Why do i not see s bends in fast electric often?

[ironjaws]

I'm getting ready for a build and i was thinking about a "s" bend over a smooth curve method in my flex tubing. i don't see it much in fast electric. Can someone explain why not? Are there pros and cons of each? it's gonna be a single larger cat and i want to get the cg low, and like the look of level motor. Thanks.

[fweasel]

I've only ever seen them in gas/nitro builds. The theory behind it makes sense, but then again, single bend tubes on the FE's have proven to be just as reliable.

[RaceMechaniX]

S-bends have more friction. You use to see it more prominently with FE boats where the motor was mounted near horizontal to clear a cowl.
I have tested S-bend's versus single bends with and without Telfon. The single bend always has lower friction. With or without Teflon depends on how the cable was prepped and the clearance between the cable and liner.

The length of the total bends also has a significant impact. S-bend's over short distances are significantly more friction compared to a long distance.

S-bends are tolerable with .150 and soft 3/16" cable, but I would strong advise against a 1/4" S-bend.

[Stillwet]

I had to on a Dragn'-Fly 20 conversion (from gas to FE) because of a crossover beam above the motor, (battery compartment, motor & servo fitment), i read that the "S" takes out the slap in the drive. runs excellent.
it works fine for this boat. i used .150 cable with liner.
anyways when i came across an almost dilemma i searched and read and found i could do it. this boat had to be electric and the motor just could not go forward any more to run on a sizeable 4 and if RMX says against a 1/4'' "S" then it goes in my note book.

[HTVboats]

Tyler is spot on as usual. My experience to compare is with a 29" Mean Machine cat. I have a 1/4 stuffing tube with an "S" bend. Going back and forth with 36X60 spec motors to 40X74 power I use a .187 cable no liner and .150 cable with a liner. Using the larger .187 cable over the .150 with the smaller motor I see maybe a 1 mph loss. MPH loss not really measurable with the larger 1.5 to 2 watt motors. Bottom line is what real percentage of friction are you worried about? For a SAW record boat yes. For normal use go with reliability and ease of setup. You can get more percent performance gain with the right propeller and trim setup over a small shaft loss.
Mic

[RaceMechaniX]

I should also add that the length of the S-bend and amount of centerline drop have the greatest influence. If you put an S-bend into a stuffing tube that is 24" long and only drop 1.5" from motor center line to prop centerline you may not see a big difference. However the same 1.5" drop over a 6" distance will have noticeably more drag.

I tested a Mean Machine with a Castle 1515 motor and collected data from a Castle ESC. The difference between the S-bend and single bend was between 50-65W for a 3/16" cable without liner.

Since you mentioned it'a a larger cat I am assuming it's 1/4" cable. Unless you mount the motor far forward to have a long stuffing tube I would advise against the S-bend. If you have to use an S-bend to get the motor to clear the cowl, only bend as much as needed to clear the cowl. i.e. mount the motor at the highest angle to reduce the S-bend.

[HTVboats]

Tyler,
Was that a .187 cable that showed the 50-65 watt loss? Also what was the peak or total watts on your 1515?
Mic

[RaceMechaniX]

Yes, 187 cable. Total power was around 2000W. So a 2.5% penalty.

[grsboats]

I can't say too much about losses( %) but I have used the S bend with 3/16 cables on some of my riggers (nitro/fe) with zero issues. A S bend properly done with the right ID brass tube won't affect your performance but as stated if your flexshaft will be 1/4 I would stick to a single bend..this is what I use on my gas riggers Gill