another post of a carbon flavour…

I feel as if I should apologise to my cycling readership for the recently rather kayak-heavy flavour of my posts… It’s not that I am not riding, I am.. it’s just that nothing exciting is going on in that department right now.. Just cruising around on my Storck and DeSalvo fixed and not really missing the racing scene and attendant training schedules at all :-) I may have some adventure cycling flavour of news to share soon however but in the meantime however it is back to kayaking and things of a carbon flavour… :-)

The Greenland Paddle.. the latest iteration has proven to be the nicest paddle I have ever used I think.. the word that sprung to mind while out testing it on a choppy day was “silky”.. the blade is wonderfully well behaved in the water and appears to be very efficient. I’m enjoying the wing-paddle effect one can get with a greenland stick with the right stroke. Effortless :-) The 600g weight is thoroughly spoiling me.. I have continued to use my euro-blades with my Tiderace just so I can enjoy the Greenland all over again when I get back in the skinny Tahe boat.. hence this picture taken by a friend last weekend while exploring the nooks and crannies of Godrevy Island on a rare perfect summer day. Nooks and crannies of a different kind appeared to be on offer when our planned lunch stop turned out to be a secret nudist beach… we didn’t stay long.

black paddle.. black boat

perfect match for the Tahe Greenland

I’m happy enough with the design that I think I’ll offer it for sale later this year…. drop me a line if interested.

Fins then.. I didn’t really plan to write any more about these but I feel compelled to. I have a couple of sets of 3.5″ fins in use by friends and the feedback has been of the <quote> “.. fu**ing fantastic..” and “amazing” flavour.. Modesty suits me I think… <cough> One of my friends has been selected for the GB team at this years surf kayak world champs.. and he’ll be using my fins which is a very cool thing :-) The performance of them as compared with commercial glass fins does appear to offer a significant improvement in speed and responsiveness. Durability appears to be excellent too. Now that I refined the construction I might just have to start offering these for sale (to order) as well. Price I think will be £70/set, a price that compares very favourably with Rainbow glass fins, generally considered to be a very good fin. I think it is fair given the cost of carbon and the amount of work in a set. There is the added advantage for the owner in that damaged fins can be returned to me for repair and should one get broken or lost I am happy to make single replacement fins.. which is something you definitely don’t get with standard commercial fins. Later this year I’ll get around to developing some more templates.

mmmm

All of that, and the ongoing Boatbuilder’s Story project is going to have to wait until the fall.. sorry, autumn. You see in 10 days time I’m off up to the Outer Hebrides to pick up a job working as a sea kayak adventure guide. A summer of week long kayak/camping adventures among the wild coastlines of Barra, Uist & Harris. Can’t wait.. but it is also going to be the longest period away from my bike and riding for, oh.. 15 years or more . Hmm.. will probably do me good :-)

a final bit of fintology..

hmm, fintology.. that’s a stupid word but it’s all I could think of for the minute. I’m stuck in waiting for a courier this morning so I may as well fill some blank space on your screen.. This is probably the final carbon kayak fin post for now.. it needs to be posted as the fins have been through a reasonable amount of testing now and appear to be doing very well.

Despite being hollow and quite light they’re standing up to rough launchings and landings very well.. just the usual scuffing/abrasion from sand and pebbles. These fins haven’t got any form of additional clearcoat over the moulding.. at the time I didn’t see the point in the extra time and expensive in finishing with, say, a 2-pack polurethane for a set of prototypes.. but in future I think I will, it is tough stuff and should help keep them looking nice a little longer.

Here are some pictures of the setup I have on my XS.. the center fin is a smaller, higher aspect ratio fin than is standard.. the reason for that is a regular 3.5″ fin in the center box on this boat stiffens up the turns way too much – it is a relatively long boat and doesn’t need all that ‘finnage’. Running with thrusters only kept the boat very loose in the water but I found myself wanting more grip and more drive in certain situations.. hence that fin design. It is 3″ tall with a base measurement also of 3″.. and it has worked a treat.. I find the boat now has exactly the kind of the behaviour I was looking for, it has turned out to be, for me, a perfect set-up.

center fin on my XS

The thrusters are a pretty standard shape, 3.5″ tall, flat on the inside face with a 7mm deep foil shape but significantly stiffer than regular fins. I’d hoped the stiffness would give me a sharper turn response… and that is exactly what I got. Not much more to say about that except they work great. They were a little more difficult to make than the center fin due to the ‘depth’ of the detail in the root, took me a few goes to get it right but now I know what I’m doing I have myself an ‘endless supply’ of fins.

thruster fin

People have said I should be selling them, mainly based on the looks I think.. but as a commercial exercise they don’t really make sense.. it is time consuming and fiddly to make a fin with all the local reinforcement necessary so I couldn’t sell them at a price competitive with the commercial glass fins on the market.. and the market is tiny relative to surfboard fins. I am however in the process of meeting requests from a few friends for sets so if you did want a set, or even a custom fin design drop me a line.

another carbon Greenland paddle

I’ve just finished making myself a second carbon Greenland paddle. The first one has been a great success, very nice to use – comfortable and very efficient, and has proven itself more than tough enough. The reason for this new one is that I wanted to modify the blade profile slightly and vacuum bag the components rather than just rely on a hand layup.

Rather than start again from scratch I simply modified the original plugs and made new moulds. Saved me a lot of time. The vacuum bagging of the components has resulted in quite a significant weight saving, this paddle at just 600grams for a 2.19m paddle is noticeably more feathery than the last but using the same number of plies (4 of 200g/sqm twill carbon) ahould be easily as strong, probably more so thanks to better consolidation of the laminate. The only ‘issue’ I found using a vacuum bagged laminate is that the thickness is noticeably less than before, joining the blade components was an exercise akin to gluing paper sheets edge to edge so rather than joining using an internal fillet of epoxy/microfibre paste I’ve used an external wrap of bias cut carbon over the join. It looks fine but not quite as tidy. Still, it is a handmade thing and the delight of it is more in the using of such a light blade rather than the admiring of it… though that is nice too :-)

I'll get better pictures next time I head out on the water.. The black fade on the loom looks rather nice I think. Unnecessary but nice..

While I’m on.. an update on the carbon fins.. they are proving themselves more than up to task of withstanding rough launchings and landings and the performance improvement on the boat is noticeable. I’m very happy. I’ll write more about those shortly.. stay tuned!

p.s if you want to know why I’m not using the arguably simpler route of carving a foam core and laminating directly on that… it was simply an issue of cost, locally I could not get the styrofoam I wanted in quantities less than 70 or so sheets, and mail order courier costs plus small quantity orders were not economical.. so I made it hollow again. It makes a lovely paddle but is more work.

carbon surf kayak fin – finished article

an update on the carbon fin project is in order I think.. mission success if you like.. (previous posts on making the blank and the mould here <link>)

I’m still playing around with the layup of the fin shells but this first fin has 5 layers of carbon at the root tapering to 3 at the tip. The root area itself is filled out to the rectangular profile using scraps of carbon with a random fibre orientation – worked great. The whole lot was vacuum bagged using a rubble bag sealed with PVC tape – I did use proper peel ply and breather material however.. The valve is another homemade lashup using a threaded pump adapter, a flanged nut off the back of a chainring bolt and some rubber washers hacked out of an old inner tube. Works just fine.

mould and fins in the vacuum bag.. all a bit heath robinson but it works great

The fin halves were trimmed while the resin was still ‘green’ but once fully hard they popped out of the mould beautifully light and very stiff. Where holes needed to be drilled in the root for mounting hardware I just made an internal fillet using a epoxy mixed up some finely chopped strands of carbon – carbon ‘fluff’ if you like.. a pair of scissors and a fingerful of scrap cloth. When the shells are joined these areas will be solid.

fin shells fresh from the mould

After rubbing the shell interface flat using some 120 grit paper taped to the bench the shells were joined using more epoxy mixed with ‘carbon fluff’. Clothespegs held it all together while the epoxy went off. In terms of finishing I didn’t do much figuring this is just a prototype and may well get trashed very quickly.. a quick rub down of the joint and general cleanup with some fine wet sanding. The finished fin is quite light and incredibly rigid, I can’t put even the tiniest amount of bend in it. It feels bombproof but only time will tell how durable it is.

the finished fin with another fin blank - a smaller, skinnier central fin for my XS. The white things are the moulds for another Greenland paddle..

It’s great for me as I can mess about with different shapes for different conditions without spending anything more than a few hours work.

** 11July 11 – there is an update on these fins here http://mikesimagination.wordpress.com/2011/07/09/another-post-of-a-carbon-flavour/ and here http://mikesimagination.wordpress.com/2011/06/22/a-final-bit-of-fintology/ **

installed...

So there you go.. a bit of fun. Now I think it is time to plug my book again.. Sixty Degrees of Latitude. If you haven’t already go and read my previous post…

cheero!

p.s a friend asked me why I didn’t use a foam core instead of doing it this way. While I think a foam cored fin would be fine for surfboard or SUP use I don’t think it would be tough enough for a surf kayak. Making the fins the way I am means I can add internal reinforcement and play about with the fibre layup without changing the external dimensions.

a Thursday roundup…

Various projects have been moving slower than expected for a number of reasons, including having to repair my carbon paddle after I noticed some damage,  so I thought I would post a quick round up..

1. The carbon surf kayak fins.. I have a nice mould now, pictured. The first attempt did not work out when the mould did not release cleanly from the blanks so I went back to scratch, carved a new blank from MDF again and this time coated it in epoxy, which is what I should have done first time around. Lesson learned. It is more work but let me use conventional polyester gelcoat followed by layers of chopped strand mat and polyester resin for the mould itself. With a few coats of release wax the whole lot separated beautifully and now I have a nice mould. I am in the process of sorting a vacuum pump, a situation that should be rectified by the weekend.. so I should have the first fin by sunday evening if, as always, everything goes to plan.. which it rarely does.

fin mould in GRP

2. Boatbuilders Story.. just waiting for the text now, that part of the project is being done my another family member so the project is stalled until I get that. Shouldn’t be long.

3. Sixty Degrees of Latitude.. I received the first hard copy a couple of weeks ago, it looked really nice in print but not quite perfect to my mind so I made a few changes. I should have the second copy in my hands by the weekend.. if I’m happy with that then I’ll make it available to buy….

Other than that.. business as usual.. bikes & kayaks. I’ve not been spending as much time around bikes as I would like simply because I have noticed that I’m not tolerating hard riding as well as I should so probably still recovering from the last year of pedalling in S America. I have also just ordered drawings from the States for a cedar strip kayak, a Petrel design by Nick Schade. Building a strip kayak has been on the list of “must do things” for quite some time.. so  no time like the present. It’s a pretty boat, not sure how long it will take me.. 150 hours, possibly more depending on how fussy I get over the fine detailing. I’m thinking some carbon hatch plates and cockpit detailing would go beautifully with a high gloss wooden hull… anyway, I’ll write more about that when the timber is ordered and the build is underway. A few details of the boat below.

Nick Schade design Petrel

v pretty boat

more carbonology, a surf kayak fin project

(* for more & updates on this project click here *)

This is very much in the realm of experimental, I have no idea if this is going to work out because of the fine detail in the moulding and the strength required so I’ll introduce the project and what I’ve done so far and then say no more until it is either a huge success or a miserable failure..

Surf kayak fins have a hard life, harder than the average surf-board fin because you have no choice generally but to get in the boat while aground on the beach so as well as dealing with the enormous forces involved while flying along a wave they also have to cope with being dragged through sand and pebbles, the occasional bashing from a rock and so on. A good fin also makes a noticeable difference to the performance of the boat.. a very stiff fin gives more speed and snappier response but is probably less forgiving. Commercial fins seem to run upwards of £60 for a decent composite model so I decided I want to be able to mould my own as and when I please with the potential of being able to flog a few to my surfing buddies..

Before I go on there is some useful fin theory over on the surfkayakskills site (link) or click the image below. By the way the site exists with the aim of helping to raise funding for the GB surf kayak team who did rather well at the last world champs and are headed to North Carolina for the 2011 edition later this year.. so do explore the site and if you learn something useful you can make a donation if you so wish.

Surf Kayak Skills (www.surfkayakskills.com)

To the best of my knowledge most, if not all, commercial fins are made by simply laminating a slab of fibreglass to the desired thickness and then grinding to profile followed by polishing. It’s easy, fast and makes a strong fin.. but it is also wasteful and may well be why you don’t see carbon fins around… glass is cheap so turning it into dust is no big deal. I’m not into large scale manufacture so I decided I’m going to have a go at a proper moulded fin.. and I’ll make it out of carbon for a couple of reasons.. I have some left over from the Greenland paddle project .. and it looks cool :-) Initially I am just making the centre fin as this is the most complex – it is a symmetrical foil shape so needs two moulds, one for each side and also means I can test it for durability on my boat without having to make matching thrusters (the outboard fins in a 3-fin setup). The thrusters are a flat-bottomed foil so only need one mould each that can be mated with a flat slab laminated onto a sheet of glass or similar.

cutting the blank from a double layer of 5mm MDF

Using my existing centre fin as a pattern I cut a blank from 2 layers of 5mm MDF tacked-glued together. I’m using MDF because it is dirt cheap and easy to shape… though the downside is it is very porous so needs a high degree of finishing before I can take a mould from it.

The fin needs to be 8mm thick so the 10mm thick blank was shaved down to 8mm, 4mm each side of the centre join and then carved to a symmetrical aerofoil.. it’s all done by eye using a smidge of aerodynamics experience.. I knew a degree in aeronautics would come in useful one day ;-) In reality the shape isn’t going to be desperately critical so long as the maximum thickness occurs somewhere around 30% of the chord from the leading edge.. and that the leading edge is nicely rounded with the trailing edge tapered smoothly to a fine edge. It is not knife edge thin as the finished laminate needs a certain amount of thickness for strength.

the raw blank

The carved and sanded plug was then split into two and finished with multiple coats of a shellac-based sanding sealer, sanding with fine paper between each. At this stage the process is ongoing, I want as fine, glassy finish over the porous MDF. I used the shellac stuff simply because I had some.. and it is very easy to cut back smooth. The downside is that it means I will have to use epoxy and woven glass cloth to make the moulds rather than a cheap polyester gelcoat & resin with chopped strand mat – the styrene in polyester resins, plus the heat generated during curing would likely trash the finish on the blank. The alternative would be to coat the blank in epoxy but that’s a bitch to cut back smooth, especially on such a small part with some fine detail.

carved and sanded..

blank split into two, building up multiple coats of sanding sealer

So.. from here.. the plan is to mount the blanks on a sheet of smooth acrylic, polish the lot with a mould release wax and make the moulds. Going to use epoxy and fine 200gr/sqm woven glass cloth to conform to the fine detail around the fin root. If that works out OK then I’ll make the fin halves using first a layer of very fine 80g/sqm glass to fit the fine detail, followed by 2 or 3 layers of carbon twill cloth, maybe more cut to fit inside to taper the thickness of the laminate. The outer layer of glass will ‘disappear’ when wetted out and as well as helping to fit the detail will add a layer of protection/finish over the carbon. I’ll also add some local reinforcement around the root of the fin using some unidirectional carbon tows. The whole lot will be vacuum bagged. In theory that should leave me with two nicely moulded fin halves. I’ll glue ‘em together using an epoxy/milled fibre mix to give me a fin that is hollow around the root area. I have to drill holes through the root so with the fin inverted I think I’ll just fill the remaining void with epoxy and let the whole lot go off hard before cleaning up the edges, drilling and polishing… In theory.

Even if it doesn’t work out it’s still worthwhile.. I’ll learn something along the way and I like making shit anyway. Could be interesting.. stay tuned :-)

p.s in case you’re wondering where the general cycling flavour of the blog has gone of late… haha, yes I am still riding lots and still as interested as ever but nothing has changed in the fleet of late, no new jewellery to play with  - that is the fault of my DeSalvo fixed, it is ‘perfect’ and requires no ££ to be expended.. and it’s easy to play around making relatively simple parts for kayaking where the safety implications are less critical – other than a broken paddle say :-)

p.p.s as for the books.. well I’m expecting the first hard copy of Sixty Degrees by the end of the week.. and A Boatbuilders Story is ongoing happily.