making carbon fiber fins

[indole]

hi all. i know there are experienced people who have made carbon fiber, aramite and other composite fins. i have read some of the older posts on deeper blue and sent PMs to those who seem to have experience, but no responses yet. i am looking into making carbon bi-fins with epoxy and using an already made footpocket (the c4 or sporasub, havent decided). i am curious as to what weave of cloth people are using, what kind of epoxy, what temperature they are curing at (i will be at room temp, and im thinking a plexiglass mold), and what angle between the attachment and the actual blade part. i will probably choose an angle similar to the c4s or omers. thanks for any responses and PMs are more than welcome also.

 

[Memo]

I bet there are some tricks like different thickness along the blade is necessery and also the manufacturing process in all quality production includes pressure molding which makes the resin % really low. Making a tough CF plate can be easy but I think making a fin requires real experience...

 

[scrounger]

fins

I think a unidirectional cloth would be best, as you are only transmitting energy along the length of the blade. The problem of durability comes up when using a mat like that the woven cloth of what ever thread thickness should not crack as easily. Along with the varying weaves that you can use the epoxy that you choose will make a huge impact on blade flex and durability just think of all the loading that you will put on that thin bit of what ever it turns out to be, I am interested to hear about how things go. sorry for the rambling and i hope it makes sense
Lance

 

[ADR]

Hi pal,

As well as making my own monofins I have also made a set of carbon/glass composite stereofins/bifins. I used unidirectional carbon cloth for the top layer and then used a series of standard bidirectional weave glass cloth layers (13 in total) to create the taper I wanted. It's a lot of work and carbon cloth and epoxy resins are expensive and by hand it is difficult to get a vacuum bag like finish from. Having made my own to work with omer footpockets I wouldn't do it again. Carbon is king but the new gear you can get from waterway is almost as good and the finish is much better. They cost me less than what it cost just for the materials to make my own. If you do make your own then use peel ply for the non mould side and work it really hard to get as much of the resin out of the consolidated layers as you possibly can.

Good Luck

ADR

 

[icarus pacific]

As a composites guy, here's the lowdown-

For the money you'll piss away on just the materials, go buy a set. For the money you'll piss away on the tooling and the related equipment, go buy a set. For the time you'll piss away, go buy a set.

Having said that, you'll want to use a fabric with carbon in both it's warp and weft. Also look for additional fibers in the weft to allow for flexural and compressive stresses. Kevlar is good for this, S glass only less so. I believe that TAP Plastics has both of these fabrics in stock. You might luck out at any one of the number of airplane design/repair shops that surrouns an airport. Another source for lightweight materials is the back of model building publications.

Resin-wise, unfilled epoxy is the way to go and then you need to get into the tooling and the vacuum set up. The model building pubs will have this also, but be ready for the wallet hit.

 

[Bogdan Waterway]

fibre-glasse much better then carbon

Hi Indole
we use 6 tonn of fibre-glasse/year.
the pressing must be for about 150kg/cm.
and 130grad. Cel.
it is not possibilly to make in garage, it should be factory space with expensive equipments.
My opinion that BEST fibre-glasse is much better then any carbon materials. Carbon it's just fashion.
I spend 5 years to find the BEST fibre-glasse with best prices.
and now very happy )
welcome to www.finswimworld.com

 

[cece]

but don't you think that fiber glass loose its caracteristics with years???

 

[Bogdan Waterway]

Hi Cece
Offcourse all type materials lose characteristicks. even carbon.
But our fibre-glasse "swim" ~ 40km/week and I give quaranty for 2 seasons ( 9+9 monthes). It's about 2.500km. after that fins don't have so good reaction but still usufull for training.

angle has Sporusab footpockets, our blades is 1,7-1,9mm what is easy to put inside of strong Spora rubber.

I 'll be glad to give some more answers.

 

[derelictp]

I have had fantastic results using "pregpreg" carbon sheets and baking it in an "autoclave" in vacuum.

The temperature is very high but I have to ask my partner about how warm.