Sprint Cat .40 Winter build

[Rumdog]

where is your strut?!

[sailr]

You are gonna have to go 2P on those battery packs! Mine are located amidships behind the motor. If you mounted your motor too far back, it will be difficult as you can't get standard packs into the sponsons in that hull. You will have to build long skinny packs from 3S packs. You will need two 3S in series x 2 in parallel.

I used the Sportmaster .21 strut. It is nearly all the way up! I'll try to find some time to get a measurement for you.

[Raydee]

My packs are right behind the motor. I made the mistake of making a wood battery tray so it makes it just a tad bit to high and the 6s packs hit the hatch. I didn't like the way the cells were sitting with the slight vee in the hull so I made the tray. I am either going to remove the tray and lay the cells on the bottom of the hull or build another hatch.

[DISAR]

I have similar performance-speed with same setup, 1527 1y, 6s2p, 447/3, 235, 646/3, difference in speed is very small. What I tried though is to lower the strut a bit, and it seemed that the boat was a bit "lighter". Still testing though. Where I saw a difference was with 8s1p, 645

[Raydee]

Well If I can't get better speed out of it without pulling 200 amps I am going to try this 1717 motor I have next.

[Fluid]

I run the same motor in my SC and the x455 has been the best racing prop. Detongued and with a bit of trailing edge cup it sees 60+ in race water - lots of fun to play with the slower Q Sport hydros.

Setup:
6S2P 30C/4500 mAh
Schulze 32-170 or 40-160 - ~15 degrees advance
x455 detongued and cupped
Strut 1/2" above sponsons, prop end angled 1-2 degrees up
CG @ 11.25"

This setup pulls between 4000 and 5000 mAh in a one-mile heat, that's an average of around 150 amps. But nothing gets above 130F, even on a torrid Texas Summer race day.

The best I ever got with an x450/3 was 50 mph, just not enough pitch. I never tried an x450/2, just not enough prop for this sized hull and it slips a lot even with the strut lowered. The 1Y motor should probably be running around 25,000 rpm or a bit more topped out.

BTW the hatch is within 1/8" of the top of my packs, but after two years of racing no problems. Try removing the Velcro under the packs and use blocks at the ends to limit movement.


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[Raydee]

Well I have some good G3 6s packs that I will run in parallel and I will try a larger prop next time out. I have a nice X452/3 blade that has been detongued and backcut.

[Raydee]

I hate to revive a old thread but I ran a X455 prop today with a bit of work and the boat is a whole new animal. It may have not been the fastest boat but it definitely came to life with a larger prop. My buddy has a pair of cupping pliers so that may be the next prop mod, I would like to get the rooster tail down a bit and get some of the water directed toward the back instead of up.

[Raydee]

Ok I did a little more prop work today and got a few runs in. I ended up thinning the prop some and back cutting it a little more than it was ,lost 2 grams of weight and got it nice and sharp. End result was 1mph more speed, over 50* lower temps on the esc and about 30 amps less draw. Now I have to decide if I want to try and prop up or add some cup to the 455 I am using now. Speeds are in the low to mid 50's and the boat is glued to the water. I am sure I could get another 10mph out of it before it becomes to hard to drive. I am running the boat for about 1.5 minutes and my packs and motor are in the 110*-119* range with plenty of juice left in my packs to get more run time. I did notice that my rooster tail is up like a mono instead of back so I am thinking adding cup to the 455 might be the ticket. I have never ran a cupped prop on a FE boat but I have run cupped props on some of my Gas hulls and found that cup really makes a difference. I am not sure if cupping will cause the electronics to heat up like it does when going up in prop diameter though or if it has less of a effect?

Sprintcat X455.jpg

[knpc]

Glad you got it performing well. I have the same setup in my sprintcat(my avatar), it's a great boat to drive. Once I got it dialed in I maxed out in the low to mid 60s and still really stable.