Stuffing Tube issue

[Scott Miller]

Gents,

Need some advice with my JAE 45 stuffing tube. As you can see from the pictures the tube is bending from the flex shaft whip?

This is my second JAE and I did have problems with the first one too, but it has been fine since I repaired it and replaced the motor (but its running with a K&B 7.5 now).

This is the second tube for this boat and this happended after only 9 laps.

CMB 45 VAC with mild modifications and running 1657 prop. I checked the balence of the prop and its OK.

Could it be that my tube doesn't have enough of an "S" bend? I also plan to replace the flex shaft this time as it does appear to have a kink in it at the collet side. But I don't know if that was an effect or the cause.

Any advice would be much appreciated.

Regards,

Scott

 

[Steven Bryant]

how much gap do you have between your thrust washer and the strut? What the inside diameter of the brass tube you are using?

 

[Mike Hughes]

That kind of looks like its rotating. Grab it with some pliers and see if you can get it to spin back. If your not running enough lube it will heat up and then you will lose glue bond with the brass.

 

[John Knight]

Scott,

I found out, the hard way on my 21JAE, that too much S bend will cause excessive heat in the tube and cause it to fail. I replaced mine with a more gentle bend and have not had any further problems.

John

 

[Scott Miller]

how much gap do you have between your thrust washer and the strut? What the inside diameter of the brass tube you are using?

I am running between 3/16" and 1/4 " gap, the tubing is K&S 1/4 OD, .239"ID...

 

[Scott Miller]

Mike, I thought I had enough lube but maybe it is the type of lube? Is standard bearing grease OK?

John, It wasn't a good day for the JAE yesterday, but the Eagle 90 ROCKED! Ask Al he saw it.

 

[Greg Bonahoom]

Scott,

I found out, the hard way on my 21JAE, that too much S bend will cause excessive heat in the tube and cause it to fail. I replaced mine with a more gentle bend and have not had any further problems.

John

Same thing happened to my 21. Because of this I built my .45 JAE with the motor mounted at an angle with just a slight bend and I have not had any problems so far. I run automatic transmission fluid for shaft lube.

 

[RodneyPierce]

too much of an S bend in the stuffing tube causing a whole lot of heat.

 

[moparbarn]

Thought the same thing when i saw the discoloration on the brass. when i built my .21 jae, i used very gradual bends, used up ALL the provided slot in the bottom sheeting. had to bevel the edges some for a nice fit. 2 1/2 years, no issues.

 

[NITROSNIFER]

1/4" OD tubing and a 3/16 shaft??? If the stuffing tube is too large will also cause this issue. It's possible you have allowed the shaft too much room and it's whipping around.

 

[anthony_marquart]

Same size shaft that I always use..

 

[Scott Miller]

Thanks for the input guys, I will try increasing the gap bertween the strut and drive dog.

 

[Hydro Junkie]

Mike, I thought I had enough lube but maybe it is the type of lube? Is standard bearing grease OK?

Are you referring to an automotive bearing grease? I know most automotive bearing greases are very sticky and thick when compared to other styles of grease.

 

[Roxyflash]

Looks like a miss alignment problem at the bulkhead.For whats its worth i never have run a s bend.Never had any flex shaft issues either.

 

[dr gary turner]

What I see is TOO much bend with friction and heat melting the glue, Also use a oiler to lubricate shaft,Doc's Oiler and others available. Also cut a wedge of wood or dvynicil to go under tube from where it inters the radio box to the front bulk head. Rough up the brass tube and glass tube to wedge which is glued to the bottom of the radio box. Have been doing this for about 35yrs. It works on more boats than I can count that we have built. Alighnment is paramount. This can be achieved by mounting the motor, place a rod that fits the motor collet and the other end fits perfectly the inside diameter of the stuffing box tube. Slide the stuffing box tube over the rod and tack glue in place. Give plenty of room at the bulk head opening to allow alignment, then complete the glassing and as described above.

If alignment is not spot on you will have trouble as depicted and loss of performance. I would take the entire assembly out and start over

This is a neat trick I learned to take the stuffing box tube assembly out. Take a battery and clamp one end with the Red cable and the other with the black cable. It will heat up pop/crackle and smoke a little, It doesn't take long!!!!!!!!!!!!!!!!!!!! Then the tube is free from the glue and it will slide right out.

 

[Neil LaGarry]

I agree with doc start your bend 1/2-"3/4" behind the engine bulkhead, gradually aiming the hole in the bottom of the tub. No Z-bend

 

[Blackout]

What I see is TOO much bend with friction and heat melting the glue, Also use a oiler to lubricate shaft,Doc's Oiler and others available. Also cut a wedge of wood or dvynicil to go under tube from where it inters the radio box to the front bulk head. Rough up the brass tube and glass tube to wedge which is glued to the bottom of the radio box. Have been doing this for about 35yrs. It works on more boats than I can count that we have built. Alighnment is paramount. This can be achieved by mounting the motor, place a rod that fits the motor collet and the other end fits perfectly the inside diameter of the stuffing box tube. Slide the stuffing box tube over the rod and tack glue in place. Give plenty of room at the bulk head opening to allow alignment, then complete the glassing and as described above.

If alignment is not spot on you will have trouble as depicted and loss of performance. I would take the entire assembly out and start over

This is a neat trick I learned to take the stuffing box tube assembly out. Take a battery and clamp one end with the Red cable and the other with the black cable. It will heat up pop/crackle and smoke a little, It doesn't take long!!!!!!!!!!!!!!!!!!!! Then the tube is free from the glue and it will slide right out.

Dont use a LiPo

Or use a soldering iron.

 

[Chilli]

I've got a few high rpm riggers and cats with some pretty good S bends in them and have never had a stuffing tube/flex problem. I also dont use any oilers either. Just Mercury 2-4-C. What I do which seems out of the norm is glue the stuffing tube directly onto the tub. I don't use a second short outer piece of brass where the tube enters the tub. I would think in smaller riggers, if a S bend is required, putting a nice smooth kink free bend in the interior portion of the stuffing tube would be hard if it had to be slid through the guide tube first. So I bend the tube out of the boat, making sure there are no kinks (sometimes it takes a few attempts), align everything up and glue the tube in place. Also, I don't care much where the pre cut opening for the stuffing tube is on the bottom of the tub. I'll elongate it or move it slightly if needed to suit my installation.

 

[dr gary turner]

I would rec the outer tube. There are times there inner tube issues from hitting something, cable breaking issues and the inner tube can be removed without taking the boat apart. Also once you use an oiler you will not return to grease. With the oiler the shaft will feel like it is in roller bearings, No "Black" oil or skip areas on the flex shaft. BTW in the "GOOD OLE DAYS" we ran solid shafts [MR GEE SHAFTS] on roller bearings, FREEEEEEEEEEEEE, but issues! BTW the reason for the S- bend is because every rotating body creates a sign wave. Ever see a solid shaft sign wave and if TOO restrained. It will act like a bull whip and disapate the energy at the prop????????????? Wild, shaft will be bent at a Right angle or break. Sooooooooooo the S bend will help control the sign wave, GENTLE S-BEND.

 

[Scott Miller]

Thanks for all the input, I reworked the stuffing tube and added a support wedge under the tube in the radio box, also increased the space between the drive dog and strut slightly. Success so far!