Prop Shaft Log Replacement

[Alii]

I've been side-tracked prepping and painting the hull before the NE Monsoon -- back to work on the shaft log.

Here is the culprit, along side the G-10 tube that we've had machined from 43 up to 45mm ID. Turns out this stainless tube was WELDED and the main areas of rusting and corrosion originated along the weld.

We are awaiting new bushings from Germany for our AquaDrive. Should arrive next week. Will then realign the prop shaft (the torque plate on the AquaDrive is currently pulling the prop end of the shaft a bit to starboard) and once the shaft is centered proceed with glassing in the G-10.

[jimbunyard]

Was wondering what happened...

That SS log is pretty ugly, but I guess after almost 30 years that's to be expected.

Just out of curiosity, could you show us an overall picture of the scene of the crime?

And if you don't mind a bit more advice, don't cut the tube until after it's glassed in, the length will make the alignment more precise. I think I mentioned wrapping tape around the shaft to center the log tube a while back, but I'm never sure if my explanations are clear or not so here's a couple pictures using some stuff I had lying around to illustrate what I meant.

[Alii]

I think I'm clear on all that, Jim, plus plan to place the old Volvo seal on the inboard end of the tube while glassing it in so I can see how and where the new seal will seat. Will send a photo next time we back the prop shaft out of the hole.

[Alii]

Prepare for more angst. There are 4 other glassed-in pipes in my hull: engine water intake, center cockpit drains (2 drains join in a stainless manifold which then goes through the engine compartment in 2-inch exhaust hose, to a seized-up shut-off valve on the pipe), and 2 aft cockpit scuppers.

I am shaking myself out of denial. Having seen the state of the shaft log pipe, I know it's time to closely inspect and most likely replace at least the intake and center cockpit setups. The aft scuppers are out of the water except when heeling, usually bathed in fresh air and rinsed with rainwater, so I'm thinking they'll be OK.

This short haul-out, now approaching month 5, will never end ...

[Cheechako]

Ahhh yes.... boating at it's best... "I think I'll tear out that widget this weekend and renew it.." after the dominoes fall............6 months later things related to the original project that must be done prior to finishing the original project are still being fixed....

[Alii]

Here is the ugly hole left after removing the stainless tube. Found 2 peach pit-sized voids in the polyester under the tube. Plan is to trim back and smooth out the polyester that was built up around and over the tube, leaving the outer hull skin as a base on which to start rebuilding with cloth and resin.

Did a test-glassing on the extra length of the G-10 tube. One wrap of 12-oz took the OD from 53mm to 55mm which will nicely fall back to 54.5mm (perfect) when sanded and faired.

The ID of the G-10 has been increased from 45mm to 48mm but now with the benefit of seeing how beefy the tube is with the added layer of fiberglass I'm considering having the ID enlarged further. One positive about the old SS tube -- it did not attract marine growth. I anticipate that the fiberglass tube will be a friendlier substrate for growth, so will apply primer and a couple coats of Ultra, which will decrease the tube ID. Although Vosbery Marine blessed having just a 45mm ID shaft log with using the Volvo shaft seal, I don't want to be on the fringe.

[atoll]

Originally Posted by Alii

Here is the ugly hole left after removing the stainless tube. Found 2 peach pit-sized voids in the polyester under the tube. Plan is to trim back and smooth out the polyester that was built up around and over the tube, leaving the outer hull skin as a base on which to start rebuilding with cloth and resin.

Did a test-glassing on the extra length of the G-10 tube. One wrap of 12-oz took the OD from 53mm to 55mm which will nicely fall back to 54.5mm (perfect) when sanded and faired.

The ID of the G-10 has been increased from 45mm to 48mm but now with the benefit of seeing how beefy the tube is with the added layer of fiberglass I'm considering having the ID enlarged further. One positive about the old SS tube -- it did not attract marine growth. I anticipate that the fiberglass tube will be a friendlier substrate for growth, so will apply primer and a couple coats of Ultra, which will decrease the tube ID. Although Vosbery Marine blessed having just a 45mm ID shaft log with using the Volvo shaft seal, I don't want to be on the fringe.

looks good!
make sure you grind back thoroughly that white gelcoat,and de-grease the surfaces.

clean well with acetone,and use epoxy resin for the repair.

it might also be an idea to use a heatgun on surfaces to be laminated as the humidity in Singapore is very high.

set in place with an epoxy/colloidal silica paste to get alighnment correct,then grind back ,acetone and fully laminate.

[Boatyarddog]

One of the most important aspects to this refit is proper alignment in the hole.
I'd suggest you install the tube, packing box,prop shaft, strut(if you have one) as well bolted to the trans coupler with a relatively straight engine alignment.
Support everything so it feels very easy to turn the prop shaft,aka the sweet spot, then glass the tube in enough to hold it in place well, then remove the shaft and whatever you need to finish the glassing.


Sent from my iPad using Cruisers Sailing Forum

[Cheechako]

Originally Posted by Boatyarddog

One of the most important aspects to this refit is proper alignment in the hole.
I'd suggest you install the tube, packing box,prop shaft, strut(if you have one) as well bolted to the trans coupler with a relatively straight engine alignment.
Support everything so it feels very easy to turn the prop shaft,aka the sweet spot, then glass the tube in enough to hold it in place well, then remove the shaft and whatever you need to finish the glassing.


Sent from my iPad using Cruisers Sailing Forum

Mo Debbley!

[Alii]

Almost finished! The first set of photos was taken after the first 4 (of 8) layers of cloth. The last two photos show inside and out, ready for a few coats of Interprotect (then bilge paint/antifouling).

[jimbunyard]

Looks really good, better than new. So launch date approaches?

Don't feel good not asking though. The original glass appears to be about 1/4", or a little more, thick.



I realize the glass shown here



is tapered forward, but is it overall at least as thick as the hull layup? There are small twisting forces involved, but their effects could build up over time. A little overkill is a good thing in this instance I think....

[Alii]

Thanks for double-checking, Jim.

The covering over the old tube looks looks thick, but it was mostly chalky gelcoat over the "ears" that had been welded onto the tube, plus a healthy coat of bilge paint I put on 4 years ago. When I dropped the new tube into the slot, I was able to lace a 6" wide strip of my thickest cloth under the tube, up each side and into the interior of the hull. I think that served as a solid foundation and anchor, and the total thickness of the cloth + resin on the top the tube where it exits the hull is at least 1" thick. The hull is around 1.25" thick. Seem like enough?

You are right, unlike the old lay-up I have tapered the glass on the inboard end. The walls of the G10 ended up 5mm thick. They seem good and beefy.

By the way, the engine water intake was a similar original design -- 1.5" stainless tube, with a 90-degree elbow welded into it, glassed into the hull. When that was sawed out and the glass chipped away, it looked brand new, not a hint of rust or corrosion.