Thanks Bob!! Very good info...I was about to ask about the difference between kevlar and CF construction. If Kevlar was considered slightly more durable...why the switch to Carbon? Is there a significant weight difference? I find it interesting that they reduced the number of bulkheads...again, ??weight savings??

hi jl,

Dont be afraid to add a spin to your A. disagree with those saying you have to stiffen the mast. 2x A worldchampion Bunkenburg (~85 kg) as well as myself were using F18 kites in up to 20 knots of wind. He used a saarberg mast while I used marstroem masts without problem. don't advice 21 m² so... in this case less is more! as soon you want to sail competitive against other boats and the course is not a triangle ur up+down, its more important to be able to run the same angles as the others. I was constantly running about 10° lower than F18 and co. The result was that in a lot of long distance races I couldn't use my kite while others could. Two main problems have to be solved: you need a kind of crossbar to prevent that the siteforces generated by the spi pulls the hulls together. A's are sensitive to windage, so snuffer, lines, bars will cost you deeply upwind speed and angle if not designed with care. Best concept how to support your spipole is shown with the marstroem M20 and M18 (widened A-cat with spi) using carbon tubes (masts for rc modelboats) to support the pole while dealing with compression forces same time. I would recommend an F16 spi for the A: the luff lenght is quite short (so you don't have to mount the spi halyard block to high) and the shapes are pretty flat nowadays. ask AHPC for a 2nd hand spis. you could even consider the AHPC (former Boyer/Fibrecraft) alu-tube snuffer, although it will be not the most less windage one, but its quite cheap and works well.

a marstroem A would suit your weight fine and construction quality is probably the best available. 2nd choice would be mk5 or AHPC flyer.

good luck!

I got to agree with Bob. I thought I'd get bored without a spin when we got our Marstrom A, but they go down wind well, and when you are racing in class who cares. Plus when the wind builds up you can do the wild thing - which is just about as fun as having a kite.

Chris.

Joe,
Boyer had his construction technique, mainly the hulls get their strength from the bulkheads, thinner foam. These were the Boyer Mark....up to V. You could get Kevlar outer skin with either 1) glass inner skin, 2) carbon inner skin, or 3) Kevlar inner skin. The choice was up to you, and you could also get Al or carbon beams. Also, boards and rudders could be either carbon or glass. You could therefore get a boat with quite a range of $, depending how you ordered it.
Flyers were not built in enough numbers to satisfy Aus, or US, so AHPC (Boyer) contracted to build the boat for those markets. The build was stipulated by the designer to be thicker foam so the boat gets its strength from the skins and not the bulkheads. There were no options on the construction...carbon, foam, then Kevlar outer. Also, no option for Al beams, carbon only, as well as only carbon foils. He designed (copy) the Mark V to be as close as possible to the Flyer underwater (if you can not beat them, join them). Above the water the boats look different.
Because the Flyer was so popular, Boyer stopped making the Mark V (he did not get any orders for 1-2 years). Last we talked he was working on a new design, but AHPC has gone through some changes recently.
Hope this helps,
Ken

Wow!! Lot's of good info....thanks all...

Dirk (or anyone else who knows...) regarding the spin setup. I assume one possible spinaker solution would be to order the Marstrom M18 spin setup, and shorten the front braces for the narrower platform?? Thoughts?? I'm not sure I like the snail, but it would have a lower windage factor than a tube snuffer...I guess I was thinking of doing something similar to the Marstrom setup, except to use a snuffer bag and mid-pole hoop on the pole. Sounds like an F-16 spin would fit the bill nicely?

Hey Joe. For my two cents the Marstom would be the package for you. It'll carry your weight and you can order the factory spin package. It is a tough, strong and fast boat, known for it's build quality. If you can get in touch with Dave C ask him how Brett M. is doing with his Marstrom with spin. The only thing you won't have is wave piercing bows. The only way around that is the DK-17 but then you have plenty to work out to do the spin right I would think. I too lust for a spin but will not go there with my Flyer. Ed

The problem with a Marstrom is that they are quite scarce in the US and I doubt one in decent condition could be had in the price range I am restriced to.

I'm sure the F16 spin would work fine on an A, although you may want a longer pole than the F16s use. Of course, an F16 itself would fit all your criteria as well, except class size smaller than As. Even so, F16 will easily carry the weight; typically stiffer masts; less expensive. Send me PM if you want more info.

Hi All

The new A they were working on is called 'The Tool' designed by Wayne Mercer, a long time Australian A Class sailor.

Jim Boyer and Pieter Saarburg? checked out Waynes prototype at the 2005 Nationals and both wanted to help build and market the boat.

Check out www.thetool.com.au or www.boyer.com.au and click on the tool link, the rest of Jims site is under construction and 'the tool' link is the only one that works, no photos on Jims site from memory.

Regards

I hate to write this down Bob, but the story was that :

-1- It was said the MK5 wasn't as good as expected and Boyer decided to build the orginial flyer to replace the MK5. The MK5 was only build for a short time frame.

-2- Boyer doesn't build any A-cats anymore and he nor AHPC are tooling up to make a new A-cat. As a matter of fact Boyer doesn't build ANY catamarans anymore as he sold all his tooling and terminated his boat building business altogether.

-3- For a while, till Boyer ended his boat building business they had build the Tool A-cat which is not a Boyer design, he only builded it. Since then the mould have returned to Wayne and Geltek (Ashby and the former foreman of Boyer) is building the new Flyer A-cat.

-4- AHPC (which is not Boyer fibrecraft anymore) is however tooling up for a F16 which will be launched this summer, maybe you confused the two boat types.


Wouter

Kevlar ; More impact resistant then carbon and also lighter then carbon.

Kevlar is more and more replacing carbon in hull construction. Some designs simply skipped the carbon phase in their hulls and went from glass to kevlar straight away. The downside of kevlar is that it is a hard material to work with. Try cutting it for example.

Wouter

Carbon and Kevlar are very different. They each have their strengths.

Kevlar

Lightest
Great impact resistance
Excellent strength is tension
Poor strength in compression
Absolutely sucks for finishing. It does not sand clean, it's fuzzy like an old sweater
Best in cored construction.

Carbon

Excellent strength
Easy to finish
Problems with sharp impacts and crack propogation
Stiffer
Current studies say it will last longer before it starts flexing, if it's prepreg. Hand laminates are about the same. Infusion should be almost as good as prepreg, I have some doubts.
Best as solid carbon, because the preregs are so good.

My personal favorite is 60-80% carbon with 40-20% kevlar near the middle. Once the limits are exceeded, it bends before it breaks and holds togather after it cracks.

I would suggest you try an A without a spinnaker first. They are fast in light air.

wouter, why do you assume kevlar to be lighter than carbon?

besides, it does not offer significant improvement over glass (besides side impact), far less strong than carbon, fibres don't 'soak' epoxy (try sanding it...), no prepreg available etc...

haven't seen any turn to kevlar in (A-cat) mast design either... what would be reasonable if it would offer any advantages...

The Flyer '2' is build in carbon in Germany (maybe they again use the strange ~75% carbon/~25%kevlar mix (only useful after collision as the kevlar keeps the broken carbon in place) while the Geltek Flyer '2' is build in kevlar. I assume there are two major reason for the later being a kevlar boat again: 1. costs 2. more sideimpact resistant.

Jl, try contacting Hakan

hakan.frojdh@bostream.nu

He sailed the M18 with spi to a 2nd or 3rd round texel a while ago. more remarkable he published a video showing speed differences on an A with and without spi (gps reading). he probably can answer you how to build the marstroem system. stay away from the spi-drum. upwind it might be better but malfunctions , spi life and limited angle for rise and lowering of the spi are not worth the better windage.

those who say you don't miss a spi on the A for open class sailing or long distance races just never tried it. you are so much faster. you can beat the M20 with an A+spi on line honours. you laugh about F18. In less than 10 knots Tornados become swimming obstacles. Raised some rating discussions once when beating the new crowned F20 European champions by half a lap in a three lap race in 10-15 knots of wind. Without spi they would eat you before the first downwind mark. The advantage of the spi decreases with stronger wind on triangle courses as hoisting and pulling in take (relative) more time.

If someone dont share my view, please don't feel offended, its personal view based on personal experience.

...that is, until you realize that you're the only A-Cat with a spin on the course.

Maugan, of course you will be lonely in front and better know the course. And the A's without spi are no company either as they are miles behind! ;-)

We talk about handicap racing, not class racing. In class racing all A are same slow downwind, same fair fate, no need for spi...

Thanks Dirk. And yes, you are correct. I am ONLY talking about using a spin in OPEN class racing...and then likely only in light winds (under 10 knots). There are NO Acats currently at our lake and I would be racing against other spinaker boats regardless of whether I had a spin or not purely based on standard Portsmouth numbers (and yes...I do realize my number would be modified with the spinaker!).

I have seen the video (didn't know who it was)and it is quite impressive!! Also your comments regarding the snail are consistent with what I have heard and are why I will likely stick with a more traditional pole snuffer even though there may be a slight upwind windage penalty.

Also, thanks to the folks commenting (educating me) onthe diff between Kevlar & Carbon construction.

If you contact Hakan (who also frequent this forum from time to time), why not ask his opinion on the Marstrøm "snail" snuffer? He should know.

The A-cats are not easy to keep up with to windward in less than 10 knots. Agree fully with Dirks assesment.

Dirk,

Please read my post a couple of times before replying. Most of the answers you seek were already given in the original posting.



I didn't assume that, I was told it is like that by a well known catamaran builder.



Strength is not a consideration in the hulls when viewed in the traditional sense, resistance to crack propagation and impact resistance is. This because both mechanism really limit the strength that usage of a material delivers in real life application with respect to laboratory measured material properties. Resistance to buckling (compression loads) is the 3rd such mechanism but I have not seen any reports that kevlar hulls are significantly inferiour to the other materials in this respect. Probably because adding bulkheads to the hull keeps the skin in column and thus negates any inferiour properties. In laymans terms; an easy fix is available to solve that particular issue.




I wasn't talking about masts but about hulls and said so clearly in my posting.

An added advantage of kevlar is that it is available at reasonable prices. This is very much NOT the case for carbon these days.





Try availability and the fact that most of the superior properties of carbon fibres are not really needed in hull construction, this in contrast to masts.

I'm noticing that more and more boats are using kevlar hull construction like some Volvo ocean boats and an increasing number of beach catamarans.

I can name at least 2 modern A-cats that have full kevlar hull construction at this time. And also several other catamaran types that either offer full kevlar hull construction or partially kevlar construction (with glass making up the remainder). Carbon fibre usage here seems to be on the retreat.

As such I recognise a shift away from carbon with respect to hull production.

Wouter

I can whole underscore this statement by Dirk. While I have never sailed an A-cat with a spinnaker before I can testify that an A without a spinnaker will be caught before he reaches the downwind mark. In most irrespectibally how far the A was in front at the A-mark.

Wouter