Shrike, a lightweight sea kayak for home construction.^

[PlymouthDamo]

So, I have no choice - home-made hatch it is!

As you know, I'm very pleased with my home-made flush hatch in my Shrike-R, but you do have another option, i.e. fit a recessed oval hatch. This is what I've retrofitted to the front of my Vember, and if you search back through this thread, you'll see my summary of how it's done. It's heavier, and less pretty than a home-made curved, flush hatch and they can leak if you're not meticulous about cleaning/lubing the rubber cover, whereas my home-made flush-hatch is always bone dry. However, on the plus side, they provide a whacking great opening, which is great for expeditions, and it's a bit easier to install.

Your Vember's looking great though and I'll be interested to see how that paddle comes out. In the past, I've just hacked my paddles out of single blocks of cedar, but that's really wasteful of the wood, and it doesn't allow for harder wood to be used along the tips and blade edges. Laminated ones usually look extremely smart when they're just finished, but that might be a disadvantage - i.e. it's just a matter of time before you're smashing your work of art against granite when your rock-hopping goes wrong...

[ChrisJK]

I won't necessarily deflect you from making hatches on the bow section but I have managed a multi day trip using a 6 inch screw hatch in the foot bulkhead.
I do wish that I'd put in an 8 inch one but its in there good and proper so no point in changing it.
The tricky item was my sleeping bag which goes into a Lomo gun bag and gets well compressed and threaded in.
If you make a laminated paddle please add it to the Greenland paddle makers thread.

[Devon Dom]

Thanks Chris, I will re-think and research Lomo gun bags!
I can't find a specific greenland paddle thread... could you point me at it?

[ChrisJK]

Hi Dom
It worked for me, with some struggles and I guess you can fit an outside hatch at anytime if you find it doesn't work for you. My boat is Shrike which may have a little more volume than a Vember? https://www.lomo.co.uk/products/extra-l ... th-window/
Here is the thread i was talking of re paddles and it has a couple of videos. I can email some instructions if you need them viewtopic.php?p=827564#p827564

[Devon Dom]

Thanks once again Chris. I've realised, now I've cut out the foot bulkhead, that the 8" hatch will actually - just - fit in it, which is a game changer! So I'm back to plan A, or is it B, I've lost track...🤗

[ChrisJK]

Thanks Dom
You can always fit a front hatch later.
My internal compartment is generally dry though I did get some ingress around the sheer clamp join after a capsize.
I made some ply hatch covers with a cross beam handle which camouflaged the outside hatches and make them relatively easy to screw in and out. My foot bulkhead hatch also has one so again fairly easy access you can see what they look like on pages 34 and 37 of this thread.

[ccrowhurst]

Face palm..... I put a new foredeck on a Shrike this week and completely forgot to put maroske fittings near the bow.....

[PlymouthDamo]

Face palm..... I put a new foredeck on a Shrike this week and completely forgot to put maroske fittings near the bow.....

I feel your pain. There's something I've done to mount a compass on my Vember which might help out here: I got a couple of bits of scrap wood and shaped them into small (<1cm tall) arches (i.e. rainbow-shapes), epoxied them and stuck them onto the outside of my deck. That leaves a little hole under each one just big enough to poke a bit of elastic through. It's really compact and low-profile so it looks smart enough and is easily strong enough to stand up to being clubbed by clumsy attempts at paddle stowage.

[Devon Dom]

Advice please from all you 3D printing folk. I thought I had my Maroske fittings sorted when Exeter Fablab said they could print them for me. I went in yesterday to check out the trial run and they have printed them with some sort of "support material" within the tube, which is obviously wrong. The guy said he hadn't printed anything like this before (?) so I wondered if anyone has some advice I could pass on to him? Here's a picture of the fitting as he's done it with more support material yet to be removed from the outside, which comes off easily. It's inside the tube that doesn't look straightforward.

[ccrowhurst]

Last Spring my car was hit by an 85-mph gust from the side during a tornado. At the time there were two shrikes on the roof. One a skin-on-frame the other a standard stitch and glue Shrike-R. All of the lines snapped holding them down (bow stern and cross-straps), and the Shrikes shot sideways about 80 feet, and then plummeted 50 feet off a bridge. The plywood shrike snapped about 30 inches from the stem and the skin-on frame lost some sections of skin. Here they both are, repaired and ready for another season. A true testament to the repairability of home-grown kayaks.

[DavidDeWitt]

Wow, That sounds truly scary. Hopefully it was only the boats that were damaged. It is stunning to me that the webbing straps holding the boats to the roof rack broke. Were the boats in J cradles or were you carrying them flat? Any chance you could share some pictures of the reconstruction process. I have a hard time even imagining how one would go about such a task. David

[nickcrowhurst]

David, Christopher is travelling for a couple of days. Meanwhile I can say that the photo of the damaged Shrike-R is impressive.
Nick.

[ccrowhurst]

This image shows the initial damage.


These two show how I added tongue depressors temporarily around the break to hold the hull in shape. Then I removed the deck and glasses the inside. Then removed the supports and replaced the deck then refinished the outside.




The kayak was in V-bars, they have less sideways support than traditional J hooks on the roof. This accident probably would not have happened if I used a different sort of rack. The V-bars are convenient, but clearly demonstrated they have limited support when exposed to horrendous sideways loads.

[DavidDeWitt]

Amazing reconstruction. Very impressive

[nickcrowhurst]

The earliest 3-piece sectional kayak I know of is the Lochaber Canoe of 1930's vintage:



The story of its discovery is here: viewtopic.php?p=836719#p836719

The first sectional Shrikes we saw were two orange ones from Sussex, seen at the first Shrike Gathering in 2016:




There are now several different published methods of achieving a sectional kayak, including one by Damian in the Shrike Build Manual. Over the past few years a pair of local paddlers, Alistair and Simon, have distilled these methods, stirred in their own considerable expertise, and the result is now a zip file in the Shrike Plans Download. https://cnckayaks.com/shrike/downloads/
It works, it doesn't leak, and the method has been designed to be within the skills ability of most Shrike builders. Great work.

[CATMANDOO]

Building a Shrike

Now got both decks stuck on and not with out a lot of fiddling work . took hours !
. the trouble is it bends in more than one direction particularly around the Stern end of the cockpit . Also trying to keep to the centre line and minimise the gap at the joint between fore and aft decks butting at the masik. It was a bit of a struggle because then is where it drops down from a big curve to a flat deck at the cockpit stern . As you apply pressure on the clamping belts the forward edge of the stern deck rotates and the gap widens( between fore and aft decks ) and the stern deck moves aft . .. meanwhile the aft end of the centre line goes off centre

After a lot of fiddling I worked out what was wrong and put in 3 small removable screw nails to keep it in position but was unable to keep the panel completely on centre . I had previously precut a small hole for the keyhole cockpit to make it easier to bend with an allowance for later adjustment . What makes it difficult is that the rest of the deck starts to be come flat at the cockpit back bulkhead and if you push down one side it pops up at the other despite running a strong back across the deck at that. location .
I even used a laser to locate the centreline( from bow to stern) but even then the cock pit back is now 1/4 inch out (ie squint )( Need to have eyes in the back of your head and long arms)so I now have to adjust the symmetry of the cockpit opening trying to make the edges symmetrical across the centre line on a now curved opening . Difficult!

Perhaps I should have glued the edge to the Masik first and let it dry before proceeding with rest a day later

[CATMANDOO]

by the way . Has any one used Gorilla Wood glue to fix the plastic hatches or is too too brittle when set?

I don't want to use Sikaflex 291i because of small quantities and rest in tube gets hard after a few months and so its is a waste

[Yellerbelly]

by the way . Has any one used Gorilla Wood glue to fix the plastic hatches or is too too brittle when set?

I don't want to use Sikaflex 291i because of small quantities and rest in tube gets hard after a few months and so its is a waste

I've kept some Sikaflex in the freezer for several years. Might still be OK.

[PlymouthDamo]

1. Re. the difficulties getting the aft deck on: I do it different to the build manual in that I get the deck glued on before I cut out the cockpit hole. I've never found any problems with doing it this way, and it removes the need to get the deck panel accurately lined-up at that tricky stage of the build. I've never needed to screw either of the deck panels to the masik when I'm installing them, but I do lots and lots of dry runs - strapping the panel in place with the ratchet straps and each time marking a bit more of the overhang, which I then remove with a jigsaw or hand plane. By the time I'm ready to actually install the deck, there's not much more than 1cm of overhang all round, which means the panel can't wander too far, and you can make micro adjustments to get it in position as you're gradually tightening the ratchet straps. There may be a gap of 1 or 2mm where the two panels meet on the masik, but filled with thickened epoxy and sanded down, this straight white line looks more like a feature than an imperfection. (I realise the above is a bit late for you now, so here's one other thing I do differently to the build manual: I fit my cockpit rim to the upstand before I cut out the cockpit hole in the deck. I then trim the bottom of the upstand so the whole thing sits flush on the deck, before finally cutting out the cockpit hole and attaching the whole assembly to the boat. I find that doing it this way makes it easier for you to get a nicely-built cockpit rim assembly with a pronounced concave curve, which really makes a difference to the appearance of an ocean cockpit. You can put the rim in a vice or use large clamps to force it to curve, and then superglue, then epoxy fillet/glass the upstand to it.)

2. Re. sticking down the hatches: on my first Shrike build, I used polyurethane adhesive for sticking on the skeg glide box, as that's what Nick had specified. However, I'd got the wrong stuff - an expanding foam product for wood - and it didn't work. I've recently reapplied a plastic hatch on one of my boats, but this time used a polyurethane adhesive/filler from Toolstation like this: https://www.toolstation.com/puraflex-40 ... KCnamX7g This is the stuff that I should have got in the first place, and it has done a great job. (I had a nightmare on Sunday - paddling in rough conditions in an ultra-low volume boat when I discovered my ancient spray deck is full of holes. As a result, my cockpit was fully flooded and the rear of my boat was permanently underwater whilst I was being battered for several miles. Despite this, my submerged day hatch had let in no more than a cupful of water, and that probably got through the hatch cover rather than where the rim was stuck on. So the polyurethane glue obviously did a good job attaching and sealing the hatch.) My engineer mate knows a bit about this stuff, and he agrees that polyurethane adhesive is the way to go, and warned me to avoid silicone products as they'll eventually come away and then nothing will stick to that area afterwards.

[CATMANDOO]

unfortunately I followed the manual despite having the deck lined up several time before hand so I finished by cutting the hole . roughly .
Surprising ly at that I originally had the gap between both panels no more than a crack . I should have stuck to my basic instincts . as I cut the cockpit and hatches out that way on my Guillemot

nevertheless I have a recovery plan to apply tomorrow . Lets see if it works

[nickcrowhurst]

unfortunately I followed the manual

I sympathise with CATMANDOO. Trying to tame the stern deck panel can be like wrestling with an octopus. A slight change at one end of the panel is multiplied many times at the other end. That's why the Build Manual at page 24 describes how to fix both ends of the panel before making any cuts. First, to centre the panel at the front (masik) end:

The stern deck main panel uses the full length of the third plywood sheet, and stretches from the masik, aft to a short distance from the stern. Cut a panel to fit this area, with a 20mm overlap on the gunwales, as for the foredeck.
Mark the centre of the short side of this panel, and preserve the previous mark on the centre of the masik. Ensure these marks coincide throughout the remaining procedure. Use a temporary stainless screw if necessary.

Now to fix the aft (stern) end, as also described on page 24:

The aft end of the panel tends to move during the fitting process. Locate it by fitting a plywood butt strap to the panel under the aft end, tightly between the sheer clamps. This butt strap will be used later to join the final small section of deck.

Now the panel is fixed at the front, and secured at the back so that it can only slide forward the small mount required when the curve is cut at the front of the panel. The octopus is tamed. Also, to give some wiggle room in the fitting, again from Page 24:

Cutting a smaller approximation to the cockpit opening in the centre of this panel will ease the bending strain required, so, from the plans, scribe a shape at least 50mm smaller than the final opening, and cut it out later on the bench.

When I built the prototype Shrike I was using a very high (12.5 ") masik so that I could bend my knees so to take the strain off my decrepit back and tight hamstrings. This put more tension in the stern deck panel, so I cut a hole 50mm inside the cockpit perimeter shape to relieve some of the tension. With lower masiks, as Damian describes, this can be avoided. However, I like to feel inside the cockpit to check the fit and to remove excess epoxy glue before it has set.
With my next Shrike I followed the above described process as at Page 24 and found it worked well, and I then wrote the Build Manual accordingly.

I reply here in detail as I am concerned that those considering the construction of a Shrike might be discouraged by perceived inadequacy of the Build Manual.

[Devon Dom]

I'm interested in Damian's approach to the cockpit build, as I'm just about to fit my stern deck. How do you get the right bend on the rim, do you just go by eye? And do you need to allow some extra depth on the upstand for jiggling about to get everything flush?

[ccrowhurst]

It’s been my experience that there is not a great deal you can do to influence the plywood, it’s going to curve how it wants to. By pre cutting a rough cockpit you will dramatically increase the flexibility of the section which then will form a natural curve as you pull it down to the sheerclamps and deck beams. If it looks good it is good is my rule here. You can accommodate any curve with the uprights, and then the cockpit rim will easily bend to match the deck curve with a few clamps to hold it in place. I always have cut the top of the upright parallel with the deck’s curve once it is epoxied and supported in place with a fillet.

[DavidDeWitt]

On my recent Vember builds I have switched to building carbon fiber rims (fussy, but pretty). The plans I use recommend an “upstand” of 4” with a couple of inches above the deck and a couple below. Using a wide upstand help keeps it vertical. Once the epoxy fillet between the upstand and the deck hardens it get to the correct height above the deck and trimmed flush below the deck. See attached photo which is from my Vember Tandem (I am using bendable” birch plywood which bends easily in one dimension)

[DavidDeWitt]

The other interesting thing about that approach to building rims that is applicable to building Shrikes and Vembers is how one goes about marking the final opening for the cockpit rim. The first picture below shows the rough opening (in this case on my wife’s Vember on which I put a smaller rim recently). The second picture shows a template of what I wanted the final rim opening to be sitting on the deck (this pattern was based on a Tiderace cockpit). The third picture shows how the desired opening is projected onto the curved deck. A series of points is marked at 1” spacings around the entire template. The dots are then connected to produce a smooth line and the final opening is but by following the line

[Devon Dom]

Once again, it's been a while, but I inch along. Jura in May is my absolute deadline, and I need her in the water before then to make sure she doesn't leak! So there are some late nights ahead...
I gave up on the 3D printing, got my money refunded by the nice man at Exeter Fablab, and spent £10 on some plastic tubing instead. I got some black aquarium tubing which is quite stiff but I was able to bend it without distorting with some electric cable inside. This, plus little plywood half-moons, as described in the manual, seems to have done the job. Phew...


I also fitted an 8" hatch in the foot bulkhead and planned the location for a 6" hatch in the flat bit of the front deck near the bow, as I think that will be useful for wrangling gear into the large front compartment via the foot hatch.
So at last I was ready to fit the front deck. All went to plan apart from one mistake I'd made when fitting the sheer clamps. I didn't allowed them to project enough above the gunwale to make a solid landing for the deck where it angles in. This made me worry that the deck join wouldn't be watertight, so I've spent some time trying to apply thickened epoxy to the internal join, which really needed both more flexibility and longer limbs than I possess. Still, hopefully it's done the job. Only one way to find out!
I decided to stain the deck red, which will turn out darker than in the picture once the epoxy goes on and should look good next to the yellow/orange cedar.



I have also made and fitted the skeg box, again all went to plan, it seems!
Next step is the Maroske fittings for the rear deck and then popping that on.
I've been looking at options for cutting the cockpit and have decided to do it as per manual, now I've got my head around it. I'll report back on how I fare.

[Paul Meadows]

Shrike build No 455 . Thanks again to CNC kayaks for the plans for the Shrike, what a brilliant and generous thing to have done.

I finished my Shrike about 4 weeks ago and have since paddled it about 25 miles. It is at 100% with 1cm cut off the height of the upper hull panels. I was tempted to cut further in order to reduce the freeboard but I wanted to retain plenty of knee room for comfort. I'm happy I did, as the cockpit is perfect for my 5'11" 11.5 stone and gives me space to shift my position occasionally whilst remaining a good fit. I rarely paddle in anything other than reasonable conditions and often fish from a kayak therefore a slighlty larger platform is preferable. The boat weighs in at 18kg as I wanted to make sure I was well protected against rocky Cornish landings and have glassed the hull completely. Having said that it's still lovely and light and although it's a little front heavy to carry, a tip from a fellow Shrike builder to attach your paddle to the rear deck when shouldering it makes all the difference. I find the boat very maneuverable, although I'm still trying to work out why it doesn't respond particularly well to edging at the moment, I have however just put the seat in the correct position.....I stopped reading the manual towards the end of the build and went a bit off piste! I may find the edging capabilities improve with the seat moved forward slightly.

Thoroughly recommend the.project to anyone, I found it a bit challenging at times, wrestling the back deck into place was probably the most difficult part though that is up there with getting to grips with fast cure epoxy!

Thanks again Nick and Chris.

[nickcrowhurst]

Paul, lovely job! For a lightweight kayak, the position of 180 pounds of meat is absolutely critical. From Page 8 of the Shrike Build Manual:

"The position of the centre of the seat should not be changed. In such a light kayak, the position of the paddler’s weight is particularly critical."

[nickcrowhurst]

[simonballantine]

First trip out in my new boat today - and I'm really pleased with it. This is a full-length Vember (ie: Vembex length) but with all the other dimensions reduced to 90%, so its only 49cm wide. On top of that the shear line has been dropped by a further 20mm and I have gone for an ocean cockpit. So its a fun rolling boat, not quite as extreme as Damians rolling Shrike, but a very different thing to a full-sized Vembex!
Its surprisingly stable and is extremely well-behaved - very easy to turn and it almost rolls itself.
To aid my ageing stiff back I built the cockpit bulkhead on a 45 degree slope, which continues upwards as a sloping cockpit rim, and I kept the rim height down to just 15mm (only just enough for the spraydeck elastic). I can lie right back onto the aft deck and nothing hurts!
I also gave myself plenty of room for my knees and feet by building an inverted U shaped Masic and foot bulkhead sized to my favourite boots..
There is no volume in the aft deck so I have not bothered with a deck hatch, but I have put a simple hatch in the bulkhead behind the seat with some simple toggle fixings...My thinking is that the inside of the cockpit will not be under water as aften as the low aft deck, so there is less relience on the hatch seal..
Other non-standard features:- The hull is sheathed in 2 layers of 100g twill inside and out. The lower-weight glass cloth has a finer weave and so is easier to fill-out to achive a smooth surface without using too much extra resin. I also sheathed the decks inside and out with 1*100g glass cloth and put in several partial bulkheads under the aft deck since you need to sit on the aft deck to get in and out of the ocean cockpit...I'm happy putting in a bit extra strength and weight because the boat is there to be used!
It all weighs in at 13.2kg thanks to its minimalist dimensions!
Many thanks to Nick for his help in modifying the plans and checking that it would still float!