Traditional Build with Corecell

Discussion in 'Fiberglass and Composite Boat Building' started by fallguy, Apr 7, 2017.

  1. AndrewK
    Joined: Mar 2007
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    AndrewK Senior Member

    As you know there is no one ideal way of building a boat, every method has its positives and negatives.
    At the end of the day they all work, and as you pointed out it is important that Richard supports your choice.
    I chose the female half moulds only because I wanted a compound curve boat.
    Chose to have my stations 600mm apart and used lots of battens to get a very accurate shape.

    Alans boat was a kit boat made from balsa panels not bare balsa core.

    As groper pointed out the long pre-glassed panels take on a fair shape when placed into the jig.
    The downside is handling 32' long panels, size is more of an issue rather than weight.

    Positives are, fairer shape, better laminates as vacuum consolidation will have less voids, higher glass:resin ratio and so much easier to produce on a flat table than what was shown in the above attached video link.
    One thing that you dont know at this stage if you are going to be one of the unlucky and develop epoxy sensitivity. Working on a flat table at waist height even when wet laminating reduces your exposure greatly compared to the video.
    Sensitivity is not that uncommon, my wife came out with a rash just after a second exposure.
    Another local who posted on this forum was going to build a smaller version of Alans kit boat himself.
    After just gluing the pre-manufactured panels together and starting to do the tape joins only (no big major and difficult laminates) he got sick. If I recall correctly he took a week to recover before he could get back to the build. After the very next exposure he ended up in hospital, that was the end of his build he had to pay to have the boat built for him.

    One thing that you need to be aware of is when glassing only one side of a flat core you get cupping, it will curl on one side. I did not notice this on my build, could be due to the compound shape as well as post curing to 60'C before taking out of the mold.
    Anyhow raise this with Richard and get his opinion as I dont know if it will be a potential issue or not with your flat chine build.
     
  2. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    I have had some exposure to epoxy and thus far have been okay. I will be taking very serious precautions with Tyvek suits and gloves and I very much appreciate the warning. I will probably even add some building exhaust since you mentioned it. And I am grateful for the idea. The building is getting insulated right now, so adding an exhaust is really easy. I have about 1000 square feet at 13' high or 13000 cuft to design for, and I can place the exhaust right over the mold/table main area.

    Let's for a moment indulge the idea of flat panel construction and I do so genuinely, but with my bias. Richard's lamination schedule suggests overlapping the glass at the chines. In this boat, there are the keel and 3-4 chines per side or 6-8 chines and the keel.

    In order to overlap the glass at the chines, how would you propose to do so? Would you simply make a large rebate on each side of the panel and run two tapes, like a 6" and then a 10"? Isn't that ultimately a weaker joint than the other way? Granted, doing it this way would allow you to glass the panels on the table with vac, which would result in better bonding and less likelihood of voids.

    And if some modified version of flat panel and full female mold would be better, I'm not against it at all. I just have a hard time understanding how all the chines would not be more work on a table versus running a tape into the rebate and overlapping each full section of glass into the rebate in each direction. Keeping in mind, of course, that the rebate on the inside is only needed for about 4 meters.

    It just seems like the quality would increase of the lamination on the skin at the expense of the quality of laminating with overlaps.

    And then don't I have to fit all the panels into the female mold anyhow? Otherwise, Richard would have to give me all the offsets of each panel, right? So am I not fitting and removing to do the flat panel work? Instead, can't I just fit and leave it in place and laminate it on the mold?

    Now, all that said, there is the issue of the reverse chine. Laminating that guy which is essentially partway upside down would be extremely painful, so perhaps laminating that on the inside on a table would be the best and then I would only have to tape a/o overlap the glass from the panel below. (I am in a hurry and not remembering if I need to have a tape and two overlaps, or a tape and a single overlap)...
     
  3. groper
    Joined: Jun 2011
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    groper Senior Member

    When you apply fiberglass tapes to joim 2 panels together, the tapes ARE the overlaps!

    You do not need to overlap the glass on the panels themselves and then again with the tapes for structural reasons. If the structure deems it nessesary that you have say 3 layers of 20oz dbias along the chine, and your building with premade flat panels, then you simply wetout 3 layers of 20oz dbias tapes all at once and roll them on, its that simple! What this means os you have 4 layers either side of the seam (3 tapes + 1 layer already cured on the pre made panel) -which is also fine.

    For your hull shape- ypu would not need rebates in any of the bilge panels, its very easy to drag a filling batten along long narrow panels and fill them with fairing compound - it Requires very little sanding. Areas like this, the batten follows the raised edges of the tape join and its easy to fill the 1 or 2 layer of glass thickness between.

    The main panels you should think about rebating are the topsides... this would save you some fairing when feathering out the tape join...
     
  4. fallguy
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    fallguy Senior Member

    Thanks Groper.

    So, the lamination schedule is double over the chines and double laminate on the bottom, 600g bias out, 900 quad or 400g 0/90 and 400g 45/45 inside and 50mm overlap each side.

    So, my understanding of the lamination is that to do flat panel, I would have to have two laminations of tape over each joint, which technically means I have a 4-6 inch extra tape on every chine inside and out and two extra tapes inside and out on the keel. Or, for this hull and its 8 chines, call it 16 in and out, plus the four extra on the bottom, I would be running 10 extra tapes or about 40" of 32' of glass of each of the above? I realize I am hand laminating if I build in a full mold and that isn't a super low weight proposal, but wouldn't I be adding that much weight to build in flat panel?

    And then in order to build in flat panel and not do it on the mold, do I need to ask the designer to give me all the offsets, or would you just build the mold and then take the measurements off anyhow if you were going to build the 11 stations.

    Other than the obvious times of laminating upside down, I don't see a lot of advantage in flat panel unless perhaps the designer gave the panel dimensions, and even then, unless I'm wrong, you need more glass at the seams.
     
  5. groper
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    groper Senior Member

    You could work out the female stations from the bulkheads plua add an offset for the hull thickness, however a betyer approach ia to have the entire design in digital format so that you can sirectly export it to a cnc machinist and have everyrhing ( and i mean everything) cut all at once including your foam core.

    Yes adding tapes does add a little weight , but its insignificant in the grand scheme of things...

    I wouldnt tape every panel tho- id build the canoe first as one peice finish the bottom comoletely before turning them rigjt way up ans continuing the build from there never having to turn it again.

    Building the canoe or hull shoes as i like to call them- cpukd be done using a female melamine mold and just hand laminate into it. The finish doesnt have to be brilliant below waterline as the antifoul paint and the fact it never gets seen doesnt warrant an a grade finish such as that that will be painted in a high gloss 2 part paint which glistens in the sunshine and ahows uo every little imperfection....
     
  6. fallguy
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    fallguy Senior Member

    I think with all these chines, I ought to do this using a full female mold and some flat panel work as well.

    I am going to check with Richard to see if he would be willing to dxf the panels, or if that is really daunting for him.

    I had originally planned to cut out the molds myself. Do you think that'd be foolish? I'm pretty good with a circ saw and tape measure (I have 8' guides as well), but all those chines will be a pita to jig out, even for me, but a cnc would make it simple.
     
  7. groper
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    groper Senior Member

    Its not foolish, its just alot of work. At this point i have to remind you that building a boat is heaps of work. Thr number 1 enemy is man hours. Everything you can do to reduce time and also reduce unpleasant tasks is something you will wish you did... most of this work, happens long after yoube built the hulls too i might add...
     
  8. AndrewK
    Joined: Mar 2007
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    AndrewK Senior Member

    I would be surprised if the design calls for overlap at every chine for structural reasons, check with Richard.
    You would put an overlap on some of the chines for fairing reasons. Normally its a balancing act between using the glass cloth most economically, how it wants to lay on the job, fairing considerations, and physical access when laminating.

    With flat panel stitch and glue construction your tape only needs to provide what a continuous laminate would have done.
    Taking your outer laminate as the example, if you use 400gsm biaxial 0/90 and 400gsm double bias +45/-45 then to restore the fibre continuity at a chine you would use one 700gsm weft triaxial tape as there is no need for 0 deg fibre.
     
  9. AndrewK
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    AndrewK Senior Member

    Yes get the molds laser cut or CNC routed.
    Second best option is to have Richard nest all of the stations and bulkheads too over the top of each other and then have these plotted by a sail maker on to a mylar sheet or sheets.
    To transcribe these to what ever material you are working with you simply punch a hole through the sheet into the underlying material at appropriate points to produce reference marks.
     
  10. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    from the laminate detail; it should be mentioned this was from the build method of the female half mold for infusion and not an alternative laminate schedule for a different build method, but of course this has me wanting to build it equivalently well

    D o u b l e
    o v e r
    c h i n e s
    5 0 m m
    e a c h
    s i d e
    j o i n t
    i n n e r
    a n d
    o u t e r
    l a m i n a t e

    I'll see if Richard will produce the dxf files for the panels. I had assumed I was going to have to take the measures off the mold with strings and tape measure. Even if I use the female mold, having the measures would save a bunch of time and in and out and errors. And it would help to have the numbers for a check and verification the mold was right as well.
     
  11. groper
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    groper Senior Member

    You may have to cut the panels manually. This isn't a big deal tho, one of the nice things about working with foam is it lightweight. You may have to keep trimming the panels until they fit neatly into the female stations. Once you have the panel fitted neatly you can take the panel to the table and glass it / infuse it etc.

    Of course there is no hassles if the entire boat has been designed and CNC cut, everything should fit together perfectly and if it doesn't, you know you've made a mistake somewhere and need to work out where the misalignment has come from and correct it.

    The glass needs to be overlapped somewhere as it comes on 4ft wide rolls. it may be a convenient place to do it at the chine for various reasons especially so there isn't an overlap mid panel which needs a large area to fair out. If the overlaps occur near panel edges you only need to feather out a small area - I usually allowed 1 ft back from a glass overlap which I would fill with bog and fair it back to the surrounding area. A chine area will inevitably need some filling and fairing to get it looking perfect so might as well overlap there also. chines are also usually the first area to cop damage with the point loads possible along an edge so extra glass always is a good idea there anyway.

    I doubled all my laminates on the bottom of my hull also so I had peice of mind when beaching it with potential rocks and reefs nearby...
     
  12. fallguy
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    fallguy Senior Member

    Groper - thanks for the replies.

    The bottom of the hull is a 2x lamination in Wood's design. He has a beaching keel option as well.

    Do you think if I only use the flat panel strategy for the upside down stuff, but laminate the inside of the hull I would have any trouble with the panels shrinking or twisting when removed from the mold if I use epoxy and corecell 12mm?

    A few have commented that laminates on one side will cause warpage due to shrinkage, but I'm not sure if that was just for poly/vinylester or for all cases. The larger section of the boat is almost a full meter wide and would only be laminated on one side if I did it in the hull. It'd stink if it curved in on me after I flipped the boat and had to load it up with fairing compound.

    Is there anyone with experience with epoxy and corecell on a wide section on one side? I suppose it would be easy enough to test when I start; then I'd know if I had to do more of a panel approach.

    Again, thanks.
     
  13. groper
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    groper Senior Member

    if your using epoxy - there is no risk of shrinkage / warpage after youve glassed one side of a foam core. I doubt youd have much trouble with VE or PE resin either, but those resins do shrink a little when curing - not nearly enough to cause a drama tho.

    Ill also add this - if you make your own flat panels (or buy them premade) the build happens basically identical to a plywood build. Theres a few differences but you basically substitute plywood for foam core panel with thin glass either side. The behavior of the panels is similar, the foam core panels will be a bit stiffer tho and require a bit more effort to bend or twist them. The foam core boat wont have butt plate or scarf joints to the ply and it wont require as many stiffeners/stringers due to the inherent higher stiffness of the foam core panels compared to ply.

    The method of joining them (stitch and glue + tape) is similar, the main difference is you dont have to sheath the entire thing when its done as the glass is already on the panels.

    Ill also say this;
    If you wet/hand laminate glass youll have to;
    cover the entire surface with bog to fill the weave;
    sand it all down with 40-60grit,
    repeat bog to fill pinholes and weave that you missed the first time,
    sand again to get it flat again with 60 grit,
    apply high build primer,
    sand it all off again with 80 grit to get out most of the pinholes and make it even flatter,
    apply high build primer again this time with a dust guide coat,
    sand it all off again with 80 grit to get it dead flat,
    apply std primer,
    sand again to 240grit,
    then apply your final finish 2 part poly urethane coating.

    Think about all that for minute. Dont read on - think about all that, for every sqaure meter of panel area in your boat which you wish to have a painted surface finish... and you cant use mechanical sanders for all of it either - alot of it has to be longboarded by hand or it wont get flat!
    This is the reality of boat building a 1 off from hand laminating glass work.

    With infusion - you can cut most of that (or all of it) on at least 50% of the panel area - the side which is facing the table. The infused panels can have a finished gelcoat finish, or a finish that is good enough to take directly to the final primer and then 2pk paint stage - choice is yours. If the table is very good - every single peice you pull from it will be perfect - its a resuable contact molding surface which youll use throughout your build. You can go 1 step further and cut most of that work from both sides of the panels and have a perfect finish on both sides - but this is getting further into the knitty gritty of infusion and some of the secrets you wont find on the internet because people dont want everyone to know... youll need practice doing it the easy way first tho - i learned all this stuff by figuring it out and thinking about what i was doing as i built my boat. Youll do the same as you progress through yours...

    This is going to save you hundreds of hours of unpleasant work if you decide to use this method... however you do need to decide to use this method before you order your foam as youll need to order infusion perforated and/or grid scored foam to go this route...
     
  14. groper
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    groper Senior Member

    As to examples of the above, the following image shows a topside chamfer panel in the tunnel of my cat being offered upto the hull "shoe". The shoe has a rebate and so does the topside panel. The rebates allowed me to seam these panels together without creating a bump. No fairing, filling, or dealing with pinholes was required other than over the tape joint itself which had a thin layer of bog to blend into the adjacent panels. The hull shoe and chamfer panel were taken straight to primer and paint and the finish coat of paint came out great!
    [​IMG]

    THe next image shows a 20ft x 5ft panel being infused on the table. After i got the hang of things, i could complete a panel like this in under 4 hours working alone. Thats 40kg of fiberglass and 20kg of resin! Its all done at waist height, no mess, no fumes, no swearing and cursing...
    [​IMG]

    and the next image shows this same panel after its demolded from the table - these are the floor panels of my bridgedeck, 20mm foam. You can see the 2mm rebates i made along the edge again to join to the topsides panels - nevermind the colour - i joined 2 peices of foam together before i infused, airex is green and diab is grey :) I took these directly to primer once again and then lifted them into place under the bridgdeck - no weave or pinholes to fill and no overhead sanding :)
    [​IMG]

    By the time i got to the end of the build and i had already made all the panels i needed, i had completed many infusions. I realised then that i could have done things alot better and even more efficient. For example i beleive that i could infuse multiple panels at once, with a perfect finish on BOTH sides of the panel rather than just on the table side. Potentially - once could infuse the entire set of full length panels for the entire boat in probably 2 or 3 infusions, all panels perfect both sides. The downside is not having rebates where needed but the extra time to fair out tape joins isnt really a big deal as you still need to fill and fair these taped areas anyway - its just a little easier with a rebate. I havnt tried this method yet as i havnt needed anymore panels and my boat is finished and now sold so i cant test the idea to verify it works, but i honestly see no reason why it wont and ive thought about it ALOT and beleive i have all bases covered...
     

  15. fallguy
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    fallguy Senior Member

    Can you achieve as good a result with just vacuum bagging and peelply of the panel, or is there still going to be unfilled areas? I'm less a fan of infusion and more a fan of vac bag. I have not bought the core yet as Richard is still on vacation and my building is a few weeks from ready. So, I'm wondering if you'd purchase perf'd core for even vac bag work - I honestly don't know.

    Here in Minnesota, we have to work inside as epoxy doesn't work well at -20F, so I am insulating the space and adding work lighting, etc. this month.

    I'm realizing that cutting the glass to fit the laminate can really only be done with the panel lying on the table. It'd be a lot easier to cut the glass either for lamination on the hull or the table with the panel laying there. Then, if that piece of glass is cut and the panel is laying there; it does become something of a why not glass it.

    One of my problems is I like to overbuild, so for tape joints callouts that say 50mm overlap each way, I would be inclined to go larger, or do one 100mm tape and the next on 150mm at least. You?

    And then for your table; I was going to build a white melamine table using 4x8 sheets and build the table 32 or 33 feet long once I got the mold up or got an idea from Richard on the longest panel length. Do you simply epoxy the seams together with a tape on each side then pull the tape prior to cure?

    Thanks so much for taking this time to talk with me. It is very helpful to talk through things in detail.

    Are you going to build another boat? Was your 10M too small? This Skoota is a little under 10M and it seemed like it would be fine for me and the wife and a couple in a pinch.
     
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