How does one buld an FRP cabin door?

Discussion in 'Boat Design' started by Bullshipper, Mar 22, 2021.

  1. Bullshipper
    Joined: May 2008
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    Bullshipper Bullshipper

    I used the search function here and on ytube to no avail so I am hoping someone might have a link or a methodology to build 40mm thick 2 sides doors that measure around 165 x 65 cms.

    I have a one sides female mold built but a no cored door is too flexible

    I have also tried airex T100 cores with Poly resin hand layups but think they probably need t be vacummed bagged to not delaminate over time.

    I tried wood coring bet they warped even under pressure during the cure, so I before I try another one of my lame brain ideas, I thought I would ask the brain trust here.

    Thanks
     

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  2. Mr Efficiency
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    Mr Efficiency Senior Member

    So an external door ?
     
  3. Bullshipper
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    Bullshipper Bullshipper

  4. Bullshipper
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    Bullshipper Bullshipper

    This the other door mounted IMG_20210318_091555.jpg
     
  5. fallguy
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    fallguy Senior Member

    I am going to make a corecell M door. On the vac table. I plan to glass it a bit heavily to stop the warpage. My planned thickness is about 17mm only, but this is an inside door.

    I will decore the edge and fill it with thickened resin.

    You can make the same door with thicker core. For 40mm door, use say a 36-38mm core. You could also make the edges of the door from say a coosa or high density material to avoid the decoring work and it would probably keep it from warping.

    Another thing you might consider is post curing the thing and, of course, epoxy. Epoxy won't cure well for 7 days and would need to be kept on the vac table, ftmp. But those efforts will help with warping, as will a good core and the HD core edges. I like the 12oz x 2 glassing...it is certainly excessive for the door, but properly cured epoxy or post cured epoxy should be less able to warp.

    If you leave it on the table, you can fair it while it finishes. If you want to lay glass in it; then also plan to add the HD core where the glass frame screws. The one warning I will give you is I have had nightmares with bridging on the vac table when I have taken out the middle section. So, I would add the HD core, then add in the M core reduced as needed for the HD. Laminate the full panel and cut the M core out a second time, rout for the glass etc.

    Anyhow...I am eager to hear replies.
     
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  6. comfisherman
    Joined: Apr 2009
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    comfisherman Junior Member

    I'll be interested to see the replies. My diamond sea glaze door ended up being the wrong side, would like to mold a glass one as well but haven't figured it yet.

    Thinking might laminate the backside and proud and just deal with the reality of having to fair one side. Probably coosa 20 weight core.

    Curious to see others solutions.
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    Coosaboard might well be the answer, in one of it manifestations, router to the ready, then paint.
     
  8. comfisherman
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    comfisherman Junior Member

    Outfit now defunct (or so it appears) in Canada did a mold with a bladder then injected a 2 part foam. Probably beyond my mom and pop production capacity. It did get both sides fair and foam bonded....
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

    Seems like an awful lot of bother for a door.
     
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  10. Bullshipper
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    Bullshipper Bullshipper

    2 sided Fiberglass home doors with grain on the mold faces have a wood edge rim for lock sets and hinges with cross boards like most doors. They use a frp thick putty and a press to mold in the grain, make it stick with heat and control the temps and pressures with another press. The putty doesn't look like it has cloth, so perhaps its shreded strands. But the tooling looks very expensive.

    Coosa Board if thick might work if the amount of resin and cloth and temps during cure are the same on each side to get equal shrinkage and prevent warping but $500 for some corecell M or 1.5" coosa right out of the gate along with a press to do a temp controlled cure makes this an expensive little experiment. I was hoping to find a less expensive core like Poly boards, but unequal cure is the enemy to staying flat and straight . The surface on these cores would have to be finished and are too porus and soft for just paint. They also present the problem of needing to be pre encapsulated to degas prior to hand lamination, and again, ungeual dry times, temps are the problem with cloth.

    The solid flanged fiberglass door I made from with mat 1708 stayed staaight with its 90 angled outer edge and is not bad to finish on its rough side, but I want to leave mine 12" open using a hook stay so they also act as air scoops on hot days. Open is when I see a little wiggle top and bottom and am concerned about this causing sea sickness. When closed against its rubber weather stripping they are stiff in the frame and you get no wind whiste.

    One can always do to a painted Plastic Honeycomb inishing its cut edges, starboard, or buy doors for around $1500 each on the net, but they are one size only and the store bought ones I find makee a 2 door doghouse pretty expensive to resell, imo

    So I am looking at Honey comb, or maybe something like this at $50 a sheet. Just haven't touched it yet to see how stiff it is

    https://www.homedepot.com/p/Coropla...Plastic-Sheet-3-Pack-COR10MM4896-WT/206084782
     
  11. fallguy
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    fallguy Senior Member

    No. No. And, NO!

    That extruded sheet is a bad idea if u r worried about warpage.

    And if you want to build something flat; you start with something flat.

    You need no press.

    You can use a good shop vac if no pumps are available.

    Starboard is notorious for warpage and if you call the company; they warn it will. So, at least avoid a fully starboard door or starboard edges and opt for more stable stuff like corelite, aquaplas, coosa.

    the entire door could be made with coosa and maybe even a single laminate of 17oz glass each side

    you are creating false problems with the ideas of outgassing or prefilling, etc

    If you laminate on a vac table; just don't release the thing on a well waxed table for 7 days or after electric blanket cure and it won't move
     
  12. Rumars
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    Rumars Senior Member

    There is no need for vacuum or expensive cores for a door. The only question is the desired finished look, wich might add a little hand finishing. You have a mold with a flange for the edge, so let's start here. I presume the mold is made for the finished outside dimensions, and gives you one side of the door and the edge. For the other side you can use the same mold, but need to fit some material to the edge part in order to create a recess. A strip of PE the same thickness as your laminate works well. The rebate can start anywhere after the corner, but it's easier to have some distance from it, so you can fit a small roller in the corner when laminating. The core you bond first to the part with the rebate, either by laminating some CSM to the foam and pressing it down, or by using putty. All voids, like the rebate corner, have to be filled with structural putty. The areas where hardware will be mounted you either fill with structural putty, or use some high density core (small blocks of hardwood). For pressing the foam to the glass you use a piece of ply and stack some weights on it. Now you can demold the cored half of the door, and trim the edge. The other half, the one without rebate, gets the edge trimmed to fit, then you smear everything with putty and put it over the cored half, then the piece of ply, then the weights. The edges can be drawn togheter with screws, or you can use clamps. The edge can be further finished by fairing and gelcoating, or you can leave the joint visible.
    The core is the same foam as on the bulkhead the door fits into, or a lower grade one if the door is thicker or for interior use. Lower cost cores can be: lower density PVC/PE foam, balsa, PU foam (rigid insulation), XPS (needs epoxy putty for glueing, cure the polyester first).
     
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  13. Bullshipper
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    Bullshipper Bullshipper

    This sounds logical, practical, and do doable. Arjay Putty? What is "rebate" and "a strip of PE" mean? please
     
  14. Rumars
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    Rumars Senior Member

    Putty is a generic word for thickened resin, a paste. Almost every manufacturer has a line of "core bonding paste", the ones with "high strength" or "structural" in the name usually also contain milled glass fibers. Just ask your resin vendor for it and choose your favorite brand.

    Rebate is just a fancy word for a recess or step. You created one for example with your window cutout. For the door edges you do it in order to not increase the width of the door. One flange has a step in it to accomodate the thickness of the other one. In order to not make another mold for the other side of the door, you place something in the existing mold to decrease the width and create the step. This something is a spacer the same thickness as your finished laminate on the other side and has to be smooth and coated with release agent. PE is polyethylene, and I suggested a strip of it because it is smooth and can be bought in consistent thickness, but you can use whatever else you like. For low cost I would cut plastic bottles in strips and stack them to the desired thickness, then tape this to the mold to act as a spacer. The elegant way is to use wax strips, but those have to be bought.
    The other way to do it is to make a separate fiberglass strip, then glue it to the inside of your flange. If the flange is 40mm wide (the thickness of your door), you cut it at 20mm and glue a 40mm wide strip to the inside of the flange before you place the core. The flange of the other side of the door is also cut at 20mm, and the two meet in the middle, hopefully exactly flush, and having the separate strip inside to act as a connection and provide structural support.

    The only tricky business of the whole affair is paying attention to the individual components thickness, so you end up with a door of the right thickness. For the final assembly use some spacers of the right thickness between the plywood on top and the surface the door is resting on.
     

  15. Bullshipper
    Joined: May 2008
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    Bullshipper Bullshipper

    I think I will just use the same mold as is to laminate both sides of one door using weight and time for the slow cure expoxy I have on hand, then cut both pieces to get the proper thickness, then epoxy them to both sides a 1" insulation core that is stiff and avilable here in Mexico. I'll then fill the slit between the two perimeter cuts that met with white pimented epoxy and shreded glass as my first attempt, that I can start on this week.

    I would like to thank you and everyone else with your help as I now feel I have a better plan than I did yesterday. I will follow up with results when I come back from vacation in a month or so

    Again, thanks
     
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