Identical configuration on two different hull types...substantially different results

[fidelity101]

TP 5660 810KV motor, 10S 6200mah 30C battery packs, Swordfish 300A Pro+ ESC with Hifei capacitor bank installed. I'm using XT150 connectors for the batteries, which are basically a longer 6mm bullet connector and 8 gauge wire on everything.

Hull #1: Conquest 43"
Hull #2: Challenger Pro 48"

IMG_2390.jpgChallenger Pro - 5th run of the day using a CNC 55mm prop.jpgConquest - 3rd run of the day doing a few high speed runs with CNC 55mm prop.jpgIMG_2552.jpg

[fidelity101]

IMG_2560.jpgIMG_2558.jpgIMG_2555.jpgIMG_2561.jpg

I'm new to fast electric boats so I'd like to know if it's normal to have such a large different in power consumption.

Conquest: 150A and hitting 66mph. The entire hull is out of the water and I know catamarans are generally faster than deep V/mono hulls.

Challenger Pro: 200A and hitting 56mph. The entire hull is out of the water and I'm having problems with chin walking...I think that means I have to adjust the stinger or is it a CG/battery placement issue?

The funny thing is that BOTH models pull about 50 amps at half throttle. I'm not sure why the Challenger Pro is going so much higher in amp draw, but I may have to step down to a smaller prop if I can't figure out out as the temperatures were jumping into the 60C-65C range.

[kfxguy]

I'm no pro, but I'll give my opinion. ..

First off...if the strut is not adjusted to the optimum position, that will make a big difference. Big difference!

Next, a cat by design of the hull, provides lift off the water. Then you have some smaller and probably less draggy ride pads in the water vs the back of the v hull is in the water...more drag. Just my guess

[fidelity101]

Do you mean the Stinger? The strut on the cat has been adjusted a few times and I'm happy with the performance. It's the mono hull with a stinger that concerns me.

The stinger on the mono is in the default position, which I believe is 0 degrees. I tried moving the batteries forward and backward on the mono today and it changed my amp draw from 212A (pushing to much water) to 189A (chin walking).

I'm sure the CNC 55mm prop isn't the best solution either, but the Octura B&S 52mm prop was destroyed in a recent Tactic radio failure incident and I'm waiting on a replacement. Hopefully dasboata will chime in here as I've been told my more than one person that he's the prop master! :)

[srislash]

How much pitch on that CNC prop? I ask because most of them are 1.8's, and that will be too much for a Mono.
High pitch will lift the transom and push the nose in. I don't even mess with 1.6 pitch props on the monos anymore. Turns em into submarines,lol

[fidelity101]

http://www.offshoreelectrics.com/pro...+2+Blade+Props

Diameter Total Pitch
55mm (2.17") 3.03"

[srislash]

Well, a cat is certainly more efficient than a mono. And 189amps is not that bad. My 35'DF hull with 1717 pulls 175 regularly. Up in the 200's would be excessive except for peaks.

I should add that it will get better with the 'right' prop and trimming for your application.

[fidelity101]

The 189A run was the lowest amp draw and I think the batteries were still to far back as I had a lot of chin walk...I could not stay on throttle as it became violent and would have flipped. Moving the batteries forward seems to add current draw but stops chin walk. I think 200A was the max when batteries were installed a bit further forward and chin walk was less or eliminated.

Thanks for your help guys. It seems my setup is good then and I just need a smaller prop. I have a 52mm balanced and sharpened octura prop that I'll use when it arrives but I may even need to step down to a cnc 50mm prop as I would like to keep amp draw below 160a for the sake of my batteries.

[PowerDemon]

The 189A run was the lowest amp draw and I think the batteries were still to far back as I had a lot of chin walk...I could not stay on throttle as it became violent and would have flipped. Moving the batteries forward seems to add current draw but stops chin walk. I think 200A was the max when batteries were installed a bit further forward and chin walk was less or eliminated.

Thanks for your help guys. It seems my setup is good then and I just need a smaller prop. I have a 52mm balanced and sharpened octura prop that I'll use when it arrives but I may even need to step down to a cnc 50mm prop as I would like to keep amp draw below 160a for the sake of my batteries.

Yes 30c is not ideal for that setup. I believe ah x c rating = amp output. So in your case it would be 186a continues output with those batteries.

[madmikepags]

OK in your post you have conquest 150 amps and 66 mph and Challenger 200 amps and 56mph but you say that that you dont know why the "conquest" is pulling more amps???? Please Clarify which one pulls more amps???

[fidelity101]

The charts and information is all correct...I simply stated the wrong model in post one so my apologies. The mono hull is significantly higher than I would have expected at about 40-50A higher while being 10mph slower.

[madmikepags]

A mono has significant more hydrodynamic drag and aerodynamic drag, people don't realize that second part, also while "chine walking" back and forth there is hull in the water. Please take a picture of the back of your hull straight on and the side so we can see your stinger height and angle. I stopped using stingers on monos and I am using struts with a wet well so I can move the prop height up and down without changing the angle of the prop.

[srislash]

A mono has significant more hydrodynamic drag and aerodynamic drag, people don't realize that second part, also while "chine walking" back and forth there is hull in the water. Please take a picture of the back of your hull straight on and the side so we can see your stinger height and angle. I stopped using stingers on monos and I am using struts with a wet well so I can move the prop height up and down without changing the angle of the prop.

Agreed here with the strut. One of the things I had to do to get my DF settled was raise the stinger/stuffing tube to keep enough hull in the water so it wouldn't chine. The other was trim tabs. Just a slight amount. This kept the nose down so it wouldn't start hopping ending in a dive.

[fidelity101]

image.jpg

I'll upload better pictures when I get back from work, but the stinger appears to me 1-2mm from the bottom and zero degrees of tilt. I could bend the trim tabs down a bit as they're no doing much at the moment.

[srislash]

It did not take much tab on mine, just 1/16. I went on for quite awhile trying not to use them as I didn't want the extra drag. In the end it did not effect much negatively.