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 jqhydro@gmail.com.

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]

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

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[BHChieftain]

The difference between the stock prop and the x642 on the Impulse is worth about 5+mph. On the stock prop properly setup on 4S should be able to run mid-high 30's on x642 should get into low-mid 40's. The M445, which has less pitch than the x642 typically runs faster-- it is not all about the calculated pitch difference. But I don't like the M445 on the mono as the larger diameter can cause the boat to chine walk and I think the boat handles better with the x642.
Chief

[Luck as a Constant]

That's odd, even a prop change without changing setup should have yielded higher speed at least, even if not to potential , no?

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[lenny]

Not if it is running wet,
Just the temps on the setup and connectors and cells would go up instead.

Hey sillycon if and when you get the boat running trimmed out,
Post some video's so we can see how it is riding on the water.

[Luck as a Constant]

Oh I see


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[Luck as a Constant]

Well, in my time swapping props that were different values, without changing anything else, has always shown at least small changes in speeds, whether it be faster or slower.


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[sillycon]

I'm thinking the problem is that the boat is running really wet and isn't getting up on plane like it should; it seems like (lengthwise) there's always half of the hull or so in contact with the water. However, from watching videos over the weekend, it seems like there should be maybe only 15-20% touching the water.

I also saw one of Darins posts which mentioned that strut height should be measured from base of the keel to the centerline of the prop; I've been measuring to the bottom of the strut so I'm probably running closer to .320" strut height.

I'm going to do a once-over on the boat again this week, reset the trim tabs to 0 and move the strut down further then I'll try again.

Thanks for all the input guys. It definitely helps take the frustration out of it when I'm not trying to sort this all out on my own.

[sillycon]

So, I went back over everything on the boat tonight and in doing so, I measured the x642 I received (I also took it off the flex shaft and confirmed that it is marked "Octura X642"). From tip to tip, the diameter is ~40.50mm. Is this correct? Would shaving and balancing typically remove 1.5mm of diameter?

IMAG0507.jpg

[Luck as a Constant]

Yes


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[sillycon]

Went back out today and gave it another whirl. Ended up seeing 35.2mph on 4s which makes for a decent improvement!

Boat was riding *MUCH* higher in the water today; at a few points there was nearly no hull touching the water surface as opposed to no less than half the hull previously!

Trim tabs are 0 on the right, .5* on the left, strut is as low as it can go (there's just a hair of clearance between the hull and the flex tube), prop is neutral. CG was probably on the order of 7" or so today. The 2s batteries I have just aren't heavy enough to balance the boat further forward, and I haven't looked into a ballast solution yet.

The boat was much less consistent tonight, however, with regards to porpoising. Sometimes it would ride flat, other times it would have a bit of a bounce.

I only had one pair of batteries charged, so I didn't have opportunity to test.

I tried shooting video, but the boat is pulling pretty hard to the right so video taping with one hand while running the boat with the other made things... tricky. I'll check the footage I have later and see if there's anything of value to post.

Thanks everyone!

[lenny]

Port side trim tab down from level to 1/32 to 1/16 may help with the porpoising,
I am not sure what you are seeing as far as that go's.

If it pulling to the starboard side hard,
That sounds like you are getting prop walk.
Post some pictures of setup with the 2s cells in place,
And also some pictures of the hardware setting.

On taking the video's,
This is what I do with my cam and velcro straps I made up.
But I do not look at the cams screen at all.
camcorder 001.jpgcamcorder 003.jpgcamcorder 002.jpgcamcorder 004.jpg

Just line the cam up with the tx and aim the tx like a side arm gun,
It works pretty good when you get the hang of it.
This is how just about all my video's are taken by me.

[sillycon]

Your camera setup is slick. I, however, don't have a camera anywhere close to that size.

I forgot to mention temps; batteries 104, motor 114, esc 89, ESC/motor connectors 115, EC3 battery connectors 125.

The video I got tonight is near useless. There's about 2-3 seconds of the boat doing a pass, and the rest of it is sky/ground/sky/ground while I try to avoid a head-on into the shoreline. I'll see if I can get the wife or someone else to run a camera tomorrow or over the weekend (didn't bother to charge batteries tonight; oops!).

[lenny]

This is the first camera setup I was using, FC Daytona 012.jpgFC Daytona 013.jpg
Than I stepped up to the one above camcorder and setup.

Also,
Some member I have seen make a platform coming off the side of the tx to hold the camcorder.
image.jpgboat pic's 019.jpgboat pic's 017.jpg

[tlandauer]

.....

Just line the cam up with the tx and aim the tx like a side arm gun,It works pretty good when you get the hang of it.This is how just about all my video's are taken by me.

From personal experience, it is much easier to aim and shoot a gun than aim that camcorder on the boat. lol...
Lenny, Like that set up!

[lenny]

Hey Tim is that with a custom blunderbuss ?
You just need to get one of those custom blunderbuss dragon camcorders,
With a very wide spread lens for when your driving the boat.

[tlandauer]

Hey Tim is that with a custom blunderbuss ?
You just need to get one of those custom blunderbuss dragon camcorder,
With a very wide spread lens for when your driving the boat.