Moppie

Ray,
I’m really starting to worry about the CG on this build. I have to be a good 3 inches forward from the 30% standard. I really don’t want to add weight to the back to balance the boat. But then again, I’m shooting for 60 to maybe 70 mph and wonder if maybe 3 inches is not a bad thing. Any experience here?
Thanks,
Moppie

PS: The motors are in, ESC’s mounted, cooling, flotation, hatch is reinforced..working on the drives to include counter rotation.

Moppie

Yes, very little exposed flex wire..

BACKEMF

That is still les tan 40% so you should be good to go. I think that you will want more weight forward 40% + for those really high speeds.

Remember it's 30-40% from the 2 transoms, not the end of the hull

Moppie

Ray,
Another question, does having 2 x speed controllers put a lot of additional draw the receiver batteries?

Moppie

Ray,
Another question,
Have you ever run two batteries in series and also with two ESCM’s running duel drives?

Moppie

BACKEMF

I do not think the esc's will have much of an amp draw, no worries. Make sure if you use seperate rx battery pack that you disable esc's bec's, remove red wire.
Recievers don't draw much current and esc's don't draw much current either, not nearly what a 100 Oz/in servo would.

You are also asking about using one main pack to power both esc's? That is with a few packs in series...?

Exactly what configuration do you mean?

What I will do is use a pack of batteries, for me, 4S per side and I will use a pair of thick guage jumpers to make the 2 packs run in parellel, hopefully giving the whole system one solid power system to draw from.

I have never tried parellel jumpers in a twin, it is a concept I have seen online and i like. You don't have to jumper the packs but, it makes sense so tehy drain equally imo.

Cheers,

Ray

Moppie

Ray,
Thanks for the feedback on the esc’s.
What I like to do is mix the batteries in series to increase voltage as I test out the system for heat.
For example, for the CAT I’ll start with 2 x 3S packs, one for each motor and see how that goes.
Once I’m ok with the setup I would put a 2S in series with a 3S and if everything is ok then both 3S in series for 22,2 volts (esc max).
What I'm not sure about is whether this approach will work with two motors? I have the feeling that batteries in series it’s not a good idea as the amp load will increase by 2 also.
Moppie

BACKEMF

Well, again, what configuration do you plan on exactly? Just some packs in series that power both sides i.e. 1P ?? or do you mean each side gets 3S. 5S, 6S ???

Moppie

Hi Ray,
Sorry if I confused you. To start with I will run two 3S packs, one separate pack for each ESC & motor. What I would like to do after this is to combine a 3S and 2S in Series and feed both Motors to increase the voltage from 11.1 to 18.5v to see how the boat runs. But I’m afraid that this will be to much amp draw on the batteries as I suspect each motor can pull least 75 amps each or combined, 140+ amps. So I think I have to follow your remarks about either running one pack per motor or in parallel to make it a constant power source.
Moppie.
How far are you with your build? I think I will be able to make a run this Easter if I can get the last of the electronics installed and can avoid the fishmen who don't take kindly to me this time of year.

Moppie

First run today..
Speed was well below my expectation. I'd have to guess around 30mph at best. To much weight toward the bow. Was very wet. I need to relocate the batteries back toward the stern if I can find room.
Moppie

cowana

Can you have one battery at the front and one right at the back (behind the wood)?

That might balance it better - they don't have to be side by side.

Moppie

Thanks for the tip..

Moppie

Fellow FE’s

A short update on my progress. I relocated the batteries to the rear of the boat and balanced the boat’s CG at ~ 30% from the stern.
Here a link to a short video.

http://www.youtube.com/watch?v=SIoQOUqePjg

I had a few problems this time around that include:
1) Killed the Lipo batteries.. (they were rated at 35C ... need to upgrade to a high C rating)
2) Boat took on a lot of water.. could be the shaft with the counter rotating prop as I noticed that the small rubber tube that I use on the prop shaft to keep the water out had moved against the motor.
3) Very hard to control in a turn, it wants to “spin out” if I apply to much rudder. (No idea what to do other than reduce the steering angle)

Other than the above, seems to have the possibility of being fast..

Moppie

BACKEMF

You need to dial your steering EPA to 50% or less.

Trying to turn too quickly at that speed will not happen too easily with any cat.

Do your props turn the same way or opposite?

If opposite as they should be, do the prop tips turn toward the inside or ouside?

What props are you running again?

Moppie

Hi Ray..

Good to here from you. Hope all is well in your neck of the woods..

Thanks for the steering hint..

The props are counter rotating.. The rotation is designed to lift the stern up.. I hope this is what is best?

Prop Size, let me get back to you.

Regards,
Moppie

Moppie

A few comments about the quality of the HK hull.
If you plan to run this hull with the original motor size it should be ok.
If you plan to upgrade the motors be aware that you will need to reinforce the rudder mount as, upon inspection yesterday, this started to separate at the seam. Could explain the water issue...

Newest run with better batteries.

http://www.youtube.com/watch?v=HMHka9JfwUk

Moppie

Newest run with better batteries.

http://www.youtube.com/watch?v=HMHka9JfwUk