What would Dave Do?

Here's a question for DaveZ and the rest of you all.  So finally after sitting a week in the yard under a tarp upside down the snow and rain stopped the sun came out and I decided to give the boat some TLC.  I painted the bottom again to cover all the scratches from 3 days of floating and hitting a few rocks.  The outside looked okay, and I figured by painting I'll know where I hit rocks or scrapped the bottom on the next trip.  Then I flipped her over and boat souped the inside, here comes the issue.

 

I noticed two cracks/fractures in the inside bottom of the boat, next to splines in the center middle of boat.  Quite probably a result of hitting rocks as it is the low point of where the boat rides in the water.

 

What should I do?  Do I need to shoe the bottom of the boat?  (it's only 3/8" plywood now) Can I try to glue or epoxy the inside bottom where the cracks are?  Thanks guys for all the help.  Kinda worried about it, especially since I've named her and all.  Here's a few pics of the cracks.

 

 

Mark

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Permalink Reply by Kelly Neu on April 27, 2010 at 6:33pm
The boats I run are glassed inside and out, so your situation might be a little different... but here is what I do just in case it helps:

1. Chisel out the "soft" wood (you know, the busted up stuff) until just the good wood remains.
2. Then dry it out 100%. (Maybe you're lookin' at a summer job.)
3. Once it is dry I fill the new voids with an epoxy fillet mix (wood flours, chopped glass fibers, silica) and immediately lay glass tape over the wet fillet.
4. Once the glass is cured I just paint over it but you could sand it to smooth the edges and soup it up or just skip the glass and slather your finish soup over the sanded fillet.

The main thing is to get the wet wood out of there so the floor doesn't rot. It looks like a pretty simple repair that will be fun to do. Its a little scary taking a chisel to your finished boat for the first time! I'd wait to do it when the temps are warm and dry or you have a workshop with good heaters.

Good Luck.
Kelly
Permalink Reply by lhedrick on April 27, 2010 at 7:32pm
This stuff happens. From what I have seen 3/8 is just a bit weak. Jeremy and I have boats built from the same plans from Sandy at montana-riverboats.com. The inside chine filets were not wide enough and the bottom plywood just wasn't thick enough to stand up to major pounding. I added kevlar and bi-axial tape over wider filets. A layer of kevlar cloth went inside before the bulkheads were installed. I would have added it to the outside also but didn't want to sand black graphite loaded epoxy.

Before our Grand trip a few weeks ago Jeremy added a layer of bi-axial kevlar cloth to the outside and added another layer of bi-axial glass on top. Heavy bi-axial tape was added to the chine. Jeremy if you see this add anything I have missed about the rework you did.

As for your fix. As already stated get it dry. Dig out any soft spots and put a fan on it for a while to dry it out as best you can. I would then try to work epoxy under the cracks. Drill small holes in the bottom and add a series of small bolts with large washers on each side and wing nuts. Then add a layer or 2 of glass over the area to build it back up. If the wood is okay the epoxy will bond the fibers back together. If needed a 1/4 inch plywood plate could be epoxied on top of the area.
Permalink Reply by Dave Z on April 27, 2010 at 8:03pm
haha. My new favorite post. I have arrived. HaHaHa. Here's what Dave would do....Let me first say, that I am not an authority, but I appreciate the vote of confidence.

1. Do not worry about your boat bottom. It's still Ok. My old boat has a destroyed interior bottom, just character. The new bangs it gets every time out are unnoticed!
2. Since it is oiled, epoxy is going to be a waste of$$$ and time. You will get lousy adhesion to the oiled wood. Oil won't protect the epoxy from UV after the repair, so it will end up degrading anyway.
3. It doesn't look all that bad, so you could leave it alone, as you've already committed to the realization it is a working man's boat and you knew going into this with a 3/8" bottom that is going to happen and will need a re-bottom in the future. (mega run on sentence). Probably my first option. I tend to accept things as they are, and when she quits floating, she'll get fixed.
4. Oil the crap out of it inside. Strip that paint off the bottom and oil the crap out of it. Buy two sheets of 1/4" AC or BC (and listen to AC/DC) and oil the C grade face. Nail them to the bottom with the C face down to the original wood, and trim them to fit. Try and set one whole sheet across the waterline. You can do a partial or whole shoe. Then oil the crap out of it. I love my oiled wood bottom. In my parts, I see no need to slicken up a bottom. But everyone here floats different rivers. You could also Coat-it or Gluvit the outside of the shoe for slippy-ness. I find it un-needed and we have skinny creeks here we row.

The theory is- the 1/4" false bottom is nailed to the real bottom and while it is tight, there is still loss of energy when a hit is taken. The 1/4" shoe ends up with the impact fracture and the 3/8" gets a little thump. I rowed my 16' with 1/2" and 1/4" shoe last week in some seriously skinny stuff and we banged all day hard. no impacts on my interior.

The reason I tell you to strip the paint off the bottom is that you want breathabilty. Oil is great because it saturates the wood and is NOT a surface coating. Penetrating. Therefore any water that gets in (inevitable in even the best built wood boats with perfect finishes) will have an escape route out. Any water trapped beneath a hard surface finish will lead to discoloration and rot in the long term.

On the S&G boats that Jeremy, Ukulady and Sandy Pittendrigh make, they are encapsulated in epoxy and glassed inside and out. This is a different repair best described by ukulady and lhedrick.

Good work and good luck in whatever you decide.
Permalink Reply by mark hilbert on April 28, 2010 at 5:41am
Thanks for the replies Ukulady and lhedrick. Thanks Dave also, I ask you in particular because I have read so much information here from you and I think you are familiar with the boat that I have built from reading my previous posts (plus your from westernPA and my grandfolks had a farm outside Clarion).

One thing to remember on The Hanna Platte is that I fiberglassed the outside of the boat, then primered and painted it. So stripping off the paint to get to bare wood wouldn't be easy and probably isn't an option. Could I still shoe it? Do I have to? or are you saying that due to impact and the bottom being glassed the outside doesn't crack but the energy from impact transfers to inside and cracks the un-glassed inside layer. Again I just worry that I am creating a weak spot or potential for a possible leak or maybe as Dave said cracks will happen and as long as they aren't through the entire sheet of ply/glass-keep on floating.

The inside is just oiled and I'm not wanting to glass it now or apply a 1/4" ply patch over the crack if I don't have to especially if this is going to keep happening. Again Thanks all.
Permalink Reply by mark hilbert on April 28, 2010 at 5:55am
lhedrick, I see that you are in Park City, so we may run some of the same waters. I hope to get my boat over to the Green soon to float Red Canyon. As stated in my above posts my concern over a few small inside cracks is that they are from scrapping a few rock beds in some riffles on the slow moving San Juan. I wonder what will happen if/when I have some serious impact with a rock on say the Colorado River. I have a raft and have been floating in that for 10 years but now after building this boat I would like to take it on some of the river that I previously took the raft, nothing big like Cataract or Westwater but some class III stuff that hitting a rock underwater is inevitable. Do you think I might be safe with the boat in her current state or am I religated to having a tailwater/lake boat and need to bring that ugly rubber on my next trip down the river, I rather like the idea of "Pimpin'" in my dory while the rest of the river if a rubber hatch.

Thanks, Mark
Permalink Reply by Kelly Neu on April 28, 2010 at 8:36am
Boats built for the Grand Canyon, Cat, Green, Salmon, etc... usually have 1/2" ply bottom with a bunch of glass but no shoe. (Amount of glass varies wildly)

I think the shoe may make sense on shallow, slow rivers, but if you want to run the Colorado, even a shoe won't prevent a crack or other damage in the big water. What it will do is make repairs more difficult, especially if you have to patch things up on the river. Hits are gonna happen, keep it simple.

People row gently glassed boats down there all the time, though the consequences are a little higher for the big hits.

As for your repair, don't worry about strength of the bottom. Fillet it stronger than wood and a small patch like yours will be bomber. Take out only the soft wood and fillet the rest. If you're careful about what kind of wood flour you use you can even match your colors pretty well.

Hope I see that pimped wooden boat out there!
Permalink Reply by lhedrick on April 28, 2010 at 6:42pm
I wouldn't worry about it. If you want to run Class III stuff have at it. Take a basic repair kit so you can float out if something happens. A boat you can't put a hole in is not worth having. I took an open fishing boat down Deso at about 6000. It did just fine.

If you know the river and you think it's within your ability then do it. That's why we build the things. I hope to get over to the Green Soon.
Permalink Reply by Dave Z on April 28, 2010 at 7:18am
Mark,

It is going to happen again. You are right on- I didn't realize the outside was glassed. You are exactly correct- the hard glassed outer layer transfers the energy to the opposite side where the blowout occurs.

So.... to repair this thing..... I don't know. One thing you could do is sand your paint off of it (or wait till the end of the season when its mostly gone naturally) and laminate another 3/8" sheet to it- this time epoxying it to the old sheet. then re-glass your new bottom. This will make future bottom replacements tougher, but still possible. Anything is possible with a sawzall.

Or, bang the hell out of it, don't worry about it and rebottom this coming winter with a 1/2" bottom and your choice of bottom treatment. You know what I like.

As far as your colorado river questions- you proabbly have the skills as an oarsman. wing it!

I'm going up to camp near Clarion this weekend. Hendricksons are hatching and Turkey season starts Saturday!
Permalink Reply by Chris Patterson on April 28, 2010 at 7:28am
We knocked a pretty good sized hole in our boat's bottom once. My initial thought was simply, "Well, I built it so I know I can fix it."

We ended up cutting out the shattered plywood, building up a patch of resin and chopped glass, and then attaching a plywood shoe. It worked great and looked fine.

That was in my early years of boat building, before I knew about this site and the great guidance that can be found here!
Permalink Reply by AJ DeRosa on April 28, 2010 at 7:55am
Mark,

Here are some thoughts from a framed boat user. Dave is right on when he suggests a 1/4" shoe. This shoe will distribute the impact to the floor. We have experienced the same internal fracturing of the interior bottom. You will see no sign of the hit under the boat but the impact explodes the interior plys. Since it is oiled inside the you need to repair on bare, dry wood. A router set at 1/16" will cut to bare wood. Use a sharp chisel to clean it up. You can now fashion a patch with cloth and epoxy to fix the fracture. Since you have a 3/8" bottom you will continue to experience this interior fracturing so the shoe is important. I beleive you built this with less than marine quality plywood so this is contributing to the problem.
We built an experimental boat out of Okume and had the same problem with interior floor fractures. We used the router trick to expose bare wood and laid kevlar between the frames in the impact zones. This solved the problem. We now lay 6oz. fabric and epoxy on the interior bottom panel before hand and have had not fracturing problems. You can use scrap fabric between the frames and get it fixed but the shoe will help in the long run.
Permalink Reply by Brad Dimock on April 28, 2010 at 9:19pm
As more of a minimalist, I'd say don't do a thing. Just run her 'til the damage is too wobbly and soggy to bear, then re-bottom her. The thing that scares me about adding a shoe is the inevitable rot trap between the layers. Plus you're adding the weight of the shoe and the film of water between, so you're heavier, a bit less maneuverable, and that much more likely to hit rocks. And hit them harder. I think I'd be more comfortable with just visually monitoring the situation, enjoying the delight of a very light boat, and as mentioned below, take a good repair kit. You might get another trip out of her, you might get another ten years.

Sure, you're going to hit more rocks, but most likely not in the exact same place. Our river repairs in Grand Canyon are based on that probability. Bego once patched a giant hole in the side of his dory with duct tape on day one of an eighteen-day trip and was fine. Like he said, "If I hit right there again, it'd bust any patch I put on now, so why bother?"
Permalink Reply by Sandy Pittendrigh on April 29, 2010 at 8:04am
What to do now?
I'd sand that area, inside and out, and cover it with 10oz fabric and epoxy resin.

Being a stitch and glue guy, I'd do that to all the plywood, before assembly.
You get a much stronger boat that way. But you could do that to all framed
panels too. Is there an argument against doing so? Other than cost?

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