S&B x642 running same as stock prop!? whats the deal here?

[sillycon]

Ok, so I got my x642 in the mail from OSE today, and went out to try it out on my usual set of 4s speed-test batteries. Much to my dismay, it ran the same ~31mph that I'm getting on the stock prop on the same set of batteries. The water today was much more smooth than it was yesterday when I hit ~31mph on 4s with the stock unbalanced prop.

Boat is setup as follows:

CG ~8.875" from transom
stock hull, stock motor/ESC/battery connectors
5.5 bullets from motor to ESC
sharpened & balanced x642
OSE flex (freshly greased before the run today)
OSE fins
Speed master tabs
Strut angle ~1/2 deg neg
tabs are ~1.25deg (left) and ~1.5deg (right)
strut height .220" above keel
batteries are dynamite "reaction", 5000mAh, 30c, with ~10 cycles on them

Temps were 115 motor, 90 ESC, 120 batts, 160 connectors (both esc/motor and batteries).

Boat was nice and stable in the water.

What the heck am I doing wrong? All I can think of is that the boat is running too wet, but I'm not sure what else to do to get the boat further out of the water (I already moved the strut height down substantially).

Aside from batteries, I don't have any spare parts to start swapping to see if there's a power system issue.

[Luck as a Constant]

Smooth water is too sticky. A slight chop will be faster


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[tlandauer]

You are not seeing a jump from a plastic prop to a metal prop, stock prop is not sharpened nor balanced, but its blades won't flex as do the plastic ones.
You will not see a huge difference in all practical sense.
What concerns me is that your batteries are too warm, and the temp on your connectors are too high as well, assuming all your solder joints are good, how many minutes have you been running on each run? Do you hit LVC? Batteries deteriorate quickly if their charge is over depleted ( 30% reserve is a good guideline).
As said, smooth water is sticky and as you have observed, boat might be running too wet, but batteries should not be warmer than your motor and ESC, IMO.

[sillycon]

30 sec "heat test", followed by another 3:30min run, so 4 mins total on the batteries.

A 4 min run pulls about 3300mAh out of my batteries on the stock prop. On the x642 it pulled 3800mAh.

Connectors have 1.6ohms of resistance between motor/ESC (5.5mm gold plated Castle bullets), which as the same as it was on the factory 4mm plugs (1.6 was the resistance of the bullets before being soldered to the wires as well). I haven't tested resistance on the battery connectors, though I wouldn't expect it to be much, if any, higher. I'll check it when the batteries are done charging and report back.

I've never hit LVC. Tried twice, but chickened out both times. I actually was thinking it didn't work, but I don't want to risk $150-200 in batteries to find out for sure.

Smooth was the wrong word apparently. The water wasn't smooth, just less wavy than yesterday. We had ~10mph winds out of the east today; yesterday they were maybe 15-18mph out of the west. I haven't had glass-like water for a couple weeks.

Any suggestions on getting the boat to ride higher/more out of the water?

[BHChieftain]

Note that if your boat is brand new, the ESC default throttle curve is set as "Logarithmic" which caps the max throttle to 80%. You need to reset it with the programming card to "Linear" and that will give you 100% throttle. Set up correctly on an x642 prop (that is the perfect prop for stock motor/esc), you should be getting low to mid 40's.

I have a setup/running guide for that boat that covers that plus a bunch of other things-- if you'd like a copy shoot me an email at [email protected].

Chief

[sillycon]

Chief, I reached out to you via email and got a copy of your setup guide a week or two ago (thanks again!). I've been using it to get the boat to where it is now, but at this point I'm stumped.

So far as the ESC, it's setup as follows:

Low timing
High LVC
Brake on
Reverse Off
Linear throttle

Any other suggestions/ideas?

My only guess right now is that the motor/flex coupler is slipping at higher loads, and I'll check that this evening though I don't expect to find that to be the case.

When I first got the boat I also went through and reset the motor position to ensure that it's a straight shot to the flex with no bending or binding.

[sillycon]

Ran again tonight; same deal 31mph.

Very disappointing. I feel like I wasted $40.

[Luck as a Constant]

I'm sure you could get your money back or close to it by selling it on the forums here


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[Luck as a Constant]

i gotta say, im not sure why you bought a 642. is that not the same as stock? i would have tried something larger

[sillycon]

The reason I got the 642 is because from searching here on the board it appeared that it was a good prop to get the boat to mid 40's with a 4s battery config.

The other prop I was considering was a Grim 42x55. Got any suggestions?

[Luck as a Constant]

Well a 42/55 is smaller. Less pitch anyways.

Personally I would try an m445


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[tlandauer]

There should be visible marks if the motor,coupler and flex has slippage. I personally prefer collet over coupler, but that is just my liking.
M445 should work fine, but again it would not increase your speed from 31mph to the low 40's. X642 should have more pitch than the stock prop, if I remember correctly. I don't think you wasted the money on that prop, it's a useful one, should be in your collection.
I am sure you have already checked the throttle trim and EPA setting.

[kfxguy]

I think you need to try a x442 prop. Your higher pitch may be limiting the RPM's. Also, if your connectors are getting that hot, it's time to upgrade. Them being hot like that is giving to a hint that they can't handle the load.
Also, I prefer to run at least 45c-50c in boats. You batts may not put out enough amps to swing that steeper pitch prop as well. See if you can try so higher c batts

[BHChieftain]

Hi,
The x642 on that boat should get you into the low 40's no problem (IMHO that is the perfect prop for this boat) if you have the right setup. Note, it is not the same pitch as the stock prop. The stock prop has a total pitch of 2.5", and the x642 total pitch is 2.64".

I suspect the boat is running wet, and the negative prop shaft angle is making the boat plow. For this boat you want the propshaft at a neutral angle, // to the bottom of the boat. Try this setup procedure:

1) Ensure the trim tabs are set neutral (// to the bottom of the boat). Also ensure the prop shaft is set neutral (angle // to the bottom of the boat).

2) Adjust the COG via battery placement to adjust the nose height. When running wide open throttle (WOT), the nose should lift and the boat should run on the back third of the hull assuming calm water conditions.

3) Once you have the nose height where you want it, if the boat is running “wet” (too much hull in the water), then lower the strut 1/8” (keeping the prop shaft angle // to the bottom of the boat). Then repeat step 2 to reset the WOT nose height. If your boat is running wet, it will dramatically lower top end speed, and also will stress the ESC as the boat will pull a lot of amps trying to push the hull through the water. Conversely, if the boat is running too “loose” (not enough hull in the water), then raise the strut 1/8” and repeat step 2. If the boat is too loose, it will be difficult to handle, will rock side to side, or blow over.

4) Repeat steps 2 and 3 until you are happy with the speed and handling characteristics.

5) Now you can use the trim tabs to fine tune the nose height. A perfectly setup mono actually does not need trim tabs (none of my monos have them, as my pond has glassy smooth water 90% of the time), but they are useful if you run in changing water conditions. If the water is choppy, lower the trim tabs just a tad to lower the nose. When the water is calm, reset them to neutral. This is easier than using the strut to respond to changing water conditions as there is a lot of trial and error to find the right strut/COG combination.

Let me know how that work,
Chief

[Luck as a Constant]

S&B x642 running same as stock prop!? whats the deal here?

My bad, there's a difference of .1 on the pitch, which I'm sure makes a massive difference

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