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#133040 - 04/24/08 11:44 PM Re: Building a mast [Re: Gato]  
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-- Have You Seen This? --
#133041 - 04/25/08 02:56 AM Re: Building a mast [Re: Gato]  
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Excellent work Gato, thank you for sharing!

Where did you get the "double carbon tube" shown here: http://www.gust.ax/gallery/mast/08-04-24/p4200033-640.jpg

Where do you buy stuff like peel ply and what is the approx. price?

Any opportunity to weight the mast and look at the bending properties yet? As I said, it is very exciting to see home built masts take shape! I want to try my hand at this..


You have one sharp plane! http://www.gust.ax/gallery/mast/08-04-24/p4210001-640.jpg

#133042 - 04/25/08 03:54 AM Re: Building a mast [Re: Rolf_Nilsen]  

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Rolf,

I believe thats the F12 mast. Gato also has the drawings for an F16 one. The F16 mast has similiar static bend characteristics to the "standard" aluminium one but is much lighter and ironically probably cheaper. I believe he makes the carbon tube himself.

You can buy "peel ply" at any dress making shop.

Last edited by Scarecrow; 04/25/08 03:55 AM.
#133043 - 04/25/08 04:19 AM Re: Building a mast [Re: ]  
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Thanks Rolf, sharing is the only way to progress. Yes, It's the F 12 mast. I made the double barrel tube myself, but in the heat of the action I forgot to take pictures, but I will make another one for the Pixie of a “nice lady”, so if not to much distract by her I will try to correct my mistake... This spar is in weight about half way between alu and carbon, 5,3 kg. Bending characteristics as Scarecrow stated.

#133044 - 04/25/08 07:44 AM Re: Building a mast [Re: Gato]  
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I dont have eyes only for F16s. If this technology is feasible for the F12, and perhaps the F16, it will probably scale well up to 20 footers as well? Beyond that I suppose pure carbon is better? What makes this attractive is the relatively easy homebuilding option! Shipping masts is an expensive undertaking.

Would it be possible to buy a set of F16 mast plans, if you have them done already?


I think you both are awesome. Gato for actually doing what everybody are talking about, and Scarecrow for doing this kind of design work!

#133045 - 04/25/08 01:17 PM Re: Building a mast [Re: Rolf_Nilsen]  

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Rolf,

send me an email to chris (at) ctmd.com.au and I'll send you the F16 mast drawing.

#133046 - 04/28/08 08:05 AM Re: Building a mast [Re: Rolf_Nilsen]  
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Guess it will work fore bigger mast, my next try will be for my Mini 650 and that one is carrying some 80m2 of sail downwind and 40m2 close hauled. My Blade is a little bit on the shelf for the moment

#133047 - 04/28/08 02:52 PM Re: Building a mast [Re: Gato]  
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Quote
You can buy "peel ply" at any dress making shop.


Really? Any kind of nylon cloth? I was worried that the cloth treatment would leave residues in the surface of the epoxy. I have used some ripstop nylon from an inner tent and that worked very well..


I got the plans from Scarecrow. Think I can do this! Would be a really fun project, but not until the next winter I think.
Engineering wise, is the carbon taking all the loads or do the wood contribute as well? Perhaps especially in the "horizontal" level?

#133048 - 04/28/08 04:03 PM Re: Building a mast [Re: Rolf_Nilsen]  

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Rolf,

the ply is definitely a contributing component in the structure, primarily in the longitudinal structure. It is not considered to provide any "hoop" strength because it is stripped.

Buy a couple of samples of nylon and have an experiment. A lot of commercially available "peel plys" are [censored] and aren't easily removed in one piece.

#133049 - 04/28/08 05:41 PM Re: Building a mast [Re: Rolf_Nilsen]  
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I was worried that the cloth treatment would leave residues in the surface of the epoxy.


You should still give peel ply finish a light to medium sand before secondary bonding.

#133050 - 04/29/08 06:10 AM Re: Building a mast [Re: ncik]  
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pardon the lame question, but when do you take the peel ply off? before it is completely set, after (seems like nylon would permanently adhere to it)

#133051 - 04/29/08 06:22 AM Re: Building a mast [Re: PTP]  
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That is the beuty of it, epoxy dont adhere to nylon, so you can remove the nylon and any aborbent layers on top of it in one go. You remove it when the epoxy have set fully.


Scarecrow. If the ply strips dont add "hoop" strength, using WRC strips would be even better?
I dont have the math to understand why, but I though the carbon fibers would take all loads longitudionally until they eventually broke. Then the wood would begin to carry loads? Is that a matter of oversimplification?

Nick, I think they left the peel ply on in the beginning, and pulled it off when they were to glue something to the surface. It was thought to be state of the art and the solution to the eternal sanding. As you say, they found out differently, to their cost.

#133052 - 04/29/08 07:08 AM Re: Building a mast [Re: Rolf_Nilsen]  
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Scarecrow. If the ply strips dont add "hoop" strength, using WRC strips would be even better?
I dont have the math to understand why, but I though the carbon fibers would take all loads longitudionally until they eventually broke. Then the wood would begin to carry loads? Is that a matter of oversimplification?


I have wondered about this- are the strength characteristics of wood and carbon different? I would figure they obviously are, so how does that work then in terms of using two difference substrates in an application that will be bending all the time? Does the wood break before the carbon or vice versa? If the properties of each are very different then one breaks before even getting near the break point of the other

#133053 - 04/29/08 03:49 PM Re: Building a mast [Re: PTP]  

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Rolf, any stripped material is going to provide limited hoop strength, simply due to the fact that you are relying on the tensile strength of the resin between strips.

PTP, yes the material properties of timber and carbon are different, as are carbon/foam etc. The trick is to engineer the structure to make sure each component is not asked to contribute any more strength than it is capable of. I did quite a bit of work many moons ago with a company who were building carbon masts for offshore racing boats in a very similar fashion to what we are doing here. I know they built a mast for at least one 66' pocket maxi.

Peel ply definately reduces the need to sand but doesn't eliminate it. Leave it on for as long as possible, ie take it off when the job is done or when and if required to access an area for secondary bonding.

#133054 - 04/29/08 07:16 PM Re: Building a mast [Re: PTP]  
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It is not necessarily the strength of the materials in a laminate that determines which will break first, it is the stiffness of each material. Deflection/bending is the key.

Imagine two simple laminates; stiff carbon and flexible fibreglass. Under the same load the carbon will deflect less than the glass. Keep increasing the load and you will find as expected that the fibreglass laminate will break first, but at a much greater deflection than the carbon.

Now join the two laminates together. The carbon is so much stiffer than the glass that the deflection allowed by the carbon won't be very large, and certainly nowhere near the deflection required to stress the glass fibres greatly. Increasing the load and the carbon will continue to restrict deflection below that required for the glass to fracture, until the carbon breaks a little below what it would've alone (because the glass is providing a little bit of support).

This is a highly simplified scenario, it gets a bit trickier when considering hoop stresses and laminate shear forces, buckling, etc.

#133055 - 04/29/08 10:48 PM Re: Building a mast [Re: ncik]  

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Well put Ncik, I might have been a bit simplistic in my answer.

I don't like writing the over the top highly technical and condescending answers that some others use, but sometimes go to far in the other direction.

#133056 - 04/30/08 04:26 AM Re: Building a mast [Re: ]  
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Thanks, was hoping someone would put me straight or back me up. I haven't done much composite engineering as a professional and some of the stuff has gone missing from my mind through lack of use.

#133057 - 04/30/08 04:34 AM Re: Building a mast [Re: ncik]  

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Are you going to be around during Sanctuary Cove? Come and find me. Stand 377 (superyacht tent)

#133058 - 04/30/08 05:57 PM Re: Building a mast [Re: ]  
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Haven't decided yet. Will certainly drop by if I get down there.

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