1/4 flex cable / stuffing tube issue

Hi,
Just finished and ran for first time on weekend my U-3 1/8th scale hydroplane and after inspection of 1/4 inch flex cable, there is a burn mark about 2-3 inches on cable at coupler end. This mark lines up with support brace in hull which you can see the epoxy has got hot and started running. The boat requires a "s" bend stuffing tube due to not being able to fit the cowling on with the dummy engine in the right place. The stuffing tube is 11/32 OD with a teflon liner. The teflon line about 2 inches from couple end is softer then the rest as well due to heat.

The question is would i get away with running a 1/4 cable in 11/32 tubing without a liner, i know 5/16th is the correct size but the last thing i want to do is remove and make a new 5/16th stuffing tube for it. Below are 3 pics showing the stuffing tube and the brace near the coupling.
Hope you can assist me in what to do.
Trev

Get rid of that teflon liner and add an oiler, oil up every run. You may find it a bit difficult to get that teflon out if it got hot enough to discolor the brass but it's gotta go. Cut the 11/32" right after it leaves the hull and use the remaining piece as a sleeve to push the 5/16" brass thru. Go easy with some lube on the 5/16" brass and it will pass thru. I always use 11/32" sleeve when passing thru the hull, it makes tube replacement easier without damaging the hull itself.

The "S" bend stuffing tube is a legacy FE design that unfortunately should have been moth balled years ago. It worked fine with .150 cable and low power levels, but it will add significant drag in a modern FE setup especially a 1/4" cable. It is on the order of several hundred watts of loss.

I know you probably don't want to hear this, but I would redo your driveline and motor mount so you have a single gentle bend with the motor at an angle. As Don mentioned, ditch the Teflon and run the cable in 5/16" brass tubing.

Don Ferrette said:

Get rid of that teflon liner and add an oiler, oil up every run. You may find it a bit difficult to get that teflon out if it got hot enough to discolor the brass but it's gotta go. Cut the 11/32" right after it leaves the hull and use the remaining piece as a sleeve to push the 5/16" brass thru. Go easy with some lube on the 5/16" brass and it will pass thru. I always use 11/32" sleeve when passing thru the hull, it makes tube replacement easier without damaging the hull itself.

Click to expand...

Don,
I understand what you mean and are saying but do you think 1/4 flex in the existing 11/32 stuffing tube (the stuffing tube is not discolored, it is fine, and i have removed the teflon liner successfully) will work and save me a lot of work.

RaceMechaniX said:

The "S" bend stuffing tube is a legacy FE design that unfortunately should have been moth balled years ago. It worked fine with .150 cable and low power levels, but it will add significant drag in a modern FE setup especially a 1/4" cable. It is on the order of several hundred watts of loss.

I know you probably don't want to hear this, but I would redo your driveline and motor mount so you have a single gentle bend with the motor at an angle. As Don mentioned, ditch the Teflon and run the cable in 5/16" brass tubing.

Click to expand...

Tyler,
Unfortunately the motor can;t be tilted up even a bit ( i already have had to file flats on the water cooler) for the cowling to fit.
Is 11/32 stuffing tube to big for 1/4 Flex Cable without a liner?

Then best to remove the teflon liner and press in a 5/16" brass tube in its place. 11/32" is too sloppy for 1/4" cable.
Hopefully you have a very soft 1/4" cable.

TREVOR JENSEN said:

Don,
I understand what you mean and are saying but do you think 1/4 flex in the existing 11/32 stuffing tube (the stuffing tube is not discolored, it is fine, and i have removed the teflon liner successfully) will work and save me a lot of work.

Click to expand...

No you'll need the 5/16", there will be way too much cable whip running a 1/4" shaft in an 11/32" tube. Cut the 11/32" tube right after it leaves the bottom and about 1/8" past the tube support at the motor. The 5/16" will go thru the 11/32" tube will some lubrication. Here's an example from one of my twin builds.....

Thanks Don and Tyler for your replies, Appreciate it greatly.
Looks like a 5/16th stuffing tube is going in.

Trevor everyone has there own opinions but myself and others has run 11/32" brass logs in our 67,90 and gas hulls with no problems at all and have less friction .just sleeve the beginning 1.5" - 2" of the brass log with next size down brass at colllet end and at strut end.
Your choice.

Belly pan that motor. Then you can lower the shaft centerline. This will help with getting rid of some of the S bend.
Mike