Grady Hatch Repair

Questions about boat repairs with our resins and fiberglass: hull patches, transoms and stringers, foam, rot etc.
IpswichGrady
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Re: Grady Hatch Repair

Post by IpswichGrady » Thu Feb 08, 2018 7:33 pm

So 5 layers of 12oz biax and no wood? I like that it would never rot. And it will withstand people standing on it without bowing? When you lay that many layers do you do each layer one at a time? ie let them cure in between?



Fuzz
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Re: Grady Hatch Repair

Post by Fuzz » Thu Feb 08, 2018 9:24 pm

One thing to keep in mind is stiffness is a product of thickness. You can get stiffness with lots of glass or the core of your choice.

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Re: Grady Hatch Repair

Post by Jaysen » Thu Feb 08, 2018 11:01 pm

Or you use stratigic verticals to add “thickness” without actually using large amounts of extra glass/resin.

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Re: Grady Hatch Repair

Post by fallguy1000 » Fri Feb 09, 2018 12:10 am

Might need 6 layers. I'd run 5 layers of 17 oz glass, so 12 oz glass, maybe need a couple extra, depends on how stiff it is without any plywood.

You can do them all at once, but it might heat up on you, so I would probably run 3 layers, then wait for it to tack up and then run the other 3, or 2-2-2 same way, wait for each layer to get to the gel time or just past. You won't know if it is stiff enough until is cures a couple days, so don't go walking on green epoxy the next morning!

There are some guys that know the calculations for this type of thing, but it depends on the starting point.

I wouldn't bother putting plywood in it if it doesn't have screws in it, unless you want to finish it a little quicker, or save on resin $$.

Jaysen suggesting some strips; that can work as well, put them on the longest length, but I wouldn't until the end as they are a pita to laminate over.
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IpswichGrady
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Re: Grady Hatch Repair

Post by IpswichGrady » Mon Mar 19, 2018 2:57 pm

cape man wrote:
Thu Feb 08, 2018 1:20 pm
If it is the underside of the hatch, and you are using the wood as a stiffener, there's no need to glass the plywood. I would simply seal it very well with 3 coats of epoxy, glue it with epoxy to the underside of the lid, and paint it.
hey Cape Man.... So I am ready to adhere my plywood to my original skin and since you appear to know what you are doing (opposed to me at this point) I hope you (or anyone) could read what I intend to do and either give it your blessing or stop me before I do it all wrong :D
  • I have stripped all the wood from 2 failed hatches and with my grinder and 40 grit sanding wheels have the hatch skin prepped
  • I have my epoxy resin and wood flower
  • I have my mixing pots, tongue depressor mixing sticks, gloves, and tyvek suit
  • cinder blocks to apply some weight
What I need to know is... what consistency should I make this glue? I think this is the process.....
  • mix my epoxy resin*
  • wet down my plywood which will be attached to the hatch skin
  • wet down my hatch
  • wet down my plywood (2nd coat)
  • wet down my hatch skin (2nd coat)
  • mate the two together
  • weight down the plywood so that the 2 pieces are pressed together
*when I mix my resin should I add woodflour? If so to what consistency? Ketchup/mayo? (peanut butter is too thick and used to round off 90° angles... right?)

EDIT - Ok... I read this which was in this actual thread ...
fallguy1000 wrote:
Wed Feb 07, 2018 10:40 pm
make a peanut butter or slightly looser mix to bed the plywood. Use static weights for the cure; use a piece of plastic to avoid curing the weight on. Clean off the squeezeout once and then again after 75% of gel time. Make sure not to put dynamic loads on the part as you will end up squeezing out too much glue and leaving voids.
That's what I will do.

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Re: Grady Hatch Repair

Post by IpswichGrady » Thu Mar 29, 2018 9:26 am

Ok... The snow is still in my yard from those 4 nor' easters but that didn't stop me from working on these hatches inside. I purchased the 3 gallon resin/hardener kit... got a batch of woodflour, some 1quart mixing tubs.... gloves, tongue depressors to mix... read and re-read how to do it ... held my breath and attempted mix a batch of glue to attach my plywood to the skins of my hatches (I did 2 of them... both are almost identical) . I must admit I was a little nervous, after all I had no idea how quickly I needed to work. I made some mistakes mixing (made a mixup and put 2:1 hardener to resin... caught my mistake though in time). In the end I learned a lot and I think they came out pretty good. But, I do have some questions. First, here are a couple of pics....

Image Image

This is how I did it.. please point out easier ways or if I did it wrong correct me.
  • I removed all the wood and cleaned up old resin spots making my skin ready to receive my wood
  • I cut my wood to fit then traced a circle for my deck plate
  • I cut my hole larger than the hatch opening
  • I taped any holes so the resin wouldn't seep out
  • I mixed up a batch of resin with woodflour to a consistency between mayo and peanut butter... closer to mayo so it would seep into any voids
  • the hatch was laid down on the floor
  • poured in the resin glue and with a 4" trowel spread it around thick
  • pressed in my plywood and weighted it down all over
I let it sit overnight.... next day I
  • cleaned up any over flow (not much)
  • along the edges where the wood met the hatch I poured in more resin woodflour glue to seep into the hatch to fill any voids
  • thickened up my glue to a paste and filled around the hole (2nd picture)
  • once everything cured I cleaned up the exposed wood and put down a layer of straight resin to seal it all up
  • That is 1 coat of epoxy on the wood. I read that I should do 3 coats? I laid it on thick... maybe thicker that others might have done. Is more than 1 coat necessary?
The hatches are heavy. I have that rear hatch that covers my fuel tank to do. I think I will not use as thick a piece of plywood. I know Fallguy said that plywood is not necessary. Maybe I will do the 5 layers of biax for that repair. Im learning... experience is key!

Thanks

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Re: Grady Hatch Repair

Post by Fuzz » Thu Mar 29, 2018 1:54 pm

Your repair procedure looks to be just fine to me. For the larger hatches I would do the same thing. If you really want them to be lighter you could core them with a lighter product but that will drive the cost up a bunch. Adding more glass to the old skin will not be as effective as a core would be.

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Re: Grady Hatch Repair

Post by IpswichGrady » Thu Mar 29, 2018 3:34 pm

Thanks! I think I might put one more layer of epoxy on just to be sure it is sealed up well.

The end product is very sturdy. Like I said, a little heavy but then I think they will hold up to anything.

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Re: Grady Hatch Repair

Post by Matt Gent » Thu Apr 05, 2018 2:28 pm

I've seen quite a few hatches from 80s production boats with the "scraps" like that, mostly in 1/2" ply squares but some with balsa. Must have been a typical practice. One person made a thermal expansion argument during cure that seemed to make sense, since it seems to be more work and plywood is generally cheaper than labor.

In my DE25 the 1/2" decks are plenty sturdy on ~30" centers with no glass on the bottom side, just epoxied over. For the few hatches that I've rebuilt, I have put one 12oz 45/45 layer of biax on the under-side since it isn't that hard to do. I didn't do any fairing or clean-up after, just knock down any burrs. It will be more stiff with the fibers underneath than without.

I basically follow your approach. Packing tape works great for masking, epoxy won't stick to it. I use the notched trowel to spread out the thickened epoxy. You do want to hot-coat both parts with un-thickened epoxy prior to the thickened "glue" as a primer, usually about a half-hour before. I've done 4 or 5 hatches for friends, exactly like yours, on 80s/90s boats that are staring to rot away. The hatch will out-last the rest of the boat, as long as they don't drill any holes. I drill & fill for hinges or latches.

I'd consider the all-glass approach if it needed a bunch of holes for some reason, just to save prepping the plywood core. Otherwise I usually have plywood around, and expect it'll out-last me when fully encapsulated. It would be nice to have some 90deg angle fiberglass stiffeners around to glue in place for the same effect with less work, weight, and no wood.

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Re: Grady Hatch Repair

Post by topwater » Fri Apr 06, 2018 7:32 am

Put at least 3 coats of epoxy on bare wood.
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