Runtime - Basic Question

[rickwess]

I'm really struggling on whether or not I should be going 6s1p or 6s2p in my next boat build. I've played with the formula (before I found the runtime calculator here at OSE), but I'm wondering what's a good discharge current to use? The motor is a LP4082 and the specs say "2000w with over 3500w burst"...........90a and 157a respectively on 6s.

For sport boating, would 90a then be a reasonable average discharge current. I know it all depends of driving style, so maybe the question is how does the spec translate into throttle position. If I was to run it at full throttle 100% of the time, would 90a be the approximate discharge current?

Real life data is the best, so I'm hoping some of you can share your experience. Boat is a 35" mono.

[Chilli]

Your last sentence hit the nail on the head. There is so many things that can affect amp draw. Hull size, weight and style. Set up (is the boat set up loose or wet) and prop selection. It took me a couple years before I got a handle on being able to choose a motor/battery/ESC set up on my own. Once you have the proper set up, prop selection is going to be the best way to control amp draw.

So we know you want to run 35" mono on 6S. What are your goals for speed and run time?

[Fluid]

In my 33" mono I need at least 180 amps average for a one mile heat running 4S2P. I use around 5000 mAh of battery. Similar performance on 6S would require around 120 amps average. That is mostly full throttle, top speeds are low-50s.

The amps you draw are largely determined by the load - the prop, size, etc - not just the motor. Running extensively at part throttle - to extend run time - can be very hard on the ESC. Pulling under 100 amps average is one way to extend run time. Adding more and more battery capacity may not extend run time if heat buildup is too great. High amp draw means building heat fast, limiting safe run time.



.

[rickwess]

So we know you want to run 35" mono on 6S. What are your goals for speed and run time?

For just sport boating on the dock, top speed in the low 50's with a run time of 4-5 minutes.

I suppose my struggle is that 1p or 2p would be totally different battery layouts on the boat. I may indeed need to just stick a 1p into the boat with velco before I mount anything permanent battery trays.

My real issue is that I'm AROC (anal retentive, obsessive compulsive) and need to know everything up front.

[eboat]

If you want run time the best way is to plan on a 2P set up
Start with a smaller prop and keep moving up in size till you get the speed you want ( keep watching how much is left in the lipos after each prop)
When you get the speed then you can figure out your run time that is safe

[lenny]

Hi Rick.
What 35" mono do you have or are you thinking of getting ?
Do you have any links or pictures of it that you could post on hear ?

[rickwess]

Hi Lenny,
I haven't started yet. Looking at either the DF35 of DF Pirate 35". The Pirate looks like it would have less tendency to stuff, but so far I haven't been able to see them side by side. I run on a cottage lake so roughish water handling would be a nice thing. My neighbours will kill me if I keep running it at 7:30am.

[lenny]

Take a look at these hulls,
The one is like the pirate but at 37" and the other is a DF33.
From what I have heard the Pirate is built with a much better lay up then the plane DF33,
And with rails are a lot better way to go.
http://forums.offshoreelectrics.com/...ott-s-DF21-Mk2

[rickwess]

Cool. I saw that thread, but it didn't click it was similar to the Pirate.

I see Steve doesn't carry Pirates with the wood rails. If he can't order, where else in Canada or US are they?

[lenny]

Sorry I meant rails for the plane DF35.
Ok I found the info I was looking for,
Read this post at the bottom of the page it should help you out some.

Also hear is a little treat on how he builds them.

Quote by Punisher 67,

I never did care for the pirate hull until a friend bought one , wow what a huge upgrade from the standard DF35 hull or until I saw the hull in person or up close I appreciated the build and design quality . My DF35 was a piece of crap compared to this hull . I will be building a Pirate with a Lehner 2280/7 or about the equivalent to the 1530 Neu when I get my Pirate hull .

Millzee great choice in hulls and awesome job on this hull


http://forums.offshoreelectrics.com/...Pirate-Rebuild

[rickwess]

Thanks again. I've been finding more and more Pirate build threads here. Some are well hidden.

I see some really nice machined motor mounts and stuffing tube supports, but it seems the nicer they are, the less likely the company/person that makes them continues to do so.

[rickwess]

I've been emailing with Dave over at HRC about a motor mount. I'll be ordering one of there:

40mmmount.JPG.w300h225.jpg

[lenny]

You should have check with this guy to,
He does some nice work and not to prices ether.
http://forums.offshoreelectrics.com/...dware-for-sale

I've been emailing with Dave over at HRC about a motor mount. I'll be ordering one of there:

[ATTACH=CONFIG]107076[/ATTACH]

[rickwess]

I'll have to keep him in mind for other custom work. I like the HRC motor mount because it machined aluminum and keeps the overall width to a minimum. I'll probably need to put the batteries on either side of the mount. The 4" rail style of mount would have taken up too much space.