Fiberglass Experts

[Brian Degulis]

I've got one aft hatch on the 60C that looks like the core is shot. The outside (top) looks fine but the underside is hollow and brown juice leaks out of it. It looks like a piece of plywood was glassed into the underside and that's rotted away. I'm thinking just cut the plywood out of the underside and glass in a new piece. I'm not sure how to adhere the plywood to the underside of the hatch before glassing it in. I'm not really sure how to go about this at all so I'm hoping one of you guys with some glass experience can give me some tips?


Brian

 

[mike]

Not an expert, but FWIW, remove all the old material, grind/sand the hatch surface with course grit. Coat a piece of plywood or other insert material of choice if it's wood with a thin coat of epoxy resin (this is done to prevent a lean-epoxy resin to glue-line interface when you laminate it to the hatch surface), let it tack up, then laminate with a thickened epoxy to the underside of your hatch. You can use any number of epoxies that are on the market, such as West Systems etc. If you go to the West Systems web site they have a great series of tutorials and app notes.

 

[Boatsb]

Brian you can do it with epoxy or polyester. The hatch is polyester so it will adhere.

I just built hatches from scratch because the old ones were NG but the process is quite similar.

If you bring it to the port I have a guy that can knock it out pretty quick and at a reasonably low cost.

I think he works for $30 and hour and has everything needed to do the job.

Look at the pictures on the thread I started about mine. http://www.samsmarine.com/forums/showthread.php?t=13728&page=4

 

[Brian Degulis]

Brian you can do it with epoxy or polyester. The hatch is polyester so it will adhere.

I just built hatches from scratch because the old ones were NG but the process is quite similar.

If you bring it to the port I have a guy that can knock it out pretty quick and at a reasonably low cost.

I think he works for $30 and hour and has everything needed to do the job.

Look at the pictures on the thread I started about mine. http://www.samsmarine.com/forums/showthread.php?t=13728&page=4

I'm going to use epoxy I just wasn't sure how to adhere the plywood to the bottom of the hatch but as suggested laying it in in thickened epoxy sounds good. " Bring it to the port" I just checked your profile and now relize your in FL but what port are you talking about?

Brian

 

[Boatsb]

I'm in the Port Canaveral area.

if you already have the epoxy this is no problem but the size of the hatch and the number of layers you want to add can make epoxy expensive. laying the plywood in thickened resin of any type is not the way I would do it. If the inner skin is smooth and flat some 1.5 ounce mat ( 2 wet layers with plenty of resin ) will be better. Add weight to the top of the wood to get a good bond then add a layer on the bottom plus a cloth to finish it. Paint or gelcoat the final layer to seal and protect it.

 

[boatwright]

when you thicken epoxy the working time gets shorter ,it can get hot fast.. have every thing ready, work fast.

 

[Boatsb]

The correct way to thicken epoxy is with a base not a catalyst. if you mix it hot it will not cure to full strength and may get brittle.

 

[Vincentc]

I am not following the reference to epoxy "base" or "catalyst". Every epoxy I've used has resin and hardener which are mixed varying ratios depending on the brand. There are "fast" and slow hardners, you do not vary the hardner/resin ratio. I've always mixed the resin/hardner well then added colloidal silica and wood flour to the desired thickness, making sure to finish before it starts to sets up. It is all temperature sensitive and the epoxy generates heat as it starts to set up further accelerating things. Accurate resin/hardener ratios and thorough mixing are critical. Do not add filler until after you have thoroughly mixed the resin and hardener. Considering the current temperature, time should not be a problem.

I would not hesitate to use epoxy, especially with a plywood core. I would thoroughy coat both sides of the PW and especially the edges then use thickened epoxy to bond the plywood to the fiberglass. Polyurethane paint has worked fine for me over cured epoxy. Be sure to was off the amine blush.

Regards,
Vincent

 

[Brian Degulis]

OK your south of me when you said port I thought Port Manatee. I'm going to use epoxy it's not that big of an area the material cost is not that great.I remember reading or hearing that the ahesive used to hold the mat together is intended for use with polyester and doesn't work well with epoxy?

Brian

 

[krush]

I wouldn't make a science project out of a simple repair. If i understand you right, you want to just cut out some old plywood from the underside of a hatch and replace it.

Here's what I would do. Cut out the old wood with a router or similar and get down to "good base". Roughen up the "good base" with some sand paper, blow clean, wipe with alchohol or acetone.

Have the piece of wood cut to be a close fit. Mix up some epoxy, put in some filler (micro ballons; west has all the stuff) coat the area on the hatch and the entire piece of of wood, especially the ends. Then I'd lay it in the hole you made in the hatch and put some cloth and mat on it....at the very least put the fabric on the joints.

Lay a little more epoxy on top of the matting and squeeze out any extra. Use wax paper or vacuum bag it if you want to get really fancy.

Enginerd fact: epoxy has essentially ZERO strength. The fabric, wood, other medium is what gives the strength (hence the term COMPOSITE). Concrete is also a composite. Mortar is not very strong unless you put some aggregate or rebar in it--same idea.

 

[luckydave215]

Krush is right, epoxy has bond strength, but must not be used by itself, just use it to "glue" your structural parts together.
To thicken epoxy or other resins you can use the micro balloons sold at West and the like, or you can use cabosil (fumed silica) to thicken the epoxy to a paste. ALWAYS add the thickener before the catalyst or you won't have enough pot life to complete your bonding job.

 

[Boatsb]

OK your south of me when you said port I thought Port Manatee. I'm going to use epoxy it's not that big of an area the material cost is not that great.I remember reading or hearing that the ahesive used to hold the mat together is intended for use with polyester and doesn't work well with epoxy?

Brian

There are systems or components for them that are best matched. FWIW the 2 layers of mat between the ply and the hatch bonded with polyester resin will probably be stronger than the thickened epoxy bond plus it will have a bit of flex.

Epoxy is great stuff but too often people use it because they feel polyester is inferior. Our boats prove otherwise. it's not just what you use but how you use it.

 

[Brian Degulis]

I wouldn't make a science project out of a simple repair. If i understand you right, you want to just cut out some old plywood from the underside of a hatch and replace it.

Here's what I would do. Cut out the old wood with a router or similar and get down to "good base". Roughen up the "good base" with some sand paper, blow clean, wipe with alchohol or acetone.

Have the piece of wood cut to be a close fit. Mix up some epoxy, put in some filler (micro ballons; west has all the stuff) coat the area on the hatch and the entire piece of of wood, especially the ends. Then I'd lay it in the hole you made in the hatch and put some cloth and mat on it....at the very least put the fabric on the joints.

Lay a little more epoxy on top of the matting and squeeze out any extra. Use wax paper or vacuum bag it if you want to get really fancy.

Enginerd fact: epoxy has essentially ZERO strength. The fabric, wood, other medium is what gives the strength (hence the term COMPOSITE). Concrete is also a composite. Mortar is not very strong unless you put some aggregate or rebar in it--same idea.

There isn't any hole to lay the wood in. Picture a flat hatch with edges that curve down (like the lid of a shoe box). Then for stiffness a piece of plywood is laminated underneath the flat section but it does not touch the curved down edges there is about 2" of space between the plywood edge and the hatch edge. Laminating in a piece of plywood is easy enough my concern was the plywood seperating from the underside of the hatch. I like Bob's idea best I think putting some mat between the underside of the hatch and new plwood will make a better bond than just thickened epoxy.

Brian

 

[Boatsb]

I have to admit Krush did a good job explaining how the resins work. Since the plywood is there to stiffen the hatch and prevent flexing the bond between the wood and the hatch is important. I have redone hatches like that before and never had a problem.

The ones I just built for my deck were done differently as the design for the tray allowed me to take the wood all the way to the edge. In reality the 1" I needed to fill between the deck and the hatch bottom was a lot so the larger hatch was done with 5/8 ply ( I had that or I might of tried 1/2") and an edge gasket of nitrile rubber to get the height right, the seal best and the weight down. The small ones were 3/4 as they were small enough to handle. Look at the size and weight issues. 1" balsa can be replaced with 5/8 plywood and still be as strong if done right.

 

[34Hatt]

I keep seeing Mat mention and you all are talking epoxy!
You don't use mat with epoxy unless it is the special made mat that is stitched together.
I would use a nice layer or two of 1208 after the wood. But then again I would also use nida core or coosa keeps the weight down and never will rot.

The proper way to build a hatch or other pieces is to always use the same material and amount on each side of the core to stop it from bowing. This mainly apply's to large one that are being built new. A older hatch really does not matter as much. This is mention for the general knowledge factor guess how I learned that one

 

[Trojan]

There is no set time on epoxy set up. The only time restraint is how much hardener you add and how warm the ambient air is in the area that your using the mix. The terms Hot and cold mix is derived from the use of hardner. The more hardner you use the quicker the mix will go off or harden. But with the addition of more hardner the hotter the mix will be in tempiture when it goes off. Hot enough to burn you or catch fire. Always mix the epoxy first before adding any thickener. The thickener can absorb the hardener and mess up the cure time your looking for. The longer the curing time the more flexible the mix will be in the harden state. Hot mix epoxy will cure fast, but can become quite brittle when set. No matter how cold you mix your epoxy it will eventually go off or harden. If you think you mixed it to cold, just warm the area up in temperature. If you wondering about how long your work time is going to be try mixing a small amount first and time it. The age of the epoxy and hardener can easily delay the hardening time. Old chemicals must be tested for hardening set time before using. Hot mix epoxy if mixed in a paper cup can easily catch on fire. When we were laying up complete boats we had a mix man and it was his job to very the mix temp from a cold mix to a warm mix so all the epoxy would jell at the same time. It would take about 3 hours to hand lay a complete 30 ft hull. Unless your filling a void no thickening agent is required only layers of cloth for strength. I always thought that laying up epoxy was a fun job. Because the end product was so cool looking. Anyone can do it. You just need to have a plan and have things ready. Note grinding on finished glass is the worst job you can have. I had to sleep on top of blankets because of the amount of glass that was imbedded in my skin would itch like hell for days. These were days before OSHA.

BILL

 

[34Hatt]

Krush is right, epoxy has bond strength, but must not be used by itself, just use it to "glue" your structural parts together.
To thicken epoxy or other resins you can use the micro balloons sold at West and the like, or you can use cabosil (fumed silica) to thicken the epoxy to a paste. ALWAYS add the thickener before the catalyst or you won't have enough pot life to complete your bonding job.

Well too say he is right ????

Zero strength low strength yes 90% come's from the cloth added in-between and that goes for anything.
Pour 1" of epoxy into a container let cure for a week get it out and let see how strong you all are try breaking it with your bare hands
After all zero you should be able to do it with your toes. LOL

 

[Vincentc]

Krush is right, epoxy has bond strength, but must not be used by itself, just use it to "glue" your structural parts together.
To thicken epoxy or other resins you can use the micro balloons sold at West and the like, or you can use cabosil (fumed silica) to thicken the epoxy to a paste. ALWAYS add the thickener before the catalyst or you won't have enough pot life to complete your bonding job.

This advice re adding thickener (filler) before "catalyst" (hardener) is contrary to everything I have read and experienced. I would be very interested to see a competent reference supporting your advice.

I've read "The Gougeon Brothers on Boat Construction" (West System) as well as most of their pamphlets and the instructions from System 3, Mas and Raka (Epoxy Vendors). I've used all those products. I've built a skiff, a row boat, a transom extension for a 25' fiberglass boat, and various boat repairs over the past 25 years including blister repair on a Gulfstar. All using epoxy. I've lost more than a few batches of resin to cure before I applied it. You have to mix in small batches and plan your work.

Polyester resin is used for boat construction because it is much cheaper and it takes a lot of resin to build a boat. Unless you place little value on your time or your boat, I see no place for polyester resin in boat repair.

Microballons are for faring and have relatively little strength. Cabosil/Colloidal silicia or milled fiber will give you strength. Epoxy scarf joints I've tested never break at the glue line.

Regards,
Vincent

 

[Boatsb]

Come on Dan you know I hurt my toe last week.

I like working with polyester because I have all the stuff like wax, styrene, cloth, mat and a few thickener options. I know they are all compatible so there is not an oops factor.

When I use epoxy I make sure to get the "fixins" for that product but at any given time I seem to have 50 yards of mat, 15-20 yards of 24 oz roving, Resin, hardener and stuff so I just don't go out to get epoxy much. Cost is also a factor as the only material I have that can be used with both resins is the fine finish cloth. and polyester is 1/5 the cost of epoxy.

 

[Brian Degulis]

It's alway been my understanding that with polyester the amount of hardener can be changed within a range to suite temperature or working conditions. With epoxy you don't change the ratio just select fast or slow hardener.

Brian