Advice on what weight carbon to use

[Young Entertainer 59]

going to be starting the experimentation on building a rudder stock, rudder and centreboard for a Farr 3.7.  Will get foam for the centreboard and rudder to create a shape first then cover with carbon,  so question is what weight/type of carbon would you use?  and how many layers.

and the follow up question is what is the easiest/cheapest way to setup a vacumn bagging arrangement,  any tips as i have heard it is the way to go with making these

[Frank 157]

If you source the cloth from Gurit I am sure they would spec the layup, a few years back High Modulus Fabrics did that for mine.You can make your own vacuum unit by converting an old fridge compressor, then watch a few videos to see how its done, otherwise hire one.

https://www.google.com/search?q=old+fridge+compressor+for+vacuum+bagging&oq=old+fridge+compressor+for+vacuum+bagging+&aqs=chrome..69i57.14076j0j7&sourceid=chrome&ie=UTF-8#fpstate=ive&vld=cid:0dc9204e,vid:SxvH3EtxN-I,st:0

[Psyche 633]

Give adhesive technologies a call as well, this has been done about a million times so they can probably you a pretty good layup schedule off the cuff and supply the materials. If you are serious about saving weight vacuum bagging is the way to go but you can get a pretty reasonable wet layup job by weighing the cloth and resin aim for 50/50 or less resin. Ideally get the parts CNC shaped, otherwise a few hours with templates should get an ok result.  If you're looking for that performance edge its worth spending the time getting them as perfect as possible.

[LE Bb 25]

I drew some up for a mate a few years back, foils have got a bit better since then.

Structure hasn't really changed much.

Pm me if you want to know more

[K4309 258]

How long do you need to pull the vacuum for? Like just a one off pull a vacuum then hold it, or do you pull a constant vacuum for hours?

You can get a food vacuum packer from the Warehouse for $80. Could almost fit a foil for a 3.7 in the standard vacuum tube, pull the vacuum, seal the bag and leave it while the epoxy sets.

 

PS, I know this sounds far too simple, and you needs lots of tubes, sticky back and peel ply to make it look techo enough. I'm more interested in what the general process is.

[Jason128 6]

A cheap airless compressor plumbed backwards is a great way to go. Not to noisey, and can run for days.   Setup it up with airline fittings so you can still use it as a compressor as well.

fridge compressors are ok, but require perfect seals everywhere.

don’t cheap out on any of the seal tapes, breather fabrics or peel plys- you need it all.

[MartinRF 53]

Me on dagger board strength: https://www.reflectometrist.eu/doc/Boardstrength.pdf

Dagger board design overview: https://www.reflectometrist.eu/pages/daggers/index.html

/Martin

[Frank 157]

I can give you some detail on how I do it but really its best to watch a few videos and practice with some scrap material, it doesn't have to be Carbon cloth. I pull the Vacuum for the duration of the initial cure usually about 12 hours at Room Temp you can regulate the degree of vacuum with a bleed valve, the material supplier can advise of the Vacuum pressure required. All the bagging materials are available at NZ Fibreglass supplies and wont be expensive for a small component like a dinghy Rudder .

[Young Entertainer 59]

thanks for all the replies, will do some shopping and testing on scale models 

[MartinRF 53]

Easy Composites have produced some good how-to videos.

https://www.youtube.com/user/easycompositestv

/Martin

[Addem 95]

On 27/11/2023 at 8:32 PM, Jason128 said:

A cheap airless compressor plumbed backwards is a great way to go. Not to noisey, and can run for days.   Setup it up with airline fittings so you can still use it as a compressor as well.

fridge compressors are ok, but require perfect seals everywhere.

don’t cheap out on any of the seal tapes, breather fabrics or peel plys- you need it all.

+1 for watch Easy Composites videos.

I made my own fridge compressor vac pump and posted the details on crew about 5 years or so ago, but I can't find it.

Mine was from a small beer fridge and works well enough.  I went for this as I had one about to go to the dump and because the compressor had all the electrical bits still attached so I wasn't going to kill myself.  Took me an afternoon IIRC.  

If I was doing it again I would get a larger one from a full size fridge for a faster/stronger suck down.  Mine does lose vacuum over time, so I run it until the epoxy goes off - 3-4 hours, sometimes more.

I don't use fancy tapes etc - I run a silicone bead and use plastic which I bought in a large roll from a packaging wholesaler.  I do use proper peel ply (Gurit) but use garden weedmat as the breather layer (to spread the vacuum across the piece).  Works fine but I've learned not to fold anything but roll it in storage as the creases end up showing on the work.        

This might sound a bit rough and ready, but works just fine I wouldn't build a boat with it but have done floor boards and decorative partsgalore.  I spend the money on the cloth, foam and Peel ply.