Holes in the hull

B

bmcminn

New member
I found four holes that I have not seen before. Ugh.

This boat had a major overhaul before I got it and the previous owner hadn't even used it. He hadn't seen them either.

So it's been in the water about 100 hours total. I'm guessing there was a transducer or something there. The transducer is now mounted on the starboard side on the back not the bottom. It's possible that the person who did the gelcoat had covered them with a plate and it has fallen off but more likely I think that they just never got filled. When I took the pics I didn't think to probe them. I'm getting the boat from storage tomorrow and will poke around and see if they dead end or what.

I guess I fill them and sand it flat, but I'm concerned about what could have happened with it like this. I have two batteries in the starboard lazaret and the boat lists to that quarter a lot, the water line is below water a couple inches there. To get it level only takes a little downward force to the port quarter when I'm standing on the dock, so I think the level is just off from the batts. The holes are on the port quarter, but for all I know water has been pouring into some third-space... I don't know how the hull is constructed on the bottom.

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Thanks for your ideas on what I should check or do.
 
So, first off...I’m no expert. But, I’ve had the boat for a decade and learned a lot from people here. It may not be that bad. The hulls are generally cored with balsa. You’ll have to look carefully. But that portion may be glass only. I don’t know on your boat. Poke around a tad. See what you find. It’s a 19 so I’m assuming you won’t have a bilge in the true sense. The hull’s interior is the cockpit sole. If those holes don’t go thru, I imagine they don’t, it’s just the exterior layer and core you will have to investigate. I’d make sure if it is balsa to remove all the wet, rotted wood. Let it dry then. Once you have good dry wood, you can repair the holes. I have a how to somewhere here on the site along with pics in my album of how I repaired holes when I moved my swimstep.

Youtube Boatworks Today to see lots of how to on Fiberglass repair.
 
Yes, this is a 19', but I'm not sure if it has the balsa core or foam. It's the first one they made and I think someone told me they used foam back then.
 
My 1993 22 had balsa core. It is possible that this may have been a bracket for a pickup tube, --for bait tank/well, or a transducer. It is also possible that there was some filler put in around were the screws were placed.

I would probe it. Then grind it flat, and dish out a little to allow you to laminate new glass from the outside. From the inside you will have to remove the fuel tanks.

If there is a wet core, I believe you would see water dripping out of the holes.
 
Here are the “instructions” I wrote up on repairing small holes. Pics in my album.

This tutorial will hopefully help those that weren't able to attend the session @ the factory. I don't pretend to be an expert and I am not responsible for any outcome from the use of this tutorial. I am merely trying to convey, in words, what we all observed/learned. A huge mahalo to Scott for doing this for us. I suggest you read through this AND look at the pictures posted to get a better idea of what I am attempting to describe. Please post any questions/clarification you may require and I'm sure those of us that attended will chime in.

FIRST A WORD ON SAFETY. Please follow/use common-sense personal safety practices. Use eye & ear protection when using power tools. Use the proper gloves when handling/using chemicals and dust masks when creating dust/sanding/grinding. Properly dispose of any material used in this tutorial. Finally, make sure you have proper ventilation when using chemicals/resins. The filler & resins etc used in these procedures can create heat. Be aware of the possibility that FIRE/BURNS exists if they are improperly mixed. BE SAFE!!!!!!!

REPAIRING THROUGH HOLES:

Per Scott, this repair is for any through hole larger than ~1/2" diameter. It is the most difficult & time consuming, however, this repair is also useful for gouges and small holes that do NOT go completely through. The one caveat is you will only use the steps I will describe from the second Duraglass application on. In other words; for gelcoat gouges & small holes you will fill w/ Duraglass, followed by sanding w/ 600-800 grit using a D/A sander until smooth. From this step on it's a matter of spraying gelcoat and cutting/buffing on ALL repairs, including when you need to remove scratches. I will describe the spraying of gelcoat, cutting/buffing separately.

Materials:
"Duraglas" filler w/ hardener
Polyester resin w/ hardener
Bi-axial 0-45/90 clothe
Matt clothe
36-50 grit discs (for die-grinder)
320 & 600-800 grit discs (for D/A sander)
Acetone
latex/nitrile gloves/dust masks

Tools:
Die-grinder w/ disc head (or electric)
D/A sander (or electric vibrating sander)
putty knife(s)
small metal resin roller
disposable paint brush(es)
scissors

Begin by cleaning up the hole, removing any loose fibers/material etc. If it's a clean hole (drilled) that's good. If it's a structural location, like a transom, or visible on two sides, like a cabin wall/bulkhead this repair must be done to both sides. If not, one need only patch the rear portion with a cloth patch w/ fiberglass. Mix the Duraglas/hardener on a flat piece of plastic or clean wood etc using putty knife according to the instructions. Fill the hole with the mixed Duraglas and let dry/harden.

Once it's cured begin grinding the repair with 36 grit and the die-grinder. This is appears scarier than it is! Take your time!! Scott recommends a 3:1 ratio of repair/patch to hole; for example, if the hole is 1" grind 3" total diameter. You want to end up grinding into the Duraglas & surrounding area to create a ~1/8" concave "mushroom". Clean w/ acetone/rag.

Cut circles of bi-axial clothe starting at the size of the hole then slightly larger. You want two layers of bi-axial, the second slightly larger than the first but not larger than the final layer. Optimally, you make the center layer half of layer 1 and layer 3. The third/final layer is the matting cut to the size of the overall repair/grind-out you created (3" in the above example).

Mix polyester resin according to instructions. Begin saturating the clothe, one layer as you need/install it. Scott used a cardboard box & brush. Begin w/ the shiny side of the clothe down and saturate both sides w/ resin. If you still see white fibers after saturating, it's NOT saturated; brush on more resin. Begin adhering each cloth layer. Scott used a small metal resin roller. Roll across each previous direction @ 90/45 degree angles, varying it to remove all air bubbles. Continue the same with each successive patch. Allow to cure. Remember, COMPLETELY saturate the clothe & REMOVE all air bubbles. Scott impressed upon us that the resin/clothe is where the strength of the repair is achieved! The Duraglas is merely a filler and has no strength. It will crack if not sealed in resin/clothe. When this portion is done, you'll end up w/ ~1/16" high (convex) on the patch vs. the surrounding non-patched area.

Again, using the die-grinder & 36 grit, begin smoothing out the patch to cut down the hardened clothe/resin. You'll want to again slightly concave the patch ~1/16". What you're cutting down will be some of the matting; no problem. You can use a straight edge to make sure you're nice and concave in various directions. Clean w/ acetone.

Back to Duraglas. Mix another batch of just what you need. Fill the patch "criss-crossing" the patch with your Duraglas mixture, making sure it is completely filled slightly higher than the surrounding. Let cure.

Using the D/A sander and 600-800 grit pads begin sanding the patch. KEEP THE SANDER FLAT AGAINST THE SURFACE and take your time. You're complete when it's flat. Best way to check: using your flat palm/fingers, run your hand across the patch in various directions. Doing this w/ your eyes closed will allow you to feel even slight variations in level. Try it.
 
Like I said, I’m not expert. But I believe in the do it yourself when you can philosophy. I learned and asked and did what I could. So can you. 8)
 
Well, so there's wet core. When I sound it I can squish out salt water and if I jam some copper wire into them I can get out some wet wood chunks. The two closest to the edge may be partially sealed but I can feed a couple inches of screwdriver into the two inside ones. They are 2.75" apart and 2.75" from the edge. I slid the gas tank out of the way and they don't go through to the cockpit, so I guess they are within the depth of the transom. I'll look up digging out balsa but any more ideas about that are appreciated.

Thanks.
 
I decided to drill some holes. 3/8", one in the center and two more towards the centerline, out to about 3". Wet core, but the last one seemed to have some solid material near the top. The others were mush.



Not sure if I'm supposed to cut this out from the outside or inside, though the holes don't go through to the cockpit, so not sure if that should be left intact.

I'll call NMI down in Fairhaven on Monday and see if someone there wants to take a look and give me some in-person advice.

Bob, I read your post about replacing the floor of your cockpit. I guess you just use a cutting wheel of some type to remove the rectangular piece. I have a electric cutter. Do I save the piece and use it again? You suggested a different core material, Nida-core...

Oh man I got a lot to learn and no time.
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You will get a lot of suggestions, search back through the old posts, some will help.
I see 2 ways to go.
The fix it and pray for the best method...
Dig as much of the mushy core out that you can. Tape a little plastic tent/enclosure down from the hull, put in a little heater, not too hot and try to get it dried out over a few days. Fill with expanding spray foam or or acraglass whichever looks like it would work out best then glass over as in your earlier post.
If the hull and interior don't seem soft and flex under a rubber hammer before you start this could be all you need. Use epoxy resin.

The next fix is if you feel that the bad core has spread far enough that tapping with the hammer and it sounds "dead" and flexes away from the holes after drying and you want a good fix and feel confident in your DIY skills.

Laminate over the holes as above.
On the interior which is hopefully accessible, using a small grinder with a diamond blade cut away some of the laminate above the bad area, cut a small square and pry it out. Keep expanding the area until you find the edges of the good core. Scrape out the bad core and lightly sand/grind the bottom laminate. Straighten and even out the perimeter of the excavation. OK, now you need new core, foam or balsa of the same thickness from a fiberglass supply (on line) cut it for a tight fit in your hole. Cut a piece of 1.5 oz. Fiberglass mat to fit in the hole paint the bottom laminate liberally with resin, put the mat in. brush resin liberally on it and work out the air bubbles with the brush tip. Paint resin on the bottom of your replacement core place it down in against the wet glass on the hull, weigh down the core with weights like bricks to press the core into the wet layer of glass. After cure grind away and taper the area of the surrounding laminate out 2 or 3 inches, the core and surrounding laminate should be a nice smooth surface. Laminate over the area you have ground down with small to larger glass pieces to fill the area with a tapered patch. Use alternating layers of mat and e-glass or biaxial cloth up to the original glass thickness. Epoxy resin is much better, I use West but others are fine as long as they have measuring pumps for the cans. Try to find glass mat that has a binder that is compatible with epoxy.
This is only a very basic outline, but using common sense and if you are used to building and crafting things in general, if you take you time and think things out, do a little studying on line, you can do this. It is actually pretty simple if you are handy.
I'm sure others will chip in with good ideas also.
Good luck.
 
Diamond edged blades that fit grinders are sold for cutting tile at a building supply. They work great on fiberglass, buy dust masks.
They should also have coarse 36, 50 and 80 grit disks that with a rubber disk back will fit on your small grinder for sanding and grinding fiberglass
I do this on my phone, please excuse brevity and typos.
 
bmcminn":12iulc8u said:
I decided to drill some holes. 3/8", one in the center and two more towards the centerline, out to about 3". Wet core, but the last one seemed to have some solid material near the top. The others were mush.
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This finding illustrates why it is so important to have a survey before buying a boat.

Stop drilling holes in the outer skin--this will compound the repair. The outer glass skin is fine, except where you have holes.

You are going to have to pull the fuel tanks and start sounding (use of small phenolic hammer, plastic handle of screw driver etc) the floor to estimate the degree of water infiltration from the inside of the hull. --If the rest of the inner hull floor is dry, then use of a moisture meter to be sure that there are no more wet areas. (That is a whole different subject)

Bob, I read your post about replacing the floor of your cockpit. I guess you just use a cutting wheel of some type to remove the rectangular piece. I have a electric cutter. Do I save the piece and use it again? You suggested a different core material, Nida-core...
Click to expand...

What you read about was the floor of a 25, not the bottom of the hull in a 19 or 22. There were some reasons to use the NadiCore in that application. Some boats are built with Nadicore, although I would not choose it for the bottom of the hull because of mechanical properties of the core product. For the C Dory hull laminate, I would go back with Balsa.

As Micah suggests in his post above, You need to cut out the inner layer of the hull, starting all of the way back by the transom, and work outward. Drilling small holes to assess is one way from above. After you have identified the bad area by sanding. The bad area will most likely be further than you sounded.

You are going to have to then remove all wet core, as accessed from the top. This means cutting segments of the inner hull out, and checking the edges. In this case, I would go back with balsa for the core material. You have to remove all of the old balsa. Agree with Epoxy as being best for bottom. You are going to have to repair all of these holes now--but considering how they are spaced, I would tend to grind down the entire area--tapering to the outside, and lay up glass over this entire area, rather than a group of 7 circular repairs. I would do the same on the inside. The actual schedule of laminates would depend on what thickness you find in the bottom. Details would follow as you reveal the amount of wet core. I would have no problem using polyester resin on the top (replacing the inner layer), But there are excellent arguments for use of epoxy--depending on how you are going to finish the repair. There are ways to get gel coat to adhere to cured, and clean epoxy repairs.

Oh man I got a lot to learn and no time.
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My advice is to go slow, if you are going to do the repair, get advice before you make any move or drill more holes.

I have used multiple techniques for cutting fiberglass. In this case you want to limit the cut depth. A 1/8" rotozip bit cut adjusted to just go into very top of the balsa core, a carbide or diamond blade in any one of a number of small (3" ) saws--such as by Dremel, or Mikita, A Fein type of oscellating saw, with carbide blade will allow cuts right up to a vertical surface (hull side) IF there is no limit to the depth; I have used skill saw, Sawzall, jig saw with either bimetal or carbide blades, even a chain saw...(these latter do not apply to your use).

When you are building the deck back on top (don't put the old glass back in), you will laminate back to at least the thickness of the original inner hull laminate. That needs to be tapered into the hull inner glass which is over intact core.

Since you are in Bellingham, you have a winter to do the project. Hopefully you have a place indoors which can be heated for the repairs. Go slow and ask for help at each step.

Could you do a "temporary patch" from the outside? Yes, but I would only do that if I had some trip planned, and then were going ahead with the comprehensive repair in short order. You will not dry out the core with heat and dehumidifiers in a few weeks. If you go thru freeze thaw cycles, the delimitation would become worse. It is not rocket science.

Both Micah and I have left out some of the details--and our advice is basically the same. I have walked several members thru this repair, and Micah has apparently done some similar repairs.
 
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My plan this week had been to reseal the lazaret hatches then see if I just needed to replace them, stbd in particular has been leaky. But after learning a little about this core stuff and reading a post Bob wrote about hatches I realized there might be a bigger issue. Sure enough, it's soggy wood around this side and I'm sure the other too. I'm hoping that with these I can simply dig out to 'dry enough' and then fill with expanding foam, then epoxy. There is a small leak on the bow hatch and I had thought I'd pull it and reseal also, now I'm wondering if it's going to be core damage as well. And what about around the rub rail and windows?!? Ugh. Rub rails. Ugh. The rest I'm guessing is less a big deal if the glass is not springy. I'll order a PMM tonight.

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I slid the stbd gas tank out of the way and my rough guess is the outside hole is about where the sharpie is, but there's nothing showing from the cockpit and it feels solid. I really want to do this from the outside, that's why I made the bonus holes. But I can see how going from the inside is structurally preferable. Rats. I'll see what the folks at the factory say. This is the hard way to learn how to make an Alaskan bulkhead.

I'll keep everyone posted. Thanks for the info.
 
The wet balsa can be removed with a router bit in a drill. Remove it until it’s all dry, good wood. Hopefully it will only be an inch or so, max. Then wet the wood with epoxy resin followed by filling with thickened epoxy immediately. I’ve used West Sytems with hi density filler mixed to a peanut butter consistency. Once it goes off it’s hard as rock. Then re-bed the new hatches with something like 3M 4200/4400.

There shouldn’t be balsa around the windows or rub rail. Just glass. The balsa is only used in the bottom of the hull, roof, bow where your v-berth hatch is, top of the gunwales etc. the sides of the hull/cabin are just thick fiberglass, so you should have no issues with rot associated with windows. The bow hatch yes...like the lazarette hatches, is possible if it leaks.

Even the hole for our anchor windlass (rode) was exposed balsa. I gouged it out and used the thickened epoxy there too. Basically anywhere water can get into the balsa needs to be sealed off, or rot is possible. Even the screws that hold your fuel tanks down in the cockpit should be drilled oversized and filled with it. Same with your bilge pumps screws in the cockpit. The factory was less than thorough in this aspect of the builds. Here are pics of the same issue we had our our boat, just a different spot. You’ll see how I “gouged” out the rotted balsa and re-filled it all with epoxy. http://www.c-brats.com/modules.php?...ame=gallery&file=index&include=view_album.php

Your daughter is beautiful.
 
It certainly will be interesting to see what the "Factory Guys" say about this. While you are at it, ask them why they don't prevent these failures by putting solid core in the areas where any hole is drilled into the balsa core. This is not a problem unique to C Dorys. A very few builders have always put in solid glass or other solid core materials where any hull penetration is placed.

A few years back when a NDT scientist and my self were developing instrumentation to test core moisture and delamination, we cut up 20 hurricane damaged boats (Chain saw and skill saw) to do both testing and documentation. Some had no damage, but no penetrations. The ones which had solid core material (only a very low %) had no core damage. The instruments were never taken to market, since surveyors and most manufacturers didn't want to spring for the $2,000 for the instrument or take the time to learn a 21st century technology.

Please don't let anyone talk you into doing a repair on that boat from the outside. There are multiple reasons that it can be an issue down the line.

Expanding foam might work for a few very small areas--but I would not use it where you propose. It is not a barrier, and can absorb water. The balsa core damage will be limited, and as Local Boy says, rout out the core, (I prefer a Dremel tool, if necessary, get a flexible shaft, I have one which is only about 3/8" diameter, and will fit way back into core if necessary). I feel that the Dremel bits give a cleaner result, and are easier to control. However even an Allen wrench can be used, as well as a bent coat hanger.

I make my peanut butter consistency epoxy mix a little different. Paint in the neat epoxy to coat the balsa and sides of the glass above and below. Any screw penetration into a cored structure (deck, floor, or hull) should have an epoxy plug. The 22's have a core in the aft cabin bulkhead, but as noted all of the sides of cabin and hull are solid glass.

Keep us appraised of the work!
 
OK, I'm going to do this myself. I want to see the core myself and I figure I can learn something new.

So I'm going to cut from the inside. Any reason not to go ahead and take one of those holes all the way through so I can find a corner?
 
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