Best way to glass wood top sides

Discussion in 'Fiberglass and Composite Boat Building' started by mongo75, Mar 4, 2008.

  1. mongo75
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    mongo75 Senior Member

    I'm rebuilding a 1968 25' Luhrs flybridge. Basically, I'm starting from a BARE hull with only stringers, of which 2 out of the four (inboard ones) I'm replacing. Being that I don't have a warehouse to build a glass one-off liner, I am rebuilding the boat completely out of ply (like the original) and then plan to glass it like the original. I believe the original topsides had maybe 6oz cloth in one layer. That stuff was put on with poly and peeled off like a banana. I'm using epoxy only. I already bought a bunch of 1708 and have about 10 gals left over to glass the wood, but in retrospect, I'm wondering if that is overkill?? I would like to not have to buy all new cloth, so aside from the weight factor (neglible) is there any reason why I shouldn't use 1708? I hate how hard it is to wet out vs. 6 or 8 oz cloth, and it's not so easy around corners, but I do like it's strength and "single" layer application.

    Also, to get it to hold on a lets say, 1/2" radius, can I wet the wood, then staple the 1708 down, and then roll on the epoxy?
     

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  2. the1much
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    the1much hippie dreams

    it wont bond with your ply very well,,you should lay down mat first,, then 1708 over that,,,and depending on how (good,,smooth,) you want it,,and how much sanding and fairing you want to do,,some cases you should have mat on top too.,,, and im not an "epoxy" dude,, but stapling shouldnt hurt if you dont overkill it,,,as long as there isnt a bleed through prob.,,but the epoxy dudes could answer that.
     
  3. PAR
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    PAR Yacht Designer/Builder

    Depending on how you want to treat the decks after sheathing (painted, veneer overlay, solid overlay, etc.) the 1708 will use a bunch more resin then necessary and likely not "drape" as sweetly as you'll want, though compound curves in decks are gentle.

    I always recommend two relatively light layers of fabric (two of 6 ounce cloth, for example), rather then a thick single layer. This is especially important if you intend an overlay of some sort.

    You're just looking to seal the plywood initially, which a few coats of unthickened epoxy will do. This of course offers little abrasion protection, so fabric is used to provide this element.

    I use two layers of cloth to simulate a canvas covered deck. The first layer is applied, over a well faired substrate (plywood), then the weave filled and the second (finish fabric) applied with no attempt to fill the weave. In fact, I try very hard to get a very uniform texture on the finial cloth application, with the weave clearly showing, which does simulate a canvas covering reasonably well.

    A single, heavier layer of fabric could be used, if you are painting, say 8 ounce. Fill the weave, fair and paint.

    My logic is the first layer forms the waterproofing and the second the abrasion protection (decks get a lot of traffic). If using Douglas fur plywood for the decking, then two layers of cloth is my only recommendation, because of its propensity to check.
     
  4. mongo75
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    mongo75 Senior Member

    My end state goal is to have the boat look as if it's all fiberglass just like a modern production boat out of the mold.

    I used 1/2" ply on the gunnel caps that run from the transom to the cabin, but I plan on using 3/4" for everything else (bulkheads, decks) with the exception of the v-berth overhead, as it's over 8' wide and has a decent curve to it.

    For that I am gonna use 2 layers of 1/4" ply with mat between the layers and a good coat of epoxy to ensure a good bond and flexibility to cover the curved beams fairly easy.

    I have the same situation on the cabin roof/bridge deck, but thankfully it's narrow enough to get away with using one sheet leghtwise across, so for that I plan on using 1 sheet of 1/2" ply with 6oz under it, and two layers of 1708 on top to make damn sure it's gonna hold up to pounding so it won't ever collapse!

    Now I still have to figure out a way to glass the flybridge to the cabin overhead.....

    Jim, the reason I bought all this damn 1708 I now have is because of the mat that's built into it, I didn't feel a preliminary layer of mat was necessary??
     
  5. the1much
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    the1much hippie dreams

    so ya got roven,,,,cools,,,you wont need the mat layer first then.so to "ward" off all kinds of fairing and sanding you'll want mat on top too,,,,that will give ya a smooth finish with only 1/3 of the work
     
  6. mongo75
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    mongo75 Senior Member

    Sounds good, as I HATE finish work. I do a good job, but as you know it takes a lot of damn work to make it look good if it didn't come from a mold....
     
  7. the1much
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    the1much hippie dreams

    ya,,,,is way easier painting your boat before lay-up of fg hehe
     
  8. mikentx
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    mikentx Junior Member

    Danny,

    I respect your final goal of having a boat that looks like it was a glasstop, only you will be chasing cracks for as long as you own it. The prior owner to my luhrs had the same vision, and not only did he get cracks everywhere (these hulls flex a LOT) but the water got into them causing his ply to rot QUICK. I ended up ripping out all of the plywood on my 32 foot 1968 Luhrs and rebuilding all of the supports with Pressure treated wood with stainless steel screws (I know Ill get lots of flack on this board for using pressure treated) But it has lasted over 10 years and still looks like new! Over the pressure treated framing I used pressure treated 3/4 inch ply for the decks...VERY strong... I then covered the entire deck with Nautlux vinyl which you buy by the yard, stapled to the plywood. I then painted polyurathane (white) pickup truck bed liner over the nautolux. It is SO waterproof and UV proof, and it looks GREAT its non- skid and it CANNOT ever crack, It washes up perfectly and it will last over 30 more years... The entire re-decking project cost me just under $1000 for a 32 footer...
     
  9. the1much
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    the1much hippie dreams

    why would you get flack for using PT wood?,,,,and you should be able to galss ANY boat and have a mirror finish for YEARS,,,the cracks you were chasing isnt because it was glass and the hull flex's,,it was because someone didnt know how to glass.and water in ANY crack will cause rot,,or as glass goes..delamination.and even with PT wood,,you should coat it with whatever resin your using,,and thats after ALL holes has been cut,,then paint the resin.
    and Mike,,,did the company you bought the white "rino" liner tell you how long the white will look white?,,white is the WORST color for rino lining,,,it turns yellow in about 3 to 4 years,,,wet places even less, because of the "magnifying glass" effect water has.
     
  10. mikentx
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    mikentx Junior Member

    Rhino Lining

    Actually the Rhino lining has held up remarkably... I had to add a UV stablizer to it, so maybe that helped, which normally isnt used in pick-up truck uses, Im going on 3 years now and it looks like new...

    The reason the Glass doesnt hold up on Luhrs is because these are wood topped boats from the factory with a glass hull, so the hull to top joint is not done with glass overlap, instead there is a wood stringer inside the lip of the hull, so when you pick them up with the lift the pressure is on the rail that bulges the joint between the lip and the top, thus serious cracking occurs... the only way to avoid this would be to build the top seperately and lower it OVER the glass hull, so the pressure wouldnt be on the hull joint, but on the top lip... Its tough to describe, but these boats were never designed to be glassed over...
     
  11. the1much
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    the1much hippie dreams

    so what your saying,,is,,,,its a row boat hehe,,,and Thanks for the UV thingy,,i.ve sprayed the crap for a few years,,,and the dude i get it from has never mentioned it,,,just warns me bout white hehe ;)
     
  12. mikentx
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    mikentx Junior Member

    :)

    You could say that its a GIANT row boat... 32 feet by 13 feet wide :)

    Yeah- make sure you get the UV additive.. it makes a big difference...
     
  13. erikgreen
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    erikgreen Junior Member

    You don't. In fact, with epoxy you don't need mat at all. The mat helps adhesion when using poly resin with roving, but epoxy is so much better a glue (as opposed to a molding plastic) that it glues roving just fine.

    I'm going to be coating my stringers shortly with 1708. I hate getting it to bend around corners too, but at least it's easier than roving.

    Erik
     
  14. Roly
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    Roly Senior Member

    Double bias is easiest for compound curves and corners, stringers, floors, bulkhead tabbing. The only place I used matt (200gm) was to stop a pre-release on
    gelcoat before the epoxy system went on. (pulling peelply)
     

  15. mongo75
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    mongo75 Senior Member

    Erik- good luck getting that 1708 on your stringers!! The only way I can think to get that stuff on a stringer is if you cover the whole stringer with a huge shape conforming sand bag, so it'll act like a vacuum bag, sort of....

    Mike, I'm siding with Jim on this one- the guy you got the boat from maybe didn't do such a great job of glassing before he launched, or maybe he used poly or vinyl resin instead of epoxy. I'm using epoxy exclusively for this thing because I need such a strong secondary bond, and plus it's flexible allowing the flybridge to sway a tiny bit w/o cracking. However, I plan on building this thing SOLID, so cracking glass is not gonna bother me. I figure I fix combat helicopters that beat the hell outta the airframe and my patches hold up fine, so a boat will be even better.
     
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