Custom Extended Swim Platform

Discussion in 'Boatbuilding' started by tpenfield, Jan 8, 2019.

  1. tpenfield
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    tpenfield Junior Member

    Ok, thank you. Looks like I will let the gelcoat cure a lot longer. The open air should keep the surface tacky and accepting the resin/glass laminations.

    In about 2 weeks I'll be trying my hand at the swim platform mold, which should be very exciting :eek: . . .
     
  2. Blueknarr
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    Blueknarr Senior Member


    You can still laminate over soft gelcoat. Simply leave it in the moulds for longer. Like over night.
     
  3. tpenfield
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    tpenfield Junior Member

    I am preparing to make the 'main' mold for the extended swim platform, having completed the hatch molds last week. The main mold is 4' x 8' (2.4 m x 1.2 m) with some complexities in shape. Here are 3D drawings of the plug from which the mold will be made (not showing the rounded corners and contours). I think there is about 42 sq. ft. (3.9 sq. m) of area to infuse with resin.

    plug1.png

    plug2.png

    I am going to be vacuum bag infusing ( VARTM) the mold using polyester resin. I am concerned about the limited amount of working time with polyester resin . . . maybe about 20 minutes.

    I am looking for ways for getting the resin to flow into the mold area more quickly, so that it has more time to flow through the mold area and saturate the fiberglass. I am going to be infusing resin into 3 layers of 1.5 oz. chopped strand mat (CSM). About 3 gallons of resin. Then afterwardss I am going to hand layup some stiffeners, etc before separating the mold from the plug.

    What ideas/methods would be good for getting the resin into the mold as quickly as possible? Lots of resin runners?

    I have considered putting a little bit of pressure into the resin pot (would have to be sealed), rather than just relying on the vacuum from the mold to pull the resin in through the tubing, etc.

    Thoughts?
     
    Last edited: Feb 15, 2019
  4. ondarvr
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    ondarvr Senior Member

    Don’t use CSM, or at least limit its use. It flows poorly, it’s used to control flow through a part by restricting movement of the resin. That, and the fact that you have laminating resin will be your downfall once you scale up to larger parts.

    Use a long gel time infusion resin, or a blended catalyst, these can be a little tougher to find in the DIY world though. Composites One has them.
     
    Last edited: Feb 15, 2019
  5. ondarvr
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    ondarvr Senior Member

    The soft tooling gel is an odd occurrence, but has a couple possible causes.

    If any of the epoxy used in the plug isn’t 100% cured it can inhibit the cure of the gel coat.

    Or,

    It wasn’t mixed thoroughly after adding catalyst.

    One other possibility is that there were air pockets in those places. Any air pockets in an infused part will have a very high styrene vapor content. The styrene vapor will stop the cure, and even soften gel coat that’s not fully cured.
     
  6. tpenfield
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    tpenfield Junior Member

    Thanks ondarvr. I appreciate the guidance.

    I wet sanded the plugs with 600, 1000, 1500, 2000 grit as final sanding and hopefully to get rid of any 'blush' on the epoxy. I also applied 6 coats of release wax. So, it may be more of an issue of not enough catalyst and not waiting long enough for the tooling gel to cure.

    I hit the molds with PVA to get the gel to harden up, then washed it all off a couple of days later.

    On the big mold, I plan on using 2.5% MEKP for the gel and letting it cure overnight. I might also spray the entire plug with PVA so I'm not merely relying on the wax.

    It has also been recommended to use an inhibitor on the poly resin to slow the gel time down. I'm not sure what inhibitor would be best, so I've put an inquiry to the resin retailer.

    I'll check the composites one site.

    I had planned on using CSM for the mold and then a combination of CSM and 1708 for the actual part. I am thinking for the actual part, I will probably infuse the outer laminates (CSM + 2x 1708) and then do hand layup/vacuum bag of the core material and final laminates . . . since I'm a rookie. ;)
     
  7. tpenfield
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    tpenfield Junior Member

    Anybody got any definite sources for an 'inhibitor' for resins (poly and/or VE) ???

    It has been suggested (on a composites forum) to use 4-tert-Butylcatechol (aka TBC) as an inhibitor to extend the gel time of resins. My understanding is that the gel time can be extended by 2-3 times (so about 40-60 minutes for poly resin), without adverse effects, which will make matters easier for either infusion or hand lay-up.

    There is a TBC based inhibitor called "Pergaslow", which is a 10% TBC solution, but it is only available in Europe. I have not found anything similar available in the USA markets. The only thing I have found is crystal form of TBC from chemical suppliers, but that would have to be mixed into a solution of some sort.

    Anybody know of a resin inhibitor available in the USA market?
     
  8. ondarvr
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    ondarvr Senior Member

    TBC and HQ are the common ones, but slowing it down that much can be risky. When extended that far you may end up with an incomplete cure, or a great deal of post cure. Neither of them are very easy to buy for a DIYr

    Use a different catalyst, it will be much easier. Get a gallon of MCP 75, it should do what you need.

    Also, infusion resin will make it much easier.

    https://www.united-initiators.com/f...ted_Initiators_NOROX®MCP-75_TDS_UP-AMB_EN.pdf
     
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  9. tpenfield
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    tpenfield Junior Member

    Thanks for the suggestion, ondarvr . Perhaps the secret is in the catalyst :)
     
    Last edited: Feb 17, 2019
  10. tpenfield
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    tpenfield Junior Member

    I have both MCP catalyst and TBC inhibitor on order. I'll try each separately in some test batches of resin to see what the gel time and final cure look like.
     
  11. tpenfield
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    tpenfield Junior Member

    Quick Update . . .

    I ran a VARTM test using the MCP catalyst. A 1 sq. ft. piece, measuring 18" x 8" to see how well the resin would run along the flow media and saturate 3 layers of 1.5 oz CSM.

    I prepped 6 fl oz. of resin, got the vacuum going, and started the resin flow, timing the resin progression.
    (The stopwatch is showing 1 minute, 12.1 seconds)
    IMG_0208.jpg

    It only took about 2 minutes for the resin to flow to the edge of the media. (left to right in picture)

    It took 30-45 minutes to fully saturate the CSM, but the resin stayed 'open' for that duration. BTW - the resin was fairly cold ( 60 F) and activated with 2% MCP.

    The finished part was quite thin for 3 layers of CSM ( micrometer'd at 0.055"). The resin flowed into the part fairly well, except the last few inches were not fully saturated (resin flow was right to left as I am holding the part in the picture below).
    IMG_2093.jpg

    So. I'll have to re-think my laminate schedule for making the main mold, given the limited thickness of the test part. I have some 24 oz. Woven Roving on hand that might be good to 'bulk up' the laminate.

    I'll also need to look into the peel ply a bit more . . . Before I made this test piece, I checked the peel ply to see how porous it is . . . not very :oops: .

    So, I'm wondering if there is a peel ply that is a bit more coarse and porous :rolleyes: . I'm not sure exactly what the peel ply that I have is. Even though the peel ply worked for the test piece, albeit the last few inches, I'd like to get something a little bit more porous.

    Thoughts? :cool:
     
    Last edited: Feb 26, 2019
  12. ondarvr
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    ondarvr Senior Member

    Peel ply is used to stop the resin flow.

    Roving will do a similar thing. Combining CSM and roving makes for a slow and difficult to wet out laminate schedule for infusion.

    Rovicore is used to speed the resin flow and add a little bulk.

    Continuous strand mat will do about the same thing, but
    it’s a little difficult to work with.
     
  13. tpenfield
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    tpenfield Junior Member

    Thanks, Ondarvr.

    I have found confusing information about the infusion materials as to the 'layering' of the material.

    Some sources talk about the VARTM layering in this fashion. . .

    1) Vacuum Bag (top layer)
    2) Inlet Tube
    3) Flow Media
    4) Peel Ply
    5) Fiberglass Material
    6) Mold Surface (bottom layer)

    As pictured below . . .

    VARTM-3.png

    Yet, I hear about different layering or not needing peel ply. . . It all seems very confusing to me. :confused: :eek: o_O

    I assume that if I don't use peel ply, then the flow media layer will be embedded in the fiberglass. Peel ply is also useful when you are planning to add laminations to the part after the infusion mold is complete.

    What layering of material would be correct or appropriate?
     
  14. tpenfield
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    tpenfield Junior Member

    In other news . . .

    The ladder hatch molds are ready to go. :)

    IMG_2097B.jpg

    I should be able to get 1 or 2 shots out of these molds.

    I figure that I'll wait until the main platform mold is done, so I don't get ahead of myself. :rolleyes: Also, I still have to order the white/color matching gelcoat for the final parts.
     

  15. ondarvr
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    ondarvr Senior Member

    Well, actually the peel ply is primarily for surface prep, but in infusion it does a couple things. It will allow air to move, and resin will flow through it, but not along its length though. So it’s used near the vacuum ports to stop resin flow.

    Flow media comes in a few varieties, the type use depends on your needs.

    Using the right glass will get you the correct flow and strength without fighting resin flow.
     
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