Carbon fibre mast - is it likely to be worth it.

I have come across the opportunity to replace my stock kayak mast(s) with carbon fibre replacements & I am polling for any thoughts on whether or not this would be a worthwhile investment of some of my hard-earned $...

Basically I sail at every opportunity I can - which means most trips through our fairly long season down here - on both my single (Adventure Island hull only) and a twin masted Oasis double (I have recently added a second mast which is an excellent upgrade should any of you kayak sailing junkies want the recommendation).

Given the amount of sailing I do I get a bit frustrated that the stock masts bend so much with the knock on effect on sail shape and sailing performance. I have experimented with stays for the mast - these do dramatically improve sail shape under load but they are a bit of a pain to implement and manage while on the water. So I am wondering about the potential benefit of a much stiffer carbon fibre mast.

Clearly this would have the added advantage of a lot less weight aloft.

I have not delved too deeply into the possibilities yet but I envisage that the cheapest/simplest option will be a one-piece mast of constant diameter though it might be possible to get a two piece arrangement, either of a constant diameter throughout or one like the stock Hobie mast where the upper half is a smaller diameter and sits inside the lower half. I do not think it very likely that a properly tapered mast along the lines of the AI mast or a windsurfer mast will come in my budget but when the time comes I will investigate the art of the possible.

Has anybody out there got any thoughts/suggestions/advice/experience on the matter? If so I would greatly appreciate the opportunity to kick the idea around a bit before committing...

I like the idea! I would also like a stronger mast, but I'd probably be too cheap to spend on a Carbon Fiber mast
Two thoughts came up though:
1. The stock mast can bend if you roll (like I did) and the sail gets a bit of water weighing it down when you right the kayak. Wouldn't a CF mast just snap in that scenario? at least the aluminum mast can be bent back into shape.
2. The mast holder is probably not engineered to handle more stress than the stock sail+mast combo can, so how do do you plan to fortify that?

The AI and TI both have CF masts, but haven't seen an issue with righting the boat (not that it happens that often). If you turtle the boat you should release the block for the sail prior to righting anyways to avoid capturing water.

If you thought that the aluminum mast had a lot of play in it you will not be happy with the CF, it's meant to flex. That's why you don't see stays on the AI/TI.

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Thanks for the comments & observations.

I have turtled several times but haven't bent a mast yet - the advice about freeing the sheet before righting the boat is correct.

As to the amount of bend in the AI mast - sure it does bend (and quite a bit) but it is a tapered windsurfer mast and is therefore designed to have some bend built in especially in the tip section.

I am told that the carbon tube configuration I am being offered will be much stiffer than the equivalent alu tube - I am told that it will be a lot more fragile (e.g. if you were to stand on the mast) but I am not yet being told that it will be more likely to snap.

w.r.t. beefing up the mast base - it is a consideration I am not convinced that this will be necessary: as more pressure comes onto the sail the boat leans spilling wind from the sail and reducing the pressure in the sail. I also sailed my Oasis with its single mast in reasonably strong breezes: in that boat, with twice the 'ballast' of the Adventure to resist heeling and to be moved by the sail the mast base has shown no signs of breaking down. Also on my Oasis I have now added a second mast base for a foresail (making the boat a schooner or ketch) - this mast base has been implemented by cutting a hole in the deck into which the mast base is glued. On the inside of the boat I have taken a piece of an old scrapped Adventure hull with the fitting that accepts the bottom of the mast base in the Adventure (just a lump over which the mast base sits) and I have glued that directly below the new mast base using Scotchweld 8050 (or whatever it is) - this seems to be holding up fine). And I have linked the two with a length of a domestic aluminium tube which is jammed inside the bottom of the new mast base (it is hollow) and reaches down to locate on the glued-on knob. All this sounds pretty home-made but it seems to be holding up fine which either means that the glue is very strong, or the forces are relatively light, or the components are stronger than they perhaps appear, or a combination of all three... so I am relatively confident that there's enough margin for error in the strength of the stock mastbase set-up.

If I use a stiffer replacement mast I suspect that the boat may show a somewhat greater tendency to heel, as opposed to the mast bending to spill wind, especially upwind when there's a lot of lateral pressure on the sail but I am not expecting the mast base to collapse under the stress (and in any case my mast base is the much larger AI base with a home-made adapter to take the smaller mast).

The CF mast would probably handle the torsion a little better than the aluminum. That's what's nice about CF. I wouldn't say it's more fragile. You need to understand that CF is not very good when it comes to compression, which is why they use it in the front end of F1 cars (they want it to crush). But, at the same time it is very good at distributing bending and torsion forces. This is why they use it in bicycle frames and steering linkages. So, yes, if you were to stand on the CF mast you would be imparting a compression force, which could cause it to fail. It also depends on how they lay the CF when building the mast.

If you have the pocket change go for it.

_________________
2015 Hobie Tandem Island Hibiscus
"Third Normal Form"

• Trampolines
• Hobie cover
• Davis Spar Fly
• Kayakbob's Sprayskirts
• Spine Board Hakas

So you did get the second mast fitted. Well done. I was wondering how it had gone. Some pics would be great.
One of my mates bent his alu mast on his Oasis and replaced it with a CF one piece tube. I'll ask him about it.

How stiff the carbon mast is depends entirely on the diameter, wall thickness, taper and type of carbon. There are dozens of combinations that would all result in carbon masts, each with a different amount of stiffness/flex. You could certainly have one built in the same OD as the current aluminum one and have a stiffer mast. The question is, do you really want to do that?

If the mast does not bend and spill some air, then your sail is going to generate more power and therefore the boat will heel more. Heeling also spills air and decreases power. But the question remains as to whether or not the additional heeling will constantly place you closer to a capsize or other sailing malady.

Request for pics seconded!

Thanks again for your input & observations.

I'd be very interested to hear via Stringy from someone who has tried a CF mast...

To Tom's point about some mast bend being desirable - I guess it probably is... I think it is just a question of degree! I note that most sailboats do not have bendy masts though obviously there is not a direct one-for-one comparison between ballasted sailboats and our tiny unballasted kayaks. Also it perhaps goes without saying that there are several ways of spilling wind from a sail - mast bend being just one of them (the others that I know being sheeting out, heeling, steering upwind/weather helm and scandalising the sail). I think what I am seeking is a mast which has a lot less bend so as to maintain good sail shape/performance though I recognise that this will, in all probability, require me to be a bit more proactive w.r.t. spilling wind in the gusts because the mast is not going to do this for me.

Requests for pictures of my Oasis schooner/ketch mods noted... I will take some the next time I am at the beach and see if I can post them up here somehow.

Thanks again guys and gals.

Answering my own question I made up a carbon fibre mast over the weekend and I have to say that the results are a noticeable improvement over the standard aluminium job.

I built it from 2 offcuts of CF tube of approximately the right diameter just like the stock mast (cost $NZ100). I used an external fillet of epoxy glue round the top section to stop it from sliding down into the bottom section.

First benefit - the mast is a whole lot lighter to lift into position.

Second benefit - the mast is a whole lot stiffer which results in a much better sail shape especially as the wind increases - I was able to test it over the WE in 'very light' to 'quite strong' Hobie-kayak-sailing breezes and on all points of sail.

Third benefit - there's a lot less weight aloft so when the mast & furled sail is in the mast base there is much less swinging moment due to there being less weight aloft - you can feel that the boat is more stable.

Fourth benefit - this is a double-edged sword: the mast is a lot stiffer so, as gusts of wind hit, the sail doesn't deform to anything like the same extent as it would on the standard mast; this means that (at least in theory) more of the power of the wind will be turned into motive force to push you... forward or over! So the other side of the coin is that the boat feels a lot more sprightly under sail but also a lot more twitchy with respect to heeling (i.e. you need to respond more actively to gusts which translate much more quickly into heeling because there's so much less give in the sail).

Overall I am WELL impressed and am already planning to make another so I have two for my Oasis schooner! I am also going to have to do a 'float test' to ensure that if the mast were to slip out of the sail it will not sink (If it does sink I will have to find a way of blocking the ends of the tubes up to make them airtight - should be easy enough)

For those who asked I took a couple of photos of the schooner set up and will try to post these when I have a minute or 30.

Hi I am Stringys mate form the central coast. I replaced the standard aluminium mast after I bent it capsizing (bit underwhelmed with Hobie support) so went looking for a better design. Looked at aircraft grade aluminium but was very expensive and difficult to get the right size. I found the people at CST Composites in Caringbah very helpful http://www.cstcomposites.com/markets/marine/
The only problem was the diameters of available mast material are fixed and they don't seem to produce to specification. My order was ID 19.1 with 2 mm thickness of the tube giving 23.1 the actual OD was 23.5 mm which I sanded down to 22.8 mm giving a very snug fit after I sanded the inside of the mast step. This means that any fast furling is out of the question to furl it on the fly I twist the sail around the mast. I practice if I am travelling in a direction where the wind is not much help I take the sail and mast out and lash it to the side if the yak.
Sailing the mast performs well it has some flex but still holds the sail in good shape. Being one piece it can't be stored in the hold but is very light, with a plug in each end it floats. In 2009 the mast cost me $238.64 CST claimed that their product was at least 3 times stronger than Aluminium.
I bent my Aluminium mast back but have never used it I am sure it would be significantly weakened and would let me down again.
Cheers
Geoff

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Croc

I also bent my stock hobie kayak sail mast (actually several times, and had to straighten it often). I ended up fixing mine up a little differently mostly because I priced out carbon fiber and couldn't afford it (expensive stuff). There is another material out there called fiberglass pulltrusion which is very strong but way cheaper and more readily available (same material that is used in fiberglass ax handles). Over here fiberglass pultrusions can be ordered mail order in any diameter an length you like either hollow or solid. Actually the bow sprit and mast topper on my TI are made from 1/2"x3/4"x 3ft oval fiberglass pultrusion material and the stuff is so strong I can place a brick under each end and jump up and down in the center like on a trampoline all day long if I like (im 220 lbs). Carbon fiber is the buzz word these days, but fiberglass pultrusion is usually way cheaper and much more common out there. The hobie kayak sail has a joint in the center (2 poles), I just glued mine together with epoxy (mine can no longer be broken down into two shorter poles (I never used that feature anyway since I always had roto furlers on the sails).
What i did with my kayak sail mast was drill out the cross pins that hold the internal bungy cord, and removed the bungy. I then went to home depot and bought two 3/8" dia x 4ft long fiberglass pultrusion poles (they are orange and they call them safety or flag poles (they cost $2 bucks ea).
I then slipped them into the mast tube and put a dab of silicone on each end so they don't fall out (removable). In the lower section (larger diameter internally) I slipped a couple small pieces of 3/8 pvc water pipe around the fiberglass to keep it centered in the tube.
I've always had rotating mast toppers and jibs on all my kayaks so I always needed that little bit of extra rigidity on the mast anyway, plus I got tired of bending the masts and having to straighten them all the time.
Hope this helps.
Bob

That sounds like a great solution. Perhaps Hobie might take it up it would be a big improvement on the current design.

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Croc