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Thread: epoxy?

  1. #1
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    epoxy?

    I finally got the paperwork for my boat. Now I'm putting the transom back in, putting a new floor in, and have to glass the deck back on. The hull is made with fiberglass but has a layer of kevlar. I have been told to use vinylester, then to use west system epoxy. I have no idea what to use. Is one stronger then the other, or does one bond better then the other?
    thanks chris
    17' Sutphen

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    From what I have learned, vinylester is going to be the best overall choice.

    Durakane 411 (vinylester) will bond to most anything, and offer higher strength than epoxies (unless you are post curing the epoxy, which I assume you are not, unless you have an oven big enough to put your boat in...)

    It isn't much cheaper, but it is cheaper - $175 for 6 gallon kit, as opposed to $250+ for most 5 gal kits of epoxy.

    I am not an expert, but just learning - however, I have been able to talk to a few experts, and the consensus is that DK 411 is the best choice. One guy I spoke with now owns a fiberglass fabricating and supply store, and he formerly worked for several boat companies in Miami - he showed me samples of failed components that proved to me that DK 411 was THE choice....

    Also, straight epoxy cannot be used with mat material, as it doesn't contain the esters to release the bonding agent in the mat (which is required for proper lamination). However, you can add the appropriate materials to the epoxy to use with mat, but we are still left with less strength that vinyl, possible bonding issues, etc.

    YMMV....

    -David, AxisMoto

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    Axis it correct, the Dow Durakane ( I use 8084 ) will give bonding similar to Epoxy. Epoxy will be better after it is post cured ( you need an autoclave ). I like vinyl/poly better than epoxy as it is easier to work with.
    If you want to use Epoxy try MAS

    RT
    2023 TUFF 25

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    Well my only question is will vin/poly adhere to kevlar. Cause my boat has a layer of kevlar built into it. The guy I bought it from said to use west sytem epoxy, he said that because his buddy used to be the head boat builder for wellcraft and thats what his buddy said to use. But now it sounds like epoxy isn't as strong as vinylester and vinylester adheres to most materials.\
    thanks chris
    17' Sutphen

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    I proposed the same question to the guy I'm buying the Durakane from. His answer was that most materials adhere to Kevlar equally poorly. I'm pretty sure his answer was that Durakane will work as well as anything else, and anything can be tough to get a good wet-out.
    Also, he made some interesting observations - Kevlar will not add stiffness (it is rubbery), and won't really add "strength". What it will do, is allow the hull to crack and crumble without coming apart.

    -David, AxisMoto

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    Generally, Kevlar is used in the inside layers where it has a high tensile & shear strength and not on the outside - except for reinforcement with glass- where it is weak in Compression and prone to taking in water -hydroscopic.
    ARGO Cat 18'
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    Cool Epoxy

    Some mis information on this thread. Epoxy DOES work with mat. You need to buy stitched mat not the type thats got the dissolving binder. Also epoxy has STRONGER not less strong bonding to most materials and higher tensile strength then VE or PE. VE is the second choice for strength and bonding. Its cheaper , thats about the only reason I would choose VE. If you use epoxy then the MAS would be my choice. We compared 6 different brands and liked the MAS with slow hardner the best for most applications. Its cheaper then West and contains less fillers. The West was excellent as well though. Progressive Polymers did tend to drain out of heavy fabrics less then the MAS and was about as easy to work with and we liked it quite well also. We used the Premium No Blush. It had slightly faster cure times and showed a higher tensile at 9,000psi or so. PP reacts to UV and yellows , which is only a downside if you use it as a clearcoat. You really should do some research on the net about epoxy vs VE as a resin for laminates and make your own determination but all the info we have read and all the experience we have with both products ( AME resins for VE) show the epoxy to be superior. Kevlar is difficult to wet out from what we tried with the epoxies. West or MAS wetout was better because of the thinner viscosity then the other epoxies but not by much. This is NEW material. If you are trying to adhere to cured kevlar and resin then any of the epoxies will be far better at adhering to the already cured PE , VE or epoxy then VE or PE will be. The only time you might use VE or PE on cured VE or PE is if its new construction.

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    So for better adhesian use epoxy, ok. But will it be as strong as vinylester or polyester? I am just looking at what would be the best stuff to use. The boat is a Marauder X-15, a copy of a 15 allison. I am putting a 85 merc on it, I am just not sure what to use because I want to be safe. I'll spend the extra money.
    thanks chris
    17' Sutphen

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    Reasons for Resins...

    Ok, like I said earlier, I am just learning this stuff, so I might have made a mistake.

    However, in checking the numbers, I found:

    Epoxy (room temp cured) - 12,300psi tens, 4.5 mod, flex 12,000

    Vinyl #670 12,000psi tens, 3.7 mod, flex 25,000

    Derakane 411 12,000psi tens, 3.2 mod, flex 22,000

    So, I have a hard time figuring that there is a big advantage to epoxy, and can certanly argue that if vinyl is cheaper and easier to work with, then it is the better choice...

    Also, you can use epoxy with release agent mat, but you need to add a release agent into the resin.

    I'm not trying to "win" this discussion, so if I'm wrong, please point out why. However, when explaining to several fiberglass purveyors who seemed to have pretty good knowledge what my project is (redoing a hi performance boat, wanting to use the BEST resin, regardless of cost - almost everyone pointed me to DK411...

    -David
    AxisMoto

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    Axis, you are doing a great job. And you are right, this is about personal experience and a little research. I am not a glass guy, but I have built a few boats, and spend a lot of time in a glass shop...... and I pay attention. You are stating exactly what I have come to know to be true.

    RT
    2023 TUFF 25

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    Not to diverge too much, but I thought one of the main advantages of epoxy was you could avoid using mat (i.e., heavy, lower strength/weight ratio) altogether (additionally you would use less resin overall since your not using mat) -- right?

    I haven't used Vinyl or Poly, but I had used several gallons of epoxy -- what do folks mean by "epoxy is hard to work with"?


    --Tim
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    '75 Tahiti, 351W I/O

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    Thumbs up Advantages

    Mainly the advantage is in adhesion. Epoxy has a much better adhesion. If it doesn't stick then it doesn't matter how strong the resin. Check the MAS, West, Raka, System One websites and get some more info. on the advantages. Epoxy is no harder to work with and there are about 100 times less in the way of fumes. Never heard that one about not using mat. We used stitched 1208 & 1708 and stitched mat for our project. All worked perfectly.

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    The situation with mat and epoxy is when we are talking about bonded mat - a material which is bonded chemically. To get max strength, you want the temporary bond to release when wetted out, transferring all of the adhesion and structural loads to the resin and glass (no longer relying on the temporary bonding agent).


    If you are working with stitched mat, then it is a non-issue.

    Also, if you really wanted to use epoxy and bonded mat, you can simply add an agent into the resin to release the bond, (and this supposedly works fine).

    FWIW - I have been doing lots of homework on this (much to the detriment of my "day" job), and I am trying to use top shelf stuff everywhere. (With exceptions- I can't afford to go out an buy two new 300 drags, so my rebuilt 2.0Ls will have to do for now). Anyway, I am going to be using 1708 - a two part material, 17" wide cloth bonded to 8/10oz mat - two layers of this make for a nice, stiff, strong composite, 1.5oz mat (on the top deck covering my 2lb modeling foam - easy to mold and smooth, doesn't "print" through gelcoat), Divinycell 200 1.5" foam core and Divinycell 100 1" foam core (both for the transom), 1/8" divinymat for dash and console cores, bottom of boat crossed from tip to tip with 38" wide kevlar, and 4" wide kevlar at the chines and tunnel corners (partially for "strength", mostly so that it stays together even if we have major hull failure, and so I can feel comfortable pounding the sh*t out of it - my last boat was a 32ft Chris Scorpion (center console deep v, twin 2.4s) and it laughed at all but the harshest of waves, I would hate to feel like I needed to back off from having fun because I was going to "break" my boat...)

    -David, AxisMoto

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    I asked on here about putting my transom in and researched, it seems the epoxy will give a better bond to old material for a repair. If you are laying up all new then it does not matter as much, or the more surface area contact you are doing. Since my transom has places with limited contact to old that need to bond well I used wests. The epoxy has a better mechanical bond to the old (over about 24 hours old) where you only get a mechanical bond, as you only get a chemical bond when you lay over within that time. I think that is why many say "epoxy" for a repair as it is an easy choice. With a repair the weakest link is often the new/old bond.

    The pumps are pretty cheap and worked fine. Wests also said I didn't need to worry about the bonding agents in mat as it will be encased within resin anyway. Some still do not agree with that. I used plain old mat I had here with no problems though it is not a high stress hull I fixed, and I put in more materials than came out. It would start to come apart if I messed with it too much before cure, so maybe everyone is talking about something else. I used a brush to apply resin. The stuff stuck like mad. I got some on unsanded/unprepared gel and it pulled chips out when I knocked it off. Like I've said on other posts, people been fixing boats without epoxy forever anyway. If done right it will work fine if a quality and proper product is used for the task IMHO.

    I did cover the boat and leave it in the sun for a while to help cure if it made any difference. The only problem I had was with a crack in the bottom I did a little repair on. I fixed it and it didn't get all the way hard in about 70+F temps in the evening with fast hardener. Should have been hard in 10 minutes or less, so after an hour I backed the lawn mower up to it and let it blow warm air on it from a few foot away. It hardened right away. Maybe it was the dew setting in? It was warmer when I did the transom and it cured fast, often in 4min or so. Never had a problem with the blush, it washed right off. If I remember you only had to worry about that when you topcoated anyway, though I did sand between cured layers (all within 24 hours) just to be sure.

    I think a lot of manufacturers don't bother with the extra cost of epoxy because we all know a good resin can outlast the boat with proper care anyway. Epoxy is also waterproof and will not absorb water like other resins can. I didn't have any problem with fumes, though often at under 5 minutes cure I didn't have much chance. It didn't stink like regular resin IMO. Laquer thinner did a nice job cleaning up however, and worked better than the acetone I bought for that. There was a guy on here that had his eyes swell up from it, I'd guess he is allergic to it. I used a respirator inside the transom a couple times when there was no wind outside where I did it, otherwise it was no problem. It was pretty small in there. I've repaired a few things that I don't think glass would have held on, even plastic things. So I think it would depend on what I was doing, if the extra cost was worth the benefits it offers. I thought it was easy to use as glass, but I have not done a lot of glassing on boats either just mostly cars and such. You have to change hardeners to change speeds if that is a problem, but it was not with my project. I must have done over a hundred small cups of that stuff. It falls out of the soft plastic cups/tubs when it is hard.

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    Steve and others, one thing to consider with Epoxy and there listed strengths is that they are listed for post cured epoxy. Without post curing Vinylester Dow Durakane has the same strength with less cost. Add that Epoxy can make some people VERY sick I cannot remember what it is called, but you can get a sever reaction from it. Don't get me wrong, I love Epoxy...... and I am building an entire boat from it this fall, I just think that Vinylester, ( specially Dow Durakane ) is a very suitable product. I do not think that poly is suitable for boat repairs, as it just relies on mechanical bond. BUT, you see a lot of guys on here fixing there boats with it and it works great and without failure..... so the way I see it is the vinyl and epoxy are just a step up from something that already works.

    RT
    2023 TUFF 25

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