Broken frames over keelson

Hi everyone
Just new to wooden boat repairs after playing in them for years. I own a 30 foot carvel built boat. The boat is about 35 years old and i am in the process of giving it a complete makeover. I have stripped the inside of the boat and exposed all the interior structure. My main worry is that the frames are broken directly above the keelson. The frames are OK elsewhere.
My understanding is limited in this area on why they may have broken at this particular spot and what to do about them. Hopefully someone may throw some light on the subject. Photos are attached
Thanks very much

 

Those are tension cracks/breaks and a common problem. They're caused from movement, most often wet/dry cycling, but also from hard/long use.

There's a few different ways to repair them. The most common is a "sister", which is a section of frame stock, of the same dimensions, that is placed directly beside the break. They usually extend at least a full plank width in each direction away from the break, though more is better. They are fastened to the old frame with screws or roves (like your planking). This assumes the original frame is still solid enough to receive additional fasteners.

These tension cracks will also be present in other locations, if your hull is typical of the ones I've seen. These places would include the turn of the bilge in the aft sections and the forefoot areas. If there is a particular massive sheer clamp/shelf and strake combination, expect some tension cracks a plank of two below, on some of the frames as well.

I prefer to scarf in a repair, because this type of fix looks just like the original when finished. This is a little more difficult for the novice to fit in place, while crawling around in the bilge.

 

Scarfed or sistered, the frames will need be repaired/replaced.

Avoid travel lifts with carvel boats too whenever possible, the old patent slip is far kinder to a fragile wooden boat.

 

Travel lifts are okay, if you place the straps properly and have enough of them. Though a dock is a much better way to treat an old lady as Lubber suggests.

 

Not sure but it looks like there's not been adaquate ventilation in the keel area so making it better is the best quarantee for long lasting repairements.

 

The one image shows what appears to be mild steel, possibly an engine bed brace. I also see some mild steel fasteners very close to the bronze roves. These dissimilar materials have to be causing havoc with fasteners and their surrounding wood.

 

Thanks
Par you are correct one of the image is of the engine bed. I have been all over the inside of the boat and have located no further damage to the frames ,stringers , etc The only repair work appears to be about 12 broken frames along the top of the keelson. If not repaired I would guess that the boat hull would eventually loosen up. One question i have, would not the floor structure hold this section of the boat together and work in with the frames.
As for repairs, it seems that the best way is to scarf a join one to two planks either side of the keelson after knocking out the fasteners from the planks. I would hope this can be perform on the slip along with a few other jobs

 

Unfortunately, blocking height will limit your ability to make fastener removal and easy task. Try to get them to block her up high enough.

A scarf only works on a sound frame, so cut back until you're into good wood, then make the scarf tapers. If the frames are next to each other, consider doing every other one, to insure the boat doesn't lose shape or integrity during the process.

Get the iron (mild steel) out of the boat. It's killing the bronze fasteners, if they're not wasted away already.

The sole support structure is probably helping hold things together, but was never intended for this level of cooperation. The steel engine bed brace is also doing a fair job of it too. This is a common addition to boats. A wooden one will work too, if you have the room, because it has to be considerably thicker then metal. You can also employ athwart "tie rods", which lock the beds in place, but you don't see them much any more. The nice thing about these is they're usually out of the bilge water, so not contributing to corrosion issues.

 

Could those cracks have happend because the wet boat was grounded over a rock. Left over a tide or two, then floated off?

On one of my old wooden derilects, I found some cracks when I was wirebuffing all that trashy looking scum off the interior. They ran it aground when they thought it was sinking. Left it on the beach for a week.

My Trashy looking scum came from the engines and Bateries being submerged for awhile and all the fluids really smeard the bilges and the first deck.
I'd have been better off with a Steam cleaner but couldnt afford it at the time.

 

Impact damage makes a different type of break, plus the fasteners would be moved a fair bit too. The roves here, haven't moved (one has), the wedges haven't moved, the fasteners in the keel would have depressions around their heads, etc. with deflection damage (a strike or grounding). Tension cracks or breaks are almost always perpendicular to the frame, usually at the the fasteners. Some times they'll start perpendicular, then follow a stress line within the wood, then going perpendicular again, as if the Golly Green Giant grabbed the frame and pulled on it's ends until failure.