Two Questions: 'Caulking' and 'Trunnels'

[tmj]

Caulking: Were gaps left between individual planks to facilitate the Oakum and Pitch, like an expansion joint, or did the planks rub up against each other with only a shallow grove cut into the exterior of the planking to accept the caulking? If a gap was used, between planks, would the Oakum have been driven all the way through, to the inside of the planking? 

 

Trunnels: Were trunnels installed perpendicular to the face of the planks, or would they have been 'angled' for extra strength in holding the planks in place?

 

[Chuck Seiler]

Trunnels (tree nails) were installed perpendicular to the face of the plank.  The trunnel was often split and a small wooden wedge driven into the center to expand the trunnel and keep it in place.

 

HOWEVER...Philadelphia's external planking is nailed into place with iron nails.  They didn't expect the ships to be around long so they were not concerned about them rusting.  IRONically, the ship/boat AND the nails did survive and are on display in the Smithsonian 248 years later.

 

[Dr PR]

I can't speak for caulking on vessels from the 19th century and earlier. But mid 20th century US navy deck planks were beveled on the edges down half the thickness of the planks. This left a gap at the top about 3/8 inch wide. The bottom edges of the planks were butted together and cotton and oakum were driven into the gaps. A tar-like black marine glue was poured into the gaps over the oakum to seal the gap.

[tmj]

On 6/23/2024 at 10:17 PM, Chuck Seiler said:

HOWEVER...Philadelphia's external planking is nailed into place with iron nails.

 Hello Chuck!

I'm going to dig a bit deeper into this. As per John Bratten's book, the bottom planking was 'temporarily' "toe-nailed" to the flooring timbers until trunnels were successfully installed... then the iron toenails were removed. It was only the dry parts of the boat that incorporated iron nails. If this is true, then it only makes since that there would also be 'trunnels' on the sides, below the water line. "Hmm?" I'll study my Smithsonian drawings closely before securing the bottom planking to the flooring timbers. I'm sure that there is some needful info there that I have not looked at yet. I've so far only worked on the dimensions, not the fastening details. 

 

For whatever it's worth. I've already found a conflict between John Bratten and my Smithsonian drawings. Bratten claims that the center strake, of the bottom planking, was a full-length strake running the entire length of the boat without any butt-joints. The Smithsonian drawings show differently. The drawings show TWO seams in that center strake! When looking at the online 3D thing from Smithsonian, I can see one 'obvious' seam in that center strake, towards the stern. The stem section is missing a lot of detail and it's hard to tell if a second seam is hiding there, but it probably is. If Bratten was wrong about the makeup of that center strake... he could easily be wrong about the trunnels too!          

 

[tmj]

On 6/24/2024 at 12:00 AM, Dr PR said:

I can't speak for caulking on vessels from the 19th century and earlier. But mid 20th century US navy deck planks were beveled on the edges down half the thickness of the planks.

Thanks Phil!

 

I was thinking that it was probably this way, but then I started wondering about the expansion of the 'hull' after a new ship was launched and the hull got wet... and then I began to wonder if that expansion could actually 'break' things if not given some room to expand within. Wooden ship's hulls don't have metal bands around them, to hold them together and tighten things up like wooden barrels with metal bands have. The hull timbers that are in direct contact with the water will obviously expand more than the drier parts of the ship (frames) that are mainly only exposed to humidity and will not swell as much. Strakes of hull planking swelling a lot, that are fastened to frames that aren't swelling as much = a lot of stress on both the strakes as well as the frames and definitely the trunnels! I'm sure that you see where I'm going with this. It has nothing to do with building models, but real-life things like this fascinate me. I guess I just like to know how and 'why' things work whether it really matters to me, or not! I've been asking "How and Why" for 63 years. No reason to stop now! 🙂        

[Chuck Seiler]

The wreck in the Smithsonian shows nails above and below the waterline.

 

[Capt. Kelso]

I did some hull reefing on the L. A. Dunton Schooner under restoration at Mystic Seaport, the caulking went through the planking. That could be the result of the wood aging and sagging. When I removed ceiling planks and any excess Oakum from inside the hull, size of gaps in hull planks clearly varied. The hull planks being replaced were not milled to provide gaps for caulking. 

 

[tmj]

19 hours ago, Chuck Seiler said:

The wreck in the Smithsonian shows nails above and below the waterline.

Yep, those certainly look like nails! 

Thanks!

[tmj]

 

Here's that noticeable 'seam' on the aft section of the center bottom strake. Looks like nails there too, however. What about the floor timber just to the left of that seam. There are no noticeable fasteners in that area. There are actually very few to absolutely NO 'noticeable' fasteners shown on the 3D thing, of the bottom of the Philadelphia, as per Smithsonian's online 3D 'thingy'. Hmm, this is becoming even more curious... Perhaps the bottom 'was' tree nailed to the flooring timbers. If so, why the nails in this one isolated area and nowhere else? If you look at the second strake below the center strake, a bit to the right, you will see 'another' seam, but no pronounced indication of nails. I still haven't had the time to study my drawings. Work keeps getting in the way, but I will!  

Image courtesy of the Smithsonian Institution... online 3D viewing tool.

Edited June 26 by tmj

[wefalck]

On modern reconstructions/restorations, they typically bevel the planks that there is a gap of a few mm on the outside. This is necessary to avoid splitting the wood with the caulking iron by accident.

 

Deck-planks on iron and steel ships often seem to have a groove planed in half-way down the thickness in addition to the bevel mentioned in another post above. This served as a sort of 'reservoir' for the oakum, preventing it from being squeezed out, when the planks became wet and expanded and acting as a seal, when they shrank on becoming dry.