Looking for experienced boat builders here. I am building an okume kit
kayak and am wondering if I can save weight by not placing a full glass
layer inside the hull.

My thinking is that I can get away with only glassing the butt joints
and edges on the inside along with a thin coat of resin for
waterproofing. Yes its going to be weaker (no fiberglass to take the
compressive forces) but has anyone done any tests to see how much
weaker?

If I have to I might just glass the cockpit area to help with required
durability (feet, stones and sand). Will this create any weird foces
beyond the bulkheads? (My boat will be 17 feet long).

Links to experiments on this would be great!

Thanks
Gary

wrote:
Looking for experienced boat builders here. I am building an okume kit
kayak and am wondering if I can save weight by not placing a full glass
layer inside the hull.

My thinking is that I can get away with only glassing the butt joints
and edges on the inside along with a thin coat of resin for
waterproofing. Yes its going to be weaker (no fiberglass to take the
compressive forces) but has anyone done any tests to see how much
weaker?

It's a lot weaker. Someone on the Kayak Building Forum
(www.kayakforum.com) did a bunch of torture tests on a variety of
layups. The differences in strength were pretty stiking.

You need to put this in the context of how you intend to use the boat. Yes
the hull will be less strong with only the outside glassed, but it doesn't
mean it going to fall apart on you. I have a stitch and glue canoe that has
no glass except for 2 inch tape on the seams. My friend has the same boat
built the same way. We use the boats hard but don't abuse them, they have
never given us any cause to be concerned, granted it's only flat water
paddling. We have been in some situations that should have caused major
damage to the boat but nothing happened.
I guess what I'm trying to say is that if you foresee rough use of your
boat, then ease your mind and glass inside and out.

Bill

wrote in message
oups.com...
Looking for experienced boat builders here. I am building an okume kit
kayak and am wondering if I can save weight by not placing a full glass
layer inside the hull.

My thinking is that I can get away with only glassing the butt joints
and edges on the inside along with a thin coat of resin for
waterproofing. Yes its going to be weaker (no fiberglass to take the
compressive forces) but has anyone done any tests to see how much
weaker?

If I have to I might just glass the cockpit area to help with required
durability (feet, stones and sand). Will this create any weird foces
beyond the bulkheads? (My boat will be 17 feet long).

Links to experiments on this would be great!

Thanks
Gary

Gary:
I've built three 17' okume S&G VOLKSKAYAKs, and been in on the building of about 10 others. None was glassed inside and out - in fact, only one was completely sheathed outside. We use 4" tape on the seams, usually doubled along the keel line, and that's about it; lately, tho, we have also started to glass the cockpit floor to protect against grit, etc. We do, however, make sure that every nook and cranny gets multiple coatings with epoxy (3-4 outside, 2-3 inside).
While we don't torture-test our 'yaks, we're far from gentle with them; I've whacked rocks, banks, and beaches, dropped 'em, chucked 'em on and off roof racks, stored 'em outside in summer and in an unheated basement at the cabin in winter. My first VK, the RightWind, is now six years old, and shows absolutely no deterioration beyond the cosmetic damge you'd expect from Newfoundland's rocky shores. Pls feel free to e-mail if you want more info/pix.

Regards,
Rick Hayes
Upper Gullies/Eastport
Newfoundland
--
"You Shouldn't Have Joined
If You Can't Take A Joke"

Royal Navy Axiom

wrote:
Looking for experienced boat builders here. I am building an okume kit
kayak and am wondering if I can save weight by not placing a full glass
layer inside the hull.

My thinking is that I can get away with only glassing the butt joints
and edges on the inside along with a thin coat of resin for
waterproofing. Yes its going to be weaker (no fiberglass to take the
compressive forces) but has anyone done any tests to see how much
weaker?

If I have to I might just glass the cockpit area to help with required
durability (feet, stones and sand). Will this create any weird foces
beyond the bulkheads? (My boat will be 17 feet long).

Links to experiments on this would be great!

Thanks
Gary

How about asking the designer? If it's 4mm I would not omit the
glass, for 6mm / 1/4" sure but that's my opinion

Evan Gatehouse

If I understand you correctly, you don't wish to use any glass on the
seams formed by the hull panels.

If you ever high-center (get caught like a teeter-totter) on a rock or
log, you'll probably crack that seams.

Can you do it? Sure. Should you? Probably best to ask the designer. But
my personal vote is "no".

Matt - jemwatercraft.com


wrote:
Looking for experienced boat builders here. I am building an okume kit
kayak and am wondering if I can save weight by not placing a full glass
layer inside the hull.

My thinking is that I can get away with only glassing the butt joints
and edges on the inside along with a thin coat of resin for
waterproofing. Yes its going to be weaker (no fiberglass to take the
compressive forces) but has anyone done any tests to see how much
weaker?

If I have to I might just glass the cockpit area to help with required
durability (feet, stones and sand). Will this create any weird foces
beyond the bulkheads? (My boat will be 17 feet long).

Links to experiments on this would be great!

Thanks
Gary

Gary, I made 20' rowing shell from 4mm okoume designed by clc boats. The
instructions called only for fiberglass tape over filleted seams. Insted of
6oz prefabricated tape I used strips cut diagonally from 4oz fabric. This
creates a kind of biaxial arrangement of fibers that allowed me to save some
weight in glass. However I believe that the most weight saver are thin
fillets. Epoxy is the heaviest component in the laminate. Removing glass
will save some weight, but probably not as much as you might expect. You'll
still have to epoxy the panels. Also cut and align the panels precisely so
that there are no gaps thet need to be filled with epoxy. Remove the wires.
If the instruction calls for nails for attaching the deck, use the screws
instead. After the glue sets remove them and fill the holes with epoxy. Use
masking tape when filleting and scrape any excess epoxy before it fully
hardens. Apply thin epoxy coats with a squeegee and again scrape away any
sags and runs. Scraper will be your most used tool at this stage.

Please be aware that rowing shell is not supposed to hit rocks.

Also weight reduction is being discussed heavily at CLC forum
http://www.clcboats.com/forum/bbs.pl/

Happy building!

wrote in message
oups.com...
Looking for experienced boat builders here. I am building an okume kit
kayak and am wondering if I can save weight by not placing a full glass
layer inside the hull.

My thinking is that I can get away with only glassing the butt joints
and edges on the inside along with a thin coat of resin for
waterproofing. Yes its going to be weaker (no fiberglass to take the
compressive forces) but has anyone done any tests to see how much
weaker?

If I have to I might just glass the cockpit area to help with required
durability (feet, stones and sand). Will this create any weird foces
beyond the bulkheads? (My boat will be 17 feet long).

Links to experiments on this would be great!

Thanks
Gary

I was always planning to tape the inside seams with 4oz eglass, was
just thinking about not glassing the whole inside with a single sheet.
High center is not something I had thought about... Beach takeoffs and
landings could create that situation. The wood I am using is 1/8th
Okume and I wonder if an extra 4" strip down the keel line would
suffice on the inside assuming Im a carefull paddler (could still get
into rough conditions though)

Found some good info on stress tests done for cedar strips but none of
them were only glassed on one side.

Manufacture is liable if I sink and die based on their reconmendations
so they can only say to follow the directions.

Thanks for all your posts so far

wrote:
The wood I am using is 1/8th Okume

If you're using plywood that thin, do yourself a favor and glass it on
both sides. Unless you screw up by making huge fillets and endpours,
your boat is going to be featherweight anyway (probably under 30#), so
what difference is an extra couple of pounds for full inner glass going
to make? Unless this is strictly an experiment to push the limits of
light weight, what's the point? Do you want a boat that you can actually
paddle regularly without worrying about damaging it?

There's a concept in cycling commonly called "stupidlight", the
lightening of components to the point that you sacrifice functionality
and durability. It applies to kayaks too. Light weight is not the be-all
and end-all and there are limits to how light a plywood boat can be. If
you really want something ridiculously light, build one of Platt
Monforts "Geodesic Airolite" boats. http://gaboats.com/

I'm with Brian on this. Re. endpours, many of clc kayak builders left out
endpours and replaced them with full-length sheer clamps. First longer than
required clamps are glued, then cut to a bevel at bow and stern using a
string streched from bow to stern as a reference with side panels spread to
required width with a stick. If you don't plan to hit things directly with
bow or stern I think sheer clamps will provide sufficient strength and
you'll save a lot of weight. My rowing shell doesn't have endpours.