Thundercat 31 conversion build

[Doby]

Nice place, you had better hope that Thundercat has a tight turning radius!

[lomdel]

I'm sorry to hear that the motor didnt show up in time.

According to the South African Post Office the package hasn't even arrived in the country yet! Unfortunately we can't trace the thing... I'm getting worried Meanwhile the boat and canal beckons.

[lomdel]

Still no motor and bullets...

[lomdel]

At last my motor and bullets arrived!! I got to solder on the bullets, mount the motor, made the ESC mounting plate, Install the batts, connect everything and program the Etti for a 6S cut-off. Exciting times... Here are a few pics of the completed install without the sub-hatch. It screams like a pig on steroids!!! Can't wait to get it wet...

[lomdel]

I had it in the water today for a quick test-run (alas no GPS reading yet).
It ran well with a rather wet hull attitude, but the Etti ESC didn't give me smooth acceleration through the throttle range, it seemed to reach full speed at half throttle. As you can see from my pics I tried to set-up my cooling plumbing to run two separate diverted lines through the ESC, but the right hand side just showed a negligible trickle through the middle outlet. I will re-route my plumbling a little...
The hull took in a fair amount of water despite my sealing efforts. I think it happened at the rear, through either one of the screw holes, or the steering linkage boot. I will check it in the bathtub soon...
I also noticed a small bent in the bottom tip of the leading edge of the rudder that probably affected my speed as well. (After I ran it first still with the split fuel tube leading edge protection strip still attached... lol!)
I ran her with a Prather P215 prop (dictated by FeCalc) but will look into other suggestions for props as well...

[lomdel]

Another run today, this time with my GPS, but unfortunately it only acheived a 58kmh (36,2mph) top speed without the canopy, but with my flat clear perspex sub-hatch taped down. It looked fast but I am dissapointed. I hoped to acheive closer to 42mph. The water was flat with virtually no wind...

My set-up again :
Proboat Thundercat 31 hull (stripped out)
Feigao 13XL
Etti 150 Marine ESC
2x Zippy 4000mah 3S 20C lipo's in series
Everything water cooled
10 gauge wires and 5,5mm bullets throughout
Prather P215 prop

It took some prop spinning to get her up on plane, but once on top she took off like a bullet, I almost feared a backflip...

Please help a fellow frustrated FE boater with some suggestions!

[Steven Vaccaro]

Have you tried different strut positions? Also how where the temps during and after a compete run?

I larger diameter prop will help with the take off speed.

[txboatpilot]

[

QUOTE=lomdel;69127]Another run today, this time with my GPS, but unfortunately it only acheived a 58kmh (36,2mph) top speed without the canopy, but with my flat clear perspex sub-hatch taped down. It looked fast but I am dissapointed. I hoped to acheive closer to 42mph. The water was flat with virtually no wind...

Glass smooth water will cuase the boat to run a tad slower, mabey 1-2mph...
A little chop will help release the hull from the water surface, making it a tad quicker.. But I would look at temps on your set-up and then go to a larger prop for more speed, as long as you have the comfort room with temps on your equipment..

My set-up again :
Proboat Thundercat 31 hull (stripped out)
Feigao 13XL
Etti 150 Marine ESC
2x Zippy 4000mah 3S 20C lipo's in series
Everything water cooled
10 gauge wires and 5,5mm bullets throughout
Prather P215 prop

Looks like a good sport set-up..

It took some prop spinning to get her up on plane, but once on top she took off like a bullet, I almost feared a backflip...

It most likely needs a bigger prop to plane out more quickly..

Please help a fellow frustrated FE boater with some suggestions!

Keep the esc, motor and lipos at resonable temp's and start "propping up"..

[lomdel]

What would reasonable temps be? 120 - 140 deg F? Of the motor and the ESC?

[calcagno45]

Under 140-150F on a motor is good.

[lomdel]

Some more runs today, still 58kmh (36mph) after strut has been adjusted slightly. Temps after every 4 or so full throttle passes never exceeded 130F on the motor, so I guess I can prop up to S220...?

My lipos are 4000mah 20C's currently. Will 25C or 30C's make a huge difference?

I'm frustrated that this set-up of mine doesn't reach higher speeds! A 31" cat with a 13XL on 6S should in my opinion reach 40+mph, or not? I have a 10XL in my toolbox as well, but that would be overkill for my batts and ESC and would probably . I know there are a hundred things that could affect this, but have some sympathy for me...

[Doby]

Your Lipos should be good for around 80 amps. What are their temps after your runs?

[txboatpilot]

I would try propping up to the 220.. Try it for a few passes, bring it in and get some temps.. I would suggest buying some new lipos,,, 5000mah or higher and 25C at least..

[lomdel]

I ordered a X642 and a S220 prop to continue testing. Buying lipos is an expensive exercise from this side of the globe (South Africa), but Hobbycity have always been a good place to buy them from. 3S 5000mah 25C lipos would set me back a lot, though.

FE on a budget is myth...

[lomdel]

Had another couple of runs today after I shifted CG forward with the batts, sanded the bottom of the sponsons with 400grit and sharpened my current P215 some more. She got outta the hole much faster with far less cavitation thanks to the 30%(ish) CG. But I still could not break the 60kmh barrier. The temps were between 120-130F on the motor and far less on the ESC and Batts.
I'm still waiting for my new props and I ordered some 25C lipos. The ones I have is only 20C.

I hope to break the 60kmh barrier soon and then the 72kmh (50mph) one looms FAR away...

Much less water in the hull due to a piece of silicone tubing over the stuff tube till it just touches the flex-shaft. The shaft is where most of the water entered...