Where and how to make the cuts ?

[Dave-Fethiye]

Hi, I have recenently bought a boat that needs some repairs to the hull as it is suffering form rot in one place.

The boat is 40' motor yacht all in wood. The hull is pine and I have bought some pine planks to replace the rotten area.

I pulled off some of the rotten wood and found that the planks have been nailed in with galvanised nails.

I have done a bit of reading up pn this and I've learnt that I should be using silicon bronze screws 1 3/4" long ( my planks are 1" thich and frames are 3" deep )

I read that I should NOT put butt joints on the frames but use butt blocks. Or I could use a plain scarf jiont and glue it.

My question is this - How do I cut the plank on the the boat so as to make a nice sloping uniform scarf without damaging the adjacent planks ?

I have a gigsaw and a circular saw (electric) but dont see how I can use either to make a decent cut without touching the planks next to the plank that I want to cut.

Any ideas on this ?

Some photos below.

(Sorry couldn't upload them becuase file size limit is SOOOO LOOOWWW )

Thanks for any advice.
Dave.

[oakman]

Layout your scarfs where you want them and with the slope you desire. Drill a small hole middle of the area you wish to remove, insert jigsaw and cut verticaly, almost to edges of plank you are removing. Finish this vertical cut with hand saw of choice.

Next, layout scarf and mark ends, now with a handsaw, very sharp!, begin to make horizontal kerfs the length of the scarf. cut towards the back of plank at exposed endgrain first, keeping the saw at about half the final slope of he scarf, stop about 1/16 from the back of plank. Now, continuue cutting back toward outer surface of the plank until the edge of the saw defines the slope of your scarf. Do this multiple times till you have cuts whose bottoms define the slope of your scarf.

Finish by chopping out excess with chisels and finish surface with planes. Practice on something you don't care about. Lot's of hand work here but that is the safest when working with planks hung on the boat.

[sdowney717]

I did not plane planks. I did resaw them on a 12 inch table saw within 1/8 of the original depth. After hanging them, I belt sanded them smooth to the original dimension to evenly match the other planks. I was working with african mahogany.

I also replaced entire planks. The few I did not I butted the short replacement ends on using long pieces of SB threaded rod as dowels. I drilled holes in the plank ends, pushed in the metal rods into matching holes in the other piece. And glued it together with PL premium glue mixed with a little sawdust. and clamped it flat with a temoporary backer block. I did this with the planks attached to the boat as it would be bad to have a glued on replacement end running at an angle to the entire plank. This way I did not have a butt block, And the pieces I 'scarphed', you cant even tell they were added.

But see, I like to do things my own way even if its harder to do than everyone else would say.

If the boat is in salt water how long will galvanized steel fasteners last?

[Bruce Hooke]

Let's just say that to the best of my knowledge sdowney717's technique for joining one plank to another end to end with threaded rod as dowels is very much not standard practice. If nothing else this could cause you problems if you need to get the boat surveyed in order to get insurance or in order to sell it. Of course the surveyor might easily miss such a scarf, but this hardly seems to me to be justification for considering the method acceptable. If such an unusual technique was employed on a boat, an honest person would tell the surveyor up front rather than hoping they don't notice.

[Roger Cumming]

I would strongly recommend getting a few books about boatbuilding, such as Boatbuilding by Howard Chappelle and educate yourself a bit. There are many boatbuilding techniques that seem odd or needlessly laborious but are nonetheless proper. They may seem odd or laborious to you because you are unaware of the way the parts of a traditional wood boat work together in service - when the boat is moving through the water. Butt blocks are how planks are spliced together. They are shaped and fastened in a particular way that has proved to work well and last and to lend itself to be easily repaired. It is not a coincidence that boatbuilders tend to employ similar or identical details in building wooden boats. The amateur, armed with a few hand tools, some time and most importantly some knowledge can do a creditable job of repairing a boat. If you leave out the knowledge part you will just make a mess of it.

[kc8pql]

I pulled off some of the rotten wood and found that the planks have been nailed in with galvanised nails.

I have done a bit of reading up pn this and I've learnt that I should be using silicon bronze screws 1 3/4" long ( my planks are 1" thich and frames are 3" deep )

It's not a good idea to mix fastener material below the waterline. Unless you plan to refasten the entire hull with bronze, stay with galvanized fasteners. Mixing the two will cause galvanic corrosion problems.

[Dave-Fethiye]

Thanks for that "don't mix the metals". I have now scrapped my plans on using SB screws - I'll stick to the galvanised nails for the repair work.

The local carpenters say that they would just butt joint on the frame. This maybe because the frames they use here are pretty thick and bolted together as pairs. This makes for 4" thick frames with distancesw in between frames ranging from 8" to 12". There maybe making a butt joint on the frame is valid :confused:

I wish I could upload a photo to show the construction detail but it is 284kb jpg. Why is the limit set so low on this forum ? really there is no point - disc space is sooo cheap these days :(

Thanks for advice.:)

[Paul Girouard]

I wish I could upload a photo to show the construction detail but it is 284kb jpg. Why is the limit set so low on this forum ? really there is no point - disc space is sooo cheap these days :(

Thanks for advice.:)


Set up a account at "photobucket" (google it ) , upload your photo's to the free site , once you have that done you can C&P them over.

There are other free photo server site out there and some you pay to use.

It sound like a lot of work but once you've done 5 or 10 photos the "process" becomes easy. The first 5 are a PITA . Till you remember / know all the steps.

[pipefitter]

Thanks for that "don't mix the metals". I have now scrapped my plans on using SB screws - I'll stick to the galvanised nails for the repair work.

The local carpenters say that they would just butt joint on the frame. This maybe because the frames they use here are pretty thick and bolted together as pairs. This makes for 4" thick frames with distancesw in between frames ranging from 8" to 12". There maybe making a butt joint on the frame is valid :confused:

I wish I could upload a photo to show the construction detail but it is 284kb jpg. Why is the limit set so low on this forum ? really there is no point - disc space is sooo cheap these days :(

Thanks for advice.:)

They must be modern,rough frame carpenters. I have repaired many a fascia that used the quick and dirty butts over the correct mitre scarfs. The end grain butts swell and cause the caulking to fall out and become noticeably unsightly in a short time and this with a drip edge that keeps most of the water off of them. Look at the rest of the planks in the boat and you shouldn't find any scarfs over frames.

Believe it or not,I used to watch the old timers remove the fasteners a couple/few frames back from the joint and cut them in place on the boat without removing the plank(carvel planked) entirely, while standing on a ladder. They would cut most of the part off that was bad so that there was a short piece to fall off so as not to bind the saw as it started to complete the cut. It didn't take long at all and you couldn't tell it had been repaired. Some cases it is better to cut further back than the obvious damage if it is in a tight curve in which to move the joint to a less stressed part of the hull. if the damage was 2 ft long towards the front of the boat,they still might scarf in a 10 ft'r.

[Bruce Hooke]

The local carpenters say that they would just butt joint on the frame. This maybe because the frames they use here are pretty thick and bolted together as pairs. This makes for 4" thick frames with distancesw in between frames ranging from 8" to 12". There maybe making a butt joint on the frame is valid

"Carpenter" usually means someone who works on houses and suchlike. Unless said carpenters also have experience working on boats I would not give their advice too much weight. Boat building and boat repair is really rather different from house building and house repair, and something that might work OK on a house could be a disaster on a boat.

[Lew Barrett]

I'm with Roger in that I'm unclear why you're unwilling to join the planks with a standard between-the-frames butt block. Done with the usual care given to placement and craftsmenship, this is a legitimate and un-noteworthy approach, relatively easy to do and redo, and acceptable to owners, future owners, and surveyors.