Frame repair question from the moaning chair

[wolfietuk]

I finally got the mermaid (20' lapstrake Cruiser) down to the frames. The origional frames are steam bent fir, running solid from gunwales to gunnal. Many are getting sistered because of rot at the keel,and prior inproper repairs. These do not have to be bent on both sides. A few have to be replaced. I am worried about placeing and bending these. Is a butt joint at the keel a terrible thing. That way I only have to bend one side at a time. It will also make the frame easier to get in with the gunwales in place.
You may now beat me up and tell me to get off my lazy butt and do it right.

Rick

[Mrleft8]

(Punch, punch, kick!) Get off your lazy butt and do it right!
If you MUST do it wrong, at least use a long scarph joint and pin them together....

[Paul Maselli]

Okay, How many ways can you skin a cat? I might say that there are really right ways and wrong ways. The wrong ways don't float to the top of the pile for very long, the right alternatives will outway them very quickly.

Think Twice do it Once!

If your gunwales are in good condition and removing them seams like a sin, consider how you'll get ribs in from underneath.

Consider using Oak for your ribs and steaming them full length from gunwale to gunwale. You'll need to cut an acuurate length but the oak can be twisted and bent to get the ends under the gunwhale. I wouldn't recommend this with Fir because Fir will not bend as well as oak. Fir will not broadcast its break at all ahead of time. It will simply explode. But even with oak cut your grain straight from green stock.

Full length ribs not an option, Can you add floor timbers bolted to the keel and bolt the ribs to them. Far stronger than butt joints or scarf joints because the solid floor timber brings another element to the construction.

Whats the percentage of sistered frames? I would consider not sistering but removing each broken/ rotted frame and steaming the new frame into the original frame bay. No need to add more holes to the Hull. This also allows for old loose fasteners to be removed and replaced going up one size in gauge.

Good Luck, Themobileboatwright

[wolfietuk]

after thinking long hours about it, yes I am going to do it right. All frames in the back half of the boat need work. About half have been sistered before. These sisters are being removed as they were screwed from the top and the points ground off on the bottom. These are gong to be replaced and rivited in place. Above the floor line only about 5 of the frames need work. It will not be too visible so I am going to sister these after the turn of the bilge. New frames will be white oak soaked in penetrating epoxy. Existing frames are fir and have lasted approximately 50 years.

Rick

[Paul Maselli]

Don't soak these ribs in CPES. (or any other type of penetrating epoxy) If you soak them while they're green the epoxy wont penetrate much and you'll have a rib that is more brittle to steam bend.

If you hull is not bright on the interior you should paint each frame bay with Kirby's Red Lead paint prior to installing the new ribs. Each rib should be coated with linseed oil just before you place it in the steam box, this prevents excessive drying out in the steam box. Once the ribs are riveted in place you should coat each one with Red Lead paint. Oak is highly rot resistant if sealed well (just don't use iron fasteners). Red lead paint is the best paint for this. It prevents fungus from growing as well as slows down the drying out of the wood and all faying surfaces should have a coat of paint on it. The CPES is good for restoration of older wood and for the adhesion of a new finish, but it should not be used on a rib before steaming.

If your hull is bright inside substitute a good varnish thinned with linseed oil to paint the faying surfaces.

Good Luck
TheMobileBoatWright

[pipefitter]

I know a shipwright that if the accuracy of construction wasnt important,would take an old frame for the pattern and laminate one out of veneers the exact shape and fit as the original.It was also alot stronger than solid wood from a cracking splitting standpoint.He would just trace the frame on a piece of plywood and use nails on the pattern line to shape the epoxied veneers around like bentwood furniture.