floor cracking around seatboxes and flexing in v-berth area

[Jackie]

I am in need of some serious advice. I am in Ketchikan, Ak and have a 2008 CD16 cruiser that is having an issue with the top layer of fiberglass on the floor delaminating. I first noticed hairline cracks where the port side seat box is glassed down to the floor several years ago. Over time it got worse (I know, I know…please don’t chastise me for not doing something sooner.) Eventually they grew and I noticed water/brown sludge would squish out from the crack in front of the seat box and the entire floor in front of it would flex when I was running. I was in the middle of building a remote cabin and using the boat nearly every day, so I couldn’t pull it out then.

What I think the problem is, is that the top layer of fiberglass, especially in the v-berth on the port side, was never properly adhered to the substrate and so, as it flexed while running it started to push up on the seat box and broke the fiberglass strips loose that sealed the boxes to the floor. Eventually the cracks ran all the way around the passenger side and have started on the driver’s side too. I figured once the cabin was done and I could get the boat in my son-in-law’s garage, I could pull the seat box, at least on the bad side where I wouldn’t also have to pull the engine controls, and see how bad the damage underneath is. I’m not sure if the balsa core is exposed (everywhere) to the water under there, or if the top layer of fiberglass covers another layer which might be protecting the core.

Anyway, I used a small rotary tool and cut along the cracks to free strip that held the seat box to the floor, and loosened the front and back, but discovered that the entire side wall (which is connected to the seat box. It is an all-in-one design) is superglued to the hull by the spray foam between them. I have no idea how to get the seat box/side wall unit out of the boat, and I need it out in order to pull the floor up, which I need to do to see what the problem underneath it is. It is a compound dilemma; one which I am fast realizing I can’t handle on my own.

The boat has been in the garage since fall now while I grappled with the idea that fixing it is probably beyond my meager to non-existent skills. Now my SIL would really like his garage back so I need to figure out how to proceed. One option would be just to see if the factory would like to take a look. That would be the most expensive, especially with shipping from Ketchikan. I haven’t looked to see what the local talent for fiberglass is, but I’m a bit hesitant because I think working on C-Dorys requires some special care. We have marine shops here but they are for repair and maintenance. Another option would be to just cut out the side and then order a new full side once I’ve figured out how to fix the floor. That may be what anyone has to do that fixes it, since I don’t see how that side panel will come out with no damage. Any ideas on how to proceed would be appreciated. I thought I’d check here before calling around town just in case you had insights on removing the side wall or any other thoughts.

Thanks in advance for your help.

[tsturm]

[Marco Flamingo]

I think you might find a lot of answers in the Limpet photo album under "Balsa Core Issues." The top layer of glass is quite thin. If the balsa rots underneath it, it might not support the weight of the sea box/passenger and crack the thin layer. Seat box removal is shown in my photo album.

I didn't have spray in foam behind the seat boxes. Only Styrofoam cut to shape. Around the base of the seat box was a bead of some kind of sealant, most of which had failed. Many of the pop rivets had also failed.

It sounds like your failing balsa is a larger area than what I had to deal with. I also found when removing the seat boxes that some of the remote rivet holes had leaked and had their own problems outside of the main area.

The issue is going to be finding a covered storage area, preferably heated, where you can undertake the work if you do it yourself. I was able to dry out the balsa core for months in my garage. It's not likely that a shop would provide you with this amount of time.

Mark

[hardee]

I would wonder if the cause might be related to some water, (either) intrusion itself or intrusion followed by freeze thaw cycling which could also increase the sizes of those cracks. Either way, it is going to need some serious drying via mild heat and ventilation.

Harvey
SleepyC

[thataway]

I notice in your album that the cracks were documented in 2016. I agree with Harvey that the freeze thaw cycle, even if the boat were well covered, has entered into the picture. You might update the album and it may give us a better idea of how much damage. I seee in the last photo a screw directly into the floor.

Most disturbing is that the floor flexes when underway. This suggests failure of the core lamination to both sides, or a rotten core.

Any fiberglass repair person can fix this. There must be some folks in Ketchikan who can do this... Coming up summer is not the best time to engage them--better for the winter. There is a chance you can dry it out during the summer if you can put it into shelter.

Foam can be replaced, fiberglass cut. Gelcoat re-applied, or paint over.

Once you get started, it is technically easy. The hardest part is taking that first saw cut. Oscillating saw for this job. Dremel, Ryobi, Rigid, Dewalt, Milwaukee etc all make these saws. Use a carbide tipped blade.

I doubt that the factory will tackle this job--and it will be far cheaper to have it done locally, or DIY.

[Marco Flamingo]

I just looked at your photo album and saw that you have a different construction method than my 2004. No pop rivets. Your seat boxes are tabbed in and the failure seems to be on the tab (and maybe not on the actual top layer of fiberglass?). My leaks came from the pop rivets. Your flexing would indicate problems in the core, but I'm not sure where water intrusion would come from. It is unlikely from the cracks. Structural failure and moisture intrusion would likely proceed the cracking, not result from the cracking.

I would bite the bullet and do some test drilling. A 1/2 inch twist drill would give you a good look inside. You can put tape on the drill so as not to go too deep, but in reality the bottom layer is so much thicker than the top that you would have to hit the solid bottom and continue drilling for another 20 seconds to get through. I was very careful at first but then relaxed a little and drilled till the bit clunked against the bottom layer.

Check the swarf for moisture and discoloration. If it is okay, then it could be that your hull isn't flexing, your seat box is. But if the cracks in the top layer have radiated out from what's shown in the old pictures, then it's likely something going on in the balsa.

Mark

[Jackie]

Thanks for everyone's replies. One would certainly think that with all the fishing here, and boats, there would be a fiberglass repair shop around. If so, it is well hidden! I know there are folks that do fiberglass work independently and called the boat repair shops to get recommendations. There wasn't a single name that didn't come with reservations or warnings. That said, I have a plan and a guy and hope to get underway at least figuring out the core (pun intended) of the problem this weekend.

As noted, the seatbox and side wall are tabbed in. Screws or rivets would have been so much easier to remove, especially if the side hull had been insulated with blocks of foam. The floor is definitely flexing and I'm sure waiting so long has allowed the damage to spread. Here's to hoping most of the core can be saved. I'm sure I'll be back with questions and/or updates as I figure out the extent of the damage.

[thataway]

'As you get into the core issue, the weight of the boat on the trailer may cause a deformity which will leave the hull unfair. It may be desirable to make a cradle, perhaps even with battens which assure the hull lines be kept.

Once you make that first cut, and mix the first batch of resin--you will get the hang of doing the job. It is not that difficult, but takes time and some hard work.

[Jackie]

Update: It is bad! I think the water was getting in to the core through the screws that attach the v-berth supports to the floor. I removed the porta potty as soon as I got the boat and took out the flange that held it in place. I knew enough to fill those holes, but I really, really wish I had paid attention to the screws holding those uprights in. It is amazing that enough water got in there to totally liquify a good portion of my core in front of and under the seat box on the port side.

On the other hand, I have drilled some test holes behind the part I cut (there are photos in my album) and I think it is an area I can replace myself. I also think I may not need to remove the driver's seat box as the balsa looks good (?) close to it. I have more cutting, drilling and testing to do to determine the real extent of the damage, but I don't want to rip up too much of the flooring until I know for sure that I will be fixing the damage where it sits.

If I commit to fixing it myself, where it is, then I'd like to know more about how I should be supporting it. Right now it is on a trailer with bunks that run roughly right under the center of the strip I need to remove. I've put boats on blocks before, but Bob, you mentioned battens? Can you/someone explain the best way to block this up. I don't think my SIL is going to want me to suspend my boat from his garage rafters, even if they would hold it!

I have some heat lamps going under the boat, 'cause why not, but I'm wondering if renting a dehumidifier might be a good way to go inside before I move top heat? After I get the area all stripped back. I have a video that shows what I've done better than my pictures.My sons suggested Vimeo because I was hesitant about YouTube. Here is the link.Hope it works.
https://vimeo.com/413391696

Again, any advice is welcome.

[ssobol]

Why are you hesitant to use YouTube but not Vimeo? Same difference IMO.

[Jackie]

Ssobol, it was mostly a joke with the kids because I didn't want too many people seeing it. They were joking about 'internet sensation' and that I'd be advising people to 'subscribe to my channel'. Folks search YouTube. It's a place to go for content, but Vimeo feels less used, or used differently? I would have stuck the video just on this site if that were possible. And maybe it is, but I wasn't sure I could upload a video in my Album. The Vimeo thing was easy.

[Marco Flamingo]

[thataway]

Jackie,

You have done a great job so far. I checked the photos in your album, especially looking at the trailer, the floor and the video, which helped a lot.

You may be the perfect candidate for a Zoom meeting with some of us.

Here are my thoughts:

You should remove all of the wet core. Although there is controversy about the strength of wet core, there is no controversy that the wet core will freeze and thaw, thus expand and contract, and eventually cause de-almination, if it has not already (pretty good chance, that the wet core has already delaminated. If the top layer peels off easly, as it appears to have done with that which you have removed.

You might ask about drying the core? It is going to be really hard to do, if not impossible. I have seen boats where dehumidifier, sealing all around with heaters/heat lamps, even hot air vacuum systems, didn't adequately dry the core. Some have used various organic solvents to try and dry the core by removing moisture bonded with the solvent such as alcohols etc. The delimitation has occurred, or will occur. Replace.

So, you can either use a moisture meter and sounding with a screwdriver handle, or continue to remove core and inner skin. I think that you have pretty well delineated where the dry core is, and by careful removal of the inner layer, get to good dry core, with no delimitation. Anywhere the bottom flexed there has been delimitation.

The inner skin--throw it away. You will not use it. It cannot form a secondary bond which is satisfactory. You will be using mostly 1708 fiberglass to build the new floor. Although I love epoxy resin for some repairs, the extent of yours, I would use polyester, although vinyl ester would also be a good choice and compromise between the bonding strength. Basically you are building a "new" boat.

One worry I have is that there is some compromise of the outer layer of glass. Because of that, I probably would put a layer of 1708 and another layer of mat on the bottom before laying the new Balsa core. It will make the hull a little thicker there, but also much stronger. Fiberglass which has flexed multiple times becomes weaker as some of the fiber/resin bonds break down, leading to a "floppy hull". You don't have that yet most likely. (Even a floppy hull boat can be saved with foam stringers.)

Now as to support of the bottom of the hull. Looking at your trailer, it appears as if it should be the good basis of any extra support.

Can you run a 2 x 4 or 1 x 4 across the outer frame and under the keel? if you can, then this can be the basis of a support system, using 1x2, or 1 x 1 strips (The thickness of the strips will depend on how much "bending" or natural curve of the hull is in this area, I don't know exactly how the hull and wood will react in this hull. It might turn out that even a 1/2" thick batten is too thick, and you may end up using strips of 1/4" plywood. to get the right curve. Start with one 1x2 board (cheap grade and see if it flexes the hull as you put it bewtween "good areas" bridging under the area where the core has been removed. ). Place the battens about 3 to 4" apart running fore and aft to give temporary support and keep the hull true in the area where you have removed the core. If you cannot use the trailer frame, then it will have to be from the ground, and concrete blocks may be the best for a light boat like this. Probably won't need very many. After you have established boards across the hull, then lay the battens agains the outer skin from below and tap them in place with wedges so that they confirm to the shape of the bottom and any force from above will not cause the hull to sag or hump at one place.

You want to support the keel evenly and keep it in a straight line with out sags or humps. You want the hull contour to be symmetrical, and as close to possible the same on both sides. The area you are dealing with appears to be not entirely flat, but has some dead rise. (the V shape to the hull). This increases as you go forward. The support will have to take your weight as you lay the blocks of balsa core, and weights you put to hold them tight against the hull, in the mixture of carbsil and resin you use to bed the balsa core.

After the new core is in place, you will then rebuild the inner hull. You will want to grind the edge of the "good area" balsa core covering to a thin edge about 6:1 ratio--for every 1" of thickness you would grind back 6", but since the skin is only about 1/8" thick, you will grind back about 3/4". Good idea to mark or tape off the edge where you will grind and make the joint. There will be a little hump, after it has cured, but that will be ground fair before you paint the inner skin.

[Jackie]

Mark, my boat is always outside, but when on the trailer it is kept nose up. I think the biggest problem, after knowing there was something wrong, was keeping it in the water and using it hard for 10 months while working on the cabin. Rainwater was an issue even with a tarp, and I used it to haul lumber, etc, etc, so there was often a pretty heavy load on the floor between the seats and in front of the passenger seat. I'm sure the weight pushing on the already wet core caused it to break down and liquify so quickly. I do have it wedged into my SIL's garage right now and will be able to work on it there.

Bob, thanks for all that info. Following your recommendations, I do think I'll be able to handle the tear out and rebuild. First I need to see if I can get the hull supported. My SIL is finishing up a project that requires varnishing so I'm trying to stay out of there. Should be done tonight and I can look at shoring the boat up this weekend. I think I can use the trailer as support. I will be in touch to arrange a meeting for help if I run into trouble. Thanks for everything so far. I should have jumped on here back in October and maybe I'd have been back in business by now!