1. Get the paper plans, epoxy resin, and plywood.
2. Cut round the shapes on the paper plans, appropriate to your selected variations.
3. Tape the paper shapes to the plywood.
4. Draw round the shapes and cut the plywood to the lines.
5. Stitch the plywood pieces together with copper wire to form the hull.
6. Dot superglue between the copper stitches, and then remove the stitches.
7. Apply thickened epoxy resin to the inside of the joints.
8. Apply fiberglass tape and epoxy resin to reinforce the joints.
9. Use these techniques to build the deck and cockpit.
10. Coat the entire kayak, inside and out, with epoxy resin.
Keyhole Cockpit Design
Careful inspection of a well-designed glass-fibre kayak like the NDK Romany reveals that the side decks by the front of the keyhole shaped cockpit are moulded so as to act as thigh braces. The Shrike family decks in this region are steeply sloping upwards from the gunwales to the cockpit rim. If the keyhole cockpit option is chosen, then when attempting to brace, roll or just paddle in waves, the knees can slide inwards into the cockpit, and the kayak will not be controllable. The remedy is to narrow the opening at the front of the cockpit to the minimum that will enable your chosen size of shoe to pass through the hole when getting in and out of the cockpit. This will then provide sufficient width under the side decks to glue hard foam thigh braces. On the prototype Shrike I made the front of the cockpit opening too wide, and had to create wooden thigh braces glued to the inside of the coaming. This was a time-consuming and unnecessary task.
To improve the bracing for me (6 foot tall and 170 pounds weight) I would now:
1. Create the wings for the thigh braces in the cut-out of the deck plywood rather than in the cockpit top rim. This was my original plan, but in view of the steep angle upwards of the deck I made the wings in the flatter rim for the prototype. Shaping the deck cut-out rather than the cockpit rim enables simpler strengthening of the wings.
2. Cut the wings in the deck cut-out so that the gap between the wings is 150mm rather than the 200mm I used on the prototype. This would better suit the my normal paddling posture.
3. Epoxy glue a 3mm plywood plate, with the same shape as the wings, under each wing, extending under the side decks, so as to strengthen the wings.
4. Further strengthen the wings by covering both sides with glass cloth, and add a large epoxy fillet between the top of the wings and the cockpit rim upstand. Someone will eventually pick up the kayak by just holding a wing, so they need to be strong enough to withstand that abuse.
5. Use contact adhesive to secure shaped hard minicell foam under each wing to create a hook effect for the inner thighs.
The above picture from Morris Ho illustrates this.
From Peter M. from Cornwall, UK: For my 11” masik, keyhole cockpit Shrike I made curved thigh braces from laminated ply using a technique similar to that described in the build manual for the masik. Two pieces of 3mm ply were glued together with thickened epoxy while bent over a former. The former was a section of galvanised downpipe 8cm dia lying on a Workmate. One long edge of the ply was clamped in the Workmate and roof rack straps were used to bend the ply over the curve of the pipe (with suitable plastic covering to stop straps, pipe and workmate becoming one). After 4 days at room temperature I released the straps – there was no spring back from the bent ply. Then I cleaned off the over-generous epoxy glue and cut out two braces, roughly following the pattern of the braces on my Scorpio LV (because I have found these very comfortable and the cockpit profile is similar to my Shrike). I glued and glass taped them into position on the underside of the cockpit side deck area (used 4” tape) with the kayak upside down. Next day I filleted and glass taped them on the upper surface so that tape extended across the top of the brace and up the coaming to the lip (used 7” tape). After a bit of sanding and a coat of epoxy I attached padding (double-lined neoprene from a pair of old pogies) to the underside with contact adhesive. They have proved as comfortable as the braces in the Scorpio. Check out pictures here: http://s1186.photobucket.com/
Alistair from Cornwall left the wings in the plywood deck, and loaded them down with diving weights to achieve the desired angle. This seems a good and simple solution. Some hard closed-cell foam will still be needed to locate the thighs securely.
Made to measure spray decks (skirts)
If your Shrike’s cockpit is of a non-standard shape or size, Reed will make a spray deck to your pattern, as described here. World-wide delivery charges are listed here.
The Aquatherm fabic is light, flexible, and does not absorb water. We use these decks on the Shrikes, other than in very cold conditions, when we use thick neoprene decks and Tuiliqs. The Reed deck in the photo is fitted with the optional bale hole for pumping out bilge water without removing the deck.
Size of sheer clamps and deck fittings
On the prototype Shrike I sized the width and depth of the sheer clamp timber to be sufficient to provide a gluing surface for the deck. However, I also intended to screw simple deck line fittings through the deck and into the sheer clamp. I used 20mm stainless washers, as described in the Build Manual. During sea trials and carrying out contact tows or just being rafted up to another kayak we discovered that these washers could rub against the accompanying kayak, causing damage. I changed to 16mm washers, but this was not sufficient to avoid the damage, and I ultimately used some small solid stainless cup washers. This process could have been made simpler by using slightly wider sheer clamps to bring the deck fittings a little further inboard. I would now use 1” square timber (25mmx25mm), rather than the 25x15mm stated in the Build Manual. If Maroske fittings (see Builders’ Tip below) are used, the size of the clamps can be reduced to 25 x 15 mm. We tried reducing the width of the sheer clamps to12mm, but these proved insufficiently stiff to ensure a fair curve, and the gunwales distorted under the weight of the clamps.
Super Glue, aka cyanoacrylate adhesive, is a wonder material for this project, especially used with the accelerator spray. I use it for assembling the hull panels to enable removal of the temporary copper wires and, for example, fitting the cockpit upstand and rim prior to epoxy filleting and taping. However, the glue when set is very hard. If large drops are used in, for example, the keel joint, when the hull is turned over you will be faced with hard blobs of glue on soft plywood. It is very tricky to sand away the glue without over-sanding the plywood. Make your life easier by only using the minimum amount of Super Glue.
Hot Glue Guns
If aiming to clear-finish the hull, rather than use paint, you may wish to minimize the number of holes in the plywood for the temporary wires. In that case one can use a hot glue gun to position the external and internal molds. Just use a few small blobs of glue. When you need to remove the molds, a sharp tap will break the adhesion. Make sure the glue sticks are suitable for joining timber.
Deck line fittings
The standard low-cost and simple deck line fitting is to use short lengths of folded tape screwed into the sheer clamps, as described in the Build Manual. There are other options:
We use the 3D printed fittings whose printer files are included in the plans download:
Another simple and low-cost solution from Alec Naneti in Romania uses two copper plumbing bends:
Another option is to create Maroske fittings:
I like the simplicity and elegance of Maroske deck fittings, but they are anything but simple to construct. Google “Maroske fittings”. if you are not familiar with the standard procedure. It can be a struggle to pull the PVC tube out after the epoxy has set. To make it easy to extract the tube I first put the wire inside the PVC tube, then wrap the PVC tube with PTFE tape, and then insert the PVC tube into the fibre-glass sleeve. This entire assembly is then threaded through the deck. I use fiberglass tape over and under the sleeve to spread the load, and then thickened epoxy smoothed over the entire assembly. The PTFE tape makes the PVC tubes easy to extract after removing the wire. I use a bottle cleaning brush to remove any remnants of PTFE that stick to the epoxy.
One way of producing lightweight Maroske fittings is to bond in a semi-circle of 3 mm plywood. This minimises the use of the heavy epoxy, and also produces an even curve, thereby facilitating the eventual withdrawal of the inner tube.
When positioning the fittings near the cockpit, bear in mind the need for foot-room. Those in the photo are a little too close for comfort.
Key to open screw-in hatches
The screw-in hatches are simple to install, and they don’t interfere with the elegance of the kayak. However, they can be difficult to undo, particularly if subject to temperature changes. This is only exacerbated by having cold wet hands. I made a simple HDPE (bread or chopping board) key. One side opens the large hatches, and the other side opens the day hatch. I use both hands on the key, pushing and pulling, for maximum leverage.There are a couple of holes for a lanyard to attach it in the cockpit. (No, not inside a compartment…….)
Modifications to the skeg
Paul Krysik from the UK did not use the Kari-Tek skeg wire, but instead used a stiffer variety. To help maintain the ease of motion of the skeg cable he altered the orientation of the skeg wire as it entered the skeg box as well as the angle of the slot to hold the wire in the skeg. In the image below you can see how in images a and b (the original design) the wire has to travel through some tight curves as the skeg moves through its full range of motion. These curves can cause tension and unnecessary friction. Paul altered the angles as shown in figures c and d. His approach substantially reduced the curves the wire moves through with the aim of producing a system where the wire is less liable to kink. The bracing for the skeg box in this modification could with advantage be placed astern of the metal fitting, easing access for maintenance.
Other variations on skeg design are:
From Etienne Muller in Ireland: http://www.etiennemuller.com/SkegProject.pdf
From Erik Frantzen in Denmark: http://justerbarfinne.blogspot.dk/ and links to about twenty here: http://www.kajakbyg.dk/justerbar_finne_skeg.htm
Low profile skeg box
The skeg system shown in the Shrike plans works well with full-sized Shrikes and also with Shrike LVs where the plans are all scaled down, including the size of the skeg box and skeg. However, if only the height of the decks is reduced, as in the Shrike-R, there may be insufficient space between the top of the keel and the underside of the stern deck to accommodate the system. The deck may foul the compression fitting on top of the skeg box.
This can be avoided by installing the compression fitting in the front of the skeg box as shown in the photo below. The following instructions should be read in conjunction with the accompanying photos, and the appropriate section of the Build Manual in the download.
1. Print the paper plans for the skeg box and skeg at 90%, thereby reducing the deck clearance height by about 13mm.
2. Increase the width of the inside of the box to 15mm by using 15 x 12mm cedar internal framing. The overall dimensions of the 90% box are 346 x 122mm.
3. Make a 9mm thick skeg blade from three layers of 3mm plywood, instead of the standard two-layer 6mm thick blade. Before gluing the three layers together, the top curve of the middle layer is profiled to accept the 3mm stainless wire cable in a groove, where it is later epoxy bonded. Cut the inner layer of plywood to accept the wire by reducing the radius of the curved end to a circle centred on the pivot point, and meeting the bottom of the straight slot for the wire, as shown in the area coloured red, which should be removed:
After the three layers are bonded together, taking care to remove excess glue, shape the groove with a round file to accept and guide the free wire over the range shown in the photos, and epoxy glue the wire into just the straight section of the groove:
4. Round the leading edge of the blade and taper the trailing edge in accordance with the NACA 0012 profile, a good shape for optimizing lift at normal kayak speeds: (C.A Marchaj, “Sailing theory and practice”, 1964, pp 281 – 284 & airfoiltools.com)
Give the skeg and box a coat of epoxy, sanded hard, and then a second coat, to ensure smooth contact surfaces.
5. Fit the compression fitting horizontally, with its centre line 95mm above the bottom of the box.
6. When the outer 6mm O.D/ 4mm I.D plastic tube is inserted into the compression fitting, the plastic outer tube should extend into the skeg box by 25mm. With the compression fitting I used, this gave a measurement of 60mm from the outside of the compression fitting to the end of the tube. A pen mark or piece of tape 60mm from the end of the tube helps to position the tube correctly.
7. Fit nylon spacer washers as necessary on the pivot, and complete the box.
The box, when slotted through the keel, will require a height clearance of 119mm from the top of the keel to the underside of the stern deck. A skeg system to this design operates very smoothly, but disadvantages of this design are that the compression fitting and tube are more vulnerable to damage from stowed equipment in the stern compartment, and the available storage volume is reduced.
Joining the long panels for the hull
Building the Shrike is an exciting process, but one tedious task is butt-joining the plywood pieces to create the four long topsides and bottom panels. These are first created by cutting each of two sheets of plywood into five equal width strips. Your friendly local plywood supplier may be able to do this cutting for you, thereby saving a little awkward manouvering in a cramped work space. When you have dry assembled the pieces on your work surface, (as described in the Build Manual), you must make sure the joints are touching, and stay that way while the epoxy sets. I line up the joints so that I can run one piece of tape down several joints in one go, and then lightly tap very thin nails or pins though each corner of each joint into a piece of plywood or wood beneath the joints. I place other pieces of the same thickness wood or plywood underneath the length of the panels to keep the joints level. (If your worksurface is plywood or timber, just lightly nail into that.) A strip of polythene prevents the panels sticking to the baseboard. When the epoxy has set, I cut through the tape, pull out the nails, turn the panels over, and repeat the process, but without the temporary nails.
When cutting the plywood into strips, keep the best sheet of attractive grain for the deck. Sort the strips for color so the topsides do not have a drastic change of color at the joins. Match panel grain at joins where possible. Join the strips with dots of superglue at edges to hold position while taping the strips into full lengths. Lay strips B side up and join these. 30g of epoxy mix suffices for six joints. The next day turn the panels over and tape the other side.
In lieu of scarfs or butts, Tim Manning from Minnesota recommends a 45 degree cut on a table saw.
Bow and Stern protector
You may have noticed in some of the pictures of Christopher’s Shrike-Too and Shrike-R that there are small black objects on the bow and stern. These are protective rubber pieces formed from SuGru a self moldable rubber compound. The original Disko Bay kayak had similar shaped end protectors but they were probably made from wood or bone making these an authentic method of modifying your Shrike. SuGru is very simple to mold in place using just one’s fingers and it’s great for making “bumpers” to protect both your kayak and those things you decide to ram!
We use the excellent Smart Weigh digital scales to weigh the epoxy resin and hardener. The scales have an accuracy of 0.1g and a maximum capacity of 1 kg. They are equipped with a “tare” button, which re-sets the scale to zero after the container is placed on the scale. This is a great feature. The scales cost £6 in the U.K on eBay.
In the USA, eBay has the scales for $18 including shipping. Try “Smart Weigh SWS100” and Amazon.com has them for $10 – try “Smart Weigh SWS1kg”
Using the scales for weighing epoxy is described here.
One disadvantage of the scales is that they have a 60 second time-out, which can be inconvenient.
The importance of sheer clamps
Some kit manufacturers omit sheer clamps, and rely on taping the seams between hull and deck. We strongly advise against this when building with the 3mm plywood. The sheer clamps produce fair smooth curves and enable a very strong joint. We’ve spent too much time mending these joints on $3000 glass fibre kayaks where glass tape has been the sole method of joining the hull and deck.
Tethering Barton-style hatch covers
Peter M. from Cornwall, UK, used ½” 6g A4 s/s pan head screws and suitable washers to attach a nylon R-type cable clamp to the central molding on the underside of the hatch cover. Knotted shock cord (3mm) joins the cover to another R-clamp inside of the hatch fitted to one of the bolts holding the hatch cover rim in place. This means that when the hatch cover turns, the central R-clamp turns freely and the shock cord is not wound up.
Replacing the copper stitches with adhesive tape
Adhesive tape can replace nearly all the copper wires, except a pair at each of the bow and stern. Gorilla tape is too sticky, and liable to damage the plywood. I used Scotch Tough Duct Tape:
This tape has reinforcing strands across the roll, and the tape should be aligned so that the strands cross the joint. I then used CA glue and accelerator, with a couple of copper wires at the stem and stern. This tape did not damage the plywood, though I only left it on for a few hours, removing it once the CA glue had set.
Raising the exterior molds
In the early stages of construction it can be awkward to access the keel line of the hull between the exterior molds, particularly when attempting to adjust the copper stitches or adhesive tape at this point. This access can be eased by raising the molds by fixing them to deeper timbers.
Finishing the edges of fiberglass cloth
Occasionally a clean finished edge is required on an area of glass cloth. This can be when, for example, just the floor of the cockpit is glassed for abrasion resistance, or when a tapered extra keel strip is added. An elegant solution is to use dark colored masking tape around the perimeter of the area, and laminate the glass over the desired area, overlapping slightly onto the colored masking tape. After a few hours, when the cloth is set, but not hard, cut at the inner edge of the masking tape with a craft knife, and remove the surplus cloth and tape. The next day seal the cut line with resin.
Spacing the stern deck beams
Choose the spacing of your stern deck beams to suit and support the perimeter of your chosen hatches, if any.
Black Keel strip
When the hull is left with a clear finish, it is difficult to spot when the keel has been scratched from contact with the beach or rocks. Water can then pass through the scratch and soak the plywood. With the black painted hull on my prototype Shrike, any scratch though to the underlying epoxy is obvious, and I can put a dab of paint on the scratch, thereby sealing it from further water ingress. This issue with a clear finish can be avoided by applying a coat of black pigmented epoxy (10% epoxy pigment) in a strip down the most vulnerable part of the keel, entirely below the water-line. If you taper the ends it can even look elegant. Good quality masking tape is worth the extra expense for this task. I use the blue 3M 50mmn (2 inch) wide tape.
Feathering the edges of the glass fibre tapes
Feathering the edges of the chine and gunwale tapes can be time-consuming and not very interesting work, but one is
rewarded by the fact that the tapes become invisible when the next coat of epoxy is applied. There are several ways in which this task has been approached:
1. The entire hull and deck can be covered with glass cloth. There is a weight penalty, of course, but there are no tape edges to sand. (Dan Couette, Morris Ho and several others have used this technique. See the Gallery)
2. A random orbital sander with 220 grit abrasive paper can remove the edges quickly, but great care is needed to avoid sanding through the top veneer of the adjacent plywood. Christopher uses this technique to good effect.
3. Damian from Cornwall uses a multifunction tool that drives triangular pieces of abrasive paper. The original flexible base plate allowed too much random movement, so he created a plywood triangular plate, and fixed this with double-sided tape.
4. Scrape the edges of the tape with a craft knife blade or razor blade held in a leather-gloved hand, and finish off the feathered edge by hand, using 80 grit abrasive paper. I use this time-consuming but safe method, as did Alistair from Cornwall.
Knee tube for pump
It seems a shame to spoil the lines of a beautiful kayak by having an ugly plastic pump on the deck, however sensible and practical that may be. I install a knee tube under the deck. The knee tube construction is very basic. I use a length of 100mm diameter sewer plastic pipe as a mold, and laminate two layers of whatever glass cloth I have handy round the pipe, using either polyester or epoxy resin. I cut it to length and width when set, and glue some split plastic flat wire sheathing round the ends to protect feet, etc. I now angle the front of the tube for maximum foot clearance. I install the tube with the kayak upside down, using a few blobs of 5 minute epoxy, and later put a fillet of thickened resin down each side. I then install a piece of elastic shock cord across the mouth to stop the pump falling out. Note that you may have to shorten your pump. By removing an end cap this is usually possible. On some pumps I also temporarily remove the handle to shorten the rod.
Reed will supply spray skirts (decks) with bale tubes to enable access to the pump without removing the skirt, if you consider this necessary: https://www.chillcheater.com/aqshop/catalogue.php?id=2911
Thickening epoxy resin when used as a coating
Occasionally one needs to place a coat of epoxy resin on a sloping surface, or on an exterior corner. One example is filling the weave on an existing keel strip, where the angular keel line makes the resin flow away from the apex of the upside down hull, which is exactly where one wants the thickest resin. Another example is filling the weave on parts of the cockpit rim and upstand. On all these I use 10% black pigmented epoxy resin with just sufficient West 406 Colloidal Silica filler powder added to make a “paint” that will still brush out smoothly, but will not run and sag as much as pure resin. This gives a very hard and shiney finish. I first mix the resin and catalyst very thoroughly, then add the pigment with much stirring, and then gradually add the powder until I obtain the desired consistency.
Installing a commercial hatch system
Instructions from Damian, in Plymouth, U.K:
Buy a large oval hatch rim. I found the 42/30 Kajaksport hatch fitted my standard Shrike perfectly.
- Make an approximately 4cm-wide oval ring out of 2 layers of 3mm ply so that the bottom lip of the hatch rim just locates inside it. (You do this in the same way as you manufacture the cockpit rim for a Shrike.)
- Decide where you want the hatch to go on the front deck. Then draw the outside edge of the plywood ring onto the deck. (NB: when you sit the ring on your curved deck, the left and right sides will be dangling a few inches above the deck. Trace round the ring keeping it horizontal, and your pencil vertical to get the right shape on your deck.) Draw a line approximately 4cm outside the rim outline and cut it out, e.g with a jig-saw. (NB – I am saying 4cm here, but it’s your choice: whatever distance you choose will determine the angle of the recess from the deck down to the hatch rim. You’ll probably want to have different angles at different points on the rim to make it look nice – that’s fine.)
- Put the plywood oval ring into the hole in your deck. On a standard Shrike, the edges of a large hatch rim should be sitting on the port and starboard shear clamps. (If not, you’ll need to support it while you do the remainder of the work.) Use sandpaper/files/plane/etc. to make sure everything is neat and symmetrical and that you’re happy with the angle of the slope down from the deck to the hatch rim. Then use superglue and accelerant to stick the plywood ring in position on the shear clamps.
- Cut out lots of pieces of plywood to fill the gap between the oval ring and the deck. This gap will start at zero by the shear-clamps and get bigger as the deck rises. I used about 20 pieces in total. Shape them with a plane and sandpaper. Don’t worry if it looks a bit rough-and ready: you’ll fill gaps with epoxy and sand them smooth later. Bevel the edges of these pieces so they butt up against the deck and the cockpit rim.
- Use super glue and accelerant to fix the gap-fillers in place.
6.Apply an epoxy fillet around the underside of the top joint (i.e. where the gap-fillers meet the deck) and fill any gaps between the gap-fillers. NB: if you have any big holes, then cover them with masking tape from above, turn the boat upside down and fill them with thickened epoxy from underneath. Remove the tape when the epoxy has gone off and sand it smooth.
- Put a layer of fibre-glass over this fillet – either glass tape (cutting the edges to allow it to go round corners) or cut glass cloth to shape.
- Put a fillet on top of the bottom joint (i.e. where the gap-fillers meet the plywood ring) and use thickened epoxy to fill in any remaining gaps.
- Once this fillet has hardened, smooth off the underside of this joint with sandpaper and then apply fibreglass to it – either glass tape or glass cloth.
- Finally, sand the top surface of both top joints smooth and cover both in glass – either tape or cloth. I used 160 gram ’twill’ cloth which will lay flat over curving surfaces, so I was able to easily cover both joints with one piece. At this point, make sure you’ve painted any exposed plywood with epoxy.
- When the epoxy has just gone off, cut the corners off the glass with a Stanley (craft) knife, apply more layers of epoxy (to bury the fibreglass weave) and then sand it smooth and flush with the surrounding deck. Then finish it however you prefer – varnish, epoxy or paint.
- Fit your hatch rim to the plywood ring using adhesive. I used a silicone sealant, and then drilled/bolted it in place.
- Buy a cover to fit your hatch rim. Tie it on to your deck-lines (so it doesn’t fly away if it comes off while you’re driving.) Fit it. Job done.
Building a three-part sectional Shrike
The usual procedure for producing a 3-part kayak is to through-bolt the sections together, and rely on soft washers to prevent leaks around the bolts. Damian from Plymouth, UK has designed a system that avoids leakage around the bolts by fitting the nuts into self-contained recesses, and by using threaded studs on plates which can be epoxy bonded to the face of the bulkhead. Threaded studs with plates are available as a ”footbrace mounting kit” from Chesapeake Light Craft, Sea-Lect and other retailers:
How does the kayak perform on the water? From Damian: My design for bolting the sections together requires 4 square holes below the water-line to access the nuts/bolts. I was worried that this would cause drag, so tried to gauge this by testing it out with my regular group of paddling buddies – either I’m imagining things or the boat is now a bit quicker. There is no possibility of leaks as the compartments remain fully sealed, even when not bolted together. I’ve taken it out in big, slamming seas and it’s all held together fine. (Off the water, the boat can now be stored in the corner of a room and fits inside my little hatchback car!)