Tony Grove • Artwork - Boatbuilding - Furniture

Inga Nordic Folk Boat

A new look at canvas decks for wooden boats

Removing all deck hardware and labelling
Removing all deck hardware and labelling while
taking lots of pictures for easy assembly latter

Some people might remember a product named Arobol, later to become Thorpes Easy Deck.  Arobol was originally used to adhere a lagging around pipes, and was found to work great for gluing canvas or fibreglass to wooden decks as well. I remember using Arobol for gluing a sheathing onto decks, and found it had little odour, non- toxic, cleaned up with water and when dry it was waterproof and strong.

Unfortunately, one day I ran out and after searching high and low, I couldn’t even find it under its new name Thorpes Easy Deck. I did get a replacement product from the original supplier who assured me it was the same, but the test samples that were done left me with no confidence in this new product, finding it wasn’t the same at all and I didn’t dare use it on a boat not knowing what it would do. 

The corner knee and  transom on the starboard side had rot
The deck had extensive rot around the chain plates that were going through the deck on the port and starboard side
The corner knee and transom on the starboard side had rot that was replaced

I asked a boatbuilder friend (who’s been boatbuilding longer than I’ve been alive) if he knew of Arobol.  He did, and told me that when working on repairing old fish boats and work boats they also used to use, Tite bond II with great success, and with these being work boats under the harshest working conditions possible, I was convinced right away.

The owner is doing the work of wooding the hull
The owner is doing the work of wooding the hull (removing all the paint) and checking for hidden problems

Tite bond II which is a PVA, waterproof when dry, one part glue, used for general woodworking in wood shops, construction and marine industry, the key is that it is water proof when dry.

Since then I have used TB II for gluing down canvas onto plywood decks, several times and found that it has little odour, non- toxic, cleaned up with water and when dry it was water proof and very strong; sounds like a pretty close replacement for Arobol.

Beginning the job

Extensive repairs to the starboard side replacing many half beams
Extensive repairs to the starboard side
replacing many half beams

I have known about Inga, a 1969 Danish built, Scandinavian Nordic Folk Boat for many years. Thirteen years ago I did some work on her for a previous owner, installing a few graving pieces after removing some rot in the transom (still looks good), also extending the wooden spruce mast by about four feet.

The present owner, Roger, asked me to give her a cursory look over when we met at a wooden boat show.   He had concerns about some unusual wood decay on the underside of the deck in the cockpit area.   First off, the wood was wet and being late summer this was a concern.  

The diagnoses was quick to determine, somewhere in the life of this Folk boat, someone had covered the deck with polestar resin and fibreglass.   Back in the early sixties fibreglass was being toted as this new life extender for all those old wooden boats.  Innocently, people could not have known what was to happen after applying this coating of plastic resin and fibreglass and it wasn't until much later it was found to cause the unfortunate demise of hundreds to thousands of beautiful classic wooden boats. 

Sister of oak on the sheer clamp
Sister of oak on the sheer clamp where repairs were made to the clamp; this area is important to keep strong because the chain plate is going though the deck at this point.

What caused these problems was that often the covering was applied over already rotten wood, along with the polyester resin not having great adhesion abilities to wood and when laid on a boat that because of age is already to flexible or has the beginnings of rot, the end result was like putting wet wood into a plastic bag.  First, the fibreglass cracks or delaminates; allowing water to collect by capillary action after penetrating around fittings and through stress cracking, with the water trapped the covering of fibreglass wouldn’t allow any moisture to escape and it accumulates, causing imminent or accentuated rot problems.

We agreed that repairs needed to be done before the rot takes a foothold.   We worked out approximate prices and the owner didn't need too much convincing knowing the work had to be done.   Roger, the owner is a great character with all the ideals and eccentric romance, typical of a Folk boat owner.   He says he is the caretaker of Inga for this part of her life and unlike too many boat owners, he is constantly using his boat every chance he can get.

New mast partner knees were installed
A new stem end of oak was scarfed on
New mast partner knees were installed where there were none before, this helps spread the rigging load
A new stem end of oak was scarfed on
after finding extensive rot, which was
also found in the breast hook where
a new bigger breast hook was installed.

The boat was trucked by a boat mover to my shop to start the process of repair.  The list of jobs had been growing since I originally looked at the boat but for me the main project is the deck with the other small projects just as important to the owner but not as critical.

A new aft floor timber was installed
A new aft floor timber was installed after finding extensive iron rot in the old one.

The first task was to remove all the rub rails and all the quarter round mouldings around the cabin.  Next I started removing and tagging all the deck hardware and thanks to a camera, the job of documenting for later replacement was quick. Then to remove the fibreglass overlay this took about 20 minutes - if this had been anything else, like epoxy and glass, it would have been a very unpleasant grinding job.

The cock pit is getting 4 new ribs and 2 sistered ribs
The prop has been severely compromised be galvanic corrosion and will be replaced.
The cock pit is getting 4 new ribs and 2 sistered ribs.

The prop has been severely compromised be galvanic corrosion
and will be replaced.

Fibreglass had been applied over the original laid deck, of pitch pine which had been fastened down with galvanized iron nails. The nails were almost completely rusted with their heads coming off with the fibreglass sheets, and the iron oxidization reacting with the tannins in the wood leaving the tail black mark of iron sickness.   Surprisingly most of the deck wood was in pretty good shape considering it was so wet.   Wood needs around 18 to 40% fresh water moisture for rot to occur, which this deck’s wood was sitting between, the heavy pitch adding rot protection to the wood was its great saviour. 

About 50% of the sheer strakes were replaced
About 50% of the sheer strakes were replaced port and starboard, mid ship area.

Pattern made for side deck
Pattern made for side deck

Note: Fungus growth (without one of these wood rot will not occur) Moisture – EMC of 20% to 40% (only fresh water, which is why boats are said to rot from the top down). Temperature – 10°C (50°F) to 35°C (95°F) Oxygen – if you submerge wood in water deep enough where the oxygen levels are low, wood can be preserved indefinitely.

New decking forward
New decking forward

Now at this point we could have left it, letting it dry out, repairing the few rot pockets, and refastening.   But after weighing out all the options, like iron sickness, and what the final plan was, of properly repairing the whole deck, we decided to remove the entire old deck which allowed us to address other hidden problems underneath.

After Inga’s wooden deck was removed an overall assessment was done to find all areas around fittings and rigging through the deck, especially chain plates, mast and transom (aft chain plates were attached to the transom) where most of the problems were. 

Painted V grooved cedar under deck
Painted V grooved cedar under deck

Also a serious rot problem was found in the transoms top plank and inner quarter knees plus the stem end and breast hook, that now with the deck off could be easily repaired.  All areas that were susceptible to straining from the rig pulling on the boat were areas that water was creeping into and caused problems.  The right thing to do is to remove and replace all rotten areas and rebuild those areas anew.

Because we were covering the deck with canvas, a new deck needed to be put down and plywood was the obvious choice, being strong and dimensionally stable compared to a planked deck.  It was decided to use locally made marine grade fir for the decking.

The first step is to make patterns for the plywood, and for this I like to use 2 ½” strips of door-skin ply, fastened together with ½” #6 screws in the corners and cross-braced. 

When the patterns are made I allow at least one inch overhang on the outside of the hull, giving room for fitting the plywood around the house and other areas, the overhang of plywood, after fully installed is removed using a jigsaw, hand plane and/or belt sander. 

Tony spreading bedding compound on the deck beams
Tony spreading bedding compound on the deck beams

Is there enough canvas?
Is there enough canvas?

All plywood edges were butted on deck beams and the edges epoxied sealed before they were installed.  We used ½”marine grade fir plywood with a layer of ¼” V grooved red cedar glued and nailed on the under side and then painted off white, to keep things bright inside while giving the look of a laid deck. 

Before attaching the cedar, all the plywood decking was dry fit onto the boat first.  Then by tracing all the deck beams on the plywood under side, it allowed me to nail down the cedar to the underside of the deck so when back in place you will not see any nail holes. Also, with the cedar attached to the deck under side it was easy to paint while off the boat, as the deck beams were left bright.

Ironing out the canvas
Ironing out the canvas

The decking was then fastened back onto the boat with stainless steel screws, about every six inches in the deck beams and every two inches or closer around hatches and through deck fittings; this was done in combination with bedding it down in a marine polyurethane bedding/caulking (Sikaflex).

The counter sunk screw heads were filled with an epoxy faring compound and all sanded smooth. It can’t be forgotten that when cutting out for mast and hatch holes, room is allowed for the canvas to fold over into those areas. As well, after fitting the decking on the boat, any deck edges under the canvas should be rounded to at least ¼” radius so the canvas won’t wear through, as it would on sharp edges.  

After all that work was completed, next came the canvas.  Inga was to receive a 12 oz untreated canvas glued down to the plywood deck using TB II.  The canvas we bought was 10 ft wide by 30 ft long so as the cover the whole boat without any seams. First I draped the canvas over the deck of the boat and trimmed off all the excess (with about two feet over the sides extra), and then cut a hole for the deck house.

Roger on his new deck, with new paint
Roger on his new deck, with new paint

Starting at the fore deck I brushed evenly a liberal amount of the glue at full strength, making sure it’s not too thick and evenly spread, no more than two sq. meters (yards) at a time, so the glue won’t have time to tack up. Then lay the canvas into the glue and apply pressure from the center outwards using a wooden squeegee, its important to remember that too much glue, especially uneven glue can cause problems latter. Then afterwards, before the glue sets up, gently pull the canvas outwards from the out edges, as you go along (note gently! pulling, you are not stretching it like you would a regular canvas deck) and stapling all edges of the canvas with stainless or Monel staples.

Fred & Nancy redoing Inga’s systems
Fred & Nancy redoing Inga’s systems

After letting the glue dry overnight, I started at one end and with a squirt bottle of water and an iron, I wet the canvas and ironed the whole deck. Taking my time making sure I thoroughly ironed everywhere. This would slightly shrink the canvas while reactivating the PVA to assure a good bond. Then when done I made up a mix of PVA with about 30% water and painted the decks with that.

The saturation of canvas with the watered down PVA adds strength to the fibres and helps to ensure adhesion of the canvas that may not have enough glue, also thinning it allows it to sink into the canvas but not completely fill the weave allowing the paint to have a good bond. After it was allowed to dry over a few days, so high moisture is not trapped under any paint.

Then it was primed, using the same brand primer as the paint; after which was coated with three coats of good marine enamel: for the paint Hempal marine enamel was used, I prefer marine enamels for wooden boats over the newer polyurethanes. You can use a none-skid additive but I found that the canvas texture telegraphs through the paint and acts as a good none skid. Lastly, all rub rails and deck fittings were painstakingly and thoroughly bedded and mounted back onto the boat.

I have seen traditionally laid canvas on boats that were around a hundred years old and every time I am excited to see that there are very few problems with the decks and, if anything, because they are able to breathe and work with the boat, they are usually the reason the boats are in such good shape.

Roger sparingly sprinkling some champion on the new deck
Roger sprinkling champagne on the new deck

For doing a glued down canvas on Inga’s deck, was that the owner wished to stay as true to the original decking as possible (meaning canvas) and I like using this method after seeing it used on west coast work boats and it lasts for many years under very harsh working conditions.  Also the cost compared to epoxies and fancy fabrics was about a fifth the cost and the toxicity of materials used (the PVA and canvas) are very friendly to work with; and when the boat reaches the end of its life it will gently be reabsorbed into the environment not leaving as much of a toxic pile like our petroleum cousins.

By Tony Grove

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