Hmm...didn't expect to find this.

Chief RA · Oct 13, 2014

Will you have room to rebolt with a metal backing plate? I would check the other winch mount as well.
Chief

Benny17441 · Oct 13, 2014

The small indentation by itself does not mean a cause for concern in a close to 30 year old boat. Is the surface soft? The winch should be secured to the cabin top by a backing plate and the area may show some play when the winch is loaded but not excessive Unless the area is soft and shows crumbling I would not worry about it. Only you can tell the actual condition of the core as it is impossible to tell from the pictures. Cabin top winches are subject to a lot of stress and so does the area to where they are attached, try not to overload them. It is a good practice to protect the winches to have at least three wraps on the drum to spread out forces. This unfortunately does nothing for the mounting area so excessive loads should be avoided. Seal the surface of the base of the winch to prevent moisture getting under it as in freezing temperatures any water will expand compressing the core.

finding41 · Oct 13, 2014

Did you poke around inside the bolt holes to see if there is any rot in the core? If there is no rot or wet wood it may just be an anomaly. When they build these boats they put the hardware on near the end of the build. When the winch was installed it may have compressed that area. The fiberglass may not have fully cured. (Hence no cracks around the area in your pictures.) You wouldn't have noticed the indent had you not removed the winch.
So no rot or wet, no worry's.
When you put it back together use butyl tape so it never leaks.

Ron20324 · Oct 13, 2014

If it's like my B323, under the cabin-top line stoppers there is air gap between the inner liner and the decking. Fill it with epoxy or such.

Scott T-Bird · Oct 13, 2014

It looks like you are showing us the underside where there were washers used for backing (based on the circles around the holes)? I don't see any stress fractures on the surface of the fiberglass. It looks more like the surface was simply formed in a rounded fashion rather than deformation from stress. It doesn't even look like there is any residue from deteriorated core, the marks look more like metal to fiberglass scuffing. Is there some obvious sign of weakening that I don't see in the photographs?

I solid backing plate that conforms with the shape of the surface would be a better alternative to individual washers.

Ross · Oct 13, 2014

When I rebuilt my Islander I drilled proper size holes for mounting deck hardware and then from the inside removed a plug of interior skin and core and epoxied into place a locust plug cut with a hole saw so that all of the holes lined up properly. In that way there was no chance of core compression.

Chenega · Oct 13, 2014

IH82BL8 said:
I removed the strbd cabin top winch yesterday for maintenance and found this. It looks like the core has been stressed as in is danger of collapsing. It seems the scope of the project has been expanded. Sorry for the quality of the pics. I used the spine of the booklet as a straight edge. You can see that the f'glass is concave in the area of the mounting holes.

Check and see if there's moisture. This could be an issue of over tightening the fasteners or over stressing the winch - but there should have been some backing. If it were my customer:
- I would check for moisture
- use a 1" hole saw and cut the underside skin and remove core to the top skin
- inspect core
- remove paint (for adhesion to bare glass) and make appropriate backing plate (3/8" G-10 from McMaster.com)
- if core is okay, fill 1" holes with West Six-10 epoxy and glue G10 in place (Six-10) being sure there are no voids
- re- drill fastener holes when cured next day and install winch

no big deal... Just a little time and material and you should be good to go!
Cheers

higgs · Oct 13, 2014

I would only be concerned if you find the core is wet. Otherwise, what is going to happen if you remount it and continue on?

Ross · Oct 13, 2014

Remember that bolts must enter and exit the holes at right angles to the surface or the stress on the bolt thread is a bending moment. It is obvious that the core has compressed and that should be corrected.

kloudie1 · Oct 14, 2014

I think that the 31 is built like the 34 there where the winches are. There is a solid aluminum plate embedded in the upper skin and little to no core there. It is fairly solid fiberglass about 3/4" thick and no backing plate is needed, nor do the bolts come through the cabin liner when correctly installed.. The inner liner, the part that is showing the deformation is not supposed to be bonded to the outer and is not to take loads. The embedded aluminum plate has (had?) threaded holes to take the load of the winches without having internal backing plates. If the threads are still good and holding the winch, someone may have installed bolts that are too long and was trying to dress the ends. If the threads have been destroyed and they no longer hold the winch bolts, or someone replaced the winch with one whose bolt pattern doesn't match, the holes can be re-threaded or, as Russ notes, a heavy reinforcement plug recessed into a hole in the inner liner. Because of the solid outer section and the aluminum plate, this is almost impossible to do from the top.

BobM · Oct 14, 2014

Usually if it has been water there will be brown stains on the fasteners in my experience.

kito · Oct 14, 2014

Imo, I don't see a problem.....unless you see water dripping from the core when you removed the screws. I am guessing that your H31 is similar to my H30. The inner liner is basically floating and not adhered to the core. A little compression of the liner under a winch seems normal to me. I have about a 1/8" gap from the liner to the core. That looks like about what your seeing.

Crazy Dave Condon · Oct 18, 2014

After reading, there are some questions that need to be answered and I think Kloudie 1 hit on I t. See if there is an aluminium plate encapsulated in the glass. To do this, merely take the bolt and start screwing and see if it holds. The second question, did you ever see or feel water and possibly a moisture meter can answer that. If the bolt is holding, possibly the winch was replaced at some time or other and long bolts were used going thru the cabin liner. If that is the case, then basically a washer and nut were applied thinking it held the winch thus pulling the cabin liner in. Again, you will need to check.

If the bolt does not go thru an embedded plate for holding, then either the coring is wet and you will need to dry that out and repair as you do not want the liner to be depressed in. It depends which method you want to go on the repairs but before going any further, see if there is a metal plate encapsulated in the fiberglass deck and advise.

jibes138 · Oct 18, 2014

If it is not wet you may just be seeing a slight compression of the core from the torque on the mounting screws (bolts). The core is likely either balsa or plywood and neither is exceptionally strong in compression. Take a screw, put it in a piece of plywood and torque it down with a ratchet wrench and I'm sure you will see what I mean. FRP likewise has a certain compressive strength. This is not like a glass pane like a window, it is plastic and will yield with high compressive stress. Best to spread the load over a large area with a strong backing plate versus washers and nut. My experience with G10 is it is very strong and stiff. Seems like a good choice for this application.

Hmm...didn't expect to find this.

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