DIAB Foam

Discussion in 'Materials' started by MarineSurvey, Sep 23, 2009.

  1. AndrewK
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    AndrewK Senior Member

    Ruby Tuesday, since the bulkheads with the same biax do not show print through then the resin shrinkage is not the issue.
    If it was me I would be sending trough the gelcoated panel down to the biaxial to see what is different about it. And to make sure there are no nasty surprises hiding under the gelcoat and CSM.

    Cheers
    Andrew
     
  2. jim lee
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    jim lee Senior Member

    Marine survey, was there any spray glue used to hold the laminate together? It looks like your gel-coat or skin coat was contaminated before the dry-stack went on. Possibly was someone using PVA nearby?

    Also, what was the vacuum at when you shot the part? If you shut down your pump, could you see the vacuum drop?

    What resin did you use? Was it an infusion resin? Or did someone dump styrene in standard resin to thin it out?

    Were there holes drilled in the core to let the resin pass from one side to the other?

    How long was the resin flowing?

    -jim lee
     
  3. Ruby Tuesday
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    Ruby Tuesday Junior Member

    Hi Jim Lee,

    I think that the China yard seems to be in the same situation I’m in – they engaged DIAB as “experts” to do the entire infusion process, full stop! Also, DIAB would have checked out the suitability of the infusion resin, & their infusion core usually does have grooves & holes in it. In my case, they have not even come to the factory to do tests or to try & explain to us what they did wrong so that we don’t repeat the errors!

    I’m about to try a new moulding myself (the sliding sun roof panel) & would like everyone’s opinion on the products I intend using. The laminate schedule calls for the following -

    Gelcoat
    Tie layer - 225 g/m2 CSM
    CURE
    450 g/m2 CFM (which failed to prevent the print-through of the BE cloth)
    850 g/m2 BE (which resulted in terrible print-through to the outer skin & ‘bridging’)
    R80 PVC Core 15mm thick
    850 g/m2 BE

    I am proposing the following –

    Gelcoat
    Tie layer – 450 g/m2 CSM
    CURE
    2mm Soric
    450 g/m2 CFM
    450 g/m2 DB
    450 g/m2 DB
    R80 PVC Core 15mm thick
    850 g/m2 BE (or 2 x 450 g/m2 DB if the BE upsets the balance?)

    The DB is a bit more work, but is thinner & far softer than the BE, which is like rope. It should also pull into the corners better, stopping bridging. I’ve been told that the 0/90* of the BE isn’t necessary here. I will gain some weight, but not very much.

    All comments welcome, Landlubber, Herman, Andrew K, Jim Lee, et al?

    Thanks
     
  4. jim lee
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    jim lee Senior Member

    We are really new to infusion. But I kinda' get the feeling most are.

    Anyway, here's some notes on what we've seen so far..

    We don't use a skincoat on our parts. It looks like this is what you are calling a "Tie layer" We did use a skin coat on our molds, but it does not seem to help print through at all.

    To minimize print through, we try to minimize heat. Resin = Heat = Print through. IE no mat between layers. And, no resin piping touching the backside of the part. It looks like you are doing the same.

    Some core has thicker saw cuts than others. Some have knife cuts. We've been using the sawcut type and, no matter what way you lay it, up or down, you see the cuts in the print though. I'm thinking that each cut is a resin blob that causes heat that causes local shrink and print through. We are hoping to try some knife cut core on the next project.

    I've been told that what you are trying, multiple layers of smaller weight glass, is a good way to go. This is what the local kayak builders do for their outside skins. We've not yet tried this. (I'd like to though)

    I've seen another local boat shop that, like you show here, uses Soric over a skincoat. They seem to get very good results using this. From the quick look I took at their parts, I could see little to no print through. We can't afford the weight of Soric because we are building a ultra light sailboat. So we've never played around with it. That being said, the next mold we make I'm thinking about trying some.

    One thing we tried that seems to work was a really fine weaved cloth. We called it for lack of a better name, T-Shirt material. I don't know where it comes from. The "old hands" were all upset that we put this stuff in the mold telling us that it wouldn't infuse, flow etc. But, since we use the core as the flow media, we figured "what the heck, lets try it." It did print through, but with a very fine muted pattern that was not very noticeable. The trouble was that it added weight that we can't afford.

    What we do about print through?

    Most of our parts have a 1oz layer of cont. strand mat on the gelcoat. This is to "mask" the print through. The print through is still there, this just makes it a little harder to notice. No skincoat. Then 17oz. biax, core, 17oz. biax. Sometimes the outer layer will be a 24oz biax. Minimal resin, minimal heat build up. No piping touching the backside to transmit heat. Also we never use the biax that has the mat stitched to it. From what we've seen it only adds weight/heat and the stitching that attaches the two layers prints though like crazy.

    Using this we get ok results. Not great. In our case the plan is to tell the customer right up front; "You want it light? Then its going to have some print through. Nature of the beast." 'Cause it kinda' is.

    Looking at your pictures, yes, you have print through. But, it seems your parts are structurally sound. Be thankful for that. I've seen infused stuff come out of the mold and have most of the gelcoat just fall off. Or, have so many voids the part is completely junk. We've been learning that if you don't get -all- the details right, this infusion stuff can bite you hard!

    We need more threads on infusion. I'm sure there's people out there that have solved this stuff. And I'm sure there's a lot that are going nuts trying to get this to work. Its painful solving it all on your own.

    -jim lee
     
  5. Herman
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    Herman Senior Member

    Contact Polyworx. They know what they are doing, and they do it right.

    Gelcoat: At least use the recommended thickness, and check that. Get some thickness gauges, preferably from some different (gelcoat) manufacturers, and cross check these for accuracy. I got surprised once. If you like, I can send you a gauge from "Ferro" which is accurate. (goes for you as well, Jim Lee)

    The 450 grams CSM could cause another source of print. For skin coats I recommend a low-tex 225 CSM. (usually 10 or 12 tex, whatever is available)

    The Soric should definately help. Get a Soric TF in 1.5 or 2mm thickness. the SF or XF could cause print as well. A newer Soric version, LRC could be suitable for low weight projects. However, I only built 1 object (12 meter boat) with that, as a demo, so cannot judge properly on print. But the material certainly eats less resin.

    DB or BE: I am not completely familiar with these codes (every NCF manufacturer seems to have invented their own codes) but I can say that +/-45 oriented material usually is a lot denser, thus less resin concentrations.

    Foam: At least use perforated foam. In many circumstances this is enough. Although over here we use a flow medium on top of the laminate, usually. A so-called double-cut foam works great as well, knife cut is enough. Fast moving resin sounds great, but: A. Glass wetting can be impaired. and B. Infusion is not a race. If you need more time, change your infusion strategy.

    Behind the foam: Not so important what you use there. I suggest getting rid of the coarse materials, so use them where they do no harm. Behind the foam is a good option.
    Be very patient and accurate when laying glass. Bridging is good for nothing. All materials should be applied in the corners very well. Use (sparse !!!!) spray glue (hotmelt or cans).

    One other thing, that I cannot find back:

    Resin !!!. I probably said it before, but check your resin for shrinkage. Over here I have resins which can shrink dramatically, and getting decent results can be challenging, but I also have resins which will do the trick.

    Tests: Make a variety of tests. In the end, you will need to be the expert. I have a glass table, on which I usually make 4 or even 8 tests in one go. Takes half a day, or a night if you will, but you will gain a lot of invaluable experience.
     
  6. Herman
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    Herman Senior Member

    A skin coat should help minimising print. It needs to be fully cured, though.
    No comment on that. Always a good thing. No CSM between layers, just keep in mind laminate thickness, if needed. I guess you have that covered.

    Do some calculating on resin consumption of the sawcuts. Keep in mind that a foam surface can eat 500 grams of resin (sorry, no imperial for me) per m2. You were building lightweight, did you? :p

    Lightweight fabrics usually are finer in texture. However, ask your supplier what is possible. Heavy fabrics can also have a fine surface.

    Skip the sawcuts, and use Soric, and I guess you will use less resin. (did not do a calculation, but I guess I am right.) Perhaps the 1.5mm Soric TF or the Soric LRC is your way to go.
    As it printed as well, I guess it is of no use as well. But did your gelcoat cure properly, and was it applied thick enough? Check both. Also check catalyst level, and type of catalyst. There are different catalyst, which will give better results with gelcoat. Adding less catalyst because you need more working time is a NONO.
    CFM? Again, you were building lightweight? try to get hold of some Lantor (Soric) D7760 surface tissue, or any similar material. You could also opt for a barrier coat.


    I feel (but no proof) is that you might apply too thin a gelcoat. If you do not want a handlayup skincoat, do an experiment with 225gr/m2 CSM (not CFM) and Soric TF behind it, to help it wetout. After that, your normal layup.

    And check resin shrinkage. Make tests, with different resins and catalysts.

    Good luck, I am back to surviving swine flu now.
     
  7. Ruby Tuesday
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    Ruby Tuesday Junior Member

    Thanks Herman & Jim, there's some good advice there.

    Herman, the DB is Double Bias & the BE is BiAxial. We were told at the DIAB infusion course to avoid CSM during infusion totally, that's why I've never considered using it. You've given me new food for thought!

    I've only used the DIAB foam with the saw cuts & holes & have never seen any evidence of print through of the foam cuts? Wonder why Jim Lee's having problems with it?

    Cheers
     
  8. AndrewK
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    AndrewK Senior Member

    Ruby Tuesday; my infusion experience is only with epoxy resin so can not offer direct advice. But as you said earlier on that a bulkhead you infused with the same biaxial glass showed no print through then my thinking is that you should not need the additional CSM or CFM or Soric mat.
    All I can suggest is that you do a whole lot of small scale trials changing one variable at a time and see how all the materials behave.
     
  9. AndrewK
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    AndrewK Senior Member

    Ruby Tuesday; this may be of interest to you.
    http://www.reinforcedplastics.com/view/1902/improving-surface-quality-in-vacuum-infused-parts/
    Looks like incorporating additional CSM or other blocking material into the infusion stack is a waste of material if its there purely as a print blocker, which makes sense.
    This is what Herman has been saying, its the thickness and quality of the cured ( gelcoat and barrier ) layer that is most important.
    Also my observation is that 450g DB has a smoother surface than CSM or CFM so do not know why the former are used as print blockers.

    Can you name the resin and supplier you are using?

    Cheers
    Andrew
     
  10. Herman
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    Herman Senior Member

    Nice link.

    However, I had hoped they also would have investigated more options, like injectable surface tissue, and state of cure of the skincoat.

    And remember a skincoat can have 2 functions: Reduce print, and make the mould accessable to fill it with glass. (be able to walk on the gelcoat/skincoat)
     
  11. Landlubber
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    Landlubber Senior Member

    "(be able to walk on the gelcoat/skincoat)"........and contaminate it.......no wonder we see so many problems with boat construction........I thought China was bad enough.
     
  12. Herman
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    Herman Senior Member

    That is a question of discipline, workmanship and procedures. Leave the peelply on as long as possible, that saves a lot of problems.

    Besides that, I prefer a contaminated (footprints) peelply surface over a poorly sanded surface, and possibly even a well sanded surface. I ran a lot of tests on adhesion of infused laminates to skincoats, and peelply is the winner by far.
     
  13. Ruby Tuesday
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    Ruby Tuesday Junior Member

    Hi Andrew,

    Thanks, that was a great article you posted, very informative. Their statement that all infusion mouldings give an inferior finish to hand lay-up is the first time I have heard anyone admit that.

    The infusion resin we used was NUPOL ESTAREZ 6800 – 65 INF, & the catalyst Norox CHM – 50, at 1.5%.

    I have since heard of a yard in WA that have allegedly had problems with a Nupol infusion resin, don’t know if it’s the same one though. NUPOL state that the exothermic cure heat of their infusion resin is no more than 40*, which seems very low? Their chemist told me personally that it was impossible to have any further curing or movement of the resin after seven days, & that post-curing would be a waste of time. My hull & deck are still moving (curing) three months later!

    Hi Herman,

    From sites I’ve seen on the Internet, it looks as though most builders walk on the gel coat/tie layer while laying up. I wonder how many yards are able to post-cure at 80* for 16 hours though?

    One of the reasons I went with DIAB to do the infusion of my company’s boat was their involvement with Azimut in Italy. There is no way a company of Azimut’s stature & reputation would produce an inferior vessel? If Azimut are able to produce quality infusion-moulded yachts, surely DIAB would share this information with their subsidiaries around the world?

    Cheers
     
  14. AndrewK
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    AndrewK Senior Member

    Ruby Tuesday; the only infused boat I have seen is the Fusion 40 sailing catamaran, although I was not looking for signs of print through the finish was very good.
    Get in touch with them and see how they achieve it.

    Herman; always interested in any infusion test data, are you able to post any?
     

  15. Herman
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    Herman Senior Member

    I have loads of data, but most of it if not all is pretty useless. They are resins used here in NL, and also with the specific layup the customer wants to use.

    There are so many variables. Both in temperature, resin, laminate schedules, glass fabrics used, core materials, and resin distribution media.
    Not to mention you will not have access to the materials we sell (unless you are prepared to pay for shipping, and I do not have access to materials you have access to.

    Right now I am testing again another infusion mesh for speed. What we have now is nice and slow, and gives a very nice, high quality result. Speed in both directions is the same. Now I am testing another mesh, and I hope speed will go up a bit, without impairing laminate quality, and keeping the isotropic resin dustribution that I have now. It is so easy to make a mesh which goes really fast, has a unidirectional flow, and leaves behind a crappy laminate.
    I do like the slow one. It is easy to design an infusion strategy with not too large resin paths, so I do not see a real problem in the speed. However, some people like to speed up things a bit.

    Best thing to do is experiment. Basicly, print through can be stopped by adding hard, cured barriers between gelcoat and layup, or use a cushion-like material.

    Basicly you have 3 options:

    -barriercoat
    -skincoat
    -Soric TF

    Guess what works best? A combination of all 3 of them...

    Then also consider gelcoat and barrier coat thickness, and resin shrinkage (test that!). It is nice to have different options.

    Anyhow, the key is in getting a good cure of the gelcoat for starters. Ask your peroxide supplier what they have. Standard peroxide can be improved for good cure of gelcoats. Over here we sell Syrgis / Norac / Andos Norox MEC for that. (3 names for 1 company, I hope they will keep the Syrgis name for a longer period...). This peroxide has improved cure of gelcoats, better gloss retention, and less porosity.

    Also test your peroxide for impurities. Take a glass tube, fill for 25% with peroxide, then 25% styrene, close with your thumb, and give a good shake. If it gets foggy, there is too much water in it(more then 5%), and you should be looking for another supplier.
    If not foggy, then take the mixture, and add 1:1 with styrene, and shake again. If it gets foggy then, water level can be higher then 2,5%, or water level can be obscured by added salts. Not too much of a problem, but be cautious.
    A good quality peroxide survives these tests, and stays clear.

    Oh, about thinning polyesters for infusion: Not for the novice. Definately do not thin down a hand laminating resin. This has a thixotropic agent in it. It is a bit stupid to first create a resin which will not sag out of a laminate, then thinning it to make it easy to go into a laminate. (will work for 20cm / 8" or so, then infusion speed will drop dramatically)
     
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