Shrike, a lightweight sea kayak for home construction.^

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

Post by simonballantine »

For a composite panel in bending; the tension force on the inner face is equal and opposite to the compression force on the outer face. The tensile and compressive capacity of carbon are very similar, so we need a similar-strength layup on the inner face as we do on the outer face.
However, the outer face is subject to all sorts of abuse - impact / scratching / etc. On most boats, including kayaks with a foam core, the outer face of a composite 'foam sandwich' hull will be made significantly thicker than the inner face to cope with all the knocks.
If you need to double, or treble the laminate thickness on the outer face to cope with all the knocks then there is no need to use carbon, since 2 or 3 layers of glass will provide more than enough strength to match the single thickness of carbon on the inner face.

However, when sheathing a Shrike we have a slightly different set of circumstances. Insted of a very light compressible and easily-damaged foam core we have a heavier, robust plywood core. There is not then the same need to build up the thickness of the outer face laminate to resist impact loads and the outer laminate can be an exact match for the inner laminate.

So thats the technical explanation; but the main reason for the all carbon outer laminate is Bling!

To answer a couple of other queries on my all carbon Shrike. Yes it adds weight. My boat is 17kg, although about 2Kg of that is due to it being built it as a 3-piece. According to my calculations it is about 6 times stronger in bending than the standard plywood boat.

I bought the carbon from Easy Composites Ltd who sell it as 'Black Stuff' in 10m rolls at a very good price. If you are spashing out on carbon then it would be sensible to use a laminating resin rather than the MAS general boatbuilding resin. If your wife won't let you build it in the dining room then you will need a nice warm garage. Epoxy doesn't like the cold.
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Re: A 35% scale model from Bobby

Post by wrp7317 »

[/quote]
What cunning method did you use to secure the small loop on the foredeck?
[/quote]

I drilled 1/16 holes in the deck and inserted the bungee line in the holes and secured them with medium CA glue.

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

Post by DavidDeWitt »

Simon,

Thanks for the detailed explanation about the use of carbon on both the inside and outside of your Shrike build. I could be curious to know how much visible damage is done when you hit rock hard.

I totally understand the bling factor of carbon which was why I used carbon for the cockpit rims of my Vember and our Vember Tandem.
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David
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Re: Shrike, a lightweight sea kayak for home construction.^

Post by Chris Bolton »

I could be curious to know how much visible damage is done when you hit rock hard
That will depend how much of the rock is visible at that state of the tide, etc. If it's all underwater you won't see the damage.
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Re: Shrike, a lightweight sea kayak for home construction.^

Post by simonballantine »

DavidDeWitt wrote:
Wed Dec 22, 2021 2:20 pm
Simon,

Thanks for the detailed explanation about the use of carbon on both the inside and outside of your Shrike build. I could be curious to know how much visible damage is done when you hit rock hard.

I totally understand the bling factor of carbon which was why I used carbon for the cockpit rims of my Vember and our Vember Tandem.
Image

David
Thats a fantastic looking boat....
simonballantine
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Re: Shrike, a lightweight sea kayak for home construction.^

Post by simonballantine »

Chris Bolton wrote:
Wed Dec 22, 2021 3:15 pm
I could be curious to know how much visible damage is done when you hit rock hard
That will depend how much of the rock is visible at that state of the tide, etc. If it's all underwater you won't see the damage.
To be fair, whatever your boat is made from and however thick the laminate you are always going to put a scratch in the hull when you hit a sharp rock. Rock is harder than carbon, which is harder than glass, which is harder than rotomoulded plastic. (You just don't notice scratches on a rotomoulded boat beacause they have so many !) The stronger laminates prevent impact damage spreading any further....
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Re: Shrike, a lightweight sea kayak for home construction.^

Post by DavidDeWitt »

Got it. Thanks.
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nickcrowhurst
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St Austell bay, Cornwall, UK

Post by nickcrowhurst »

Peter M always produces beautiful images. He sent me this one today:

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

Post by DavidDeWitt »

On behalf of paddlers around the world who have benefited from his wisdom and dedication to the field of kayaking and boat building I would like to wish Nick and his family a Merry Christmas and a Happy New Year.

One can only hope that 2022 proves to be a better year than 2021.
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Thank you

Post by nickcrowhurst »

That's very kind of you. Eight years ago I said to my wife "I'll be content if just one more Shrike is built when the plans go on the Internet". After our recent CNC newsletter was circulated, there was a surge in notifications of builds, and we now know of 392 constructions in 53 countries, and over eight thousand copies of the plans have been downloaded. I'm hoping for 400 by the eighth anniversary of the project launch on the Internet, 28th February 2022.
On that topic, I've learnt of a plan by three gents to build three 105% Shrikes for an expedition on the coast of Norway in 2023.
In the past we've considered also releasing the Shrike design as a table of offsets, where x and y co-ordinates of points are given, and later joined freehand. It's been a very common method for promulgating boat designs in past years, but for the builder it is time-consuming and potentially inaccurate, particularly in aligning the topsides and bottom panels. If the Build Manual is followed, the full-size plans laid onto previously cut and joined long strips of plywood completely removes this possibility. I've received just two requests for offsets in eight years, and I've politely declined the requests, with my reasons.
It would take a couple of days of boring work to measure and check the offsets, but there may be a number of potential builders who would like to produce the plans "in house" and avoid the need to find and pay a suitable print shop to produce the free plans. What do you think?
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Re: Shrike, a lightweight sea kayak for home construction.^

Post by simonballantine »

Nick, I would direct any interested people to download a free copy of Autodesk True-view DWG viewer software, which will enable them to measure off the dimensions and cooordinates themselves!
having a drawing program has other uses:- I fiddled around with the drawings on my software and arranged the planks and bulkheads in the most efficient way so that I was able to make two boats out of 5 sheets of plywood.
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Re: Thank you

Post by eskapist »

nickcrowhurst wrote:
Mon Dec 27, 2021 11:30 am
.........and we now know of 392 constructions in 53 countries, and over eight thousand copies of the plans have been downloaded. I'm hoping for 400 by the eighth anniversary of the project launch on the Internet, 28th February 2022

Well Nick I hope to be able to help you realise your hopes, and to that end I started cyano-tacking the panels of my LV build together last week and by this evening all shear clamps bulkheads, masik and cross beams have been fitted, filleted and taped.
Over the rest of this week I hope to be able to apply glasscloth and resin inside and out, but then I'll have to twiddle my thumbs and wait until the country gets back to some sort of normality and I can get the ply for the deck delivered. I've abandoned my earlier idea of doing a Paulownia strip deck after calculating that there wasn't quite enough wood available to confidently complete that scheme but that board will make a few nice light Gps instead.
So I've got 63 days to make it 393 before your target date , and there's a least 1 other UK build which has recently posted in this thread that might well make that 394 . Fingers crossed!!

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

Post by ChrisJK »

Brilliant Eskapist
I think that for recording purposes, If I am correct the craft is registered at the start of the build eg my Shrike has the hull number 275 registered around 30th December 2020 but I think it is unlikely that it will be completed by the 28th February as I will need warmer conditions to do my final coat of epoxy and later still to fine tune finishing features. Relax and enjoy the process.
I spent a bit of time today working on building the cockpit rim piecing bits of ply together which will hopefully be epoxied tomorrow.
Let's not forget that you have already made this lovely boat :
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Image
[/quote]

Thank you for the printed plans for the Vember forms. I have not yet embarked on that build yet but I was cutting down bamboo in my garden and wondering if split cane might be part of a build?!
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Re: Shrike, a lightweight sea kayak for home construction.^

Post by nickcrowhurst »

simonballantine wrote:
Mon Dec 27, 2021 5:59 pm
Nick, I would direct any interested people to download a free copy of Autodesk True-view DWG viewer software, which will enable them to measure off the dimensions and cooordinates themselves!
having a drawing program has other uses:- I fiddled around with the drawings on my software and arranged the planks and bulkheads in the most efficient way so that I was able to make two boats out of 5 sheets of plywood.
Simon, you're a hard man! I have an image of a young kid in a remote area of the world being handed a scruffy bit of paper with the offsets listed thereon, and making a Shrike by dumpster-diving for plywood.
Have you ever compared efficient packing parts on a sheet by eye with the result of using a nesting routine such as in Fusion 360? It would be an interesting comparison.
As Chris points out, we log the builds when construction has started, as there's no guarantee that we will get a follow-up message on completion. First contact is usually a question, such as "where can I buy closed cell foam for the seat in Kuala Lumpur". Fewer than one person in 21 who downloads the plans ends up telling us of a construction. (392 0ut of 8255 today), so I have no idea how many have actually built a Shrike. Just looking at plans is a happy pastime. I do know that many builders do not tell us, and there's no reason why they should. When we send out a newsletter there will be perhaps ten who pop up with photos. It's all good fun.
Nick
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Slot in cockpit and customisation

Post by ChrisJK »

There is a frustrating glitch which may only occur to me but I can write a load of information and find that it gets timed out or something.
This a re write.
Firstly thanks to Nick for providing the plans and manual, there is now way I would have embarked on a self build with out them,

Secondly I am working on the slot in cockpit, I have half of it with 2 layers of 3mm ply and the re configured section with one layer. I tried to fit my big deck spray deck which fits my Capella and my H3 and found a couple of gaps on the underside which I am customising plus I am concerned that the square ended nature of the cockpit at present might hinder a wet excess so I have improved the curve but hope that won't get ripped in an emergency.

The damp and relative cold is preventing me from putting on my second coat of epoxy on the boat but I can proceed with this as it comes indoors to cure.
Image

Image

Image

Happy new build if you are just pondering making a Shrike
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Re: Shrike, a lightweight sea kayak for home construction.^

Post by eskapist »

Great to read and see that you're still making some progress despite the weather Chris! My workshop too has been decidedly chilly lately but after a few minutes of vigourous hand planing and sanding the shearclamps to suit the changing angles along the bow section it doesn't seem so bad!!! For when it's really cold I've bought one of the cheap Chinese made truck-cab diesel heaters from the Bay of Fleas for about £90 which are really economical (especially if you've got heating oil handy) about 1 litre will keep my 16 x 24 shed tolerable for 6 hours or so.
I made up the parts for the skegs and skeg-boxes today as well, this boat will have a bow skeg as per Nick's earlier posts for when I try out a sailing rig maybe later this year. Hope to bond these together tomorrow morning and fit them in place later in the afternoon after I've trimmed up the slots which I've cut today. I'm holding off glassing to hull until the weekend when, allegedly it's going to be warm and dry, well in this corner of the kingdom anyway. Deck plywood to be delivered next week is great news.

Trevor
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Re: Slot in cockpit and customisation

Post by nickcrowhurst »

ChrisJK wrote:
Thu Dec 30, 2021 8:08 pm
There is a frustrating glitch which may only occur to me but I can write a load of information and find that it gets timed out or something.
Chris, this also happens to me. If I'm going to write more than a couple of sentences I regularly highlight the text, right-click and "copy", so I can "paste" it back if the need arises. Alternatively, for a long screed, I'll produce it in MS Word or Notepad or similar, edit it and then copy and paste into the forum. My suspicion is that Microsoft squeezes a lot of functions into the bottom right hand corner of the screen. When one tries to scroll down while composing a post it's all too easy to destroy the post. That's just a hunch.
On a brighter note , Mike from Minnesota, USA, has found his existing strip-built sea kayaks to be very heavy, and he's just turned over the hull of the Vember Expedition he's building:

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

Post by Chris Bolton »

I have not had problems being logged out from UKRGB, but I tick the box to stay logged in. If it's a long post I write it in Notepad. I don't use Word for that as it sometimes includes formatting characters. I don't know if it's browser related; Nick mentioned Microsoft, I don't use their browsers.
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Re: Shrike, a lightweight sea kayak for home construction.^

Post by ChrisJK »

Thank you both and Happy new year.
I will check out the 'stay logged in option but where can that be found? whilst writing this post I can't see it , It helps to know I'm not alone.
Generally I manage to resend the core of what I was trying to communicate. I think that Benjamin Britten lost a whole symphony in a fire or something and rewrote it from memory whilst travelling on a ship to America (citation needed)!
I added that second layer of ply to the cockpit today and hope to glass the combing soon. I need to re read that section of the manual, I have glass tape and twill which is going to make the best job?
Anticipation is building as completion approaches but these are silly temperatures for December/January so finishing coats of epoxy may be a while off yet.
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Re: Shrike, a lightweight sea kayak for home construction.^

Post by nickcrowhurst »

ChrisJK wrote:
Sat Jan 01, 2022 12:30 am
I added that second layer of ply to the cockpit today and hope to glass the combing soon. I need to re read that section of the manual, I have glass tape and twill which is going to make the best job?
Twill, cut in strips on the bias, is your friend. It is so malleable that it tries to fall apart. Treat it with kid gloves. Tape will work, but it's more reluctant to conform.
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Re: Shrike, a lightweight sea kayak for home construction.^

Post by Chris Bolton »

stay logged in option
It comes up when you log in. The box to tick is "remember me". But different browsers may behave differently. I use Firefox on Windows and Chrome on Android.
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more customisation of cockpit

Post by ChrisJK »

I may be making this harder than it should be but on testing the cockpit with both a key hole and big deck spray decks, i find that both fit, but neither come off with ease (yes It isn't connected to a kayak and not glassed) Both seem to grab to generously over the mostly 6mm top lip. Both my P& H Capella and H3 have a fairly obtuse slope up to the lip so I am in the process of fashioning a beveled one from scraps and will use some thickened epoxy to fillet and fill.
As yet I am a non roller and don't fancy discovering that the deck won't come off whilst submerged. Does anyone have a similar experience and solutions?
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Re: Shrike, a lightweight sea kayak for home construction.^

Post by Chris Bolton »

Trying to get a deck on or off when you're not sitting in the boat is much harder. If the rim is solidly fixed to what you're sitting on, you can pull much more effectively. If the profile of the rim is similar to what you have other boats it should be fine - bearing in mind that the best way to get a deck off is to first pull the tab towards the bow, before pulling it 'upwards'.
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Re: Shrike, a lightweight sea kayak for home construction.^

Post by nickcrowhurst »

Chris, if you start the removal of a spray deck by a slight forward push, followed by a slight lift and then a pull, the deck will remove smoothly. After a couple of practice capsize drills, the procedure is automatic. If you wish, I can send you a PDF of Vember's alternative cockpit. This has a tapered front that makes spray deck removal easy, but it will be too narrow at the front for some people's comfort and confidence in ​a swift exit.
Prospective builders should be aware that you have chosen not to follow the cockpit rim and upstand construction I describe in the Build Manual. This permits the builder to cut any desired hole in the deck for the cockpit, and to build the rim on top of it.
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Re: Shrike, a lightweight sea kayak for home construction.^

Post by ChrisJK »

Thank you both.
I did realise it's not the ideal way to test.
Yes please to the pdf.
The cockpit as made as I have fits into the slot snugly. I am happy with the size of the opening.
I can further customise the front to suit as long as it is strong enough.
I have rounded the front end so hopefully that and adding a slight taper to the edge will sort that and also strengthen the rim.
I am only slightly off piste.
I intend to do first wet exits in a pool and master rolling asap.
This is the fun of making ones own boat.
Thanks again
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Re: Shrike, a lightweight sea kayak for home construction.^

Post by nickcrowhurst »

Chris, I've emailed you an A4 PDF and the co-ordinates.
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This is the alternative shape of cockpit for Vember or Shrike

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A Vember Expedition in Canada

Post by nickcrowhurst »

Gilles from Canada finished his Vember Expedition almost a year ago. One can see the high quality of his work in this photo, taken before the decks were installed. She was his Covid lock-down project, completed in 4 months. He added two centimetres to the height of the topsides in order to accommodate his size 11.5 shoes. Giles is very pleased with how the kayak paddles, and says that it fits him like a glove, and that he was previously unable to find a commercially available kayak that was comfortable. Well done Gilles!

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

Post by nickcrowhurst »

Vember's alternative cockpit shape is now included in the Shrike download at https://cnckayaks.com/shrike/downloads/
Here's an elegant view of Gilles' Vember Expedition during construction in Canada:

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

Post by DavidDeWitt »

Beautiful boat. What an immaculate shop!
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