[ds34mail]

My primary winches sit on kind of a pedestal - so the surface to support with large washers or distribute the load is limited. As a result I have quite some stress cracks

From the insdie:

I am upgrading to self tailing and size up from 40 to 44 - so I wonder how to best support the winch. Should I go withindividual washers or a large plate of aluminum or G10 and fill the pedestal with expoxy?

 

[SHNOOL]

G10, cut it to fit as best you can around the space you have AND add big washers.

 

[Davil]

could also have a combination of fitting a 3/4 inches piece of starboard (hardware will have it) as wide as you can fit and use those fender washers, might help to spread the load and will be easier to trim to size and avoid the cave in as you have now.
Am afraid the aluminum will have trouble with the stainless fasteners.
Just an idea.

 

[overbored]

starboard is the worst material to use for a backing plate as it has no compressive strength. aluminum is second worst as it corrodes and can not conform to the curved surface. the best is either fiber glass or a plate of 1/4" G 10 that is made to fit the under surface . you then attach it by using thickened epoxy to fill the gaps so the upper and lower surfaces are as parallel to each other as possible. then the bolts will hold easily with regular washers

 

[Davil]

you are right, have used starboard in the past as well as marine plywood, because so easy to work with and easy to find, the following is a very nice and complete write-up on backing plates.
thanks

The Critical World Of Backing Plates

Avoid serious boat damage and personal injuries by ensuring your hardware is properly installed. Here's how.

www.boatus.com

 

[danvon]

Use a backing plate bigger than the pedestal, and fill the gap with resin filled with glass fibers (I think Dynaglass is the one I've used). Then bolt through the whole assembly.

 

[Sailormon6]

If you're expecting to make it easier to tail the jibsheet by buying bigger, more expensive winches, you'll be disappointed. If you're finding it difficult to grind in the jibsheet, the problem isn't with your properly functioning winches. Your existing winches are two speed, and they provide all the power you should need to tail a jibsheet.

The problem lies mostly in helmsmanship. Whenever you or your crew are having to grind long and hard with the winch handle to tail a jibsheet, the reason is because the helmsman turned the boat too far during the tack. The remedy is to stop the turn when the jib is streaming along the gunwale on the new tack. At that time, the jib is not loaded, the sheet is loose and all but about 3-5 ft. of it can be pulled in by hand, without using the winch handle. Since only a few feet of line remain to be ground in, you don't need self tailers. You can hold the sheet with one hand and grind the winch with the other. Since the sail isn't loaded, it's easy to grind the winch. When the sail is nearly in trim, the helmsman should bear off and load up the sail. That little amount of fullness will be just the right amount to help the boat accelerate out of the tack.

I should add that, before you start the tack, put the winch handle in the winch and put 2-3 wraps of line on the winch. If you wait until after you have tailed the jib on the new tack, you'll waste too much time fumbling with the winch handle to insert it into the winch with one hand.

The boat's designer prescribed a winch size suitable for the boat. If you're having difficulty tacking, it's almost certainly a matter of technique.

 

[Minnewaska]

Those may simply be gelcoat cracks and not a factor of insufficient core strength, rather inferior gelcoat. If you're certain you need a better backer, I'd use G10 and take up the irregular space between it and the underside of the GRP with heavily thickened epoxy. Getting it perfectly flush with the outside requires a bit of creativity. I'm thinking you drill the mounting holes in the G10 and hand tighten some mounting hardware, while it all sets. Getting those hand tightened bolts back out might be tricky.

 

[PhilCarlson]

Those may simply be gelcoat cracks and not a factor of insufficient core strength, rather inferior gelcoat. If you're certain you need a better backer, I'd use G10 and take up the irregular space between it and the underside of the GRP with heavily thickened epoxy. Getting it perfectly flush with the outside requires a bit of creativity. I'm thinking you drill the mounting holes in the G10 and hand tighten some mounting hardware, while it all sets. Getting those hand tightened bolts back out might be tricky.

+1 on this assessment and method. I agree it's probably strong enough but see where you're coming from with the pattern of the crazing. The larger the backing plate the more the load is distributed. Use cheap steel fasteners to seat the backing plate in the curing epoxy then switch them out for the expensive stuff once it's seated.

 

[SanderO]

Is there a different hole pattern for the new winches?
If not:
Cut a round which pad minimum thickness 1"
Fabricate a 1/4" round disc for a new backing plate. Copy the hole pattern
Bed the new backing plate with thickened epoxy

If yes:
Cut a round which pad minimum thickness 1"
Fabricate a 1/4" round disc for a new backing plate. Copy the hole pattern
Fill the old holes with thickened epoxy
rotate new winch to miss old winch attachment holes
Bed the new backing plate with thickened epoxy

You can substitute stainless steel plate for teak.

 

[pdqaltair]

I say "nope" to the backing plate crowd. The cracks extend beyond the area a plate could cover, the surface is nowhere near flat, and you need reinforcement beyond the semi-flat area. A backing plate can't do this, certainly not with a bigger winch.

Sand or strip off the paint and add about 4-6 layers of 1708, in alternating dirrections, tapering, and extending about 2-3 inches beyond the winch base in all dirrections (farther than the stress cracks). No backing plate needed, but use extra thick (this is a thing--they are 2x the thickness) fender washers under the bolts.

This is how serious race boats do it, and it is the best way to deal with curved and complex under deck areas. Easy with the access you have. Won't take any longer than fabbing a good backing plate and MUCH more effective.

Obviously, if there is core that also needs to be dealt with, as well as the old holes.

 

[colemj]

What does alternating directions accomplish? 1708 is 45* biax, so an alternating direction would give the same fiber orientation.

In this case, I do think a backing plate/structural thickening will be all that is needed. The cracks are in the thin inboard end that looks relatively flat all the way to the edge. The cracks go right to the end of the layup, so there isn't a way to extend glass past them. The other side of the winch is cored and doesn't seem to be hinging, so a 1/4" fiberglass plate cut to shape so it fills that entire winch bed area, and bedded in thickened epoxy will work fine.

Mark

 

[ds34mail]

Thank ya'll for the good advise. I think I will go with the fiberglassing - I have never done that, so this could be a good starter project? I realize that the pictures make the pedestal inside appear flatter than it actually is. I wanted to extend the backing/support outside of the walls of the pedestal and I think I'd never get a proper flat surface for a big G10 plate...

I will report how it went, now I need to find out about glassing...

 

[colemj]

Actually, it will be some difficult and frustrating glass work. You will be working with curves upside down. Not impossible, but not the work I'd start a beginner with. On the other hand, it is a small and contained project, so you will be able to get the hang of it easily.

Mark

 

[Minnewaska]

I think I'd never get a proper flat surface for a big G10 plate...

If I understand the question, you make a batch of very thickened epoxy (ie peanut butter consistency), then butter the G10 with as much as necessary to take up the irregularities. Stick it on, bolt it through to hold it parallel to the outer surface, fair around the edges and wait for cure.

Sounds like you have another plan though. Good luck.

 

[Davil]

Thank ya'll for the good advise. I think I will go with the fiberglassing - I have never done that, so this could be a good starter project? I realize that the pictures make the pedestal inside appear flatter than it actually is. I wanted to extend the backing/support outside of the walls of the pedestal and I think I'd never get a proper flat surface for a big G10 plate...

I will report how it went, now I need to find out about glassing...

===========================
was thinking about the backing plate thing and I do agree with pdqaltair.
forget about the backing plate, has not use!!!
wow, heresy!!!
I start to hear the results of my post, well will run for cover but.
The forces acting on a mounted winch are basically shear forces applied and resisted by the few screws holding the winch, there is no vertical upwards force!
No way the winch will be pulled out of the base by grinding the handle!
This will be different to a mooring cleat where the forces are not only sideways but vertically.
The resistance and counterforce opposed to the grinding of the handle resides on those screws, the only logical way to reinforce it is by building a solid layer of very resistant wall, that should be accomplished by layers of fiberglass either epoxied or preferable vinyl resin plus cloth, in my installation 5200 for permanent bonding a piece of marine plywood, that is that, after 4 years of use no movement.
Because your surface is uneven, will need to build some layers only to provide that flat surface.
Even

"Shear stress, often denoted by τ (Greek: tau), is the component of stress coplanar with a material cross section. It arises from the shear force, the component of force vector parallel to the material cross section. Normal stress, on the other hand, arises from the force vector component perpendicular to the material cross section on which it acts."

 

[Jeff_H]

I agree with PDQ and Overbored. Those are stress cracks that extend beyond the rim of the winch. It will need to be reinforced with fiberglass that extends beyond the recess for the winch. (I had to do a similar overhead repair for a babystay bearing plate. Its not all that bad if you prepare properly.

If I had to do this I would grind the area below the repair to get rid of all of the paint. I make up 4-5 circular layers of biaxial cloth each larger in diameter than the last, and with couple layers that are perhaps a inch or two in diameter larger the recess in the deck below the winch. Number them starting with the largest one first then smallest on up to the next to largest diameter. I would make adisc of G10 that is slightly larger in diameter than the bottom of the recess with a couple holes that align with the old bolt holes, This will be the last piece to go on and will clamp the other layers in place until they cure. It will also create flat surface for the washers.

To do the layup, I would wet out each of the discs of fiberglass leaving them flat on a piece of plastic. (slow cure epoxy hardener) As soon as they are all wet out. I would apply a coat of epoxy to the surface and then mix thickened epoxy and trowel it onto the wet epoxy to bridge any gaps., The thickened epoxy does not need to be perfect or very thick. Then I would stack each layer of the wetted out cloth on the G-10 disk one at a time in the order second biggest to smallest and end with the biggest.

I would use a couple pre- threaded sailmakers needle and some whipping cord through the holes in the G10 from the bottom, and pass the needles through the deck. Then push the whole assembly in place while someone on deck tied the whipping cords together, and uses a couple wedges or a Spanish windlass on the whipping chords to clamp the G10 hard up against the laminate layers. From below you can place some wax paper over G10 and squeegee the reinforcing beyond the G10 against the underside of the deck. Leave the wax paper in place so you get a smoother finish. Alternately use some peel ply and put the wax paper over the peel ply and trowel through both of them. Lastly, if the edges of the laminate do not stay in place against the deck, use tape some scrap corrugated cardboard over the wax paper so that it holds the edge of the laminate in place against the deck.

I suggest doing a couple dry runs to make sure that you have the tools and the materials all laid out so you can do this easily. The actual layup with be scarily quick, maybe 10 15 minutes.

While we don't actually show the lamination, around 17 minutes into this video

you can see how we used string and wedges to clamp the G-10 and laminations in place.

Jeff

 

[colemj]

Wow, that is a complicated procedure for a simple solution to this winch base issue. Not what I would do, but nothing technically wrong with it. This really is a one hour job with simple materials.

One thing I will note is that epoxy seems to gain mystical qualities here. There is nothing about this that requires any physical aspect of epoxy to accomplish, so it could be done less expensive, with more timing, temperature, and mixing error margins, and with much better health safety using polyester resin. Particularly for someone who hasn't worked with fiberglass or epoxy before. Also nothing mystical about G10, because any sheet fiberglass will work fine. Absolutely everything about this reinforcement is in compression, where the properties of epoxy and G10 sheet are meaningless.

Not to mention that there really is no structural issue in the existing setup. The only issue is a small amount of flexing under high loads over time has caused the brittle gelcoat to crack on the surface. Fixing this is fundamentally a good thing to do, but the winch is not going to pull out or break the boat if it isn't addressed.

And once it is addressed, the much, much more difficult work of fixing the esthetic-only gelcoat cracks still needs to be done. After all, that winch mount would last forever as is and never be questioned other than those surface finish cracks.

Mark

 

[SanderO]

I am no expert on boat construction or GRP repairs. I tend to agree with Marl... this does look like a structural problem... requiring the work that JeffH describes. I could be wrong but it looks like surface crazing. It certainly doesn't look as if the winch will pull out. As I wrote I would simply add a thick stainless steel backing plate below and may a similar plate on top of the GRP.

 

[Jeff_H]

Wow, that is a complicated procedure for a simple solution to this winch base issue. Not what I would do, but nothing technically wrong with it. This really is a one hour job with simple materials.

One thing I will note is that epoxy seems to gain mystical qualities here. There is nothing about this that requires any physical aspect of epoxy to accomplish, so it could be done less expensive, with more timing, temperature, and mixing error margins, and with much better health safety using polyester resin. Particularly for someone who hasn't worked with fiberglass or epoxy before. Also nothing mystical about G10, because any sheet fiberglass will work fine. Absolutely everything about this reinforcement is in compression, where the properties of epoxy and G10 sheet are meaningless.

Not to mention that there really is no structural issue in the existing setup. The only issue is a small amount of flexing under high loads over time has caused the brittle gelcoat to crack on the surface. Fixing this is fundamentally a good thing to do, but the winch is not going to pull out or break the boat if it isn't addressed.

And once it is addressed, the much, much more difficult work of fixing the esthetic-only gelcoat cracks still needs to be done. After all, that winch mount would last forever as is and never be questioned other than those surface finish cracks.

Mark

I agree with much of this, but not all of this. I do agree that this as essentially a one or two hour repair as well.

But I respectfully disagree that "there really is no structural issue in the existing setup" , To explain my opinion, when you look at the photo from above the winch you can see that the pattern of the crazing reasonably definitively shows that this is flexural (stress) cracking. Fiberglass is a fatigue prone material so that by the time that you see that much stress cracking, you can be reasonably assured that the laminate has been weakened to one degree or another. I would be less concerned if this was in the middle of the deck with out any adjacent openings, but the photos appear to show that this is within a few inches of the opening for the sail locker lids. As fatigue further weakens the laminate the damaged area will spread towards the opening and eventually the edge condition will fail.

To minimize flexure, an area larger than the winch needs to be strengthened in bending and stiffened to minimize deflection. Conceptually, I am recommending reinforcing an area that is several inches larger in diameter than the winch bases which appears to be easily accomplished in this case using the method that I described.

(I will note that my boat has Lewmar 42 ST's for primary winches. The bases for those are also on the coaming and while the top of the fiberglass is smooth and without stress cracks after 40 years, the fiberglass in this area is over 3/4" thick (no core) and that thickness extends roughly 6" fore and aft of the winch and several inches to either side before tapering down to the normal 3/8" thickness of the rest of the coaming.)

I agree that polyester probably could be used for this repair. I personally find epoxy easier to work with since there is a more reliable working time, and so you can prepreg and layup a lot of layers at once. I have not been able to reliably do that with polyester resin,

But the other reason that I like epoxy for a job like this, is that I want the whole assembly to work as a beam using the deck as one flange and the g10 (or other fiberglass) acting as the other flange. Polyester tends to form poor secondary bonds. While it may in fact develop a sufficient bond with the existing laminate to act as a beam, I prefer to count on the higher adhesion of the epoxy.

Polyester is definitely less expensive (roughly half the price) but this project takes so little resin that the difference in cost should be minimal. In the flip side, On this point I profess some bias since, I personally keep epoxy resin and the pumps around, but don't keep polyester.

I agree that G10 is not necessary if the layup is done well. Similarly with the G-10, I usually have scraps of G10 around big enough for this kind of project so its my go-to, I like the stuff. But any flat surface will work to clamp the laminate when it is curing. In a recent bulkhead repair, I used door skin plywood screwed down over wax paper to hold the laminate in place and create a flat smooth surface while the laminate cured. I have also made a backing plate by laminating three layers of cloth (mat-roving, mat) between a release waxed pieces of glass. That would also work instead of the G10 as a flat surface to clamp the laminate to the deck while it cured, and which would ultimately become a part of the final layup.

I am no expert on boat construction or GRP repairs. As I wrote I would simply add a thick stainless steel backing plate below and may a similar plate on top of the GRP.

I would agree with the first sentence. Regarding the second sentence, 'adding a thick stainless steel backing plate' Stainless steel is hard to work with and expensive and so would be about the last material I would use. But beyond that the stainless steel plates alone would not really solve the flexural problem since the existing fiberglass surfaces are uneven and the stainless steel plate would simply create a stress riser at the edges.

In order for the problem to be solved, the area needs to be strengthened against bending. For the stainless steel plate to contribute to that, there would need to be laminate below the plate that extended out onto the adjacent laminate on all sides and beyond the stress cracking. By the time you did that, the stainless steel plate becomes unnecessary. The plate above the deck also does nothing useful since the winch base itself provides the bearing surface and shear resistance that is needed above the deck.

Jeff