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Old 03-09-2014, 20:35   #1
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Prop Shaft Log Replacement

I am seeking knowledgeable advice about replacing the propeller shaft log. The patient is a 1986 Jonmeri 40, on the hard in Johor, Malaysia. Given the policies, realities and work force at this yard, this is going to be a DIY job. The yard will not allow us to bring in outside (i.e., qualified) labour. Before I start blindly grinding away I need a lot of information, a plan, and confidence.

There are several related issues/problems involving installation and alignment of drive train elements. If you are so inclined, please see my related post in the Prop and Drive Systems forum.

After removing the cutless bearing and prop shaft I discovered extensive corrosion at the in-board end of the shaft log tube, especially on the bottom under the retaining strap for the Volvo dripless shaft seal. The tube appears to be 50mm ID and 54mm OD, length approx. 30cm on top and 14cm on the bottom (cut at an angle flush with the hull). I would think it is top-quality high alloy 316 or 317 (efforts to get info from the mfr in Finland are underway). I now realize there was no cathodic protection for this tube. This boat design is non-bonded.

Do I need to remove the entire tube, or is the following a reasonable approach -
- expose the inboard end until I find sound intact stainless
- weld on a length of new comparable SS tube
- bury the weld in fiberglass
The patched-up tube will be subject to vibration due to the Volvo seal riding on the prop shaft, the weld would not be open to inspection for cracks or corrosion, and I can't predict how far into the hull I will need to excavate (how close to the outer skin the weld line will end up). Are these fatal flaws to this approach?

If your view is that I need to remove and replace the entire tube, should the objective be to remove the absolute minimum of surrounding fiberglass, or does that leave a tougher job for bedding the new tube?

When I get to installing the new tube, is this just a sideways thru-hull, or do I need to use other techniques and materials? Do I fiberglass right up to the tube, or put in a layer of flexible bedding as you normally would with a thru-hull?

Thanks for your time and ideas,
Alii ( Laura, s/y ZEN)

(PS - apparently not able to upload photos to this post right now, so pls see my related post if interested in a look)
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Old 05-09-2014, 23:52   #2
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Re: Prop shaft log replacement

I retain hope that some helpful discussion will develop here. I have no idea why this post has been tagged "men" unless that's to scare men off.

I am going to lay out my "plan" so others can pick it apart:

I'm going to take a Dremel cutter and cut open a profile of what's piled on top of the tube, down to the point where I think I'm at the original fiberglass hull.

I believe there are 2 short tabs welded onto the tube (under the 2 bumps at the inboard end where the gelcoat/paint/whatever stops). Perhaps those tabs held the tube in place during installation; perhaps they are mean to ensure the tube doesn't twist or work its way back. A - I will put tabs on my replacement tube. B - This suggests there is no exterior flange (unless the tabs were welded on after the tube was slipped in from outside).

Even if I need to cut the old tube into small pieces, I am going to try to remove it with as little incursion into the surrounding hull as possible. It seems to me that the boat would have been built as follows:
-Lay up hull in mold
-Remove from mold
-Use hole saw to drill nearly-horizontal channel for SS tube
-Lay tube into a bed of fresh glass and resin in this channel
-Glass over further on inside
I will excavate that original channel, clean and smooth it, put down a couple layers of cloth and resin, wrap a couple of layers of cloth and resin around the new tube, and then seat it in the channel (another layer of cloth and resin here, or is it too deep and thick at this point to properly cure?)

.... OK, still gaps in my plan

As for the replacement tube, the company that acquired the Jonmeri line has offered this help: "Bring the boat to Finland and we will fit it for you." Seriously. Otherwise, they say the original tube would have been A4 stainless and can't tell me anything more.

Any ideas on how to source just 1/2 meter of 50 ID / 54-55 OD grade A4 stainless tube?
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Old 09-09-2014, 09:06   #3
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Re: Prop shaft log replacement

why not use G 10 epoxy glass tube instead of stainless steel and eliminate corrosion issues forever? 2" Od G 10 tube is available from Mc Master Carr a US catalog supplier.
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Old 09-09-2014, 18:58   #4
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Re: Prop shaft log replacement

I am considering G10 -- every option, at this point -- but the McMaster Carr catalog does not include any set of ID/OD that can be machined to my specifications: 50mm ID (2" close enough) and 54.5mm OD (2.146" and this spec has little tolerance).

I've been pointed to another source that lists a 1.5" ID/ 2.5" OD G10 tube, but:
- the tube is 48" long, expensive to ship to Malaysia on top of the base cost of $352
- it will require a LOT of machining inside and out. I've found a shop here that does good work, no insurmountable language barrier, but they don't have any experience working with this product and want a sample to experiment with before making any promises.

Perhaps I can get someone to cut the tube in half before shipping -- that should nearly halve the shipping costs, and give me a spare in case we screw up the first cut-down.
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Old 09-09-2014, 19:44   #5
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Re: Prop shaft log replacement

Quote:
Originally Posted by Alii View Post
I am considering G10 -- every option, at this point -- but the McMaster Carr catalog does not include any set of ID/OD that can be machined to my specifications: 50mm ID (2" close enough) and 54.5mm OD (2.146" and this spec has little tolerance).

I've been pointed to another source that lists a 1.5" ID/ 2.5" OD G10 tube, but:
- the tube is 48" long, expensive to ship to Malaysia on top of the base cost of $352
- it will require a LOT of machining inside and out. I've found a shop here that does good work, no insurmountable language barrier, but they don't have any experience working with this product and want a sample to experiment with before making any promises.

Perhaps I can get someone to cut the tube in half before shipping -- that should nearly halve the shipping costs, and give me a spare in case we screw up the first cut-down.
why not make up the tube yourself?

it is really quite easy,in the past i have used cardboard tube taped over with masking tape,then coated with release wax.

this i then find a bit of broomstick or dowel to put down the center with a screw in either end,mount this on a horizontal board with 2 vertical boards with holes near the top for the screws to pass through, making your mandrel,you can even make a little handle on one end to turn it with .

then using fiberglass cloth tape,and wetting out as you turn,gradually build up the thickness of the tube,running the tape from side to side to overlap the weave.

this way you can make your tube ID and OD any size you like
and i would be surprised if you used more than $50 in materials for a 2ft tube
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Old 09-09-2014, 23:10   #6
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Re: Prop shaft log replacement

The G 10 from McMaster Carr cost about $110 US. Yes 4 'long but whatever the shipping cost you will never make the quality tube like this. Pay the shipping, you will not regret it. Best wishes
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Old 10-09-2014, 02:47   #7
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Re: Prop shaft log replacement

you could try contact these guys who make filament wound tube in selangor malaysia


Lot 5181, Batu 12, Jalan Balakong,
43300 Seri Kembangan, Selangor, Malaysia

Tel : +603-89616576/77
Fax : +603-89616566
Email : enquiry@aceonfrp.com
Web : Malaysia FRP | Indonesia FRP Pipes,FRP Tanks,FRP Ducts
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Old 10-09-2014, 04:07   #8
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Re: Prop shaft log replacement

Wouldn't that be a break - I'll call this company in Selangor 2mrw. It's about 220 miles away but perhaps they supply to companies at the nearby port and I can learn more there.

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Old 10-09-2014, 04:39   #9
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Re: Prop shaft log replacement

You might be able to finagle an appropriate sized piece of tubing from atoll's source in Malaysia for free as a sample, depends on your finagaling skills and their business approach. Or they might even sell a piece, but I'd bet their business is focused on kilometers not centimeters. Or they might tell you where to get a piece.

Failing that, if you decide to go with G10, and the piece from the supplier in Pennsylvania and they won't cut it and ship it to you, It's no problem for me to cut it and ship to you. You'd have to pay the freight of course, and duties (maybe none or minimal if claimed as a sample). Been a while since I exported anything to Malaysia, but when I got out of the business about 7 or 8 years ago, the USPS had really inexpensive reliable international service for small to medium packages.
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Old 10-09-2014, 04:58   #10
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Re: Prop shaft log replacement

Quote:
Originally Posted by Alii View Post
Wouldn't that be a break - I'll call this company in Selangor 2mrw. It's about 220 miles away but perhaps they supply to companies at the nearby port and I can learn more there.

Sent from my GT-S7580 using Cruisers Sailing Forum mobile app
there is a good courier service in malaysia for parts etc generally next day service,and cheap,ask at the boat yard office or selangor branch for delivery options.

funny thing is the G10 you buy from the states was probably manufactured in china,malaysia or india to start with!.......just saving you some air miles lol
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Old 10-09-2014, 22:29   #11
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Re: Prop shaft log replacement

The company in Selangor has been very responsive, willing to talk to me about my half-meter of tube. They have 51mm ID x 55mm OD to take down to 54.5mm which will leave only 1.75mm (1/16") wall thickness -- too thin. Even if I opt for a stainless tube that seems too thin -- somehow 3mm seems the minimum wall thickness to accept.

Is there a rule-of-thumb about what minimal space I should have around the 35mm shaft and the shaft log tube? In other words, if I get

G10 FR4 TUBE, 2.250" OD X 1.500" ID X 48.00"

it is given than the OD needs to be taken down a hair to 2.14567. How much do I need to expand the ID (1.5" = 38mm)?
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Old 11-09-2014, 09:00   #12
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Re: Prop shaft log replacement

It seems that 2.25 od X1.5 id is 3/8" wall thickness. Very thick. Close to 10mm. You only need about half of that or less. Certainly local sourcing would be best. Good luck!
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Old 11-09-2014, 13:53   #13
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Re: Prop shaft log replacement

On my boat (just did the bottom in May, had the gear out too), the 1 3/4" od fiberglass tube is 3/16" thick, which gives me a shaft to tube ID clearance of 3/16" (1" shaft). As a reference.

I would probably go with 45 mm ID. That would give you 4.5 mm wall thickness (just under 3/16") and 5 mm clearance around the shaft.

Did you find a source for 2.25 OD tube? or is that a typo in #11 above? There's 9.5 mm difference in 2.5" and 54 mm.

As for machining G10, it is easily machined but very dusty and hard on tools. A vacuum while machining is a good idea. Frequent re-sharpening is too. HSS or carbide cutters will work. High speed is recommended, I'm not so sure I agree with that because of heat build up. A liquid coolant might help, but don't use the machines built in system, the cuttings will contaminate and destroy the pump.
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Old 11-09-2014, 19:23   #14
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Re: Prop shaft log replacement

Please disregard the question about typo above and 2.5" tube. My mistake. That's what I get for going by memory.
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Old 11-09-2014, 23:08   #15
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Re: Prop shaft log replacement

Here is what the Aceon (the company in Selangor) can give me:

40mm ID / 55mm OD, "contact molded" (hand-laid) fiberglass and resin. They only do vinyl ester filament-wound for pipes over half a meter OD.

So, basically atoll's recipe but by professionals. Per Jim's analysis all I would need to do is skim the exterior but remove 2.5mm around the inside. If I need to go with this, what other questions should I ask Aceon? Same techniques and tools outlined for G10?

I have queries out re 316L stainless tubing, but so far have found only 304.
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