wow that looks great, pepe47!

Next time make sure the blade goes all the way into that front corner. In the case of a weedy, that's where most of the load will be, (the line of the thickest, and stiffest part of the fin). There shouldn't be any tension strain on the base, it should all be compression. I'd forget the csm and use several layers of carbon.

Yup, todays update shows the fin reboxed, now 1cm shorter to allow for the blade to go all the way down and forward in the box. Already done Mike Also to allow the barrel nut to have purchase on new work and not fill.
2 layers of csm and 2 layers of carbon, not taking any chances. And any exposed timber is going to be coated with cyanoacrilate (super glue) to waterproof it, especially inside the fin bolt hole.

I agree Nebs. Pepe your workshop looks like a showroom, very impressive. that clamp/vice is a woodworking one i think

pepe47 said...

Yeh that's right, woodworking bench from carbatec. The one with bench dogs helps when you're clamping large pieces of timber together, or laminating.

It's one of the most beautiful bits of equipment I've ever seen, very jealous!!!!

brad1 said...
<<<<<<

Putting csm and carbon together is like putting titanium and diecast aluminium together. Only one is doing the work.

In most cases Brad I'd agree with you, but what about a carbon, csm, carbon sandwich???.
The csm is in compression the carbon in tension.

I have a tech question regarding lay-up. What advantage does epoxy have over polyester. I find that if time is not on your side it's quicker to lay-up with poly. The fin, so far hasn't delammed and I'm not worried about long term issues, can poly work if you don't want to laminate under pressure?

Great article thanks Brad1.
AUS718: more hours than the fin would be worth, but it's a labour of love, cheers
Almost forgot: I'll be trimming 1cm off the trailing edge to speed up the gybes, ( turning circle). With the amount of lift the fin generates I can trade some off.

pepe47 said...


Almost forgot: I'll be trimming 1cm off the trailing edge to speed up the gybes, ( turning circle). With the amount of lift the fin generates I can trade some off.

Geez if it aint broke Pep, if it generates great lift, its what ya been wantin, in lightish winds ya never gonna do great fast tight gybes on a big board anyway!!

Hi Pep , great effort , mucho kudos to you .
Just in relation to your question re polyester over epoxy .

The whole idea of composite construction is that the loads are taken up by the fiber be it glass fibre or carbon fiber ( english and american spellings ) . what the resin is basically doing is holding the fibres in place and protecting the fibre by providing a protective cover.

What happens with Polyester is that its modulus of elasticity is very low so what happens is when a load is applied the resin actually takes the load first then the carbon takes up the load but unfortunately the polyester resin has experienced a load greater then its elesticity will allow and cracks .

Epoxy on the other hand has a high level of elasticity and hence its toughness is due in effect to it maluabilty ( buggered if I can spell that ) any way its more flexible . So what happens is the resin flexes under load and the carbon takes up the load as its designed to do . Poly will do the job of holding the fiber in place but it wont allow the structure to perform using carbons great tensile and compressive qualities.

I guess an extreme example is say a rope encased in glass with each end attached and then force applied to try and stretch the rope then you would see the glass break before the rope actually took up any of the load . If you encased the rope in plasticine then the rope will take up the load and the plasticine ( epoxy resin will just stretch to accomodate the load and do its primary job of holding the fiber in place and providing a protective cover) .
Just remember the fiber is the strength in all composite structures

Did anyone understand that ?

Again great job , pity there is no money in fins .

One Hundred and Eighty !

Cheers , Dartboy

Have a think about why your mast bends when you crank on your downhaul.
Compession compression compression. Carbon is outstanding in compression.
Check out the comparison ult.tensile and compresive strengths for UD carbon and glass 0 deg.
www.performance-composites.com/carbonfibre/mechanicalproperties_2.asp
Apologies for hijacking the topic!

Have you than the fin out yet pepe47 or are you still waiting for it to cure some more, be nice to hear how it goes

Nice work on the MK11 looks awesome, but you are happy with first one, be nice to see them both together to se the changes
Going to use the same construction method?

A master at work, amazing we have 3 very talented fin makers in our Team, Decrep, Sammy & Yourself!!

Well, not completely surprised with the outcome. Took the shiny new mkII out this morning and put it on the 135l rocket with the 8.2m h2, just wasn't expecting a 25knot gust. Exiting the gybe fully powered up the fin decided to let go (at the weakest point).
Didn't have the right thickness at the chord either as it cavitated at speed.
Back to the drawing board? Hell no. Carbon fins just can't match g10's on the estuary.