Reinforcing a Bow

[KStepman]

On a recent ocean passage, one of my crew committed two compounding acts of poor seamanship that resulted in the primary anchor rolling off the bow, on four to six feet of chain, that repeatedly struck the boats fiberglass bow, holing it in four places, immediately above the waterline. The boat is eight years old, and like many modern boats has a near vertical bow. Slightly newer boats of the same model are manufactured with Kevlar reinforcing their bows. Even in anchoring, on rare occasions, the anchor has swung on its chain striking the bow.

For these reasons, I am looking into how best to protect the bow.

The two methods that I have seen is to laminate Kevlar or attach an angled stainless steel plate along the forward edge of the bow.

Are these feasible and which might be the better choice to retrofit? I would imagine that Kevlar would require that the bow be sanded down to bare fiberglass, with the Kevlar laminated on with an epoxy resin, and refinished with gelcoat. To attach a stainless steel plate might be more difficult to do

[boatman61]

Less work.. just drill and bolt on..

[estarzinger]

Neither is that difficult.

You say you had holes in your bow - do you still? If so, you need to do significant glass repair anyway and you can add Kevlar laminates while you do it. Yes, you need grind down to bare laminate to start. The fiberglass job, including the Kevlar is pretty straightforward. Getting the color to match the rest of the boat will be the most challenging part . . .might be best to consider it a new design element and have a different bow color/design, like say a shark teeth pattern

With the stainless option, you still need to patch the holes. You get a stainless fabricator to bend a sheet of perhaps 1/8" stainless to match the bow curve. It is them bonded on. The adhesive does the primary job of holding it in place, with perhaps 8 screws to hold it while the adhesive cures and left in afterwards just as 'belt and braces'.

[Stumble]

I have always been hesitant about the use of Kevlar. It works great when it works, but is very difficult to repair properly. Since this seems to be a recurring problem I would probably fix it in glass, then add a stainless guard.

[KStepman]

Thank you. Yes. The fiberglass has been repaired. I might as well share how we did it with the boat at a dock...
My water tank">fresh water tank is in the bow, and I have my dink on heavy custom davits extending out passed the stern. To raise the bow some feet out of the water, I used a shower hose on the aft swim platform to pump the water out of the tank, and filled the dinghy with the water. That raised the bow up about three feet. Being in the dense salt water of the Caribbean helped too.

I like the idea of plate using adhesive because it minimized or eliminates the need to paint shark's teeth, although that could be fun. Bolts are a problem, because there is no way to get at the inside of that part of the hull, but large screws or pop rivets might work to hold the plate in place, and extra assurance. I might go for 3/16" rather than 1/8" to minimize the ding factor. Any further thoughts?

[osirissail]

Repairing a sailboat bow that has been holed or otherwise structurally violated is not just a simple glue on / patch with ?? cloth and resin and that's that. It involves a section of the sailboat that is under large structural loads caused by the forestay and mast bending plus the twisting loads caused by the bow plunging into the sea in bad weather conditions.

Choosing a cloth such as Kevlar sounds nice (extra strength, etc.) but it is not that simple. Again trying to mate any repaired sections to an original hull that was made from ordinary glass cloth and resin is risky due to the differences in adhesion properties and thermal expansion/contraction properties.

The safest way is to use the same glass cloth and resin as the boat was originally constructed with way back when following the original layup and roving orientations. Then you can add a barrier like the stainless steel plating to protect the area from future dings and dents. After the original bow / hull laminate is repaired then I would suggest gluing the stainless plates with something like T5200 and stainless screws to hold the plate in position until the 5200 fully cures.

[KStepman]

Originally Posted by osirissail

Repairing a sailboat bow that has been holed or otherwise structurally violated is not just a simple glue on / patch with ?? cloth and resin and that's that. It involves a section of the sailboat that is under large structural loads caused by the forestay and mast bending plus the twisting loads caused by the bow plunging into the sea in bad weather conditions.

Choosing a cloth such as Kevlar sounds nice (extra strength, etc.) but it is not that simple. Again trying to mate any repaired sections to an original hull that was made from ordinary glass cloth and resin is risky due to the differences in adhesion properties and thermal expansion/contraction properties.

The safest way is to use the same glass cloth and resin as the boat was originally constructed with way back when following the original layup and roving orientations. Then you can add a barrier like the stainless steel plating to protect the area from future dings and dents. After the original bow / hull laminate is repaired then I would suggest gluing the stainless plates with something like T5200 and stainless screws to hold the plate in position until the 5200 fully cures.

Thank you for the considered advice. As to the repairs made... The holes were not large. The largest was 4 inches (10cm) in height by .75 inches (2cm) wide chiseled into the lead edge of the bow. The other 3 holes were 1/4 the size, in the same area. The person who did the repair was another boater, from the UK, who by chance is an expert in fiberglass boat repair. He cut up glass mat fibers and mixed it into the resin to make a paste, and worked it into the holes, finishing off the surface with a form of Bondo (I believe). When I asked him if his repair was temporary and needed to be redone at a proper yard, or if it was permanent, he said that no yard would do better.

I still need to haul the boat to touch up the gelcoat and apply ablative bottom paint where it was abraded off on the bow, but other than cosmetics and barnacle avoidance, I believe the structure of the bow has not been compromised. Any thoughts.

[Stumble]

I don't know for sure about Hunter, but I would be shocked if all they use is CSM which is effectively what you have now.

A proper repair would have been to bevel out the hole to a 12:1 angle, then replace the glass with the same weave that was there. By using cutouts of increasingly larger size until the entire hole is filled.

For the small holes it isn't much of an issue, but for the larger one... It would depend on the size, shape, and where exacally it was. But a 8 square inch hole, ay the repair is junk. Sorry.

Not that I think this is going to fail in the near future, but if there was future damage to the area, this is a major weak spot that could result in future damage being much worse that it otherwise would be.

[KStepman]

Thank you for the information.
The shape of the hole was an elongated oval, as if a shallow bite was taken out of the lead edge, crosswise. The hole-through was 3/4" at its widest, and tapered to 0", the hole-through length was 4", the approximate area of the hole-through was less than 3 sq in. However, as this was a crosswise bite across the bow, the outside dimensions of the hole was more like 2" wide by 8" long. I understand the need for a taper. He had a double-bastard file and he may have done that. As for layering up glass in such a small space in an acute angle, even if I have it redone , I wonder if it could be done, as you suggest. I would not even know who to bring it to, where I am in the Virgin Islands. I showed the repair to one shop in Nanny Cay. Any suggestions ?

[Jim Cate]

FWIW, our boat has a nearly plumb bow and we had problems with the anchor dinging the stem when weighing it in a chop. Tried a thin s/s protector, but it got dinged up quickly. Subsequently we acquired some 1/4 inch thick PVC matting, smooth finish, allegedly UV protected, in a color that was similar to the hull paint. Cut it out to fit between the waterline and the bottom of the stemhead fitting, heated it up with a hot air gun, bent it to match the profile of the stem and glued/screwed it in place using Sika 291. It is now about three years in service and has done very well at protecting the timber stem. It cleans up with acetone, has not been broached, and I'm happier with it than with a heavy stainless bit... and WAY less expensive!

Cheers,

Jim

[osirissail]

I think there may be a bit of confusion by your use of the word "hole." What I was talking about were "holes" that go all the way from the outer surface of the hull down into and through to the inside of the hull. Sort of, like a window through the hull or say a hole for installing a "through-hull." In other words, you can see inside the hull through the "hole."

If the damage was only a "gouge" or groove cut into the hull laminate that is a different matter. Gouges or grooves can be filled with a fiberglass putty - if the depth is less than 1/4" (6mm) deep, or filled with putty with glass strands ("short chop" hair) if deeper than 1/4".

The use of fiberglass resin putty with or without glass strands mixed in is not a structural repair. It is merely a filling that restores the original surface so it can be painted and cosmetically refinished.

A structural repair involves making a new area of layers of glass cloth - roving and mat - which bridges a "hole" in the hull. For that there are suggestions for the 12:1 bevel so that the "new" laminate will "grab" onto old laminate over an extensive area. In this type repair, matching the original hull's glass and especially the type of resin is very important so the "new" and the old chemically and physically match in temperature expansion/contraction and also shrinkage during curing.

If there was indeed a "window" type hole through the hull at the bow then I would also not be happy unless I had added additional reinforcing layers to the inside of the hull. That is additional layers of cloth that span the "hole" and overlap the inside of the original hull. For production boats where the insides of the boat are actually a sort of "pan" that is placed into the outer hull and then bonded together - getting to the inner surface of the outer hull is extremely difficult and might require removal or cutting away a portion of the inner "pan." Big job and complicated. A way of working around that problem is to wiggle a "plate" of fiberglass or other material through the hole and then pulled up to the inner surface with screws through the beveled outer hull. This will allow the new layers of fiberglass cloth and resin to be compressed by rollers during the patching process so as to squeeze out excess resin from the new layers which increases the strength of the new laminate.

"Bondo" is a trade name for an array of patching products from fiberglass resin to a non-shrinking "epoxy-like" putty. The version of "Bondo" that is non-shrinking would be the preferred patching putty for gouges or grooves if you could not mix up a putty with resin that is the same as used in the original hull.

Resurfacing the outer surface of the patch is usually done with the application of color matched gelcoat and sanded and buffed. Or you can cover over the patch with something else like the stainless steel sheet so nobody can see what is underneath.

I usually advise folks D-I-Y'ing such repair to consider whether they are going to keep the boat for a long time and/or use it extensively in rough waters or not. If "not," then a quick fill and polish or cover over the repair works fine. Otherwise, a proper structural repair should be considered.

[Stumble]

I agree with everything Osiris said, except that matching the goo that is used. If it was originally polyester which is most likely, new won't adhere well to the old stuff (the original hull). Better to use a laminating epoxy for this type of job, since the bond strength is much higher.

One of the tricks if you can't get to the back side of the repair is explained very well at

http://m.youtube.com/watch?v=i97TlAd...%3Di97TlAdenv4

. If you need to make a corner it is a little tricky, but not to bad, for the insert you just have to bend it around a dowel (covered in cellophane tape) of approximately the same size as the interior bending radius.

The one thing the video leaves out is once the patch has dried I like to fill the remaining hole from the screw with thickened epoxy to make sure the core is protected.

[KStepman]

Originally Posted by osirissail

I think there may be a bit of confusion by your use of the word "hole." What I was talking about were "holes" that go all the way from the outer surface of the hull down into and through to the inside of the hull. Sort of, like a window through the hull or say a hole for installing a "through-hull." In other words, you can see inside the hull through the "hole."

If the damage was only a "gouge" or groove cut into the hull laminate that is a different matter. Gouges or grooves can be filled with a fiberglass putty - if the depth is less than 1/4" (6mm) deep, or filled with putty with glass strands ("short chop" hair) if deeper than 1/4".

The use of fiberglass resin putty with or without glass strands mixed in is not a structural repair. It is merely a filling that restores the original surface so it can be painted and cosmetically refinished.

A structural repair involves making a new area of layers of glass cloth - roving and mat - which bridges a "hole" in the hull. For that there are suggestions for the 12:1 bevel so that the "new" laminate will "grab" onto old laminate over an extensive area. In this type repair, matching the original hull's glass and especially the type of resin is very important so the "new" and the old chemically and physically match in temperature expansion/contraction and also shrinkage during curing.

If there was indeed a "window" type hole through the hull at the bow then I would also not be happy unless I had added additional reinforcing layers to the inside of the hull. That is additional layers of cloth that span the "hole" and overlap the inside of the original hull. For production boats where the insides of the boat are actually a sort of "pan" that is placed into the outer hull and then bonded together - getting to the inner surface of the outer hull is extremely difficult and might require removal or cutting away a portion of the inner "pan." Big job and complicated. A way of working around that problem is to wiggle a "plate" of fiberglass or other material through the hole and then pulled up to the inner surface with screws through the beveled outer hull. This will allow the new layers of fiberglass cloth and resin to be compressed by rollers during the patching process so as to squeeze out excess resin from the new layers which increases the strength of the new laminate.

"Bondo" is a trade name for an array of patching products from fiberglass resin to a non-shrinking "epoxy-like" putty. The version of "Bondo" that is non-shrinking would be the preferred patching putty for gouges or grooves if you could not mix up a putty with resin that is the same as used in the original hull.

Resurfacing the outer surface of the patch is usually done with the application of color matched gelcoat and sanded and buffed. Or you can cover over the patch with something else like the stainless steel sheet so nobody can see what is underneath.

I usually advise folks D-I-Y'ing such repair to consider whether they are going to keep the boat for a long time and/or use it extensively in rough waters or not. If "not," then a quick fill and polish or cover over the repair works fine. Otherwise, a proper structural repair should be considered.

That is great advice. To resolve the confusion, it is a hole-through, "a window," but a sliver of a window. The confusion may be on the size and extent of the damage, which seemed minor. If we were looking at the damage in cross-section, from the top, the anchor abraded away the leading edge of the "V" until the inner hull was just reached, not very deep, along a 4" vertical line along the bow, and barely 3/4" wide at its widest, narrowing to 0" up and down from there, resembling the narrow eye of a sewing needle. If you took a 4" wide rasp, with a curved face, and ran it horizontally across the vertical bow, and stopped just as you saw inside the hull, that is the size, shape, a extent of the hole. It was so narrow, that I doubt that a plate of fiberglass could be inserted and forced against the inside of the "V" unless the hole was enlarged. I understand what you are saying. But, given how small the actual hole-through was, the extent of the fiberglass exposed around it, and the acute angle into witch the glass/resin filler was forced into the hole creating a mechanical as well as a chemical attachment to the hull, I am not certain it can, and should be redone as you recommend. If the hole-through was larger, or not where it is, I would automatically agree with you. Given its small size, >3 sq in, long, narrow, tapered shape, and location, I wonder. Perhaps there is the confusion. Or am I being obtuse, or lazy.

And, yes, this boat sees longer ocean passages than most hunters.

Thank you for your time and patience.

[osirissail]

It does sound like the "wound" was merely a narrow very deep groove that reached the inner surface of the existing hull. In which case any good matching resin with fiberglass strands filler would do the trick - which is what it sounds like your repair person did do.

You did not mention what "resin" the repair person used since there are polyester resins and epoxy resin. Either of the two will work on a narrow groove where you do not feel like you want to enlarge the wound enough to patch with new fiberglass cloth.

The problem with using epoxy besides the very different expansion/shrinkage characteristics of epoxy versus polyester resin - is that nothing likes to stick to epoxy once it is cured. So it sounds like your repair person took care of that by adding the surface coating of a type of "Bondo" material before the underlying repair resin was fully cured. That is a proper way of dealing with it.

The only reservation I have is how he treated the top and bottom sharp corners of the V-shaped groove. There is a possibility of a hairline crack existing as an extension at the sharp top and bottom end of the groove. Hopefully the repair person ground out the corners to a round shape that upon close inspection did not have any extending cracks. Then filled the "wound," etc. If you don't know or cannot find out if he checked for possible extending cracks then just keep an eye on the area for signs of the crack expanding. Painting a little acetone or styrene liquid on the area then wiping it off will reveal if there is any cracks as the liquid migrates into the cracks and shows up as a visible line of darker color than the surrounding material. If no such line is visible then things are fine and press on with a happy cruising experience and take some of the advice on how to keep your anchor from inflicting further wounds to your bow.

[KStepman]

sirissail
Thank you for your help. I may have spoken generically that he used an epoxy resin. Specifically, it was Celcote "Fiberglass Resin." I cannot attest to how he addressed the edges of the whole for possible cracks. I know that I gave him a half round, double bastard file, which he used. I will do as you suggest, and paint the area with acetone I have aboard, to see if there are any cracks forming.

Thank you. It has been a needed education.