Carbon topcoat / build options

Discussion in 'Fiberglass and Composite Boat Building' started by dcnblues, Jun 7, 2011.

  1. dcnblues
    Joined: Apr 2011
    Posts: 117
    Likes: 3, Points: 0, Legacy Rep: 39
    Location: San Francisco

    dcnblues Senior Member

    Well, you sound like you know a hell of a lot more than me, we're thinking alike. Thanks for the post.
     
  2. themanshed
    Joined: Sep 2009
    Posts: 135
    Likes: 12, Points: 0, Legacy Rep: 162
    Location: Palm Beach County

    themanshed Senior Member

    The original design was for wood and not exotic composites so I had it redesigned and a new layup schedule. This is the schedule from my NA.
    One thing I saw that was not quite correct earlier in this string was how Carbon Fiber sanded:
    Kevlar does not sand well it gets fuzzy.
    Carbon fiber will sand and pretty easy it just needs to be sealed with epoxy and remember you are cutting into the weave so you lose the strength.
    Make sure you have enough carbon to sand on.

    On my boat with just two layers of 200g cloth there is not room for faring the cloth. I am actually faring the foam before the outside skin.
    Then I will apply the outside skin.

    With most builds like this after the outer skin has cured, you fill the cloth weave with epoxy by coating it until the weave is full plus a build-up to sand smooth to keep from cutting the fibers for the final finish before painting.

    With a female mold that will not be a problem as with a one-off. My AMA’s will be built from a female mold.
     
  3. dcnblues
    Joined: Apr 2011
    Posts: 117
    Likes: 3, Points: 0, Legacy Rep: 39
    Location: San Francisco

    dcnblues Senior Member

    Damm that sounds like fun, Seacart 30 style (or better). :D
     
  4. PAR
    Joined: Nov 2003
    Posts: 19,126
    Likes: 498, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    What's the displacement of that tri? It doesn't sound all that light. I just finished a plywood 18' mono without carbon, Kevlar, foam or other fancy stuff, just plain 'ol 1/4" Okoume plywood and a 6 ounce sheathing. The hull is 350 pounds with all the hardware attached.
     
  5. themanshed
    Joined: Sep 2009
    Posts: 135
    Likes: 12, Points: 0, Legacy Rep: 162
    Location: Palm Beach County

    themanshed Senior Member

    This boat has been re-designed from the stock plans which called for Okoume and glass sheathing. The stock spec are as follows:
    Length overall: 20' 0" (6.1 m)
    Length at waterline: 19' 9" (17 m)
    Beam: 17' 0" (5.18 m)
    Draft: 10"/2' 4" (.25/.71 m)
    Weight: 497 lb (225 kg)
    Displacement: 906 lb (411 kg)
    Sails: main: 147 sqft. (13.66 sqm)
    jib: 47 sqft. (4.4 sqm)
    spinnaker: 161 sqft. (14.93 sqm)
    upwind total: 194 sqft. (18.0 sqm)

    I had a flare added above the water line, more room in the cabin area, same wetted surface. Ama volume increased by height and some width about 15%. Taller rig 30' carbon mast and it will carry more sail area. Cross beams, rudders, seats, and boards will also be carbon. Unlike the Seacart there is not in hull sleeping area just a day racer.

    website www.themanshed.net
     

    Attached Files:

  6. groper
    Joined: Jun 2011
    Posts: 2,483
    Likes: 144, Points: 73, Legacy Rep: 693
    Location: australia

    groper Senior Member

    i developed my own process of achieving a clear carbon finish laminate, ill elaborate later.

    First, you have a problem with clear carbon laminates get VERY hot in the sun. They get so hot that most (if not all) epoxies will start to soften and loose integrity - this is not related to UV stability but the temperature alone. As a solution, i had to move to a vinyl ester resin for my clear carbon laminates, no epoxy i could find would handle the high temperatures a black carbon surface will reach. Vinyl ester resins have much higher softening temps.

    Secondly, for a very strong UV protection clear coat, i ended up using a surfboard PE finishing resin (waxed) that was further thinned with 'wax in styrene' so it could be sprayed using a spray gun setup for your typical 2pack polyurethane paints - 1.6mm nozzle.

    You need to get the layup completed with zero pin holeing. Any pinholes will ruin the finish, so dont get too agressive with removing resin from the laminate - what you leave in there you dont have to add in further filling steps.

    Cover the laminate with peel ply and squeegy the excess resin out until it looks good - using skill and experience is all i can say here. Once the peel ply is removed, simply spray on the thinned PE resin like a paint job and let it cure. A nice clear carbon laminate with UV protection results - no sanding and filling involved.

    If your looking for a finish off a mold, it goesw like this... simply lay a very lightweight cloth - i used 98gr woven cloth - and apply this to your prepped mold using an unwaxed PE laminating resin. Get all the air bubbles out, squeegy off (not too much, we dont want pinholes) and let it cure. It will stay tacky and its ready for chemical bond to Vinyl ester resin - this forms your protective layer. Complete the rest of your layup using carbon/glass and vinyl ester resin core material etc. When you pop it from the mold, you have a perfect finish showing the carbon beneath and a thick UV protective layer of PE resin/glass. No sanding or further coats required etc. Its hard wearing and resists scratches etc - better than paint.

    The catch is, you cant use epoxy for clear carbon finish laminates - unless you can find an epoxy with a very high softening temp - i dont know of any...
     
  7. Eric Sponberg
    Joined: Dec 2001
    Posts: 2,021
    Likes: 248, Points: 73, Legacy Rep: 2917
    Location: On board Corroboree

    Eric Sponberg Senior Member

    Dcnblues,

    A number of people have given you some good advice. For my take, here is what I can offer:

    An all-carbon boat will be stronger and stiffer than a Carbon/Kevlar boat. The weight of a carbon/kevlar boat will be insignificantly lighter than an all-carbon boat. Kevlar is very good in tension, comparable to carbon, but it is terrible in compression, equivalent to glass. Since stresses on a boat structure are in tension, compression, flexure and shear, Kevlar can be a poor choice for a laminate other than for bullet-proofing, i.e. guarding against impact penetration.

    Also, carbon is typically sized (coated) for adhesion of epoxy resins. If you want to use vinylester resin (acceptable) then you have to make sure the carbon fiber has the appropriate sizing for vinylesters, which are styrene based resins. Some vinylester resins are based on epoxy chemistry (better than those based on polyester chemistry) but all vinylesters have styrene in them, about 45% or so by weight. Check with your suppliers for appropriate resins and carbon fabrics that are compatible.

    If it were my boat, first, I would probably not use a female mold. I would build over male forms and lay up from the inside out. I'd probably use a core, probably Core-Cell, and I would use an epoxy laminating resin. I would use a wet impregnator with a vacuum bag cure, and then I would post cure the boat after all the laminating was done.

    I might use a thin layer of Kevlar against the outside of the core, and then cover that with the outer carbon fiber laminate. The carbon fiber inside and outside laminates would be mirror images of each other for structural balance. The Kevlar would be considered the "bullet-proof vest" to prevent any sharp object or impact from penetrating the core and the inside of the boat, but it would be deep enough in the laminate to prevent it from being abraded by minor impacts. Once Kevlar is breached and abraded, it is practically impossible to repair well. That is why you should never put Kevlar on the outside surface of a boat laminate.

    After the last layer of carbon, I would coat it over with fiberglass cloth using the same resin as throughout the entire layup. This glass layer, also considered non-structural, would add UV protection and would serve as a base for the outside coating. It will be fairly resin rich and may get abraded in the sanding/fairing prep for final coating.

    I would NOT clear coat the boat, for a number of reasons. It may be sexy looking, but it is totally impractical in this application. First, as already mentioned by others, a black surface gets really hot in warm climates, even in the ocean under a hot sun. The heat in the laminate will not be friend to the laminate and will cause it to degrade more quickly over time. Also, living inside a black boat will be unbearable as the heat soaks up inside. Finally, this is an offshore rowing boat, which means there is a good chance you could need assistance at sea. Rescuers will NOT be able to easily see a black boat on a dark blue ocean. White is the next worst color because it is the color of foaming waves and from air rescue or ship rescue, you will be indistinguishable from the waves. The best colors are bright yellow or bright orange. I prefer a light bright yellow which would be reflective enough to keep heat build up down, and easy enough to see should a rescue be necessary.

    That's the best advice I can give. I hope it helps.

    Eric
     
  8. dcnblues
    Joined: Apr 2011
    Posts: 117
    Likes: 3, Points: 0, Legacy Rep: 39
    Location: San Francisco

    dcnblues Senior Member

    Groper, thanks for the detailed response. However, I've read that a carbon boat in cool water will stay the temperature of the water, so if I'm careful not to leave it out in the sun when dry, temp shouldn't be a problem. Let me know if I'm wrong about this. But I'm very grateful for the assurance that a VE / PE combo will give good results. I assume your PE topcoat is a thinned UV resistant gelcoat, right? Same material, different names? I guess I'd also like to hear from the pros about the subjective differences between keeping a gelcoat finish and a LPU finish polished and looking good.

    I'm getting a good education from this forum and other internet sources, and I keep going round and round and back to where I started, but I'm starting to gel (npi) some preferences: pre-preg and autoclave are pretty much out for obvious reasons, although building a hot room for a finishing cure may be possible. Aramid is pretty much out, and carbon and fiberglass are in. Epoxy more than poly resins, though I'm final on this just yet (the need / practicality for an intermediate fiber layer between the carbon and LPU is a question mark).

    I think making a female mold would be fun, and I like the idea of infusion (particularly since I just found out that you can buy a venturi vacuum pump for $100 or so if you already have an air compressor), but if there are easier / better ways I'm still open. However, I do flatter myself that my design will be sexy enough that others may find a use for the mold, and maybe I can get it to pay for itself. All this tech stuff is pretty obvious to the guys on this list, but I keep hoping that threads like this will be useful to newbies and lurkers just looking for information.

    I'm also leaning towards a stiff boat rather than one with some flex. I had thought some flex might be desirable to absorb heavier sea states, but not so much now. I've also been fascinated by this build technique of an A-Class cat, and think it's corecell foam core could give me a stiff hull strong enough that I wouldn't worry about cracking it:
    http://lindahlcompositedesign.weebly.com/

    I also can't help but think about wave-piercing hulls for a rowboat application, but that'll have to wait until I start playing around with design software. Thanks again...
     
  9. groper
    Joined: Jun 2011
    Posts: 2,483
    Likes: 144, Points: 73, Legacy Rep: 693
    Location: australia

    groper Senior Member

    the boat will stay cool if it's in the water, but are you ever going to leave this thing on the beach? or what about on the roof of your car to/from your destination? The resin softens in the sun, the kayak goes soft and than can deform or otherwise change shape, then it resets when it cools down and is often warped from its original shape... i know this as ive tried it and learned the hard way... 1 mistake and your kayak will be history, are you going to risk it?

    you may be thinking that epoxy is stronger, but once it heats up - all that goes out the window and a vinyl ester will be stronger... most epoxies have a softening point around 60deg C... some boat builders even have problems when painting their boats with a dark coloured paint, in the hot sun their hulls are ruined by cloth print thru when the resin softens... epoxy is great, provided you can keep it cool...
     
  10. dcnblues
    Joined: Apr 2011
    Posts: 117
    Likes: 3, Points: 0, Legacy Rep: 39
    Location: San Francisco

    dcnblues Senior Member



    Eric, thanks very much for the advice. It's much appreciated, and we're thinking alike.

    a) Yeah, I'm off aramid / kevlar. I think the canoe and even guideboat guys are looking at rough river / lake use, with sharp rocks etc, and I needed to find other build methods to suit my beach launch, open bay/ocean water use. Thanks, and apologies to Tunnels who was smarter than me in Post #2.

    b) I had read that, but it hadn't really registered. I don't think I would have bought fiber without getting at least 2 opinions on the match with the resin, but that's a good thing to remember, I'm sure. Is there a general rule about which resin can take thinner fibers and coatings? I'm curious.

    c) I'm not clear on this. You'd wet layup the external layer to the foam core, cure with vacuum, flip the hull, fair the foam, wet layup the interior layer, cure with vacuum, then post cure? I'm not objecting, I just want to understand. I haven't seen a build yet that used multiple vacuum steps, but if the bag material is protected by peel ply, I don't see why you couldn't do it this way.

    d) You state that a Fiberglass layer would offer some UV, so I assume that it wouldn't, on its own, block UV? I haven't yet found an answer to this. I'm assuming at this point whatever resin in used with a fiberglass outer layer would be the decisive factor.

    e) aw, Eric, I was hoping I can have the total high tech carbon look. I've read posts which said the following: "Carbon fiber takes on the temperature of the environment that it’s in. If the water temperature is 75 degrees, your boat will be 75 degrees." Again, this boat will only be in water cooler than 70 degrees, ever. Do you really think, if coated with fiberglass and LPU, this would be an issue? I'd like to hear other opinions too, so anyone who has experience with this, please chime in. Small skinny rowboat, probably less than two feet of freeboard. I am NOT locked-in to the carbon look, but am trying to hang on to it as an option for as long as possible. Paint would be much less stress. I know paint (even if not marine paint).

    f) Thanks for this advice as it's very practical and excellent. I do plan on having enough buoyancy that I'll want to stay with the boat in any rescue situation, but your thoughts on color and surf are spot-on. So don't be offended please if I was thinking of a sexy black carbon exterior and decks, and white (possibly light reflective paint) interior. The boat will be equipped with a parachute drogue, the better to loaf and read while keeping the bow into the wind, and I'll have a portable VHF with MMSI and probably GPS (not to mention cell phone, which does cover much of my rowing area). I'm actually surprised I'm not able to easily find an emergency inflatable buoy, reflective and bright I could carry with me. I'm not too worried about emergency situations as I like to be prepared for worse-case scenarios, and will have any equipment I'll need.

    Thanks again for the excellent help. :)
     
  11. dcnblues
    Joined: Apr 2011
    Posts: 117
    Likes: 3, Points: 0, Legacy Rep: 39
    Location: San Francisco

    dcnblues Senior Member

    Great info, thanks. No, I don't have plans to leave on beach or car-top, and if I did, I'd make a good cover for it (not too hard to do). But that's good knowledge to have, and with which I wasn't clear.
     
  12. PAR
    Joined: Nov 2003
    Posts: 19,126
    Likes: 498, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Use "black 'glass" and save yourself a huge chunk of change. No it will not be as light as carbon, but you can top coat with a good LPU clear and get some millage out of the finish.

    The car guys with the carbon hoods are now finding out what happens to it when they leave it in their mom's driveway from a year or two. It no longer looks cool and they'll have to paint it or lose the hood. You can buff and get a little more time out of it, but the process just repeats and you'll be wearing down your resin in the process, with each compound and buff.
     
  13. Eric Sponberg
    Joined: Dec 2001
    Posts: 2,021
    Likes: 248, Points: 73, Legacy Rep: 2917
    Location: On board Corroboree

    Eric Sponberg Senior Member

    Counterpoints:

    c) You will find that to date, carbon fiber is extremely difficult to resin-infuse well, and that is because wet carbon looks exactly like dry carbon, and you cannot easily see the resin edge as it infuses, and so you'll have considerable difficulty controlling the infusion. Also, a good infusion never works the first time--you will make mistakes and waste a lot of material just trying to get the infusion right. Why throw that money away? Finally, if this is a one-off boat, you are going to spend a lot of money just to make an expensive mold, which in all likelihood is going to be used only once.

    Don't kid yourself that others will be so enamored with your design that they'll want one too--that hardly ever happens, so don't plan on it (this is one of the greatest fallacies of boat design--"Oh, my boat is so unique I'll sell thousands!" It does not happen, and if it did, you would have enough money from deposits to build proper tooling. Otherwise, you will have to win the lottery, or get a big inheritance from a wealthy relative.)

    You understand the process correctly: Far better that you build simple formers (boat upside down) over which to lay up the foam, fair the outside, and lay up the outer skin completely. Flip the hull over and set in form-fitting cradle, remove the interior formers, and lay up the inside skin completely. The inside of the foam will need little to no fairing. Leave the boat in the formers to build in the bulkheads and other structure. The cost in both time and labor for the formers and cradle will be a mere fraction of the cost of a mold. It is OK to work in multiple stages, vacuuming each time--it's cheap, easy to do, and it is done all the time.

    d) The UV protection is for the resin, not the carbon. The glass layer will likely be 50% resin and 50% glass, and any resin degradation from UV will be in that layer, not the carbon layers underneath. That is, if it happens, you'll see it soon enough and be able to make appropriate repairs when necessary. This may not happen for years, but when it does, the resin within the carbon should still be good. The glass layer is the sacrificial layer.

    e) The boat will still get hot. It can be hot on the water, and it will be hotter on land. I know--I design carbon fiber masts, and we always paint them a light color to keep them from getting hot. But here is a compromise. Paint the deck and the bottom with light-colored PU paint, but leave the topsides clear-coated with the carbon pattern visible. Sun comes down from above, and the topsides don't get a direct hit from the sun. So a light colored deck will reflect the heat off when the boat is upright, and should you ever be in the unenviable circumstance of having to survive in an upturned boat, a light-colored anti-fouled bottom will perform the same function of reflecting light and being easy to see by rescue services. That's probably the best compromise.

    Good luck,

    Eric
     
  14. dcnblues
    Joined: Apr 2011
    Posts: 117
    Likes: 3, Points: 0, Legacy Rep: 39
    Location: San Francisco

    dcnblues Senior Member

    I didn't know about this option, thank you PAR, for all your help. You learn something new every day, especially on this forum. I was wondering about the car applications.

    I have loved the carbon-look I've seen in cool pictures, wallpaper, etc, and was always curious why I didn't see more of it, putting it down to exotic material pricing. But now I'm getting a clue about what experienced car / boat / airplane builders seem to already know: that glossy carbon fiber look is impractical for most applications that will see extended use.

    This is actually fine. I can worry a LOT less about getting the construction and layup perfect, and just concentrate on a smooth fairing and good custom paint job.

    For a dry row (boat won't kept in water) boat, I'm not even sure I'll need marine paints. I guess I'll have to research what auto clear coat is made of. A whole different line of research on what would be best. I will want clearcoat over paint.

    One last question for you pro guys: I haven't jumped in to hull building software yet, but once I have something I'm happy with, do you think I'll be able to figure out a 'laminate schedule' by myself, going with advice from fiber distributers, etc, or will I need the services of a marine architect? I had thought that overbuilding a little wouldn't be bad for an ocean rower, but am becoming more interested in having in no heavier than it really needs to be. As well, I'm not sure if software will tell me how much it'll weigh with different laminate plans, and where the water line will then be, so predicting the handling will then perhaps be too variable.

    Were I to hire an architect to confirm a boat hull like this (18' sliding seat rower with custom hull), what would be the range of my fee? I really have no idea. Any advice most welcome. I do want to do it right.
     

  15. dcnblues
    Joined: Apr 2011
    Posts: 117
    Likes: 3, Points: 0, Legacy Rep: 39
    Location: San Francisco

    dcnblues Senior Member

    Eric,

    Many thanks. Everything you say makes sense to me.

    c) Could you have a quick look at the Lindahl A Class cat hull build? I'd like your opinion about a rowboat build and whether to do it as you suggest, or inverted as they do: female frames, foam strips (done like strip planking), the interior hull, then flipped and after fairing the foam, external hull. (I can add the decks later). http://lindahlcompositedesign.weebly.com/

    e) That's good advice and a cool suggestion. I wasn't thinking of a different color below waterline / and or bootstripe, but now I am. Even if I just paint the boat, I'll keep that in mind.

    Any tips on getting a good price on Corecell foam most appreciated. I'm starting to suspect the supply chain is limited enough that it'll be hard to beat the price at Jamestown Distributors.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.