Fiberglassing an older hull

[rsn48]

This question for me is purely hypothetical though others might benefit from the discussion. My boat is 50 years old and has a fiberglass over wood hull original build. The hull is in amazing shape. Everything was gutted below deck, all tanks, engine, everything taken out, the inside of the hull was washed, every area inspected for wood damage, and then the bottom third repainted with an epoxy paint to preserve the wood later on down the line from water damage. A few small soft spots around through the hulls were repaired.

While this refit was underway I came across a 1972 Grand Bank that was in amazing shape and I almost purchased it. I do know that all wood boats are a labour of love scenario. The work is endless. But the hull on initial inspection, not a survey, looked in decent shape, based on an interior inspection. Now for the sake of the argument, lets assume the hull is in amazing shape.

Rather than deal with the work involved in the long term with an all wooden hull, why can't the exterior of the hull be finished professionally.

The one disadvantage to a refinished hull would be added weight. But given the amount of work concerning wooden hulls and based on my experience with my 50 year old hull, wouldn't the owner be better off glassing the hull? Since almost no one does this, there must be something I am missing.

So what's the scoop, I guess a wooden scoop covered with fiberglass.

I have linked this before, but thought I'd throw it in as to why I have thought about fiberglassing the hull as the boat owner in the video does continual repairs on his hull:

 

[Lepke]

Years ago, when there were many more wood boats, several yards around the country did fiberglass over wood hulls. Especially commercial fishing boats. But it's expensive. A proper job is not just one layer of cloth, but a fiberglass thickness of near what a regular fiberglass hull would be.

If water gets in, the wood rots, just like cored boats. Cracks in the fiberglass means water can get in. Changing rotted planks means removing the fiberglass. Back when we had wood preservers that actually worked, pre-EPA, it was better to treat the wood. My current wood boat was treated with a now illegal treatment in the 1960s and still shows no sign of rot in the hull. But the wood is considered hazardous waste.

Another point on planking, planks are an important part of hull strength. When we had big trees and good lumber, a plank ran from the stem to the stern without splices.

 

[rsn48]

The fiberglass on my boat is thin, less than a quarter inch thick, yet the hull has held up. In fact I was surprised at how thin the glass was. I am guessing the original builder was also concerned about weight and cost.

 

[O C Diver]

It's certainly more common on work boats. Lots of Chesapeake bay oyster / crab boats are glassed over wood. The really slick trick is 2 layers of bi-axial cloth with West system or other epoxy. The boatyard where I get my work done, has done this numerous times. They start by sand blasting the bottom clean. This not only removes the paint, but roughs up the surface for better adhesion. Obviously they check all the wood and survey fasteners. As the wood will be covered, and new fasteners are stainless steel screws. When they are ready to cover the hull, they wet it out first with West system and then apply the first layer. After it has gotten tack free but not cured, they to the second layer. The idea is to have the wet out, first layer, and second layer cure together as one. I'm told the epoxy sticks much better to the wood and makes the hull much stronger than fiberglass. The strength and rigidity is amazing after only these 2 layers.

Ted

 

[Sailor of Fortune]

Alan Vaitses did lots of FG covering of both yachts and commerical fishing boats at his yard in Mattapoisett, Ma in the 60's and 70's. He wrote the boat on it,literally. He used matt and polyester resin but would staple the first layer while it was still "green". Often these boats floated higher on their lines due to the layers of glass. I can't remember the number of layers he used but it seemed to work well.

 

[Simi 60]

Generally the kiss of death on a timber boat , especially something like ours as glues and resins do not take well to the timbers used.
Its usually done in a last ditch effort to squeeze some more years from her.
Inside skin is not glassed, planks move, glass does not and delaminates, water gets behind it and the end is nigh.

Different story if its an actual strip planked boat that was designed to be glassed inside and out making a sandwich.
Timber used here is generally western red cedar, balsa or Kiri, epoxy resins used and waffer thin glass,built light.

 

[MRRiley]

Not sure if this stuff is still available but I always thought it was an interesting product-

http://seemanncomposites.com/cflex.htm

The down side as I understood it was the fairing once glassed...

"C-flex is an excellent solution for preserving the life and character of vintage wooden boats, because it can be attached on a wooden hull to create a stronger and more durable hull structure. The C-Flex is applied to the prepared hull with an Elastomeric Adhesive, which creates a strong but flexible interface between the wood and the exterior fiberglass. The hull is then laminated with additional layers of reinforcements to the desired strength level."

 

[swampu]

My Rose was built in the 50’s out of cypress, it was c-flexed in the 70’s. She’s still stong as the day those trees grew today. No rot, no soft spots. As anything if done right it’s bullet proof

 

[78puget-trawler]

Generally the kiss of death on a timber boat , especially something like ours as glues and resins do not take well to the timbers used.
Its usually done in a last ditch effort to squeeze some more years from her.
Inside skin is not glassed, planks move, glass does not and delaminates, water gets behind it and the end is nigh.

Different story if its an actual strip planked boat that was designed to be glassed inside and out making a sandwich.
Timber used here is generally western red cedar, balsa or Kiri, epoxy resins used and waffer thin glass,built light.

This. Last resort to keep it afloat a few more years.

 

[PMF1984]

You can get the book by Alan Vaitses at Amazon. Some wooden boats with really nice interiors had low hours on the engine and been designed too poorly or worked too hard. Vaitses’ method solved that problem. If I remember correctly, it was three layers of Fiberglas, then staples 4” on center. Then another 3 layers of mat or cloth, can’t remember which. If you are serious get the book.

 

[PMF1984]

And just want to add why you don’t see it anymore. In the 1980’s and late 1970’s there were a lot of nice old bots in yards that would sink if you put them in the water, but they had fine lines and you could get them cheap. Now you go to any yard and there are no old wooden boats, but lots of Fiberglas hulls that won’t sink and are cheap.

 

[Nomad Willy]

Glassing or should I say re-glassing a glass over wood boat should be non-problematic. If the glass is firmly attached adhesion re the new glass should adhere well.

But considering the weight and strength of both materials would be recommended.
However the resin contracts as it cures and that may give problems.

There must be something wrong w the old fiberglassing or adding more wouldn’t be on the table. So considering removing the original sheathing should be considered.

Lastly you’re adding a lot of weight to an existing boat and if that boat was already heavy creating a cumbersome overweight boat could happen. Most likely the boat was plenty heavy as a wood boat and became heavier when the first sheathing was applied. It would be a good bet that the original sheathing was put on heavy. So the possibility that an overweight boat will result is high.

Just my rambling thoughts.

 

[DNT99611]

I have often wondered how well a couple layers of 1/4 plywood applied cold mold style would do?
Using C-flex over a wood hull might give a work boat a number of years longer life but it would be a bunch of work. If you want a yacht type finish it would take a huge amount of work. I have built 3 hulls with C-flex, up to 32 foot, so have some idea of the time needed for fairing and finish work.

 

[78puget-trawler]

We did one like that in the local yard here years ago. It was an old planked, long and skinny boat about 60'. Had a bunch of rotten planks which I replaced with house lumber! Then a couple of yard dweebs smeared black tar all over it and pounded on a layer of 1/4 plywood onto it. I refused to take part in that end of it. What a mess! But that's all the owner wanted so that's what he got. IIRC they didn't even glass over it.

 

[boomerang]

I owned a wooden boat that was C-flexed over 20 years ago and back then the cost was something like $22k. It showed like a fiberglass boat ,which it essentially was. Contrary to the belief of some, the process doesn't buy a few more years of use, it's basically a new boat. If I remember correctly, it was about 3/8" thick (the glass) & when an old-timer waterman stopped by the house to look at it, I remember him telling me that I could tear out the wood inside and still have the same boat. It was super rigid and the hull never showed any signs of delamination. The only places there was bad wood was where rainwater was allowed to sit, which was in the open part of the boat. I simply dug the bad area out, filled it with fiberglass mud & repainted the patch. The integrity of the boat wasn't compromised at all.
It has since gone back to work like she was intended to be, a commercial working boat plying the local waters. Rot on the non-glassed wood on the inside isn't as much of an issue now since everything is doused with salt water daily.
Attached are pictures showing the outside of the hull and the un-glassed inside 10-12 years after she was C-flexed. The boat will easily go for another 25 years.

 

[Pau Hana]

Generally the kiss of death on a timber boat , especially something like ours as glues and resins do not take well to the timbers used.
Its usually done in a last ditch effort to squeeze some more years from her.
Inside skin is not glassed, planks move, glass does not and delaminates, water gets behind it and the end is nigh.

Different story if its an actual strip planked boat that was designed to be glassed inside and out making a sandwich.
Timber used here is generally western red cedar, balsa or Kiri, epoxy resins used and waffer thin glass,built light.

Absolutely correct- it creates a bath tub. Fiberglass over wood not original to the vessel makes the vessel uninsurable- I can’t think of a market that will offer coverage on such a risk. I know there are boats that have insurance that are glass over wood (post new construction), but many have been represented as glass boats vice their true construction methodology. If there is a claim, and this is discovered, coverage may be rescinded back to policy inception.

 

[TDunn]

As others have said glassing over a wood hull not designed to be glassed over is normally just to get a few more years from the hull. Any deck leaks will result in the wooden part of the hull rotting out from the inside. Furthermore, to properly glass a wooden hull you first have to repair all the wood to get rid of any rot. If done right, that step leaves you with a wooden hull in good shape that would likely last longer than the glassed over hull.


Now, as far as the video in the first post. I happen to have some knowledge about that particular person and his boat. His boat has needed quite a few topsides plank repairs because it had deck leaks in the past that caused the topside planks to rot from the inside. As such that boat is likely not representative of other wood boats in terms of the need for planking repairs. That said, that guy is very conscientious and fixes everything as soon as it is noticable. He is also very experienced in all aspects of both wooden and fiberglass boat construction. Of course I am saying that because the guy in the video is me.

 

[O C Diver]

Say what you want (which isn't always correct), there are lots of Chesapeake bay work boats that are fiberglassed over wood going on 20 years. Course these aren't your delicate Maine built recreational boats from 50+ years ago. The Chesapeake bay work boats such as those pictured in Boomerang's post (very nice Chesapeake bay round stern!) usually have 2 to 3" bottom planks and are built to carry thousands of pounds of oysters. Totally different from the delicate wood boats of a bygone era. The other big difference is that these boats are used 200+ days per year, often in conditions most of us wouldn't go out in.

Ted

 

[Nomad Willy]

Boom,
Love you’r old boat and picture #2

 

[moparharn]

A couple thoughts

1. As long as you are glassing over clean dry wood it should be ok. Anything you glass over is now in it for the long or short haul. Water, bacteria, etc are now untreatable and will not dry out. Start clean and dry.

2. DO NOT use stainless screws, most importantly below the waterline. Silicon bronze is the recommended screw below the waterline. The explanation is longer than I care to type.

The engineering in the world of composites is currently off the charts, spurred mostly by the transportation and renewable energy sectors. Epoxies and glass, kevlar, carbon, and more is better than it has ever been. More expensive too. A simple glass with a simple resin will seal the boat as long as flexing cracks do not open up the sealing surfaces. How stiff is that boat or how flexible is the lay up? How inflexible is the lay up?

Is the amount of time and money much less than just keeping up with the bad wood from time to time?

 

[rsn48]

Boomerang, if there is a classic boat festival in your area I hope you are entering your boat in it.

As such that boat is likely not representative of other wood boats in terms of the need for planking repairs. That said, that guy is very conscientious and fixes everything as soon as it is noticable. He is also very experienced in all aspects of both wooden and fiberglass boat construction. Of course I am saying that because the guy in the video is me.

When some one here asks whether they should purchase a wooden boat or not, attracted by the cheap price, I link your video to my reply.

 

[SteveK]

As others have said glassing over a wood hull not designed to be glassed over is normally just to get a few more years from the hull. Any deck leaks will result in the wooden part of the hull rotting out from the inside. Furthermore, to properly glass a wooden hull you first have to repair all the wood to get rid of any rot. If done right, that step leaves you with a wooden hull in good shape that would likely last longer than the glassed over hull.
..............

Thank you for following up after the video. The bolded had me wondering as well. If fresh water leaks are rotting out the planks from inside I would not want those planks sealed in with a fibreglass skin preventing further repair.
Also, glassing over is made to sound as a cheap solution.
If a wood hull boat owner sees value above the planks (and too many require replacement) then why not remove all planks, lay on a skin of pre-made glass sheets for foundation and then layup a glass hull.
Insurance guru, would a replaced wood hull with glass be insurable?

P.S. while on the hard this summer a wood hull boat with copper skin came in for plank replacement. Within a day all that could be seen is the ribs, most needed to be replaced, and replaced it was with new planks.

 

[Pau Hana]

Thank you for following up after the video. The bolded had me wondering as well. If fresh water leaks are rotting out the planks from inside I would not want those planks sealed in with a fibreglass skin preventing further repair.
Also, glassing over is made to sound as a cheap solution.
If a wood hull boat owner sees value above the planks (and too many require replacement) then why not remove

• all planks, lay on a skin of pre-made glass sheets for foundation and then layup a glass hull.
  Insurance guru, would a replaced wood hull with glass be insurable?
  
  P.S. while on the hard this summer a wood hull boat with copper skin came in for plank replacement. Within a day all that could be seen is the ribs, most needed to be replaced, and replaced it was with new planks.

• 
  
  To me (wearing my underwriting hat) I see much pain for little reward.
  
  The proposal to replace planking with glass layers brings up a number of questions:
  
• How much does this modify the naval architecture of the vessel (center of gravity, structural integrity, general seaworthiness, etc)
• The condition and longevity of the keel timbers
• How to keep the glass skin and keel timbers from shifting
• Thickness of the glass skin and repairability

I don’t know of an insurer that would entertain this type of risk unless there was substantial professional documents on to include naval plans, work, and a survey.

And, there still would be good reason to not offer coverage.

Wood boats are proven- fix wood with wood.

 

[SteveK]

Wood boats are proven- fix wood with wood.

I agree, just wondered if a new skin not over wood made a difference to insurers, but I see your point that unless it was an architect re design why should insurers consider it. After seeing the restoration pictures from a GB 32 done in one year which included more than planks, it really does not make sense to glass over wood for pleasure craft anyway.

 

[Bill Wells]

There are plenty of classic yachts out there that have been fiberglassed up to the waterline. Many of them were glassed in the 1960s and they are still going fine. When I was young in the 60s I had an El Toro that was glassed and later a strip planked Whitehall boat that was glassed, as far as I know they are still sailing today. Glassing a hull works fine if it is done properly and you don't view it as a cure all for all problems. A friend of mine glassed over a 36' Carvel hull sistership to my boat it only added a couple hundred pounds of weight, one thing that happens is the wood drys out and you lose the weight of the moisture it has absorbed over the years.

 

[philfriedman]

FRP sheathing older wooden hulls

Here are a few tips derived from my own experience in formulating and applying several tons of reinforced polymer coatings to both older and new wooden (and some other) hulls.

1. The major obstacles to a long-lasting job are a) failure to properly bond the sheathing to the wood substrate and b) cracking and eventual delamination due to movement in the wood substrate from changes in temperature or flexing.

2. Therefore, the type of planking in the wooden hull is an important consideration. For example, FRP sheathing a carvel planked hull without taking special measures is a formula for disaster. Too much movement in the wooden skin. You can, however, stabilize carvel planking by replacing the caulking with softwood splines set in an epoxy based adhesive. (Use heartwood only and avoid sapwood for the splines like the plague.) Or you can first sheath the carvel planks with a thin wood strakes laid diagonally, again in an epoxy-based adhesive. Double planked, double diagonal, and strip planked hulls are not as difficult as carvel to do well. Riveted lapstrake? Forget it.

3. Always us epoxy-based resin in preference to polyester or even vinyl ester. Epoxy forms chemical bonds with virtually all materials, unlike polyesters which bond well with themselves but not really well to other materials and poorly to moist or oily materials (which an older hull is likely to be). My personal preference is for an epoxy resin co-reacted (cured) with a polyamide such as Versamid 140. This produces a polymer that is relatively flexible with excellent abilities to bond to slightly moist or even slightly oily wood substrate. Mix one-to-one by volume, produces an approximately 60/40 mixture by weight. Depending on ambient temp, pot life will likely be about 30 minutes. Do not use mixed material that has stood around too long.

4. Always sand the hull exterior to clean wood. You could then use a vacuum bag to lower the ambient atmospheric pressure, which will literally boil out much of the residual moisture that's collected in the hull skin. Sand with coarse grit to open up the wood grain and to improve the mechanical bond of the cured polymer. When clean and dry, apply the sheathing in the form of fabric pre-wetted in a tray with the epoxy adhesive. Use stainless steel staples to hold the wet fabric in place. Squeegee out excess resin. You can remove the staples after the last layer of the sheathing takes an initial cure, but you could also simply overcoat with more epoxy resin. Always lay anepoxy layer over the previous layer within 24 hours to assure that maximum active chemical bonding takes place. After about a week at normal temperatures (77+ degrees), sand lightly and apply an epoxy bottom paint primer/barrier coat, then bottom paint.

5. Your best chance of success will be if you use a stretchier fabric, but these are often a bugger to sand. S-glass works, but comes in many different forms, so check with your local distributor for availability and recommendations. And understand that applying a sheathing is not the same as laminating a "second" hull on the outside of the first. In the case of a sheathing, you don't want to build up unnecessary thickness, you want maximum strength and resistance to delamination and cracking per unit thickness. And flexibility works in your favor to absorb differences in coefficients of expansion between the wood and the FRP covering. Remember, the sheathing is a protective, leak-resistant covering not intended to replace the structural properties of the wooden hull. If your wooden hull can't support the structural loads of being at sea, forget the entire project.


Good luck and cheers! -- Phil Friedman

 

[Andiamo2018]

Repair wood with wood...and maybe a lot of epoxy. If you plan on having a boat for 40 or more years then wood is probably less maintenance as long as you keep up with it. Fiberglass does absorb water and if the boat is used, flexed etc it will eventually (at best) need to be ground down and gel coat re-applied.

I have a wood sailboat and a fiberglass trawler and there are big pros to both. The sailboat is from 1963, trawler 1984.

The sailboat is strip planked and I did have to put in a lot of splines (routed out 1/4 in between strips) and epoxied in new wood. I did it in the summer wearing mostly just shorts. For two weeks every morning I would use a hand plane to fair out the splines I epoxied in the afternoon before. Then fill the holes left from the guide. Mid-day I replaced keel bolts (which were mostly fine), some more keel work and had the prop balanced. In the afternoon I routed out for new splines and epoxied them in. Fairing the epoxy early when it was only around 70% cured was pretty easy - a nightmare when I was hungover and didn't start till later in the day.

The funny part though was a guy a few boats down whose hull was tarped off. He was grinding for days on the gel coat. He came out one afternoon, dressed like an astronaut, covered in dust and looking like cancer waiting to happen. He said I was brave having a wooden boat.

 

[Vashon_Trawler]

This is passionate about not fiberglassing over wooden boats--particularly vintage ones! I can't imagine the cost of removing all that fiberglass!

 

[Pau Hana]

For all who are proponents of glassing over a wood hull (not of original construction)- do you have such a vessel insured, and if so, by whom?

 

[Simi 60]

.

The sailboat is strip planked and I did have to put in a lot of splines (routed out 1/4 in between strips) and epoxied in new wood..

I would suggest you had a carvel planked boat.

Strip planked is a construction method using thin, light timber core like western red cedar.
Both sides are then glassed in a stitched fabric and epoxy resin making a lightweight composite sandwich