Shrike, a lightweight sea kayak for home construction.^

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Chris Bolton
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Re: Shrike, a lightweight sea kayak for home construction.^

Post by Chris Bolton »

Looking at the clamps necessary to position the sheer clamp, how would a triangular section be fitted? I can only think of customised jaws on the clamps.

That leads me on to wondering if that joint could be done with stitch and tape, at least for most of the length. The taping of the inside seams on slalom kayaks demonstrates that it's feasible, with a bit of practice,to apply tape using a long stick, but making the epoxy fillets would be tricky.

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by Oisin »

Chris Bolton wrote:Looking at the clamps necessary to position the sheer clamp, how would a triangular section be fitted? I can only think of customised jaws on the clamps.

That leads me on to wondering if that joint could be done with stitch and tape, at least for most of the length. The taping of the inside seams on slalom kayaks demonstrates that it's feasible, with a bit of practice,to apply tape using a long stick, but making the epoxy fillets would be tricky.
The spring clamps I used have a notch in the pad for clamping angles, rotating regular clamps to near horizonal would prob do the trick also.

I rounded off the inside of my sheer clamps, not as severe as a triangle, but between the clamps and kerf sawing didn't have to use screws

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by nickcrowhurst »

Sheer clamps are necessary when the hull is 3mm thick. The gunwales only take their proper shape beacause the sheer clamps pull the 3mm ply into a fair curve. 4mm ply does not always require. sheer clamps. One gentleman, who shall not be named, built his 3 mm Shrike without sheer clamps. Oh dear.

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by simonballantine »

Yes, I meant to write "no significant loss of strength" when using a triangular section at the shear line. Yes they will be trickier to clamp - whenever you depart from the Build Manual the complexity increases! On the boat I am building at the moment I used 25mm*25mm triangular section and tapered the timbers for the last 500mm towards the bow and stern. I also kerf-sawed them towards the ends in the direction which allowed them to follow the rising shear line. I then glued them to the plywood before building the boat, using bricks to weigh it down and with small 'clothes-peg' type claps at the bow and stern. This is contrary to Nicks advice, which is to fix the shear clamps after assembling the hull, and please bear in mind that he has built many more kayaks than I have! Assembling the plywood hull panels was definitely trickier, due to the stiffness of the shear clamps, but I ended up with a nice smooth shear line and nothing bad happened.

As for using glass tissue over a lightweight twill cloth; the best bond and minimum resin useage will be achived by going wet-on-wet. This comes with the risk of making a mess of rolling out the tissue, but it is surprisingly resilient to creasing up and I have not had any problems. Cut the tissue to do one side of the boat at a time, with a joint at the keel. A joint in glass tissue is barely visible and an extra layer at the keel is no bad thing.
Waiting for the twill layer to go off before appling the tissue risks amine bloom problems. The safest method would be lay up the twill, cover it with peel ply and then remove the peel ply and apply the tissue the next day. However, peel ply costs almost as much as glass tissue - so it pays to be brave.

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by Beryl »

I preformed the sheerclamps together to get them used to their duties…..
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I also gave consideration to fixing the sheerclamp prior to building the hull but wimped out.
Growing old disgracefully

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by Paul-C »

Another option for clamping triangular sheer clamps would be to temporarily glue small triangular block to them with CA adhesive.

I partially triangulated my sheer clamps by planing them with a block plane prior to fitting the deck, but it sounds like I could have taken more off. Quite time consuming, but I don't own a band saw, so probably the most efficient option I had. Hand planing long shavings is quite therapeutic.

The only downside of kerf sawing the sheer clamps that I see is that it leaves one area on the boat where the wood isn't fully coated in epoxy, so there is some potential for water ingress and rot with time. Probably not a big issue but it has given me some cause for concern. I wonder whether we could taper the sheer clamps enough to allow them to bend without resorting to kerf sawing.

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by nickcrowhurst »

Paul-C wrote:
Thu Nov 04, 2021 9:44 pm
The only downside of kerf sawing the sheer clamps that I see is that it leaves one area on the boat where the wood isn't fully coated in epoxy, so there is some potential for water ingress and rot with time. Probably not a big issue but it has given me some cause for concern.
There's always a smear or two of resin left in the pot. I add some lightweight filler to make it like stodgy peanut butter, stick my index finger (gloved) into the goop and smear it in the saw cuts after the clamps are off. Strangely satisfying :)

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The joy of customising

Post by ChrisJK »

I took a shine to an Ocean cockpit as shown in an earlier post but I found from trying one supporting the boat on a couple of ton sacks filled with other ton sacks that I could well come a cropper when afloat . So I worked at enlarging till I was happy which basically ended up as a keyhole. I have remodelled the previous version with the help of the heat gun. I then made a sgraffito trace of the new shape on wallpaper. I cut out the shape and traced onto some chipbaord to produce a new template.

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The method may take time but I might as well be comfortable with the result.

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by nickcrowhurst »

Gaetano Celenta from Italy says he is a complete beginner, but he's progressing nicely with Shrike #368, shown in his video:

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From Michael in England

Post by nickcrowhurst »

A pretty Shrike, courtesy of Michael in England:

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From Transylvania

Post by nickcrowhurst »

Ovidiu from Transylvania graces the one thousandth post on this thread. At the top of each page is "search this topic", so one can quickly find topics of interest.
Lovely job, Ovidiu. For those like me, with a poor memory, Transylvania is part of Rumania.


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Dug has completed his Shrike

Post by nickcrowhurst »

Dug, from the UK, has now completed his Shrike, and very pretty she is. That blue really suits her:

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by eskapist »

Well the fitting out stage of my Vember build took me longer than the actual construction did because of making the skeg cables, but it's finished at last and as soon as I can get a spraydeck made to fit my narrow cockpit, she'll be on the water.
I bought some Paulownia boards and cut my own 22 mm strips (mistake!! I should have used narrower strips!)
The slightly enlarged shear clamps , masik and framing timbers were also cut from these boards. The basic shell lifted from the forms, weighed 3.4 kg, adding the decking ply , bulkheads, skeg box, glass cloth and resin brought this up to 11.7kg and finally the hatch, skeg gear, deck lines, foam seat, stainless hardware and other odds and ends brings the finished weight to 13.24 kg. So I'm quite happy with the result that I've got a boat that even my small and ageing frame can carry easily, and with the total cost for all the materials being £397 & a few pennies she's not an expensive boat.
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Re: Shrike, a lightweight sea kayak for home construction.^

Post by nickcrowhurst »

Escapist, lovely job! That's the same weight as my prototype (32 pounds), for which I used 19 mm wide strips. I see no need to use expensive cove and bead. As you will have experienced, a couple of passes on the inside edge of each strip with a block plane is enough. As David Dewitt stated earlier, it's no more difficult to build than a Shrike, but the hull takes 50 hours for a beginner, so it takes patience.
You will need to build into your schedule some time chatting with admiring bystanders wherever she is. It happens every time.
Congratulations.
Nick.

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by eskapist »

Thanks for the compliment Nick, but the attractive result is down to your design!
Yes, 19 mm strips definitely preferable to my 22mm ones which caused me some problems getting around the curves nicely but luckily my strips were cut 5 mm thick which allowed enough thickness after shaping and sanding the shell. Should I ever build another ( though it'd be a 85% version to better suit my weight and size) then I'd cut the at strips 17 X 5mm. An added penalty of course with several extra splices👎
Another deviation from the manual was that rather than "guesstimate" the positioning of the shear clamps to allow for bevelling to match the foredeck line, ( because I'd lowered the masik by 20 mm or so) I glued mine flush with the topmost strip and then glued on tapered pieces , from the masik centreline to the buckle point and from masik centreline to cockpit rear bulkhead. Then shaped them to suit by trial fit of the deck pieces.
Because this Paulownia seems to be quite soft, the gunwales were bevelled off and an 8 mm square strip of black walnut glued on and then rounded off to shape. Same on the bow and stern curved edges. I hope that this might be a bit more 'ding proof'.
Thanks again for your design !

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by ChrisJK »

Thanks Escapist that looks a good boat. That build cost is lower than that of a few costings of Shrikes. Where did you get the Paulownia from? I include a link to Fyne boat kits for comparison as this is considerably more expensive by the look of it https://www.fyneboatkits.co.uk/supplies ... ia-strips/ . I had some difficulty getting a piece of WRC for paddles and suspect finding planks of Paulownia in the UK won't be easy.

In regards to my Shrike build. I tried firstly to use the heat gun to bend some wood for the front section of the keyhole cockpit but it snapped so I tried the score method but that split and was irregular when mitre glued. I re attempted the heat gun method firstly shaping what will be the outer section and then successfully moulded and mitre glued the piece ready for glass tape and epoxy. Which I have done. The assembly was portable so it is now in my house where the temperature is warmer and will assist the cure.
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Re: Shrike, a lightweight sea kayak for home construction.^

Post by eskapist »

Hi Chris, yes I brought my wood from the very helpful Fyneboats back in August.
Regarding the build costs, in a previous life I was an aircraft engineer and repaired and later built my 2 wooden aircraft so I am uber conscious of the size, weight and costs of materials with the absolute minimum of wastage. MEAN some people call it 🤣🤣
I purchased 5 rough sawn boards of Paulownia 25mm X 150mm X 3100mm which cost £227 delivered. After planing and sanding them I took the most uniform looking set of 3 and cut off strips for the shear clamps and framing and sawed the remainder into 5mm thick strips . So the cost of the Paulownia was £227 X 3/5 = £133.
By careful positioning of paper patterns 1 sheet of 3 mm ply sufficed for the decking and bulkheads @ £45
The shell was assembled with a little over 1/2 ltr Everbuild D4 @ £6
Glass cloth and tape cost £47
3 1/2 Ltr MAS £108
Everbuild HV superglue £4.50
Hardware and odds and sods £14
Foam seat from Fyneboats £40 delivered.

I've never had any success using just a hot air gun without soaking the wood before and keeping it wet while bending. It is very important to keep the outside of the bend under compression with some sort of strap while you force the wood around your mold or form, otherwise it will most likely split. Plenty of good YouTube videos on the subject.
Like you I didn't feel confident enough in my abilities or experience to have a traditional ocean cockpit and so I built my keyhole with laminated vertical grain strips around the sharp bends and horizontal strips for the straighter pieces. When it's all filled and sanded down the results are, in my view, perfectly fine and not really distinguishable from horizontally bent. Anyway, invisible with the spraydeck fitted!

Good luck with your remodeling of your boat, I'm sure that it'll all come together in the end.

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by ChrisJK »

Thanks Eskapist.
That's interesting, I thought you might live in a country where Paulownia was produced but I now have no excuse if I were thinking of building a Vember. However I think I would need a better space to build it than I have at present. I spotted condensation forming on the deck in the dusk so I stowed it back in the garage and blow dried it with the heat gun and covered it over.

Thanks re bending the wood. I seem to have managed to get the rim to fit using the mould and template with the help of some wedges. The bending does need care in warming and slowly fitting the space. I joined the sections with wetted glass tape with some scrap tent nylon to prevent it sticking to the mould. I went out for the afternoon/evening and when I returned I found that the C clamps hadn't pulled it tight enough so with the epoxy being green I screwed it all together and went to bed.
Today I took it out of the mould and checked it fitted which it did with a little help from the heat gun. I then moulded the outer rim onto this and have screwed it in place. I will leave it like this till I have time to epoxy it back in the mould. This version will be tight but not as tight as an ocean.
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Time to re read the manual on this subject for how to proceed once that'sdone

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by eskapist »

A different country 🤔 , well out here just above sea level in the flatlands of Norfolk it does sometimes seem quite different from the rest of the country🙃.
Seriously, if you want to build Nick's lovely Vember you don't really need any more space than that for a Shrike, the bench space needed is the same. I cut all my wood strips outside the workshop on a dry day, got everything ready for the build, spliced strips as I went along. The paper patterns for the formers were printed on architectural paper which you can have freebie if you pm an address, I'll not build another one.
Your modified cockpit looks to be working out well, I've never used the sawn to shape rim method, preferring to laminate thin strips around the vertical grain upstands as it uses less ply or wood.

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by simonballantine »

Here are a few work-in-progress photos of my super-strong Shrike, built for rock hopping!
The cockpit floor is reinforced with foam/carbon ribs and the boat is sheathed inside and out. I used a large 25mm triangular shear clamp and ate into it by about 5mm as I rounded off the shear line - all now hidden under the sheathing.
Hope to post a few photos of the finished boat next week...
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Re: Shrike, a lightweight sea kayak for home construction.^

Post by nickcrowhurst »

Simon, it's great to see such innovation. The two after-most cockpit reinforcing ribs have their V-shape on the keel eased with a filler. Is this a lightweight filler or fairing compound? Did you smooth out the Vees for structural reasons or to give a flatter area to support a seat? Have you considered water drainage of those areas? A limber hole is traditional. For readers not familiar with the term, from Wikipedia:

A limber hole is a drain hole through a frame or other structural member of a boat designed to prevent water from accumulating against one side of the frame, and allowing it to drain toward the bilge. Limber holes are common in the bilges of wooden boats.

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by simonballantine »

These two ribs have an additional layer of foam to fill in the V at the keel. The photo shows some a lot of filler because I wasn't very neat cutting the foam! I will form the seat from a piece of shaped foam to fill the gap between these two ribs. I have not bothered with limber holes in the other ribs since they are only 10mm high and the captured water will not amount to much, but it could be done quite easily by incorporating a short length of plastic tube in the foam.

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High quality video of Shrike building

Post by nickcrowhurst »

This excellent video of building a Shrike (they call it a Yura) is from Berger-Boote, a professional boat-building company that is the authorised seller of Chesapeake Light Craft kits in Germany. It shows many variations worth viewing. Scroll way down the page to find the video:
https://www.bergerboote.de/shop/Yura-p132014545

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by simonballantine »

Some very interesting methods there. I particularly like the way the part-assembled upper planks are fitted onto the wired-together lower planks and hold themseves in position. Thats a very fiddly job made very easy...
The cockpit rim is another neat option.
I am not so sure that the vertically-laminated Masic will be quite as strong as the original; but adding a couple of layers of glass tape to the inner curve would strengthen it considerably...

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by nickcrowhurst »

Simon, the video shows the taped inner seams being laminated not with straight resin, but with resin thickened with some brown filler powder. (possibly wood flour) This starts at 12.30 on the video. The thickened resin had earlier been used to fill the angle of the seams, as is standard operating procedure.
Do you know of any benefit from this? I've always valued the fast wetting out of glass tape with low viscosity straight resin.
Nick

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by darylf »

Nick, what I think he does is masks the joint he is going to filet, mixes the thickened epoxy, puts it in an icing bags and does the fillet and smooths it off, removes the masking tape, lays the cloth tape on the still wet fillet and wets it out with clear, unthickened resin. He doesn't wet the tape out with brown thickened epoxy. The fillet that appears to be there when he starts is just the small fillets that he tacks with before removing the wires. (I think) Cheers m dears

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by nickcrowhurst »

Daryl, you're right. I didn't notice that at 14.40 the pot contains clear resin. I don't apply tape to the thickened resin until it has at least partly set. Otherwise, my seams appear to have been trampled by a herd of miniature elephants. Once there is the slightest dent from a finger or a brush, the dent cannot be removed. One needs plenty of experience to tape it as he does. I like his cake icing technique.

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by darylf »

Nick, yes I know what you mean, I think there is a lot of good stuff to take from this video, the precision and neatness of his work, and the way he has his workshop laid out like a laboratory are things we could all aspire to, and many useful techniques to pinch! I tried the icing bag technique, but it was early in my build and I didn't have the experience with the materials to pull it off, the whole lot started to heat up and go off in my hand and had to be placed out side to melt!!, and I proceeded by wodging it on with a stick and then smoothing it out, I may try it again though.

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by nickcrowhurst »

Daryl, yes, I admire the skilled techniques, but, for example, I'll stay with my trusty tongue depressors. Tongue depressors simultaneously apply and smooth the thickened epoxy, plus they're re-usable and sustainable, unlike polythene bags used for epoxy.
Aspiring builders should not be over-awed by the high level of skill displayed in the video. The project is aimed at builders with little or no wood-working experience, and with limited money. The Build Manual describes the simplest and cheapest way I know to build a first-class high performance Greenland-style sea kayak. There are many ways of making a Shrike more complicated and expensive, and several of these can be found in the apppendices to the Manual.

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Re: Shrike, a lightweight sea kayak for home construction.^

Post by adventureagent »

nickcrowhurst wrote:
Fri Nov 26, 2021 11:57 am
Daryl, yes, I admire the skilled techniques, but, for example, I'll stay with my trusty tongue depressors. Tongue depressors simultaneously apply and smooth the thickened epoxy, plus they're re-usable and sustainable, unlike polythene bags used for epoxy.
Aspiring builders should not be over-awed by the high level of skill displayed in the video. The project is aimed at builders with little or no wood-working experience, and with limited money. The Build Manual describes the simplest and cheapest way I know to build a first-class high performance Greenland-style sea kayak. There are many ways of making a Shrike more complicated and expensive, and several of these can be found in the apppendices to the Manual.
These productions are fabulous. I read this entry and felt that even such a bufoon as I could build one. Obviously, this offering of plans is a really marvellous celebration. The joy of sailing such craft is icing on the cake, as they say. I haven't the tenacity nor place to do such a build (yet, anyway), but seeing these finished boats, I can just imagine myself riding a wave or skimming silent, except for my paddle. Just unspeakably marvellous. A big applause from me to the designer, the builders, the paddlers. This is an endless story and adventure, for sure.
CELEBRATE LIFE: PADDLE by ALL MEANS !

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