1708 vs woven for cabin top and deck recore

[Eastward ho 24]

I've used 1708 ( with epoxy)on my cabin sides and am familiar with it. However I've never used plain old woven roving (with epoxy)until the other day when I did some patch work.wets out nice and lays nice to.from my understanding the 1708 offers more strength then the woven roving. I got to recore my cabin top and fore peak before I put a new (316ss)bowsprit in. It's quite a big area I'll be doing. My original foam core (1/2") has delaminated due to the fact my Sampson posts were just cut and inserted through and same for all deck hardware. The core wasn't sealed properly at the penitrations water got in and well...so I'm going to recore with 1/2" corecell and where all my penitrations and Samson posts go through I was gonna cut in some g10 so I won't have this problem again. G10 inlays are gonna be quite expensive is there a better option? I use West system .would it be just as good to just use thickend epoxy(404 high density filler peanut butter ) in these areas instead of the g10? I don't know if it would be actually cheaper (given the price of expoxy and filler)but the g10 inlays would be less work ( mixing and applying materials). 1/2" soild glass lay up seems to be quite a lot of cloth too..I'm kinda getting the feeling cutting a piece of g10 to size dropping it in place then glassing over it might be worth the extra $ for the sake of saving labor....and am I correct in the choice of 1708 over woven for the decks ( which are basically flat)?

[coopec43]

I think I've used 1708: certainly a bi-axial cloth anyway with epoxy as well as woven roving. It is hard to advise from a distance but I think the problem is that it wasn't done properly in the first place and the materials used are not the problem.


Here is a couple of links to Downeaster 32 with bowsprit problems


Downeaster 38 - Cruisers & Sailing Forums


www.cruisersforum.com › Cruisers & Sailing Forums › The Fleet › Monohull Sailboats
Jun 23, 2015 - 8 posts - ‎3 authors
1975 DownEast 38 Cutter Sail Boat For Sale - www.yachtworld.com ... wanted it so bad . Only problem was the termites got there years before we did . markwesti is offline ... The bowsprit was originally mahogany laminate. It is attached to the .... What Do You Think of the Downeaster 32 ? KenH, Monohull ...Back to the dreaded bowsprit material construction ...15 posts 7 Nov 2018

6061 t3 aluminium vs 316 ss bowsprit considerations..13 posts28 Oct 2018

What Do You Think of the Downeaster 32 ?7 posts 22 Jul 2011

Downeast 32-38 - Good Boat ?4 posts 29 Mar 2010


Cruising World

- Sep 2003 - Page 110 - Google Books Result
https://books.google.com.au/books?id=MtWRH6DfI-UC

Vol. 29, No. 9 - ‎Magazine
The few reported bowsprit problems are also attributed to poor maintenance. ... Cyndi and Scott Perkins sail their DownEaster 32, Chip Ahoy, on Lake Superior.

[Eastward ho 24]

Yes I’ve read all of that. I’m no expert maybe I got a bad boat ,but I’d say there’s nothing “well” built or “over” built about my boat. 5/16 thick hull at the bottom of the keel,a huge barely glassed seam running the length of the keel,a rudder that’s not cut away so shaft and prop work is done by removeing the engine, Lack of a keel stepped mast and a compression post that’s not centered under the mast nor ran to the keel. And a list of other things that are common rework issues of most factory boats......sigh...anynhow under the deck the coach roof isn’t supported below(enough) it makes the whole coach roof and decks bounce and flex. I don’t know if it’s due to the fact it’s to thin, design flaw, poor workmanship,water intrusion or a combination of all.I’ve added knees at the chain plates and a compression post at the galley. Still the places where the deck hasn’t delaminated bounces and flexes when walked on. I’m not sure if it’s just my de32 or what but my coach roof and walkways don’t give me the impression of a well built boat. The only places my deck and roof are solid, are the place where I added knees and added a compression post. So after the recore if It still flexes I will address that with knees etc from the inside. I’m holding hope that it’s just the foam core that was used and there is more water intrusion then I know of. I can’t say what type of foam it is ( looks like the core cell in color and texture but I can’t say) contrary to what I’ve read the foam does take up water and a lot of it But that being said I do know my forepeak is saturated and needs recoreing before I install my bowsprit. I just today removed the old wooden one and it was dry rotted under the paint. So good riddens. I’ll be installing the 316ss sprit soon after I recore the forepeak. And I’ll be recoreing the whole coach roof. So I’m trying to decide what’s the stiffest . Biaxail 1808 or roving 24oz with the Matt backing or a combination. I’ve read balsa is better stronger but it’s heavier then the original design so I don’t want to add the weight. So it’s gonna be 1/2 corecell and either 1808 or 24 oz roving with epoxy.

[deltaten]

More glass in the laminate with 1708. Long, straight, opposing runs of fibers vs fibers bent over each other at every junction? No contest, in my estimation .

AFA springy, large areas? I re-glassed my foredeck from below using 5/8" EPS foam "ribs" ,12" oc. Two layers of 1 708 in the field, lapping over the truncated cone foam forms from each direction, for a total of 4 layers plus some woven tape to smooth the radii. Very similar to cast in place beams of a parking garage.
In addition; 1708 is much easier to fair, and does not require subsequent lams of chopped strand to become smooth. It avoids having to cover/fill the "waffle weave", to a great extent.

HTH,
Paul

[Eastward ho 24]

Good idea with the rafter beams. The de attempted to do this from the factory with a u like stringers below. And that’s what I thought about the 1708 since I used the woven the first time it wets and drapes so nice ...I see your in north east? Nautigoose? I used to keep a boat in hdg.and I drive through ne to get to my boat every weekend.

[Eastward ho 24]

Just came across sp corecell m80 I've only used the a500 can't d anything on the differences..?

[deltaten]

Eastward,
I'm inside BayBoatWorks. 6 yr there and never been to the NG.

IMHO, roving is best at tabbing and curved areas that require masses of resin to build thickness, structure notwithstanding, ie: engine beds.
I usually pre-wet 1708; particularly edges, to avoid dry layup and feather edges into curves.

Spongy cabintop? YEs, me too! I need to redo the salon overhead soonish. Already completed the area fwd/ under the sliding hatch. Core was 1/4" 5 x5" squares of luanp!y that denominated glue joints from beating sun heat. 3 layers of 1708 replaced the core and tied sub-lam to re-installed top skin.

While an industry standard, I'm leery of ( continuous,solid) foam sheets as core. Top and bottom chords of any structure must be directly and firmly tied as to act together. Under stress, these separated skins move at differing rates. imho, tearing foam apart in shear.
It seems that deck engineers don't realize a that the bottom/inner lam of an upwardly curving "truss" do NOT go into tension; but relax when compressed, kgoing "floppy" just when you want it to become more stiff.!
Can't weigh In on the honey-comb celled products except to say that without direct, absolute connection between the laminations, failure will occur eventually.

Clear as mud, huh?!

[Eastward ho 24]

Makes sense with the compression/relaxing and differing movements. You always hear the I beam example the foam acting as the webbing in the beam. Foam core doesn't seem like it would be as good as one is lead to believe in my inexperienced mind.My boats a 77 and delaminated. Maybe it's the foam maybe maybe not. Maybe I ought to go balsa and be sure.

[deltaten]

One boat core foam uses scored/sliced one side that "opens" as it's laid on the up side. This apparently allows resin to seep into the gaps and provided an "egg crate" reinforcement to the bottom of the top skin. May be fine;but it it doesn't attach to the inner skin, as soon as a(n over)load is placed, the webs of resin will separate from each other and become useless.
If you desire to use foam, may I suggest simple and cheaper builder grade foam? Cut to fit in squares, strips or however itworks, then applied with thickened epoxy with a gap to the next piece. Assuming the inner lam is intact and scheduled thick enough; bed the shapes in Cabosil thickened epoxy and fill whatever gaps to the surface with same with a squeegee if need be. The foam,as long as it's compatible, PIC for one, is only to create the form work for the resin lattice joining the lams.

Naturally, the thickness of foam and the gaps will depend upon the given load and spans involved; just as I-beams are sized by weight, flange and web dimension. YMMV

Reinforcement of specific areas, such as the mentioned sprit, may be built-in or appied. Yanno, you can make a reasonable facsimile of G10. While it won't be factory hi-pressure product; some poly film, plywood, resinated glass and a few cinder blocks does wonders. In fact, I have cut up a glass resin laundry tub that yielded several large bits of 1/4" "G10" for just such use as solid fillers and backers.

HTH,
Paul

Pau

[Benz]

For a flat (or slightly cambered) area like a deck, 1708 VS roving doesn't really matter that much. Yes, the 1708 is stronger, but by the time you build up the thickness, there's enough dimensional stability in roving to be fine. You can use any high-density foam instead of G10. Coosa board is popular, but there are others. Are you sure that the existing core isn't balsa? In the 70's it seems like it was that or plywood as the most common core. Either way, don't use balsa again!
If you're concerned about core-sheer as the upper and lower skins move differently (I would make sure that didn't happen by having a thick enough laminate), drill a bunch of small holes in a grid pattern through the core material before laminating. This is pretty standard in boatbuilding, just to give the skin more grip on the core.
Lastly, I wouldn't bother with 1808. If you think the roving has a big pattern when dry, wait till you see 1808 that hasn't been surfaced over.

[Eastward ho 24]

Yes it's deff foam ive ripped the headliner out from the inside I can see the foam and I have recored a few small areas already.i used a500 corecell, I got a pretty good quote on corecell m80 apparently it's better then a500 due to better elongation properties, and gruit has replaced the a500 with m80. That's from the vendor so..?.. . I was gonna use the flat sheets I figured less epoxy and less areas to possibly leave voids but i see how it would discourage delam with holes or even a crosscut?