Fiberglass Ice Chest and Generator Box Project

Discussion in 'Fiberglass and Composite Boat Building' started by Biloxi Bertram, Feb 19, 2018.

  1. Biloxi Bertram
    Joined: Feb 2018
    Posts: 9
    Likes: 0, Points: 1
    Location: Biloxi, MS

    Biloxi Bertram Junior Member

    First time post as well as my first fiberglass project (other than helping with minor repairs) so please excuse any ignorance I may portray on the subject. I am currently building a mold for a gen box that will be mounted in the cockpit at the center of the transom on my Bertram 28 and I at a cross roads on what to do in regards to lay up methods as well as how to finish the mold surface itself.

    I have my mold to the point where I am ready to spray the top coat which I will be laying my fiberglass to. It seems everybody uses Duratec as the surface coat but to save time and money and being I already have it on hand, will polyester gelcoat (with wax) suffice for the actual mold surface being this mold will be a one time deal? Also, I will be spraying it through hvlp so any advise on thinning and what to use for thinning would be greatly appreciated. From what I have read, some have used acetone for thinning but is not recommended. Would MEK work better? If so, what percent should I thin for spray application through HVLP cup gun?

    My original plan for gen box layup schedule was to spray gelcoat (with wax) on the mold then after it cured (and I sanded and removed all wax) I would follow up with 2 layers of 1.5 oz CSM, 1 layer of 18 oz RW, 2 layers of 1.5 oz CSM, then finish the inside with a few layers of gelcoat... But after talking with a buddy who has several years of boat building and fiberglass experience I am stumped. He said not to use the RW because I would get some dimples,waves and/or print through on the outer layer of gelcoat of the box even if the gelcoat was cured before laying glass. He also said he wouldnt use wax gelcoat on the outer gelcoat and would just let it tack over night and follow up with a layup schedule of CSM only to prevent print through from the RW.

    As I mentioned, I have very little experience in fiberglass work but I am thinking one of us had to misunderstand the other because some of his tips just don't make much sense to me. First of all, how would I get print through, dimples, waves, etc. on my outer layer of gelcoat if it was cured hard before I ever started my layup of CSM and RW? Second, it seems to me that if I used (no wax) gelcoat for my outer layer I would most definately get print through due to the pressure applied when rolling out the CSM and/or RW even if the gelcoat was allowed to tack over nigh?
    Can someone clear this up and point me in the right direction please? Thanks.
     
  2. jorgepease
    Joined: Feb 2012
    Posts: 1,620
    Likes: 49, Points: 48, Legacy Rep: 75
    Location: Florida

    jorgepease Senior Member

  3. fallguy
    Joined: Dec 2016
    Posts: 4,953
    Likes: 902, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    roving will not conform and you will struggle

    Biax behaves much better.

    roving is for wide expanses, for the most part

    As for the gel v wax; not sure I understand. Male or female mould?

    There would be little need to gelcoat the inside of a box, so regardless of male or female; one of the gelcoats would be unneeded I’d say. The wax done well; perhaps with pva would allow release.

    If you want a nice box exterior; you made a female mould?
     
  4. Biloxi Bertram
    Joined: Feb 2018
    Posts: 9
    Likes: 0, Points: 1
    Location: Biloxi, MS

    Biloxi Bertram Junior Member

    I forgot to mention, I will be using polyester resin.
    Yes, it is a female mold. Sorry for not explaining my process very well but here is a link to another build i used as a guide that will help explain what exactly I am trying to do.

    Fiberglass Ice Chest Project - The Hull Truth - Boating and Fishing Forum https://www.thehulltruth.com/boating-forum/827765-fiberglass-ice-chest-project.html

    I have pretty much followed this thread step by step up to the point of applying the ice chests outer layer of gelcoat and layup schedule directly to mold surface (which in his case was enamel paint that had only been waxed with release wax and PVA). I know this would not work as the polyester resin would react to the enamel paint and ultimately create a big mess. So with that said, rather than buy the Duratec primer I have seen is highly recommended for mold durfaces, I was wondering if I could just use polyester gelcoat (with wax) for the mold surface the same way I have seen tooling gel utilized as the mold surface. After it had cured I would then apply my release wax, then spray the gen boxes outer layer of polyester gelcoat to this surface followed by the layup schedule.
     
  5. jorgepease
    Joined: Feb 2012
    Posts: 1,620
    Likes: 49, Points: 48, Legacy Rep: 75
    Location: Florida

    jorgepease Senior Member

    the tooling gelcoat is basically the same thing except it's been optimized for hardness and polishability. If your just pulling one part, the regular gelcoat will work fine.
     
  6. Biloxi Bertram
    Joined: Feb 2018
    Posts: 9
    Likes: 0, Points: 1
    Location: Biloxi, MS

    Biloxi Bertram Junior Member

    Ok good deal. Thanks!
     
  7. fallguy
    Joined: Dec 2016
    Posts: 4,953
    Likes: 902, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    Yup; plan sounds good.

    I’d skip the roving. It’d be much easier to use some biax..

    Print through occurs after the part is finished. The sun heats things up and they move and change. A very heavy thick fabric will especially offer greater likelihood. At least on this part of the advice; I’d heed it. Using 3-4 layers of 17 oz biax would be better. Your friend can probably offer an idea on the thickness or counts.

    Some of these other guys have done more moulds than me, but I am book smart some. I used Duratec the first time last month. -stinky stuff- my mould is making 2 parts only most likely... prior to that I used paint. Dries too slow...
     
  8. ondarvr
    Joined: Dec 2005
    Posts: 2,685
    Likes: 412, Points: 83, Legacy Rep: 506
    Location: Monroe WA

    ondarvr Senior Member

    You can use regular gel coat for the mold surface, it won't level and flow that very good, so you'll need to do quite a bit of sanding. You can use some MEK to make it spray and level better, but not more than 5% or so, it will degrade the the gel coat a bit, but since you're only making one part it should be fine.

    You can use the waxed gel coat on finished part, but start glassing on it before it becomes tack free, which depending on ambient conditions could be in just a few hours or less. So plan to spray in the morning and glass by noon.

    Roving can print, but a layer or two of CSM can help prevent it, most fabrics and CSM can lead to print through unless you do a few things to prevent it. The skin of CSM helps a great deal.

    Tip size on a gravity feed gun should be about 3mm for gel coat, and 3.5 wouldn't hurt.
     
  9. Biloxi Bertram
    Joined: Feb 2018
    Posts: 9
    Likes: 0, Points: 1
    Location: Biloxi, MS

    Biloxi Bertram Junior Member

    As suggested, I will not be using the RW. My buddy said that 4-6 layers of the 1.5oz CSM should be sufficient for the gen box being it shouldn't be under any strain or weight and if I wanted to ensure it was rigid enough I could laminate 1/8" ply between the layers of CSM. Or I might just spend the extra money and go buy some biax as suggested by you guys. As for the coffin style fish box I will be building after I complete and master this project, I will most most definitely utilize a stronger layup schedule as it will involve laminating a few layers of foil faced Polyisocyanurate foam board and will need strength to stand up to the abuse fish boxes tend to take.

    As far as the outer layer of gelcoat goes, should I use gelcoat with wax and let it cure out before moving on to the layup? Or should I just use no wax gelcoat and let it tack over night before layup? Seems that going with the former would be the safest route to ensure I dont push the fiberglass through the gelcoat when rolling it out but then again I am not sure how much of a PIA it is to sand the paraffin wax off between gelcoat and layup???
     
  10. fallguy
    Joined: Dec 2016
    Posts: 4,953
    Likes: 902, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    I wouldn't mess with 1/8" ply. It sort of has a mind of its own and might move things on you...

    Reread ondarvr on the tack...he was pretty clear for you. Glass B4 tack free. You won't need to push much on 1.5oz csm.
     
  11. Biloxi Bertram
    Joined: Feb 2018
    Posts: 9
    Likes: 0, Points: 1
    Location: Biloxi, MS

    Biloxi Bertram Junior Member

    Here are some pics of my progress. I dint have any pics since I applied the enamel and final coat of primer sealer which got it really nice and slick but you can get the just of it
     

    Attached Files:

  12. Biloxi Bertram
    Joined: Feb 2018
    Posts: 9
    Likes: 0, Points: 1
    Location: Biloxi, MS

    Biloxi Bertram Junior Member

    Ok, yea I had posted that before reading his reply. I will stay away from the 1/8" plywood and do the layup once it tacks as suggested.

    Thanks again for all of the help everyone!
     
  13. SamSam
    Joined: Feb 2005
    Posts: 3,900
    Likes: 197, Points: 63, Legacy Rep: 971
    Location: Coastal Georgia

    SamSam Senior Member

    I've used spray can enamel with wax and pva release for mold surfaces and then laminated using polyester resin and never had a problem. I have more problems with gelcoat mold surface. I think because gelcoat is polyester resin based, that polyester resin in the layup naturally has a chemical affinity for it and relies totally on the release agents to keep them separated, whereas polyester resin and enamel paint are two different animals and don't want to bond so easily to begin with. That's just a guess though.
    When using cloths or woven materials it is a problem, when trying to get it all smooth, that when working in one corner/area, it pulls out of the opposite corner or area, leaving air pockets. CSM tends to be much easier in that regard. It works much better if you have a bubble buster roller instead of just a brush for smoothing the laminate.
    With that inside ledge around the top of the mold you'll have to destroy the mold to get the part out, hopefully that will be easy with no buried screws or difficult joints as it's easy enough to damage the part even when demolding from a regular re-usable mold.
     
  14. fallguy
    Joined: Dec 2016
    Posts: 4,953
    Likes: 902, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    I didn't notice the ledge either until SamSam mentioned. That will be trouble...hope you plan for trouble..
     

  15. Biloxi Bertram
    Joined: Feb 2018
    Posts: 9
    Likes: 0, Points: 1
    Location: Biloxi, MS

    Biloxi Bertram Junior Member

    Hmmm, working for a marine/industrial blast and paint company for many years, I have a decent amount of experience and knowledge of paints and coatings. So knowing how temperamental enamel can be with solvents and knowing very little about polyester resin and fiberglass, I decided to do a test patch. Just as I suspected, the polyester gelcoat de-laminated the enamel paint right off the substrate withing 10 min of application. With that said, I'm curious how this works for you and apparently the guy who made the thread I am following as well??? Only thing I can think is that the area i tested on was an area of the PVC trim which the enamel paint does not adhere to very well. So maybe the enamel just never obtained enough adhesion to the trim to deal with the solvents in the polyester... Interesting at very least...

    As for the breaking the mold from the finished product,
    I thought that one out already. I actually made the mold in two pieces. After making the box, I basically cut it in half then used 2x4 scabs to tie the halves back together. I then fared the seams with bondo, sanded then painted. Once I am finished, my plan is to remove the 2x4 scabs and hopefully with a little coaxing, it will slide off each side of the finished product. If not, I can just remove the screws from the PVC lip and/or unscrew each side of the mold and pull it off piece by piece. I am hoping I will not have to do this and destroy the mold as I have future plans for it. If I CAN get the mold off without destroying it, my plan is to simply add to the center of the mold (to make it 4' long) and VOILA! I have my mold for my fish box ice chest. Yes, I know this sound good on paper and is a gamble at best but if figure its worth a shot.
     
Loading...
Similar Threads
  1. garage monster
    Replies:
    9
    Views:
    1,712
  2. boatymcboatface
    Replies:
    1
    Views:
    1,615
  3. outdoorjunkie
    Replies:
    3
    Views:
    2,372
  4. Iantheman
    Replies:
    8
    Views:
    26,217
  5. BlacK_Blade
    Replies:
    1
    Views:
    1,952
  6. blairg
    Replies:
    14
    Views:
    3,491
  7. kermy
    Replies:
    3
    Views:
    7,399
  8. old man
    Replies:
    2
    Views:
    8,981
  9. bucketlist
    Replies:
    53
    Views:
    621
  10. PickNasty
    Replies:
    17
    Views:
    820
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.