Reglassing 50' cat hull bottoms - overhead?!

Hi, Yes I am going to have to apply 3 layers of 17 oz biax/epoxy to the entire underwater area of my composite one-off, hard-chine cat after haul-out.
I have many years of wood- fiberglass construction experience, but NOT fiberglassing against gravity. I have done a smaller portion a few years ago, when I applied 3 wetted-out coats over each other, but there were some delamination spots.
This time, together with 2 helpers, after thorough sanding of the original surface, 1) wetting out a 50"+ width of one hull side, and overlapping the small keel rub strip, 2) wet out a suitable biax first layer on a piece of peelply, over a sheet of Visqueen, 3) wait for the two mating surfaces to get gelled over, 4) using 6 hands lift the 'sandwich' into place, while it can still be adjusted into gapless skin, 5) after epoxy hard remove peel ply, 6) repeat for 2nd and 3rd, final layers, 7) continue by overlapping down the hull and over onto the other side. Estimated time, daily 2 hrs, for a month.
I have used in the past about 250 gal of laminating epoxy, and about 3 rolls of biax...

 

This sounds like a major project for sure!
But you certainly have the experience for it, not to mention the enthusiasm.
Please do keep us updated (carry on with this thread?) re your progress over that month of work - and everybody loves to see photos as well of boatbuilding and repair projects, so please do post some to show your progress.

 

You are very brave (or?) to even attempt that. Have you considered vacuum infusion?

 

Good thing it's not a tri.

Wouldn't this be a great application for vacuum bagging?
I've never used it, and it seems like a real hassle, but worth it in this case.
Or even inflating air-bags under the hull to press the e-fiber.

 

I share those thoughts, but would suggest a small practice area first. Or even a simulated hull section. I would not be keen to try such a major project as a first attempt at infusion without gaining a little experience. Which should make it at least bearable, even if the subsequent fairing and finishing is arduous and messy. The end result may justify all the effort.

 

I am sorry, but this is a terrible idea, with a capital T.

17 oz biax I have about ?50 yards experience and it is really your friend with gravity and contours, but a horrible enemy on vertical or upside down sections...it is snaky and two sided wetout means it can't go on dry.

I have done a lot of wet bagging, never upside down and would not bother.

This job is made for infusion all the way.

You can layup all the laminates with spray glues, bag it, test the bag, and pull the job. No snaky biax errors need to end up in the final, and 6 hands will not be enough and cost way too many days.

If you insist on handwork, I can tell you how. You make jigs of the bottom, cover them in ship tape and lift them to hold the dry then wet snakes in place, but it is a nightmare. You may need some of these jigs to hold the glass even prepping for infusion. Making the jigs will also be hard to do..but if you use mold wax and partall; it can be done with 1708x4 pieces, they need not be real wide 6"? and it may cure your dreams of laying up 1700 upside down.

Another idea is 1700x3= 5100, two layers of 1708 = 5000 and hardly likely you gain much one versus the other, 1708 will hold its shape. Neither fabric will wet upside down and through, so the problem is the substrate needs a lot of resin which makes it a greasy mess.

There are other, wiser contributors here than me, but I have done enough to tell you the plan is bad. The glass will not cooperate and you'd need like 15 hands.

I wonder if @ondarvr or @rxcomposite have seen these attempts.

But the idea you propose is terrifying and I have 300 gallons epoxy work as well.

Another issue is biax may not be best.. the problem is wetting cannot be done through glass stuck on. If you used a different glass, you might be able to spray and stick the glass on alone and then roll it on while it drips all over you. Yuk.

Infusion is your friend, please believe me.

 

Hi Tevake
You can do this..
As I have, the fabric is slit to half width. Whe applying transvere do not overlap but close to butt.. Use an extra layer to compensate. Pre wet the fabric on a table then roll onto 90mm storm pipe.. That is about 150mm longer each end than the fabric is wide... Have plenty spare pipes and use a few disposable layers of buildefs plastic on the table so clean non gelled area can be revealed. Work from stern towards bow in sequential steps unrolling and consolidating as you go, like fish scales, cover with peelply as you go. You can stop any time of day but need to resand/grind in new days work.
Have fun, use tyvecks and have spares.
Jeff.

 

What is the existing lamination schedule on the bottom of your cat?
It just occurred to me that we have not asked you WHY you are doing this.
Did you have rampant osmosis, and you had to grind away a lot of bad fibreglass? Or something else?
Can you post a photo or two of the cat, and her bottoms please?

 

I can see doing this in half width as the roll will not be fighting hull curvature when laying off so much. He would need help to hold the fabric in the beginning.

He could also try hot tacking the beginning.

 

Fallguy, true..

Definitely need an assistant, once started the person consolidating just follows the unrolling tube. Needs slightly overlength and wet trimming at the bottom, there's probably no reason that bottom to top wouldn't go fine as easier to trim but the bulk of the application visibility better going top to bottom. The technique slightly more material but worth not having the lumps caused by a typical overlap, just needs to stagger the layers.
It would be roughly nearly 20 years since I've done this, the last time a petite lady assisted(her boat) me, about 3 to 4 days on the bottom on a 40' mono powerboat, the keel details a bit longer, the transom very easy in about 2-3 hours if that, the topsides an easy day each side but longitudinal on those and not pre wet, just the slit rolls suspended to wet out as we went & not a high sheer, pretty sure it was 600gsm double bias(45/45). The prep work takes as long as it takes...
When I was an apprentice we used to do overhead work(around 4 decades ago), the apprentices x 1 or 2 would unroll top to bottom with 2 or 3 tradesmen following to wet out... with another consolidating.. we had to wear suits made from vinyl that would get acetone wiped & would apply tar paper to the floor to collect all the drips and slush( & chucked out at end- it was a sarking material but pretty tough, worst part was at the keel pushing the glass into the rabbet line while the slush was applied. Once an area done 3 or 4 would get into it with chopper rollers. We did have Tyvek suits back then but the resin would mess them up... the place I worked had some laundering process, we would also wear gunners flash balaclavas to soak the head sweat and keep grinding dust from getting in to much, the firm invested in a crossflow grinding room, full climate control and very good extraction... this for smaller workshop & bench jobs, boats were still out on the floor but often tented for sanding, though there was a lot of spangles in the air when sun streamed through the alsonite skylight roofing panels, some jobs done out on the end of the wharf, the dust would just go wherever the wind blew, there was an extra rate for overhead and another for dirty work so that would add a bit extra to the pay.
Some nice scissors important & maybe a spare set, I've got some with a facing that go well.

Jeff.

 

Hmmm. No-one has suggested the obvious.
Lay the infused resin on strong plastic sheeting with perimeter re-enforcing, then offer the glass up to the underside using straps, supports, then squeegee it onto the hull.
You can even roll it on a pvc pipe on a supported roller, and then unroll it in stages like spreading a pool cover.
Peel the plastic off like peelply once cured

 

Hi I appreciate your concern, and agree - from experience - that 27 oz biax doesn't wet through, when stuck on, and smoothed out, on an inverted surface! Therefore my idea as described above. I W I L L, however, do a trial run first, on a smaller section, going from top down, A N D use a half width (25"). This will occur in about 6 weeks, as I am now in the process of winching the boat about 15' up my 7 degree ramp. Then I have to wet sandblast off 3 layers of bottom paint, exposing the original , single layer of epoxy/biax over ply core. I have to say, guys, that I hesitated for a long time to to make public what I am about, because I don't want to be discouraged: I already have over 20 000 hrs work in this project.
I appreciate all of you advising me, and I will post an update in about a month from now. ( I have not the skills to post fotos here, sorry). I have research vac. bag., even started buying materials, but concluded against it.

 

Hi, Thanks so much for your comments: yes, that is about what I plan to do. Please see my reply above to "fallguy", for more about this project. I will keep you all posted as I proceed. Thanks, guys!

 

Hi Jeff, Yes, you are describing what I plan to do, to some extent: but now, applying what has been said by all 9 of you, I will proceed as follows: on a table lay out a half width of 17 oz biax over peelply and viskween, then first wet out the corresponding hull section, (gel consistency via Cabosil), wait until it's sticky, wet out the 'sandwich', and using 6 hands and the finned roller and squeegies, work from upper edge - tacked on - downward, over the hard Chinese, then overhead ( about 6" to 12") to the keel (which protrudes about 2x2 inches), and tack with a batten. In about 10 hrs strip off the peelply, ready for the next layer. Very little sanding, as the peelply will negate amine blush.
Please feel free to critique, but I will also let you know as soon as I finish winching the boat up the ramp, and wet sandblasting, and/or sanding off the b.p.. this will take about 6 to 8 weeks before we can start laminating...

 

YES! That was the protocol I was attempting to describe in my original post, starting this thread. Thanks so much for reinforcing my plan..