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Stick to 4 ounce cloth. *Pic*
By:Paul G. Jacobson
Date: 10/31/2007, 9:53 pm
In Response To: Material: Fiberglass (Dave)

: Hello All,
: I am about to order fiberglass for my Outer Island and I have a few questions
: maybe someone can help me with.
: 1) Can I get away with ordering 6 and 4 oz in just the 38" width?

Yes. You are being charged by the running yard, but using it by the square yard. Grab a calculator and do the math. You may find that buying a wider width is more economical.

A big thing to consider is how you will cut the cloth. If you use the cloth in line with the boat then you'll cut out a large oval piece for covering the hull. That leaves a lot of waste in the left-over corners. However, by spacing the pieces which you are cutting from the bolt of cloth, you can get large enough "waste" to supply you with the extra reinforcement you want for the football area under the hull, reinforcements under the deck, and for the floor area inside. A good layout means you can buy less, and save money. Tape together a few pages from the daily newspaper, make a piece twice as long as your boat, and 38 or 60 inches wide. You don't need to be exact, but come fairly close. Try to warp this around your boat. use a marker and see where you are going to make your cuts. Realign the paper and use a different marker to see where you'll cut this time. Remember that your deck can be done in two pieces. One in front of the cockpit and one behind it. Take a look at the picture (below) of a possible cutting pattern when using wide cloth. See if you can do something like this by using your paper mockup. it only takes a few minutes, and it will give you the answer on whether 55 or 60 inch wide fabric is going to be the best buy, or not. Cloth sizes are nominal, by the way So called 38 inch cloth may be only 36 inches wide, and 60 inch cloth may come to you at about 55 or 56 inches wide. If you are cutting off the selvedge edges you'll lose another inch or so on both edges.

: Will
: it be wide enough when the 'glass is laid on the hull on the bias?

ANY width will work when you lay the cloth on a bias.

There are three reasons that come to mind for why people apply the glass on a bias.

1). One is to get the best strength by having the glass fibers running at 45 degrees to the axis of the strips. I thinnk this was tried, and didn;t work as well as expected. As I recall, you'd get the best strength with the greatest number of glass fibers perpendicular to the length of the strips.

The second is to get the greatest usage from the cloth. By putting on bands of cloth at 45 degrees, you would clip any overhang very close to the gunwales or sheer strips. The next strip would start with that angular-cut edge and have little waste. You just have to remember that you'll have seams, or areas where the cloth will overlap as you apply one bias strip next to another. If you overlap the selvedge edges of the fabric you'll have the thickest bumps to sand down. If you cut off the selvedge edges your overlaps won't be as thick, but watch it when you apply the resin so you don't fray the edges .

The third reason I've heard for using cloth on a bias is that the cloth can deform to fit the curvature of the hull better. If you clip off the selvedge edges and tug gently you can put a very deep curve into a flat sheet of glass fabric, which is great to get it to fit over the ends. If you go this route, be VERY gentle with the tugging. Once you get the fabric to curve it doesn't like to return to being flat again.

Personally, I use the cloth straight in line, and use pieces applied on a bias just at the ends for additional reinforcement.

: 2) In the instructions that came with the plans, it said to put the football
: and stem pieces under the outer layer, while this method seems to be a
: little less work and less mess, does it leave an outline that shows
: through the outer layer and if so will fill coats and a little sanding
: clear that up?

When you cut the football shaped piece it is going to start unraveling. As you squeegee on the resin you'll be dealing with lots of loose straggly strands. However, if you cover the football piece with a solid sheet of glass, then your squeegee can not easily snag the freshly cut edges. They are physically under that overcoat of glass fabric. With a tight weave glass it can be difficult to force resin evenly through the top layer to get a good wetout of the bottom layer. There are ways to deal with this. A slower setting resin will have time to wet things through. You can paint a layer of resin on the hull and roll your football piece right into it, then cover immediately with the next layer of glass before trying to work the resin in. Or, you can buy a normal glass weave, which should be open enough to not give you problems.

I've found that I do get some air bubbles trapped under the glass, and I get more in the area right at the edge of that buried footbalL. I've ignored them and they have caused no problems, nor has anyone ever noticed them. (except me.)

I found reinforcing the football area was overkill. My suggestion is that you skip it. Build without the extra glass on the football area. Paddle the boat for a few weeks before you think of varnishing it. The UV it gets during this time won't hurt it. You can let the lake water wash off any amine blush, and you can take a look at where you are getting scratches on your boat. If you get several deep scratches, put patches over those areas, and only those areas. Since there is no varnish on, you won't need to sand off the varnish to get your reinforcements to stay attached.

My partucular put-in area tends to scratch the sides of my canoe, about 2 inches below the gunwales. So that area will get more glass. Probably I'll put on a 4-inch-wide strip about 10 feet long, and feather in the edges with gentle sanding. I get scratches right along the keel line. It is the deepest part of the boat, and most likely to hit the rocks. Again, a 4-inch strip. If it looks like DEEP scratches, then I can put on a second strip.

I'd stick to 4 ounce cloth for all your work. In the areas where you have expressed a desire for the greatest reinforcement, if you REALLY want to go that heavy, you can put on 4 layers of 4-ounce cloth. That will give you exactly the same amount of glass (12 ounces per square yard) as two layers of 6-ounce glass. But two layers will be 8 ounces, and a good compromise, being thicker and stronger than a single layer of 6-ounce glass.

If you stick to 4-ounce cloth and the 38" width you may end up buying a longer length of this--and that may entitle you to a quantity discount. So, instead of buying , say 12 yards of 6 ounce and 12 of 4 ounce, you would buy 24 to 30 yards of 4 ounce, and maybe get a 10% to 15% discount when you buy 25 or more.
It pays to ask.

: 3) Has anyone done this with 4 oz under the 6 oz outer layer? Is there much
: durability that I sacrificing over weight savings?

For the outside you are getting "ding" resistance by making the layer thicker and heavier. you pay for that in increased use of resin and overall weight. You are probably better off going with a single layer and patching any serious dings at the end of the season. The patches tend to be invisible, and you can put on a second layer of fabric if you keep seeing dings in certain areas.

: 4) With the standard 6 oz outer layup on the outside, can I get by with 4 oz
: on the inside of the hull?

If you have heavier cloth, use it on the inside. If you are going to double layer for strength, do it on the inside, do more than just the bottom football, and put one layer at a 45 degree bias and the other layer straight in line with the strips. That is probably overkill. If you want ding resistance on the outside, consider adding powdered graphite or aluminum powder to the epoxy. This makes a tougher epoxy, but it is not clear. Check the last few weeks of postings. Pruden is playing with a white boron material for the same purpose, and some people have tried Teflon(R).

: 5) can I use 4 oz on the inside and outside of the deck?

Absolutely. And in the areas close to the cockpit, where you'll put the most strss on the deck, put one of two extra layers on the inside. That give you 8 to 12 ounces of glass (on the inside)in a band, say 12 to 18 inches fore and aft of the cockpit. The outside is covered with the thin, transparent layer of glass, and the reinforcing is un noticed underneath.Do you weigh more than a couple hundred pounds? No reason not to put 4 layers of glass under the deck. Mke each layer an inch or two wider than the one on top of it, and you'll be able to taper the edge of the stack to blend neatly into the rest of the boat, which really doesn;t need the extra weight.

: I am using 3/16" strips and its alot thinner than that in some areas,
: like probably 1/8" so I want to avoid as much oil canning as
: possible.

Let's do some quick math. A canoe or kayak with an area 16 feet long and 2 feet wide in the water has about 16 square feet of wet surface area. At 144 square inches to a square foot. this is 2304 square inches. I'll make the calculations simpler and work with 2000. If the boat weighs 40 pounds and you load it with 160 pounds of paddler and gear, you are going to displace 200 pounds over those 2000 square inches. That works out to a measly 0.1 psi, or one-tenth of a pound per square inch. As long as the boat is supported by the water, it is being squeezed evenly by those 200 pounds of displaced water. Should the boat come out of the water (say surfing on a wave) then all the weight and pressure will affect a much smaller area. Will it oil can? Maybe. If the pressure is great enough that can happen to any boat. But the nice thing about these boats is that should something like that happen, a few seconds later the forces will change and the boat will spring right back into its old shape. It has a tremendous memory, and those thin strips will flex under sever loads, rather than snap.

: The boat will see some action on the rocky shores of Lake Superior.

Keep the action on the water, rather than on the rocky shores, and your boat will last longer. If you are going to have frequent encounters with rocks you might want to consider epoxying on "grunge strips". These are simply extra cedar strips along the sides and the keel line. They can be bare, or coated with two coats of resin, but you don't want to glass them. They serve as fenders and get scratched up by the rocks. Every year you sand them smooth, until the time comes when you have sanded them completely away. Then you glue on another one. They don;t look pretty, but they do a good job in bad environments. Alternately, look for inflatable or foam fenders. Pool noodles can be used, too.

Hope this helps.

PGJ

Messages In This Thread

Material: Fiberglass
Dave -- 10/30/2007, 8:20 pm
Re: Material: Fiberglass
Pedro Almeida -- 11/2/2007, 9:38 am
Stick to 4 ounce cloth. *Pic*
Paul G. Jacobson -- 10/31/2007, 9:53 pm
Re: Stick to 4 ounce cloth.
Mike Savage -- 11/1/2007, 8:01 am
Re: Material: Fiberglass
Pedro Almeida -- 10/31/2007, 8:11 pm
Re: Material: Fiberglass
Bill Hamm -- 11/1/2007, 1:11 am
Re: Material: Fiberglass
Bryan Hansel -- 10/31/2007, 11:28 am
Re: Material: Fiberglass
Bill Hamm -- 10/31/2007, 1:24 am
Re: Material: Fiberglass
Paul Kueffner -- 10/30/2007, 11:03 pm
Re: Material: Fiberglass
JohnK -- 10/30/2007, 10:39 pm
Re: Material: Fiberglass
Oliver Bloch -- 10/30/2007, 9:49 pm
Re: Material: Fiberglass
charlie -- 10/30/2007, 9:08 pm