TP 5680 800Kv 4Y Prop Size?

[wedgewalker]

I am running a single setup in a Central Marine 51" Victory Cat, I am running 2x 6000Mah 6s Giant Power Kitty sticks for 12s= (6000Mah) w/ a Swordfish 300a X+ esc. on a TP 5680 800Kv 4Y. I am looking for suggestions on good prop size. I have tried Octura X455,X457 and X460 2 blade but seem to have heat issues. My Prop is 3 5/8" bellow transom overhang at centerline on stinger w/ slight upward angle, my temp on my first run with X457 was 54c to 59c on esc, I didn't IR motor but I feel this is too high, Surface water temp was about 84F to 86F on a hot Texas evening. This was a 2 min. run on straight runs turn and repeat. What would be a good prop size to run for better times and lower temps? Could or should I go with a 3 or 4 blade prop and would this have any benefits or should I stay with 2 blade and drop down to X445,X447 and X450?

[TRUCKPULL]

Try raising your strut up by about 3/8" then adjust 1/16" or 1/8" at a time - up to run cooler or down for warmer.

Larry

[wedgewalker]

Thanks Larry, If you notice my pic the strut is touching overhang, do I cut some off or purchase a shorter strut? and will I have to put a bend in stuffing tube to take out pitch when raised? I've got the SM Strut XTD now do they make a shorter version that's still extended?

[Fluid]

Temperatures of 60*C and below should be just fine considering the high water temp, but a lot depends on how you are running - WOT most of the time or lots of part throttle with slow downs and speed ups (the latter is worse). The low cell capacity also comes into play, running parallel packs could help with ESC temperature. But really, 12S is a lot for that motor and that big hull. That requires a smaller than optimum prop for good efficiency, running 10S would be better IMO, that or a lower Kv motor. That size hull should use a minimum prop diameter of 60 mm. Two blades is fine, more blades means more load.

I agree that raising the strut will help by reducing the blade area in the water and by loosening up the hull. This may allow you to keep the more efficient prop sizes. Do whatever you need to do to be able to raise the strut with the right angle. I can tell you that boat will barely move on an x445!

And what amp draw and ESC temperature does the ESC log?


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[wedgewalker]

Hey Fluid, I wasn't able to get info from esc yet?? I also have the wifi dongle installed from OSE and was talking to Steven and I haven't figured out why my first run didn't have any recorded data. The kitty sticks are 2/3s packs end-to-end. This boat was originally a Aggressor from the fine brothers, They set that boat for 12s and I was never able to chase down heat problems. They had a TP5670 720kv 5Y and 400amp flier esc setup rtr. The timing was set at 30 and the strut was almost all the way down. I am new to boats as I mean this is my first (try to fix problems that I don't know anything about) so that boat didn't make it and now I am working on this setup. The X457 runs good but I can only get 2 min. safely with temps. The first setup puffed batteries, cogged motor and esc will only see 5 cells out of 12. I don't want to grenade this investment so any help is greatly appreciated. I was looking for a short version of my SM EXT .250 strut and I think I found it. If I can't find one I will cut off this one. Do I need to put a bend in stuffing tube to take out pitch from raising prop? The esc temps were 54c to 59c. in 2 min.

[wedgewalker]

What size packs for 10s in parallel would be optimal for this set-up?

[Fluid]

Okay, lots of good info, thanks.

- A 30* timing advance is way too much for any reasonable BL setup. Instead try 15*.

- It appears that x457 is still too much for that voltage and motor if you want more than 2 minutes running. Lower voltage and a slightly better prop would help.

- By all means cut down the strut, it won’t hurt anything. And bend the stuffing tube as needed to get the strut angle you need - start with the strut bottom parallel to the table.

- The position of the CG matters, what is the distance between the bows and the actual transoms (not the extreme back of the boat)? How far ahead of the transoms does the boat balance (put it on a broomstick and roll it back and forth until it stays level)?

- Did you buy the boat from Fine Design or from someone else who did? It is no surprise that the original setup you had burned things up, it was ‘way over the top for a sport boat. Fine should have known this.

- My suggestion would be 10S2P using these packs: a 6S and 4S pack in series then paralleled with another identical pair in series. Cells should all be the same and have a minimum of 5000 mAh and 60C. This will give a reasonable run time and be easier on the ESC.

Once the boat is trimmed out with the above setup an x460 or x462 should give good performance but run time will still be under five minutes depending on how you run it. What kind of running would you like to do, speed runs, oval racing or bashing about? That will influence how you prop and trim the boat.

Where in Texas do you live? If you are within a few hours of Katy you really should visit the HOTMBC club, they have experience with large FE boats hpand can give you good advice after actually looking at your cat. And they are a great bunch of guys to run with - everything’s better in a group.


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[wedgewalker]

Thanks Fluid for your time, I got this hull from Central Marine, I didn't talk to the brothers after I started to uncover the problems I was having. I will have to check cg. I have been flying for many years and cg is very important.

About the battery situation, I purchased 4 Giant power Kitty sticks, I don't see them on the site as of now but these were custom made. They are 2 3s end-to-end 6000 Mh 6s 70c-140c to make one pack and I bought 4 of them, and I dropped $700.00+ for 4 packs. I was looking for equal cells to match what the brothers had sold me with the first setup. They supplied 4 Dinogy Lipos of the same size which was 6000Mh 6s 65c. Those puffed after 2nd run����.

I really don't want to have to invest in more batteries if I can get away with it. I would like to be able to practice oval and have good controlled runs instead of straight wide open turn and repeat.

I live in Montgomery, Tx. so not that far from Katy.
I will have to find someone to look up from their club and possibly get some time with the pros.

Again, thanks for your time I greatly appreciate it!!

I will post my results for cg when I get time, and I need to make another run to see why I didn't get any data logs.

[wedgewalker]

Looks like CG is at 31 3/4" measuring from tip of sponsons to stern. on a 51" hull w/ a 4" overhang!

[TRUCKPULL]

Is that 31 3/4" from the tip of the sponsons to the CG point?

Larry

[wedgewalker]

Yes!! Larry, Boat rides on a little less than 4" of pad and is stable at wide open. Do have to slow down through turns.

[TRUCKPULL]

Glen

We usually measure c/g from the rear, 30% is a starting point.
Your 51' hull with a 4' overhang, sponson length is 51 - 4 = 47" X 30% = 14.1"
Now you add the 4" overhang back on = 18.1" from the rear of the boat
51" hull minus your measurement of 31 3/4" = 19 1/4"

So your cg measurement of 31 3/4" from the front is about 33% from the rear.

You can try moving your CG forward to give a little more ride surface, this also should allow a little more speed in the turns.
Doing this is good in some ways but can be bad in others, you have to find your balance between heat, speed, handling, and run time.

Larry

[wedgewalker]

Thanks Larry!

[wedgewalker]

Larry,Boat is actually 51.5" including overhang, measuring from transom to cg point is 15 5/8" so I'll work with moving batteries forward 1/8" at a time and see what I get.

[wedgewalker]

Larry,15 5/8 to 15 3/4 it's hard to get exact measurement due to CG is directly on a step

[TRUCKPULL]

Moving the CG 1/4" at a time is small enough.
Even 1/2" is OK.

Larry