Deck Core Soft Spot? -a Low Budget Amateur Repair

[Hudson Force]

Lojanica, Thanks, I get it. I've also used the rolling out over plastic sheeting to form a smooth surface when working from above, so I understand your purpose here. You don't mention the application of a coring layer when working from below, but I also see that this can fit well into your procedure.

Nicholson58, You final outcome looks as though you have a very neat repair. I would be a little nervous about the "house of cards" that I would build with all the stick struts.

I like knowing about the underside repairs; however, I'm advantaged with my amorphous quartz sand non-skid that allows me to match my patch without evidence of the repair if I'm careful with my finishing and spend some time.

[colemj]

Originally Posted by Nicholson58

We do this from the inside. I drill 2 to 3 inch holes with a hole saw from inside the cabin.

I then dig out the wet stuff and keep expanding the holes pattern until I reach dry balsa.

Let it dry and then lift a saturated Fab-Mat & epoxy layer to the cabin top - very messy.

Locate the high and low points of the hollow structure. Insert a fill tube at the low and a vent at the high point(s).

Pump the cavity full of slurry until it reaches the vents. Mix in balloons until you risk the inability to pump.

This is a totally permanent fix.

I would never put the work into a repair of this size and re-use balsa.

I don't understand how you prep the upper skin (and what is remaining of the lower skin) for adhesion. Removing wet balsa leaves a top skin surface that nothing will ever bond well with. In real repairs, this skin is always ground to good clean glass.

People are making too much about the OP's use of balsa. In his case, he has totally encapsulated the repair area with epoxy (more so than I think is necessary), and the only deck penetrations are solid epoxy under them. How does everyone think water is going to get to that balsa core? Water doesn't magically appear just because balsa is present. I prefer the OP's repair many times over the slurry repair above.

Mark

[Lojanica]

Originally Posted by CaptForce

You don't mention the application of a coring layer when working from below, but I also see that this can fit well into your procedure.

I would use polyurethane foam core like coosa (Coosa Composites manufactures structural panels made of high-density, polyurethane foam reinforced with layers of fiberglass. No-rot and light-weight).

I would build layers and laminate glass in between. When I get to the top or bottom of the repair you just sand away the foam to a smooth even finish. The foam is so easy to work with. Then you put your final layer of glass over the laminated foam core and feather into the existing fiberglass. Super esay light no rot. The coosa is made to soak up the resin so it is meant for strucural applications.

I do not work for coosa just like the product alot

[minaret]

Originally Posted by colemj

I don't understand how you prep the upper skin (and what is remaining of the lower skin) for adhesion. Removing wet balsa leaves a top skin surface that nothing will ever bond well with. In real repairs, this skin is always ground to good clean glass.

People are making too much about the OP's use of balsa. In his case, he has totally encapsulated the repair area with epoxy (more so than I think is necessary), and the only deck penetrations are solid epoxy under them. How does everyone think water is going to get to that balsa core? Water doesn't magically appear just because balsa is present. I prefer the OP's repair many times over the slurry repair above.

Mark

Perhaps through the cracks that will appear in the non glassed seam? Or through failed bedding in deck hardware? Or through a stress fracture? Or through a deck leak far away elsewhere in the deck which is migrating water through a void, most commonly at the outboard joint? In other words, all of the usual places. Not likely in this case, given the OPs method. I would be most concerned about the seam with no glass, and about how brittle the high volume of filler in the deck will be. I would guess if you open this repair up again in ten years, you will find cracks in the epoxy filler. If you must use epoxy in place of light weight, flexible core bond, use 610.


I, too, prefer the OPs method many times over injection.

[Hudson Force]

Originally Posted by minaret

................. I would be most concerned about the seam with no glass, and about how brittle the high volume of filler in the deck will be...........

Just so myself and others can best understand your advice, what is the "seam with no glass" and the "high volume of filler"?

Also, you suggest the West System Six-10. I was not promoting a particular brand; however, I was very pleased with the G/Flex expoxy that I had used earlier with my hull/deck joint covering under my rub rail and now for this deck repair. The same G/Fex epoxy is recommended for use by West System with a greater flexibility and resistance to stress cracking than the Six-10. I'm not rejecting your suggestion of Six-10, but it's not a product that exceeds the peformance of what I've used.

[Nicholson58]

Originally Posted by minaret

How does this method address the common problem of the upper skin deforming once the core is removed? If you are replacing say 1" core, and you decore a large area of the deck from underneath as described, the upper skin is almost certain to deform, probably causing a low spot. If you were replacing with sheet material from beneath, as normal, the upper skin would be forced back into place by the process of coring. This will not happen with injection. You cannot be assured of a fair outer skin this way, on anything but very small repairs. Shrinkage of injected material when post-curing will also create deformation, particularly on thicker cores.

Wouldn't you also need to grind off all the gel, or at least prep grind for adhesion if bare, the underside of the lower skin as well, before applying your fab matt? That is a whole lot of overhead grinding inside your boat.


Aren't you also concerned that the lower skin generally has at least one ply of heavy roving or biax to achieve its structural purpose, and you have made it into Swiss cheese and replaced it with only a layer of fab matt? How does this not have a negative affect on structural integrity?




For those who, in future, insist on doing this sort of repair; you might consider using a grease gun to inject your filler and screw in zerk fittings threaded into the deck. You can inject at vastly higher pressures this way without blowing the tubes out of your deck. Much fewer voids remaining this way, though there are always some when you inject. If you go to a pneumatic grease gun with disposable cartridges and crank the air pressure to max, it's even better. But still not a pro repair.

Never had any issues with the deck above. This is all LOW pressure, thus the calking gun & refill cartridges. The injection port must be large so that there is little resistance to the flow of the slurry. A grease gun, designed for small for and high pressure is the wrong tool. As to filling, if you inject at the low point and vent at the high point(s), you can easily see the resin front pass all of your windows until the vent is reached. With very low pressure, there is no chance of distorting the deck. I have used this process in three areas, the largest was about 12 square feet X 3/4 inch thick. This required more slurry than you are likely to pump through a grease gun in your life. Also, the filler, glass microballoons is more abrasive than a grease gun will tolerate.

If the layers of pre-saturated glass, 6 mill poly film, corrugated cardboard, plywood, compression struts is followed, the glass mat will be well bonded to the inner cabin top and the surface will be extremely smooth.

If you do not have demountable head liner panels, this becomes a seriously more difficult repair. Ours is upholstered plywood panels with mahogany strips.

Compressive strength of the slurry material is 3000 psi and the bond to your inner and outer skin makes this a stronger deck than the original.

I also used the 635 THIN resin, 3 gallons, and microballoons, 10 gallons to make filler with a drywall paddle. This was poured in my rudder form to rebuild our rudder. It was then faired & skinned with carbon fiber - vacuum bag. It took a total of 30 gallons of this mix to fill the rudder. This brings up another feature of the 635 resin - very slow cure. With a cure time of 4 days, there is no heat induced run-away, even in our 6-inch thick rudder.

Rudder and deck repair photos are here.
Member Galleries - Cruisers & Sailing Photo Gallery

I can't imagine the art work to try to flawlessly repair the deck from a top-side repair.

[Terra Nova]

Originally Posted by Nicholson58

...I can't imagine the art work to try to flawlessly repair the deck from a top-side repair.

Especially amidst molded-in non-skid.

[Lojanica]

Originally Posted by Nicholson58

Never had any issues with the deck above. This is all LOW pressure, thus the calking gun & refill cartridges. The injection port must be large so that there is little resistance to the flow of the slurry. A grease gun, designed for small for and high pressure is the wrong tool. As to filling, if you inject at the low point and vent at the high point(s), you can easily see the resin front pass all of your windows until the vent is reached. With very low pressure, there is no chance of distorting the deck. I have used this process in three areas, the largest was about 12 square feet X 3/4 inch thick. This required more slurry than you are likely to pump through a grease gun in your life. Also, the filler, glass microballoons is more abrasive than a grease gun will tolerate.

If the layers of pre-saturated glass, 6 mill poly film, corrugated cardboard, plywood, compression struts is followed, the glass mat will be well bonded to the inner cabin top and the surface will be extremely smooth.

If you do not have demountable head liner panels, this becomes a seriously more difficult repair. Ours is upholstered plywood panels with mahogany strips.

Compressive strength of the slurry material is 3000 psi and the bond to your inner and outer skin makes this a stronger deck than the original.

I also used the 635 THIN resin, 3 gallons, and microballoons, 10 gallons to make filler with a drywall paddle. This was poured in my rudder form to rebuild our rudder. It was then faired & skinned with carbon fiber - vacuum bag. It took a total of 30 gallons of this mix to fill the rudder. This brings up another feature of the 635 resin - very slow cure. With a cure time of 4 days, there is no heat induced run-away, even in our 6-inch thick rudder.

Rudder and deck repair photos are here.
Member Galleries - Cruisers & Sailing Photo Gallery

I can't imagine the art work to try to flawlessly repair the deck from a top-side repair.

That is very interesting. The microballoons act as heat sink? I can't imagine mixing 30 gallons of epoxy for one pour in something 6 inches thick. FIRE!!! But I guess the mix works. Does it dry gummy or hard or rock hard or? Seems cool and another trick in the toolbox. On stuff that thick I always core but your core is mixed in the epoxy I guess. But I am confused by the lack of woven fibers wouldn't it be brittle? That's why coring and glass is used the epoxy is only the waterproof binder. So we need a material scientist here. Seems that epoxy and microballoons only would be brittle? I under stand though using it as a "super foam" core expensive but very cool.

For thick things like your rudder I alsways just laminated coose together and then shaped it and the glassed it. Strong as hell.

[minaret]

Originally Posted by Nicholson58

Never had any issues with the deck above. This is all LOW pressure, thus the calking gun & refill cartridges. The injection port must be large so that there is little resistance to the flow of the slurry. A grease gun, designed for small for and high pressure is the wrong tool. As to filling, if you inject at the low point and vent at the high point(s), you can easily see the resin front pass all of your windows until the vent is reached. With very low pressure, there is no chance of distorting the deck. I have used this process in three areas, the largest was about 12 square feet X 3/4 inch thick. This required more slurry than you are likely to pump through a grease gun in your life. Also, the filler, glass microballoons is more abrasive than a grease gun will tolerate.

If the layers of pre-saturated glass, 6 mill poly film, corrugated cardboard, plywood, compression struts is followed, the glass mat will be well bonded to the inner cabin top and the surface will be extremely smooth.

If you do not have demountable head liner panels, this becomes a seriously more difficult repair. Ours is upholstered plywood panels with mahogany strips.

Compressive strength of the slurry material is 3000 psi and the bond to your inner and outer skin makes this a stronger deck than the original.

I also used the 635 THIN resin, 3 gallons, and microballoons, 10 gallons to make filler with a drywall paddle. This was poured in my rudder form to rebuild our rudder. It was then faired & skinned with carbon fiber - vacuum bag. It took a total of 30 gallons of this mix to fill the rudder. This brings up another feature of the 635 resin - very slow cure. With a cure time of 4 days, there is no heat induced run-away, even in our 6-inch thick rudder.

Rudder and deck repair photos are here.
Member Galleries - Cruisers & Sailing Photo Gallery

I can't imagine the art work to try to flawlessly repair the deck from a top-side repair.

Haha, you think you can pump more epoxy faster with a caulking gun than a pneumatic grease gun? Lol!


I don't think you are getting it, as usual. Simply decoring a large area will cause the upper skin to deform. Your method does nothing about that fact, in fact it exacerbates it due to epoxy shrinkage. And once again you fail to address the issue of grinding for prep. If you haven't ground the inside of either skin, which is impossible with this method, the bond will be very poor. Delamination is likely down the road. I know you are very enamored of this method and think you invented it, but people have been doing it for decades. I've had to clean up that mess more than once. This is a terrible method, for all the reasons I have enumerated. How about actually addressing some of those issues? Are you saying that you believe you are getting an excellent bond to the inside of both skins and the underside of the cabin top, all with zero prep? Because that's what it sounds like your saying...

[minaret]

Originally Posted by Terra Nova

Especially amidst molded-in non-skid.

Do a forum search for my method of repairing molded in skid. Talking two different forum members through this process by PM now, and it's going well. Makes perfect repairs in molded in skid relatively simple, if time consuming.

[colemj]

Originally Posted by Terra Nova

Especially amidst molded-in non-skid.

Flex-Mold makes this type of repair easy (as long as you can color-match gelcoat). Alternately, it one is replacing a large nonskid panel, it is very easy to take a mold off the deck before the repair and make a new nonskid piece to glue back on. I just did a whole lot of that - it takes a couple of hours and looks like factory.

But the OP did not have molded nonskid to worry about.

Mark

[minaret]

Originally Posted by colemj

Flex-Mold makes this type of repair easy (as long as you can color-match gelcoat). Alternately, it one is replacing a large nonskid panel, it is very easy to take a mold off the deck before the repair and make a new nonskid piece to glue back on. I just did a whole lot of that - it takes a couple of hours and looks like factory.

But the OP did not have molded nonskid to worry about.

Mark

I've done a whole lot of flex mold, I'm the go to guy for that around here. It is NOT easy. Whole pieces vacuum bagged down is what I do, and it does indeed come out factory. Been posting about it here for years now. Much much better results than flex molding.

[colemj]

Originally Posted by minaret

I've done a whole lot of flex mold, I'm the go to guy for that around here. It is NOT easy. Whole pieces vacuum bagged down is what I do, and it does indeed come out factory. Been posting about it here for years now. Much much better results than flex molding.

I was talking about repairing a small area with the flex mold (no more than 1sqft). That has been easy for me to do. I agree that for large pieces, flex-mold is much more difficult (and expensive) and requires a lot of post-production detail work - which is why I mentioned making new pieces for replacing large nonskid panels.

Mark

[Nicholson58]

Originally Posted by Lojanica

That is very interesting. The microballoons act as heat sink? I can't imagine mixing 30 gallons of epoxy for one pour in something 6 inches thick. FIRE!!! But I guess the mix works. Does it dry gummy or hard or rock hard or? Seems cool and another trick in the toolbox. On stuff that thick I always core but your core is mixed in the epoxy I guess. But I am confused by the lack of woven fibers wouldn't it be brittle? That's why coring and glass is used the epoxy is only the waterproof binder. So we need a material scientist here. Seems that epoxy and microballoons only would be brittle? I under stand though using it as a "super foam" core expensive but very cool.

For thick things like your rudder I alsways just laminated coose together and then shaped it and the glassed it. Strong as hell.

This resin cure rate is so slow that heat can escape. This also means you have way more work time than you will ever need. I have used many epoxies but this is my go-to stuff. Build-up of my rudder was in the basement over a winter. Basement temperature was about 65 - 70. The stuff could be worked for several hours. The mass became tacky/gelatinous after about 4 or 5 hours. It could not be sanded for 4 days. It never became warm. The mix i used had an extremely high loading of balloons and the final consistency was about like Kraft Marsh Mellow creme. The only way you are likely to do this is with a drywall mixing paddle and a low speed high torque drill motor. The material does not appear wet. You can poke your finger in and it wont stick but if it lays against another surface for a few minutes, it bonds very well. Density is low but the strength is high. The strength of the cured mass is greater than that of the neat resin. If you consider that most rudders are urethane foam fill with crappy compressive and near zero shear strength, this material is massively stronger. Since it cannot hold water, it is the best material for below water use. Once a fiber skin is added. you have a stressed skin sandwich where the foam is the shear layer. It cannot be made to fracture unless the skin fiber fails. Since the skin is well bonded to the core, this is unlikely. My rudder rings when struck. Freaked out the surveyor. I hired the vacuum bagging at the marina. The guy who did the job described my rudder as superior & a lifetime repair/bullet-proof. He was aware of the method but said it is rarely done because of the labor involved and the difficulty of making large structures with runny filler.

Your observation regarding heat & dilution of the mass with the high balloon loading is certainly true. 3 gallons epoxy to 10 or 12 gallons of balloons does spread out the reactants. The blend for deck filling is way less balloons. Probably 2:1 or 4:1. If its too thick, it will be very difficult to pump.

Several people I have told about this have re-cored a weeping rudder by opening a few small windows or an entire side of their rudder, digging out the foam and filling solid with syntactic foam. The joint needs a proper structural repair to close the holes. Living in the north, you can walk the yard in the spring and watch the water dripping from many rudders.

Note that only the 2:1 version is non-blush.

[geoleo]

Here is my 2 cents on non-skid repair. While rebuilding a sunken Island Packet 44 (from Hurricane Charley in Punta Gorda FL in 05)....I had the deck edge and deck all done perfect by a guy named Tom he was very good- but he could not work in the boatyard due to (Salt Creek marina) previous personality problemas---I had to move to--- So island Packet factory mad me their non skid in "skip panels" 4ft wide and 14 ft long . These were ultra thin and fragile and came rolled in 3ft dia rolls which gave them a 'set' and I had to unroll them and place under plywood in the garage floor for a few weeks then roll them up and hurry to boatyard and unroll before they took a new"set'. I hired a guy named jonny as he was good with FG we cut the pieces with scissors to match the deck on other side , then jonny made a Fg resin with a little thickener and we spread it on the 12ft long piece and put cement blocks on top! Rushing to get it right before it set-- Jonny yells "its stinkin" and we pushed all the raised areas down into the slurry but they kept popin a 1/16th or more we went nuts --but finally we had it all pressed down.as it was set firm.....Results were it was firm andc ould not be told it was repaired. Jonny also regelcoated 1/2 of port hull to perfection--Sold boat for $215000 as it looked totally new after being sunk for 10 days and dismasted.