Rebuilding International Canoe 257

A Major rebuild of a middle aged Nethercott International Canoe, with a bit of a diet involved.

Mast Hacking!

257 Rebuild Home - Latest Updates

The first half of the rebuild
Weekend 18/19 August 2007 - Weekend 1st/2nd September 2007 - Weekend 8/9th September 2007 - Week 1st-7th October 2007
Weekend 13th/14th October 2007 - Weekend 20/21st October 2007 - Fortnight 10-25th November 2007

The second half of the rebuild
Week 4th-9th December 2007 - Weekend 15/16th December 2007 - Christmas Week 23rd-26th December 2007 - 29th December 2007 to 13th January 2008
Weekend 19th/20th 2008 - Week 2nd-9th February 2008 - February 2008 & Launch

Altering the carbon mast
UK IC Web Site - International IC Web Site
Email the Author

Mast Hacking (1)

I mean that in the old computer industry sense of modifying things to work differently to the way they were originally designed, and not in the sense of vandalising other folks' systems, or for that matter in the sense of assaulting with a hacksaw... At least I think not the latter...

Anyway, to give you an idea what I'm up to, I've formulated some theories about how I think a better Canoe rig might work. Of course they could be complete nonsense, indeed that's got to be where the smart money is. Anyway, in order to trial this idea I would really need a new mast, but that's a lot of cash to shell out, so I thought I might try modifying the existing one.

The thinking behind it is that I really admire the function of recent multi spreader skiff style rigs, especially the gust response and bend characteristics. What I don't admire is the forest of wires to keep them up. One set of shrouds and one set of spreaders seems to me as much drag as an IC should be pushing through the air. The current rig on 257 is rather unsatisfactory. Its nice and light - indeed its a rather lighter section than most ICs, being an ex Andy Paterson Cherub mast. Wanting gust response as I do my spreaders are raked aft, whereas most ICs have neutral or slightly forward of neutral spreaders for power. When I tried setting mine like that the boat staggered in the gusts and seemed nasty to sail, so they went back again. The trouble with this is a definite tendency for the rig tension to force bend into the bottom of the mast, which is where I don't like to see it. This seems fairly common on ICs. So I want to take bend out of the mast below the spreaders, and encourage it to start bending at spreader height, but with most bend above the hounds. One way, of course, to stabilise the bottom of the mast would be lowers, but I dislike the extra wires, one of the reasons why I have the mast stump which stops kicker induced bend.

So I was thinking that maybe I want a mast which, instead of being tapered to the hounds, and parallel thereafter, keeps on tapering to spreader height, and has a stiffer lower section. I reckon this should bend like a check stay restricted skiff mast, but without the extra washing lines out in the breeze.

However getting one of these made would be rather expensive, especially if the thing turns out out to be an abject failure, so I thought I'd see what I could do with the current mast to test out the concept.

The idea, then, is to add something over a millimeter of carbon to the front face of the mast below the spreaders, and taper this off above the spreaders, probably going down to nothing extra in the region of an old break and sleeve some way below the hounds. This means cutting back the spreader fitting so that the fibres can run uninterrupted past it, and then building it up again afterwards.

It has to be said that this mast modification is way past my comfort zone - I'm quite happy about gluing bits into hull shells, but masts are the next level up in the challenge stakes. Still, as these things go, gluing a bit extra onto a mast that already works is about as simple as it gets. It probably ought to be vacuum bagged and all that, but I haven't got the facilities or the experience, so I guess it will just be a question of consolidating down thoroughly with tape. Heat shrink plastic would be a good choice too, but you guessed it, I don't have that either... I wonder if Marineware in Southampton stock it, and I wonder if I'll be able to get over there this week (if you're not in the UK, South east England is currently under a foot of snow. As this happens about every fifteen years everything has stopped!)

So Monday was spent sanding the paint off the front of the mast where the extra carbon will go, and then masking up as much of the tube as possible for the inevitable drips and bits of epoxy.

Tuesday morning was taken up finally getting the boat remeasured after the rebuild. Embarrasingly she doesn't quite meet the old one design restrictions. I hadn't read the rules before doing the rebuild, and the foredeck, which I thought I'd measured exactly from the old one, turns out to be 5mm too high for the old one design restrictions. Moral - always read the rule book! The gunwhales are also bang on the old width limit which I think is more by luck than judgement - again I forgot to check. I guess its because the last big projects were the PlusPlus, for which there was no rule book to consider, and then a conversion job on the Cherub which only involved one measurement: I suppose I've got out of the habit of checking the numbers regularly. Its not a serious problem - if a future owner wants to turn the boat into an AC it will be easy enough to lose the odd 5mm whilst the fordeck is off to do the kite chute and related bits and bobs. Tuesday afternoon was over to Marineware to pick up some carbon unis and the heat shrink tape which they stock.

So Wednesday was time to get the hands - or rather the disposable gloves - sticky. The challenge with any kind of lamination job on masts is getting it all on in a decent cure time. This job is of course trivial compared to a complete mast but its still worth taking extra time on preparation to make things less stressful. Make an area where you can wet out the cloth off the spar - a piece of flat timber on the bench and covered in polythene will do. The longer it is the easier of course. Cut the fabric and peel ply to size and lay it all out bench ready and get other consumables within reach, together with extra disposable gloves and whatever tools you need. I also made up a two foot diameter tube of polythene which was going to go round the finished layup so that I could direct warm air down it for curing. Basically its just a question of wetting out each layer in turn and putting it in place, but there's all the issues of making sure you don't get wrinkles and ends tuirning over. Then the peel ply, and finally, working outwards from the spreader bracket, winding on the heat shrink tape. You can use ordinary PVC tape of course, but for me I tend to find that it stretches unevenly, and I get a scalloped effect where the laminate is more compressed in the centre of each tape wind than the edges. The (glueless by the way) heat shrink tape is much more stable, and it was quite easy to wind it on and get the laminate flat. Then its got to be heated up to shrink the tape and consolidate further. Obviously this should be a controlled constant temperature, but I used a paint stripping heat gun... Then on with the tube, direct a blast of warm air through and leave to cure...

Mast Hacking (2)

I never got round to finishing that story did I?
So yes, the mast was left to cure. Then of course I stripped all the consumables off, did various tidying up, including some reinforcement of the mast foot, added paint (mixed up two pot by the disposable teaspoon full which was handy for such a small quantity) and went sailing.

The mast bend does seem to be more to my taste now. I've lost a bit of gust response with the extra low down stiffness, but not enough to cause too much of a problem. next on the list is new sails. I'm experimenting with a larger jib - most IC jibs seem to stop well short of the mast, which seems odd to me, so I've had a new jib cut which is fully battened and just about touches the mast which is more like practice in the skiff classes.

I've also added a N12 style dangly pole. Jib cntrol offwind has worried me for some time. My original idea was to have a self launching pole from the boom which could be used to goosewing the jib to run square, especially in lighter conditions. So I visited the local fishing tackle shop and came away with a two metre length of tapered carbon tube for a tenner! I prototyped up a launching and retrieval system using bits of timber and plastic chopping board (useful source of high density polyethylene) but soon discovered that the idea is quite impractical. Its the jib sheets that kill it - you need vast lengths of free jib sheet for a goosewinged jib, especially on the lee side, and this is quite incompatible with having the sheets led to the plank for easy tacking. I suppose if one were really into string some sort of arrangement could be managed, but I just sulkily abandoned the idea...

So now I've got a more conventional dangly pole. If you're not familiar with these basically there's a stainless ring glued into one end of the pole, with a block running into the pole next to it, and the other end of the pole is left open (but well reinforced!). There is fixed line on the mast from gooseneck to spreaders, and the ring is threaded through this. A piece of shockcord runs round a turning block on the mast at the spreaders and pulls the pole up, and a line runs from a cleat back on the boat, up the mast, through the turning block on the pole and through the end, and then tied on the jib clew. For upwind sailing all this is left loose, and the system doesn't affect the sail setting at all. For downwind you pull on the line and the pole is pulled to the jib clew and down the mast, tensioning the jib leech and tending to boom the jib out until restricted by the jib sheets.

So how's it working? Downwind speed seems better, quite a bit better with the dangly pole. Upwind speed is proving an issue. I am having no end of problems sorting out the tuning settings, which is something I normally pride myself on. However I don't have the matching mainsail yet, which will make a difference... All the rubbish in the slot, dangling pole, extra lines in front of the mast etc can't help either, and that is why the first idea was to use a boom launched pole.

257 Rebuild Home
The second half of the rebuild
The first half of the rebuild
Altering the carbon mast
Email the Author

HTML check . CSS check