinner, more flexible and better glue that doesn't leave any residue.

[BHChieftain]

On the prop difference- I had a situation where I ran a x637 prop on a mono, then one day I dinged it up, so had to use a backup prop which was an x440. The 440 has less pitch than the 637 but my boat ran a little faster-- I think the 637 was not allowing my motor to hit peak RPMs. Also ran cooler with the smaller prop which is nice.
Chief

[mikeochs]

So yesturday was a warmer day. Temperature was 50 and water was 49. Topspeed today with 642 was 56.6. 4 MPH faster so it definatly makes a difference

[Gary]

I always warm my SAW hydro batteries to at least 90 degrees before I put them in and it makes a huge difference in performance. It could be the dif between 8 mph or not.