How to: Stitch and Glue building method

Stitch and glue building method:

The stitch and glue

building method for kayaks

has been around since the 60’s.

It mainly consists of tying

wooden panels together with

pieces of copper wire

(stitching) then using epoxy in

the seams to hold them

together (gluing). Very often

the whole thing is coated

inside and out with a sheet of

fiber glass and epoxy. This

produces a very strong and

light weight kayak.

 

Below is a brief overview of the materials and process. The following is merely

our recommendations based on our experience and not meant to be implied as being

the best or only way to do things.

 

Any recommendations we make for products in this guide are not paid

advertisements. They are simply things we found helpful in our own experiences.

 

Wood

 

The recommended wood to use for a stitch and glue kayak is BS1088 3mm or

4mm thick Okoume. This is marine grade African mahogany plywood. People might use

4mm for the hull and 3mm for the deck. Some choose to use 3mm for the whole

thing as to reduce the overall weight of the boat a bit but we do not recommend

doing so. We prefer the whole thing in 4mm.

 

Visit www.Okoume.org for a list of BS1088 suppliers.

 

Epoxy

There are many good epoxies out there. System Three and West System are two

very good ones. www.jamestowndistributors.com has a nice selection of epoxy and

many other things for boat builders. The more you know when it comes to epoxy and

how to handle it the better off you will be.

 

The epoxy you will want to use will be a two part system. The resin (part A) and

the hardener (part B). BE SURE TO LOOK AT THE MIXING RATIO FOR THE

RESIN AND THE HARDENER. The mixing ratio is crucial. Any other mistake you

make while building can be fixed with sand paper or epoxy or fiber glass or a little TLC.

But, if you get the mixing ratio wrong while scarffing the joints or wetting out the

fabric, you are in big trouble! If not done correctly, the mix (if it even cures)

will be too brittle or not strong enough to be safe and will need to be undone

and fixed.

 

The temperature of the environment you are working in will affect the cure times

for the epoxy. Warmer temps will result in faster curing times.

 

The epoxy reaction between the resin and hardener is exothermic meaning it

produces heat. Since heat affects the cure time and the curing process produces

heat, the less surface area the mix has the shorter the working time will be.

This is because less surface area equals less heat dissipation.

 

Another thing to know about epoxies is there are different types of hardeners; fast,

medium and slow. These are used in different temperatures and have different

working times.

 

For a complete guide to using epoxy please download The Epoxy Book from System Three.

 

Fiber glass

 

You can use 4 oz. or 6 oz. fiber glass cloth for glassing the insides of the shell and

the deck but we don’t recommend using 4 oz. cloth for the outside hull simply

because it will be less durable than a heavier 6 oz. cloth. It would be a real

shame to run your boat up on a rock and have it put a large gash deep in your

hull.

 

Fiber glass tape is a narrow cloth with woven edges to avoid unraveling. For the seams you can use 3 or 4 inch fiber glass tape.

 

Varnish

The only kind of varnish we recommend is Z-Spar Captains Varnish. It is a little more expensive than the alternatives but the results are well worth it.

 

Just like when working with epoxy, working with varnish has its challenges. To avoid getting bubbles in the varnish, stir it slowly instead of shaking. Be sure to avoid drips and runs when applying the varnish to the kayak by not overloading your brush. A light sanding or wet sanding is needed between coats to ensure proper adhesion to the previous coat.

Straps

 

It is very important not to use nylon straps to secure your hatch covers. Nylon

tends to stretch when wet and also rots after time when exposed to the elements.

Polypropylene webbing will not stretch and is water/rot resistant. Visit

www.strapworks.com for webbing, plastic slides and buckles.

Scarffing plywood sheets together

 

Scarffing is a technique by which two sheets of plywood are connected to create

one long sheet. This can be done many ways but our personal favorite is simply

to stack the plywood sheets with a two inch space between the edges and use a

belt sander to sand them down smooth.

 

Be sure to sand evenly as to avoid a wavy edge. Once the edges are all uniformly

sanded down they are ready to be put together with epoxy.

 

Cutting out paper plans

 

When ordering from us, you will be emailed a zipped jpeg image of the plans for your boat. Take the jpeg image to a print shop to have it printed out in full size. The plans will include the full sized panel plans for the deck and hull as well as the bulkheads in the kayak. You will connect the paper panels directly to the wood either with tape or some other adhesive. The paper panels will need to be cut out before being taped down to the wood.

 

 

 

 

Take your time to cut the paper plans out carefully. While cutting out the plans

remove excess paper and tape the paper panels down to secure them to the plywood

to prevent shifting. If the paper bends and shifts on the plywood it will cause

incorrect panel shaping when cutting the wood. Do not rush through this step.

 

 

Drilling out stitch holes

 

Our plans have predetermined stitch points marked to help ensure accurate

alignment of panels during assembly. This is critical in producing a straight

and properly assembled kayak. Under Edit/Preferences in the software you have

the option to specify how far apart you wish to have the stitch marks in the

full size plans. The default is 4 inches. You also have the ability to set the

stitch mark length which has a default setting of .25 inches. Before cutting out

the panels drill a hole through the end of each stitch mark inside the panels.

Drilling out the stitch marks before cutting is important because the paper

usually gets torn up and ruined during the cutting stage.

 

 

Cutting out wood panels

 

It pays to take your time during this step. Some builders like to use a Japanese

hand saw for this step because it gives you good control. Personally, we like the

saber saw with a metal cutting blade. If you use a saber saw, do not use a blade

made for cutting wood; the teeth are too large and will tear up the edges of

your wood panels.

 

Remember, you must cut through two layers of plywood to create two sets of

panels (port side and starboard side). This will ensure that the panels are

identical and will help keep the boat straight and aligned correctly. While not

unfixable, mismatched panels are a bit of a pain to deal with.

 

 

 

 

Wiring the panels together

This step involves lining up the panels according to the predrilled stitch marks. Using 20 gauge copper wire, tie the panels together by running the wire pieces through the holes and twisting them tight. Your finger tips will be very sore by the end of this step but it’s worth it because you will finally have something resembling a kayak.

 

This is when we install any bulkheads that will go in the kayak. They help hold the unglued panels in place.

 

 

Notice the sticks sitting next to the hull. They were used to ensure proper

alignment the hull panels. This was done by laying them perpendicular across the hull and

comparing them to each other. If they all appear parallel then the alignment is good.

 

 

Filleting and taping seams

 

After the deck and hull are stitched together and you have ensured proper

alignment of the panels, you will begin using epoxy mixed with a filler to glue the

seams together.

 

In this step you will be filling the seams from the inside of the boat with an

epoxy/filler mixture. The filler is used to thicken up the epoxy for strength and prevents the

epoxy from running. There are several fillers available but the one we prefer to use is

wood flour or very fine saw dust. Mix the filler with epoxy until it does not run but also

does not appear dry. 

 

Only work with small amounts of epoxy when filleting the seams. This will avoid

waste, haste and excess epoxy on the seams. Keep the seams neat by using a plastic spreader

instead of your fingers and wear strong disposable gloves.

 

After the seams are filled and the mixture is still wet you will apply the fiber tape

to the seams. Wet whatever portion of the tape remains dry with regular epoxy to ensure

the tape’s adherence to the wood.

      

For a complete understanding of how to use epoxy and what to use for epoxy

filler, please download The Epoxy Book by System Three.

 

 

After the inside fillets dry you will cut off all the wire twists on the outside

of the boat and fillet the seams on the outside. When the seams are totally dry,

it will be time for sanding. 

 

 

Sanding Sanding Sanding 

 

If you are the type of person who hates sanding, don’t build a kayak. You will be sanding

the entire time from making scarf joints to sanding the entire surface area the deck and

hull to wet sanding the finish (and much more). There will be no shortage of sawdust in your

workspace so be safe. Use proper ventilation and wear breathing masks. Although

some sanding will have to be done by hand, an electric palm sander is great for most of

the sanding that you will be doing.

 

Hatches 

If you wish to add hatch covers to the deck, this would be a good time to do it. At this time, Stitch –N- Glue Light does not have a hatch design feature. You will have to design your hatches by hand. This isn’t too difficult if you have poster board, a ruler and a round edge for the corners (a roll of tape works great). Simply draw the shapes onto poster board, then trace them onto the deck to be cut out.

Save the cutout portions of wood as they will serve as your hatch covers. You will glass them and varnish them when doing the rest of the kayak.

 

 

Glassing

 

Before applying the fiber glass to the boat, it is recommended that you apply a

thin coat of epoxy to the entire wood surface and let it set. This allows the wood to

absorb the epoxy which will prevent further absorption after the glass is wetted out (to

‘wet out’ the glass means to saturate it with epoxy, bonding it to the wood). If this is not

done prior to glassing, then the wood could absorb the epoxy out from under the glass

creating air pockets underneath. Even if visible air pockets are not present, there could be

weak spots in the wood/glass bond that could delaminate under strain. Such delamination

would compromise the structural integrity of the craft possibly making it unsafe.

 

Allow the glass to lay spread out on the surface overnight to allow the folds in the

glass to settle to the shape of the kayak. Also, be careful not to crease the cloth in any

way, it is delicate and imperfections will be visible later on.

 

When applying the epoxy to the cloth, use either the flat side of a plastic spreader

or an epoxy roller. Remember, working with small amounts of epoxy is very important

during this step. We would not recommend mixing more than 4 to 6 oz at a time.

 

Apply an even amount across the surface of the cloth causing it to become

transparent. Work out any air pockets and remove excess epoxy as to not allow the cloth

to float off of the wood. Excess epoxy adds weight but does not add strength to your boat.

 

 

Apply glass to both the inside and outside of the deck and hull. When doing the

insides, be careful not to allow the epoxy to pool at the bottom of the hull and the upside

down deck. This can be avoided by using only enough epoxy to saturate the cloth.

Remember, if you need to add more to fill out the weave, you can do so later on.

 

After the epoxy has set, trim off the excess cloth around the edges with a razor

blade.

 

Cockpit Coaming

 

At the time of this writing, Stitch–N- Glue Light does not provide forms for the

cockpit coaming. It is possible however to use the cockpit cut out portion of the deck

panel from the original plans to obtain the shape of the curve of the coaming. Using this

curve you can then expand it inch and then 1 inch to get the shapes of the coaming

pieces. Trace and cut out the shapes onto poster board.

 

When connecting the coaming pieces to the deck use spring clamps. The perfect number of clamps to own when building a kayak is about... two million. In other words you can’t have too many. You will also use them to connect hatch cover lips.

Connecting Deck and Hull

 

The two shells are now ready to be joined. You can use ratchet straps and packing tape to hold the deck to the hull when gluing them together.

 

Fillet the inside seams, and around the bulkheads to make them water tight. This may get a little tricky down around the ends of the kayak so use a small cup on a stick to reach these seams through the hatches.

 

Again, use small batches when working with epoxy. This will prevent it from pooling in any one area.

 

After the inside seams are set, remove any straps and tape that were used to hold

them together. Now fillet the outside of the deck/hull seam to complete the connection.

 

 

You will need to sand down the newly filleted seams and an overall light sanding to get

the surface ready for varnish.

 

Varnish

 

You can take as long as you want on this step doing as many coats as you wish. We prefer four or five coats. Between coats of varnish you will need to do a light sanding or wet sanding to ensure adhesion to the previous coat.

 

Remember to varnish the hatch covers as many times as the kayak to ensure consistency.

 

 

End Pours

 

The purpose of the end pours is to strengthen the ends, secure the deck to the hull

and to provide reinforcement for hand loops (for carrying the boat). You will only need

half a cup or so to do the job on each end. Mix the epoxy with micro-balloons to the point

where it’s thickened up but still able to run. Stand the kayak on its end and pour the mix

into it allowing it to settle at the tip. Once set turn the kayak over and repeat on the other

end.

 

Inside the cockpit

 

It is now time to think about the seat and everything that goes with it. You can either use a pre-made seat or make your own. Most builders prefer to use minicell foam for their seats. Minicell is easy to shape using course sandpaper or a grinder. A two inch thick block of foam will give enough cushioning for a comfortable seat.

 

Foot braces also need to be installed. There are many types of foot braces and you will need to decide ahead of time which type you will be using. If you will be the only user of the kayak you can install wooden blocks for foot braces.

 

For aesthetic as well as performance reasons, we prefer not to use bolts through the hull to install the foot braces. Instead, we install our foot braces with studs glued onto the hull inside the cockpit. If you use studs, it is easier to glue them in place before connecting the deck to the hull.

 

Deck Rigging

 

Finally, it’s time to finish out the deck rigging. Remember, not to use nylon for webbing on your hatch covers.

 

We use quarter inch shock (bungee) cord for the elastic deck webbing. The amount of webbing you use will be up to you but will be dictated by the number and position of hatches you have.

 

Pictured right is the pattern we like to use for our shock cord installed on the deck. Below, the Double Fisherman’s knot is the knot used in this pattern.


Finished!!!

 

Congratulations! You have designed and built your very own work of art. Go show it off

and enjoy!!!