Flex Size issues

[longballlumber]

Mike, a few questions.
1. Did those stuffing tubes have a teflon liner?
2. How many nitro boats have 8 horsepower and turn 40,000 RPM?
3. Can you name a nitro or gasser engine that has the bottom end torque capible of twisting a flex shaft in half?

Why Stainless Steel VS brass stuffing tubes?
1. SS requires no teflon liner.
2. No teflon line = less resistance.
3. Even if you run your boat up on a rocky beach, it's unlikely you will dent or even bend SS.
4. SS will never get discolored or loose it's silvery shine.
5. SS can be easily shined/polished to look like chrome, and will stay that way.
6. Price wise, SS is equal to or cheaper than buying brass tubing from your hobby store.
7. SS will never corrode an aluminum strut due to dissimilar metal electrolytic corrosion. (I've had brass groumets corrode thru a 1/8" thich 2" dia aluminum tube on a full sized sailboat)
8. SS can't be beat for the COOL factor.

In the last couple of years since I got into FE boats I've had 3 brass stuffing tube failures. All were at the strut connection.

So that's the way I see it. JIM

Morning Jim,

While I prefer to stay out of pissing matches; I still feel the need to reply to your post directed at me… First and foremost, I was attempting to help the OP with his question. The OP never listed what is power source was going to be. Could be 4S P-Limited, 6S, or 8S; each one could have a better answer than the other. Historically, I try and base my answers to this question (and any others for that manner) on the principal of function and what will work… With that being said…

Questions directed at me:

1. No they don’t have Teflon liners. In all the years I have been around Nitro boating they have NEVER used Teflon liners in their stuffing tubes.

2. I am sorry I can’t quote numbers but I can tell you that many big block nitro boats, twin nitro boats, and maybe a few gas powered boats are capable of speeds in the triple digits at the end of a straight in heat racing trim. It takes some decent horsepower and RPM to make that happen… On top of that I am not sure the OP is running a system of that magnitude. Quite honestly there are probably less than 20-30 individuals who race FE boats that have a power system capable of those types of numbers (8HP 40,000 RPM)…

3. First of all see #2 above… Secondly if you’re twisting flex shafts in half, I would be more inclined to understand why it happen vs. making the assumption the brass was too weak. Were you running an S bend or a J bend in the stuffing tub…? Regardless, I still think #2 answers the question as well.



Reflecting on your reasons to use SS:

1. Don’t need Teflon in Brass either…

2. See #1

3. If you’re running your boat up on shore, you have bigger problems than a bent or dented SS stuffing tube. Perhaps you can reuse your unbent/undented during your process of rebuilding the destroyed 8 horsepower 40,000 RPM boat. I am sure it wasn’t going 20mph when it went up on shore….

4. This a purely ascetic reason and has nothing to do with function

5. This a purely ascetic reason and has nothing to do with function

6. Cost is always a big deal in this hobby and I will applaud anyone who can find more for less. However, I am willing to assume that unless you live in a major metropolitan area the SS tubing MAYBE more difficult to fine. I can pick up brass tubing for $4 bucks at my Local Hobby Shop. That’s not exactly breaking the bank, and your supporting those who support your hobby…

7. Again, I have never had to replace a brass stuffing tube due to corrosion in a model boat, nor have I ever heard of anyone else needing to do so in the hobby. Perhaps you situation in the full-size sail boat had different alloys of aluminum and brass… Don’t know, I don’t have a full-size sail boat just toy RC boats…

8. This a purely ascetic reason and has nothing to do with function

Sorry for your brass stuffing tube failures… it seems to me the issue would be more wide-spread (do others have this same problem?) unless there were other contributing factors with your boat… Lots of variables in this boat stuff; what works for one may fail for another.

Later,
Mike Ball

[drwayne]

Sorry for your brass stuffing tube failures… it seems to me the issue would be more wide-spread (do others have this same problem?) unless there were other contributing factors with your boat… Lots of variables in this boat stuff; what works for one may fail for another.

Later,
Mike Ball

Mike
In 33yrs Ive seen dozens of brass liners fail.. with/without teflon... mostly for over enthused under edumacated newbs who have combinations of obtuse angles, bound flex, too short at collet, flex vibration, teflon winding to flex, etc etc ad nauseum
Never heard of it happening twice to same bloke though.

The SS does look nice & purdy, else zip additional benefit IMHO.

W

[JIM MARCUM]

Mike, I love a little criticism in the morning!!!

Make your list of the 8 HP 40,000 RPM FE boaters you know 31. I'm holding one in my hands in the above picture, building an Avenger cat that fits that description also, and after I put two motors in the above Segad it will have 16 HP at 45,000 RPM. But you probably SAW that comming JIM

PS: Thanks Wayne.

[drwayne]

Mike, I love a little criticism in the morning!!!

Make your list of the 8 HP 40,000 RPM FE boaters you know 31. I'm holding one in my hands in the above picture, building an Avenger cat that fits that description also, and after I put two motors in the above Segad it will have 16 HP at 45,000 RPM. But you probably SAW that comming JIM

PS: Thanks Wayne.

8Hp at 40krpm or 6KW at whatever rpm is any 6S2P capable 70+mph
I run SC40 6S1P 2x1518/1800 6KW 70+mph ..... oval

BrianB recently hit 100+ on 2S ......that's true electric superwhizz stuff.!

Good luck with SAW.... lots of advice available from experienced ppls.

Thank me, for what ?
W

[JIM MARCUM]

Wayne, thanks was for agreeing that you have seen brass stuffing tubes fail. Plus, I just love you Aussies! JIM

[drwayne]

Wayne, thanks was for agreeing that you have seen brass stuffing tubes fail. Plus, I just love you Aussies! JIM

shut up and pass me another beer .........

[JIM MARCUM]

Shut up I am. Here's the beer Doc. JIM