Rough as guts building instructions Skin on frame kayak.

Building the Frame.

1. Mortise the gunwale members at 25 cm centres.

Size the width and length of the holes to suit your rib material

Set the depth of the mortises to about 20 mm (3/4”) ish.

According to the plans you will need to make 17 mortises down each gunwale

starting 25 cm from the end.

Cut gunwale members to length (4.5 meters)

2. Determine the size and shape for the cross member immediately behind the cockpit.

The closest form drawing to this is form number 11... that will be close enough.

On the form drawing, draw in the position of the gunwale member at full size.

The gunwale member should sit with its upper outer corner on the junction of the

dotted outer line and the sheer line and its depth running parallel to the curve of the

form ie its lower outer corner should touch the dotted line.

Now measure the angle between the sheer line on the form and the gunwale

member you have just drawn in... use a protractor or an adjustable bevel gage to

transfer this to your cross member. Cut the angle.

Now measure the distance along the sheer line from the inner upper corner of the

drawn gunwale position to the centre line on the form, double this and this will be

the total length of the cross member.

Now mark the same angle on the other end of the cross member and cut to length.

3. Determine the position of this cross member.

From the plans the aft edge of the cockpit is 35.5 cm behind the paddlers centre of

gravity (LCB) is the same thing. The plans show the LCB at 248.2 cm from the front

so mark the gunwales to position the cross member at 283.7 cm from the front (35.5

+ 248.2).

Position the cross member behind this mark.

Fix the cross member to the gunwale by drilling 2 x ¼” holes and driving in ¼” dowels

or similar. (glue if you are confident)

4. Make and fit the next cross member

Using form drawing #12 prepare a cross member as for the one just finished.

Place this cross member 25 cm behind the first (centre to centre)

Fix as before.

Note: at this point in the construction, the gunwales are running parallel to each

other but should be sitting at the angle set by the bevels on the ends of the cross

pieces.

5. Cut and fit 1 or 2 (as desired) braces between the 2 cross braces you have just fitted. This

provides a little stronger area you can sit on if necessary as you enter the cockpit. (see

drawing) Dowel these as before.

6. Now rope or tape the front and rear ends of the gunwales together... you can now get a feel

for what your kayak looks like.

7. Make a temporary cross member to fit across near the front of the cockpit using dimensions

from form #8. Tack this temporarily into place with some nails, 90 cm in front of the rear

cockpit cross member. You will take this one out and replace it with the arched cross

member when you build the deck.

8. Now is a good time to cut out your two end forms (Bow and Stern) from some pine board or

water proof ply. Cut these to the size of the dotted lines on their former drawings.

9. Now mark and cut the ends of the gunwales such that the bow and stern formers will fit

between the gunwales and a nice “fair” shape is formed. (look at some of the web sites and

photos to see how others have done this) The ends of the gunwales should end close to the

tips of the formers (use some licence here and adjust the positions until it looks right... a

little plus or minus here is nothing)

10. Drill through and fix the formers and gunwales together with cable ties at this stage.

11. Go back to the rear of the kayak and add in 2 additional cross members at convenient

locations (ie: not lining up with rib mortise holes) spaced approximately evenly over the

distance between the 2 cross members you have already placed and the stern. Use

dimensions from nearby frames to help get angels but adjust lengths to achieve a nice fair

curve in the gunwales... keep standing back and sighting along the gunwales. Again use some

licence here but try to stay close to the overall dimensions in that area as measured from

the former drawings.

12. Now you get to make an “anthropometric” decision. You need to make and fit a cross

member ahead of the cockpit which will become your foot brace.

Sit with your back to a wall and have someone measure the distance from the wall

to the balls of your feet when your legs are in a comfortable position.... ie not

completely flat on the floor.

Add 10 cm to this distance (to allow for your seat back etc.) and this is the position

(ahead of the rear cockpit cross member)for the back face of the foot brace.

Determine its approximate length and cut angles by estimating from former

drawings in that area. (it is unlikely to line up exactly with a actual former because it

is based on your sitting length) Try not to have this line up with a rib mortise....

move it out longer if necessary.

Fit this temporarily and check the gunwale shapes for “fair”. Trim the foot brace if

required. Check that the kayak width is still close to that defined by the former

drawings for that area.

Fix this in position permanently as before.

Later when building the deck you will double this up with a curved member added

above this foot brace to give you some more toe room.

13. Add an additional cross brace ahead of the foot brace. Position this approximately half way

between the foot brace and the front.

14. Add an additional (temporary) cross brace half way between the foot brace and the front

cockpit cross brace. Tack nail this temporarily into place. It will eventually be replaced with

another curved member when you build the deck. Check for fair.

15. You have now completed the basic kayak frame.... time to start making ribs!

Making and fitting ribs

1. Cut rib material to the approximate length (longer) of the rib you intend to make. Adjust the

bending strap to near the needed length and then trim the rib material to be a very tight fit

between the notches in the strap handles.

2. Not all ribs will need to be bent... ie ribs near the ends are virtually straight and may only

need a small packer behind the stringer to get a fair line. Those ribs will be made in two

pieces and meet on the keel member.

3. Some of the next few ribs (moving in from the ends) will have bends near the keel which are

too tight to bend... these ribs will also be made in two pieces with the bending confined to

the mid area of each side.

4. Rib length is measured by measuring down the Black Line of the appropriate former drawing

from the sheer line and subtracting the depth of wood left in the gunwale member after

cutting the mortise holes.

5. Set up your bending jig so that you bend ribs that after allowing for some spring back will

approximate the curve shown in the former drawing.

6. Bend ribs so that they lie inside the black line. (when you add stringers along the outside of

the ribs and the cloth on the outside of the stringers the outside surface of the Kayak will lie

approximately where the dotted lines are) You can always pack a rib outwards to help a

stringer lie fair.

Steaming Ribs

1. The golden rule of steaming is..... 1 hour for every 1” of thickness (ie a ¼” thick rib will need

a minimum of 15 minutes in the steamer (timed once the steamer comes back up to

temperature after loading the rib material.) There does not seem to be a down side to

leaving it in longer.

2. The absolute rule of steaming is... you are not steaming unless the steamer is capable of

reaching and holding greater than 95oC (preferably nearer 100oC.... you will never get to

100oC) keep adding heat energy and insulation to the steamer until you can get that

temperature.

3. If the wood has been pre-soaked overnight in hot water (fully submerged) success may be a

little better.

4. Expect failures...... even the professionals who do this daily expect to loose about 10% of the

time.... if you are loosing 80% of the time there is something wrong... check the basics, time

temperature, moisture, timber species.

5. Note: timber that has been kiln dried or which has spent time drying out in very hot sun will

be very unlikely to work. It seems that the extreme drying conditions in kiln drying does

something to the intracellular “glue” which is irreversible... even if the moisture is returned

to the wood. Steam bending relies on softening this glue and allowing the cellulose cells to

slip past each other... cooling allows the glue to set up again thus locking in you bend (more

or less).

6. Mark the centre of the bending strap with a felt pen and mark the centre of your forming jig

so that you can line these up quickly without hesitation.

7. When you bring a steamed rib out of the steamer you have about 10 seconds to get it into

the strap , onto the bending jig and bent to shape... so have everything set up and ready to

go.

8. Place the loaded bending strap into the bending jig with centre marks aligned then pull the

handles smoothly but firmly around the jig keeping the rib in firm contact with the former.

9. A cord or bungy can be used to temporarily hold the handles together while you add clamps

as necessary to hold the strap and rib in place while it cools.

10. Cool for about 15 minutes

11. Remove the strap and transfer the rib to a holder to fully cool and dry out. (overnight)

12. A holder is anything which will help you hold the rib in approximately the right shape while it

cools/dries. ... the completed kayak frame will work for the full sized ribs (won’t help for the

two piece ones.) you may need to use string or tape to hold the middle of the rib down

otherwise the rib could try to change shape to a more rounded circular shape.

13. Check your shape against the drawings once in the holder..... again a rib that is inside the

black line is better than one which bulges outside the line.

Stringers

1. A lot of your ribs will be sitting in the frame already... add in the two piece ones and tie or

tape them temporarily in place.

2. Run you keel member along the centre of all the ribs and see how fair it looks.... temporarily

tie it into place.

3. If you have cut your keel member to about 4.5 meters long it will be longer than the kayak...

this is good.

4. Mark and cut notches in the bow and stern formers to allow the keel member to sit in flush

with the former forming a smooth fair line from the tip of the bow former along the keel

member through to the tip of the stern former.

5. Drill and temporarily tie the keel member to the bow and stern formers and to a couple of

ribs.

6. Check for fair and make sure the keel member is lying down the centreline of the

kayak.....check.... check... check. A twist here and you will be going around in circles on the

lake forever... you may never get home again!

7. Cut and fit the two piece ribs at front and rear.

8. Check each rib one at a time ... is it vertical to the base frame and does it cross the keel

member at right angles? If so, and if it looks fair by comparison to its neighbours then drill a

1/8” hole through the gunwale member and the root of the rib in the mortise and slip a light

nail into the hole to temporarily hold the rib in place... you will later replace the nail with a

skewer and glue.... tie the rib to the keel member with a cable tie.

9. Temporarily tie or tape the stringers to the ribs (2 each side).

10. Play with the position of the stringers at approximately equal spacing between the gunwale

and the keel to achieve:

A nice fair line along the length of the kayak

No ribs likely to be touching the skin.

Place a straight edge across each pair off stringers and stringer to gunwale and

stringer to keel at each rib and look to see that the straight edge does not touch the

rib. (this simulates where the skin will sit)

Move stringers up or down the rib until the straight edge does not touch the rib at

any point.

One stringer will sit quite near to or on the point of maximum bend of the rib (ie the

chine line)the other stringer will sit between the first and the keel.

Recheck for a fair line... do this in an iterative manner until satisfied.

Tie off the stringer/rib joints with cable ties

At the ends some of the stringers will overlap each other... experiment with placing

one stringer over the other forcing one stringer to point into the kayak. This way the

inside stringer will leave the skin surface without causing a bump at the end of the

stringer.

Take care where the stringers meet the bow and stern formers look for ways to stop

the ends poking out into the skin. Tie in place with cable ties.

11. Spend time just admiring your work and looking for things that appear wrong, out of line,

not fair.... correct this now by adding spacers, replacing a bad rib.... whatever.

12. Replace the cable ties with lashing. Try to make the lashing on the outside of the kayak as

smooth as possible as these will show through the skin as little bumps. Tie all knots inside

the kayak for the same reasons.

13. Check all the time for fair lines as you tighten up the whole frame and it becomes more or

less permanent.... up to the end of this point anything can be removed, modified or

tweaked.

14. When sure that your shape is good....Replace the temporary nails holding the ribs in place

with small dowels or skewers and glue the ribs in if desired.

15. Now is a good time to stain and varnish the frame.....you will have to do more when you put

the deck on but at least you wont have to reach through wet ribs to paint the insides of the

kayak.

I will do the cockpit and deck and the skin directions later.