Custom Extended Swim Platform

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

  1. tpenfield
    Joined: Dec 2016
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    Location: Cape Cod, MA

    tpenfield Senior Member

    I'll be back at it, working on the main platform mold this weekend. It seems that I am only getting a few days a month to work on the platform, but with warmer weather a couple of months off, I need to get things moving along.

    I'm going to run a test of the TBC inhibitor to see what approach (MCP catalyst or TBC inhibitor) seems best , then move onto the platform mold. The lower temps in the northeast USA will make for an interesting time, as I try to maintain reasonable curing temperatures in the workspace (my garage).

    Saturday will be 2 coats of tooling gelcoat.

    Sunday will be infusion set-up and the actual infusion. I'll let the infusion sit for a week, then add some stiffeners by hand layup. After all is cured, I'll pull the mold from the plug.
     
  2. gonzo
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    gonzo Senior Member

    You can eliminate the struts by bracing the platform from above. The aluminum pipes can be made to do double duty as handrails.
     
  3. tpenfield
    Joined: Dec 2016
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    tpenfield Senior Member

    TBC inhibitor test update . . .

    I did a resin 'pot life' test on MEKP activated poly resin w/ 300 ppm TBC inhibitor, in similar fashion to the other tests that I did a couple of weeks ago.

    The TBC inhibited resin started to gel at about 75 minutes and reached a temperature of 150 F at 120 minutes.

    So, in summary

    0.75 fl oz of resin for each sample starting temperature 55-57 F

    2% MEKP gel @ 30 minutes, peak temperature 140+ F

    2% MCP gel at 70 minutes, peak temperature 75 F

    2% MEKP inhibited by TBC @ 300 ppm gel at 75 minutes, peak temperature 150 F

    It looks like the TBC inhibited resin really kicks into gear after the 70 minute open time, where as the MCP activated resin had a similar open time, but did not generate nearly as much heat as the TBC/MEKP combination.

    I'm not sure what is best . . . a slow low temperature cure . . . or a presumably faster and high temperature cure. :confused:
     
  4. ondarvr
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    Location: Monroe WA

    ondarvr Senior Member

    If you have a thin laminate the higher exotherm isn’t an issue. Add a foam core, plus more glass, and the exotherm can become higher than desired, this is where MCP comes into play.

    You will get more shrink with the higher exotherm, this may lead to the fabric printing through.

    But if ambient temps are low, the higher exotherm will allow for quicker de-molding of the part.
     
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  5. tpenfield
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    tpenfield Senior Member

    Yes, that is what I was thinking . . . thin laminate, colder than ideal temperatures, might be a bit of shrinkage, but the other factors may offset.

    I won't de-mold for a week or 2, so speed is not a concern.
     
  6. tpenfield
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    tpenfield Senior Member

    Here are the resin test samples . . .

    IMG_2263.jpg
     
  7. tpenfield
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    tpenfield Senior Member

    Tooling gelcoat on the platform plug. . . .

    It seems to be curing OK.

    IMG_2266.jpg

    Getting ready for infusion tomorrow . . .
     
  8. tpenfield
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    tpenfield Senior Member

    Quick Update . . .

    I had trouble getting a perfect seal for the vacuum. So, rather than risk it, I am doing some re-engineering on the bagging material.

    I'll take another run at it within the next couple of weeks.
     
  9. tpenfield
    Joined: Dec 2016
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    tpenfield Senior Member

    Infusion Update . . .

    I did the infusion this morning (March 23, 2019). It went pretty well considering it is my first attempt at a large infusion. (4 ft. x 8 ft.)

    I put the resin bucket at an elevated location to promote resin flow into the runner system, and used TBC inhibitor at 300ppm to slow the gel time to about 75 minutes.

    Here are a couple of pictures.
    IMG_2286.jpg
    .
    Here is the resin flow in the first few moments of opening the valve on the distribution manifold.
    IMG_2290.jpg
    .
    This is after about 45 minutes.
    IMG_2299.jpg

    The resin started to kick at about 90 minutes and there were a few small dry patches left, which I should be able to wet out by hand.

    Overall, I'm happy with it.
     
  10. tpenfield
    Joined: Dec 2016
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    tpenfield Senior Member

    I de-bagged the mold and fixed the few dry spots.
    .
    IMG_2312.jpg
    .
    Next steps will be to add some stiffeners and a layer of glass in a few places.

    Based on my schedule, I won't be pulling the mold off of the plug for about 2 weeks So, it certainly will be fully cured by then.

    BTW - in terms of slow catalyst (MCP) vs. using an inhibitor (TBC), my preference, after having done a couple infusions, is to use MCP in warmer temps (70˚ F) and TBC/MEKP in the colder temps (60˚ F +/-), since the TBC/MEKP combination results in a fair amount of heat after about 75-90 minutes.

    For this infusion, the starting temperature of the mold and the resin was around 59˚ F. Once the resin started to kick (90 minutes), the temperature of the resin/mold rose into the 80-100˚ F range.
     
  11. tpenfield
    Joined: Dec 2016
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    tpenfield Senior Member

    Quick Update . . .

    I will be pulling the mold from the plug this weekend, which may prove challenging, based on the size of the mold. Hopefully, all will go well and I can be making the parts from the molds (platform + 2 hatch molds) next week.

    I was not a fan of all of the wrinkles in the bagging material on the platform infusion, as it made for a messy surface with lots of irregularities. So, I have ordered a different bagging material - Stetchelon 800 - which will stretch up to 4X to conform to the various shapes of the mold, rather than needing pleats.

    If you noticed on the prior infusion of the platform mold, I did not use any peel-ply. My thinking was to promote saturation of the glass with resin. The plan for the actual platform 'part' is different in that I will be adding the foam core material and final layers of glass as separate steps/infusions. I plan on using peel ply in initial the 'stack' so that I will have a textured surface to accept the core material.

    For the first infusion of the platform I am planning on the following stack:

    Vacuum Bagging
    > Flow Media
    > Peel Ply
    > 1708 Biaxial
    > 1708 Biaxial
    > CSM
    > Gelcoat
    Mold Surface

    I'll be infusing VE resin, using the same gravity feed method as before, but with a few more runners to promote the even more distribution of the resin.

    Making of the 2 hatches, should be much more of a slam-dunk. I will probably just dump the resin over the glass in the mold and then use a vacuum bag rather than infusion. The hatches will be solid glass with no foam core.

    I have not run any pot life tests of the VE resin to see how it does with TBC inhibitor. So, that will be on the docket for this weekend along with separating the mold from the plug.
     
  12. tpenfield
    Joined: Dec 2016
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    tpenfield Senior Member

    It took a while, but I got the mold separated from the plug.

    IMG_2361.JPG

    IMG_2362.JPG

    IMG_2363.JPG

    IMG_2364.JPG

    Next steps will be to inspect and touch-up the plug. I'll be doing the infusion next weekend (April 13-14, 2019) . . . hopefully.
     
    Last edited: Apr 7, 2019
  13. tpenfield
    Joined: Dec 2016
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    tpenfield Senior Member

    I did some touch-up on the mold and also cut the 'navtruss' strips. These are 1/2" thick urethane foam strips.
    IMG_2367.JPG
     
  14. tpenfield
    Joined: Dec 2016
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    tpenfield Senior Member

    Another update:

    I plan on using VE resin for the actual parts. Like the catalyst and inhibitor testing that I did with the poly resin, I did the same with samples of the Vinyl Ester resin.

    3/4 oz. resin for each of 3 samples starting at 59 degrees F.

    1) MEKP @ 2% , time to get was 40 mins, max exotherm was 235 F :eek:

    2) MCP @ 2% , time to gel was 90 mins, max temp was 70 F :)

    3) MEKP @ 2% + TBC @ 300 ppm, time to gel was 65 mins, max temp was 240 F. :rolleyes:

    The high temperatures of the MEKP samples made for an irregular cure. There was mostly a solid mass in the test cups surrounded by a small amount of liquid. Not sure what that was all about. :eek: :confused::(

    The MCP sample cured perfectly. Looks like I’ll be using MCP for the infusions.
     
    Last edited: Apr 8, 2019

  15. fallguy
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    Location: usa

    fallguy Senior Member

    Still a bit worried about your strips, but sure hope it works for you!

    It might be some early bias about the cloth running between the strips driving my concern.
     
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