Cloth weight and alignment for strip plank boat.

I'm at that most nervous of stages for Canoe builders, ready to apply the first outer layer of epoxy/glass... (Using West System 105/207 epoxy)

The bible (Canoe Craft) talks about 6oz x 60 inch wide cloth - (160gsm x 1500mm wide)
I'm only able to source 1m wide cloth.


I see there being two options here:



Either use 160gsm cloth and lay 1m wide strips across the hull and have 4 - 5 overlaps along the length of the hull


or


Use 100gsm cloth, run two 1m wide strips longitudinally with an overlap under the middle of the hull. This configuration would of give 100gsm cover on the sides and 200gsm on the base of the hull and bow/stern.


I'd be keen to hear what others have done in this instance or advice as to which configuration might be better?

Roy.

Hi Roy

With my stitch and glue kayak (under construction), the hull is glassed (with 6oz fabric) before the deck is attached. The join between the deck glassing and the hull is about 50mm below the sheer line. The actual keel is reinforced with a 2" wide strip of fibreglass tape.

hope this helps

I am in the process of very slowly building a strip kayak. The plans recommend a double thickness of glass below the water line for additional hull protection. Thats the way I would go.
Tony

Thanks people, im tempted to go the two layers of 6oz on the outside then 4 oz internal. Fingers crossed. Excited about the next phase.

The ideal weight of glass depends on the design, the conditions in which the craft is used and the way the craft is treated, particularly during launch and landing.

I have the luxury of being able to launch from sand rather than gravel or rocks, so all my dozen or so strip built sea kayaks were built with one layer of 125gs (4oz) inside and out and my racing kayaks and my racing canoe have one layer of 85 gsm (3oz) inside and out. The oldest of the sea kayaks is 15 years old and the oldest racing kayak is 5 years old and none of them show any signs of having needed any more glass.

People who bounce their canoe or kayak off rocks need an extra layer on the bottom. I don't.

If your design has a noticeable V along the keel, that would be a very good reason to have the doubling up running along the keel. Even without a V shaped hull, I think that the best place for the extra thickness of glass necessitated by the width of glass are working with is along the keel. Run the cloth the full length of the hull.

Unless you need a bullet proof canoe, I don't think you would need a full second layer of 6 oz on the outside. What is the design and how do you plan to use the canoe?

My thoughts are similar to Allan's. I'd rather use lighter cloth for a number of reasons. One is weight because with a hull that is handled by 1 person the weight can be the difference between having a boat that is used often and having one that sits in the shed all the time because it is difficult to move. In your case I suspect this is less of an issue because I'm guessing this is an 18' prospector and it's going to need 2 people to handle it anyway. If it does turn out to be a smaller one then you might want to consider the weight.

I've made 1 S&G and 1 strip hull and used 84gsm cloth on both. The strip boat goes on the sea at least as much as in rivers and spends some time during launches being ground around on pebbles and sand until the right wave floats it fully. This has required some patches over the years but not for any structural damage - it's to make sure the glass stays sealed. I think that no matter how heavy the cloth there will always be areas that wear through the outer layers of varnish and resin and expose the glass. This needs to be maintained.

By doing a strip down each side of the hull with overlap underneath as already mentioned you will have the best of both worlds - a bit less weight, less resin used and thicker glass in the main wear area along the keel. An additional patch each end would be a good idea too as there will be extra wear there when launching and landing in most situations.

The other good thing about the 84g cloth is that it drapes and conforms very nicely. This makes the wet out easier.

The only thing that might really rule out lighter cloth is the size of the canoe - my kayaks are nowhere near that big and it may be a structural issue rather than external wear.

How about some photos of the build so far?

Typically, fabric runs continuously fore and aft and if necessary, a seam down the centerline, where some overlap is beneficial for additional abrasion protection. If the hull is V bottomed, the next logical location for any overlap, is along the chines or bilge turn (round bilge), which is where the hull will flop over and get dragged along the beach. On a V bottom, what I usually do is run a continuous length down the bottom, assuming it can make it around the chine or bilge turn. I trim it to permit the overlap desired, often just above the waterline. Next I do each side separately, overlapping the bottom piece. This seals the bottom fabric seam (at the overlap) and places the fabric in the prefered over lapping from above position.

If the desire is a clear finish, I'll use very light fabric say 2 ounce (70 gsm), because it will still be transparent, with a total of 4 ounces (135 gsm) overlapping at the waterline. If it'll be painted I'll use heavier fabric say 6 ounce (200 gsm), knowing the weave will need to be filled, fairing and paint will cover any sins.

Hi everyone, many thanks for the wonderful feedback. lots to consider.
Firstly the boat is a 16' Bear Mountain Prospector. Western Red Cedar so it will be clear finish.
definitely running cloth longitudinally.
I am also making a glue stich dinghy with my daughter so this will be the glass technique honing arena as this is to be painted.
Going to use 6oz on the dinghy and see how it looks, I'm leaning towards 4oz cloth on the Prospector.

If you want a clear finish, nothing more than 4 ounce fabric or the weave will show through.

I think you have already made your decision and given you want a clear finish probably the right one.

However I'm going to just throw this out there, your strips are your longitudinal fibres so ideally the glass should compliment this rather than duplicate it, if you weren't going for the clear finish and wanted max strength from your cloth you would run it at a 45 degree

angle over the hull so your glass fibres are at +45-45 to the strips, you could sand a 50mm wide strip under the join for the overlap.

Yeah I know, lotta work !

Some people just like being different. ;)

RR