Rabbet

[Don Case]

On the Discovery for at least half of the ship the bottom is almost flat. The garboard plank will be almost 90° to the keel. Does this mean that the rabbet is very shallow, almost non-existent in that area? 

[amateur]

Not according to this drawing

 

https://commons.m.wikimedia.org/wiki/Category:HMS_Discovery_(ship,_1789)#/media/File%3ADISCOVERY_1789_RMG_J2021.jpg

 

Jan

[Don Case]

Well, I wondered about that but I was under the impression that the edge of the plank should be left square. Wouldn't the angle on the edge of the plank limit the amount of caulking the could be squeezed in there?

[wefalck]

The rabbet is there to keep the garboard plank close to the keel, even if the ship is flexing and twisting in a sea. So most larger seagoing vessels are constructed with rabbets in the keel and the stem.

 

When the garboard sits more less vertical on the keel, theoretically, you have two options for the rabbet, you can cut a square groove (or square notch, if there is a keelson sitting directly on the keel) or you can cut a triangular groove, as usual, but then have to sharpen the edge of the plank to fit. The square groove/notch arrangement would be difficult to get water-tight, as the slightest variation of thickness of the plank in the groove can cause it work loose and the caulking to fall out. If you have a triangular groove, you will be wedging the garboard plank into that groove and it cannot move in any direction.

 

However, whether it is worth to replicate this on a model is another question. One cannot see this, once the planking is finished and you can arrange the rabbet in the way that is easiest to make - that is when you only care about appearance and don't want to reproduce actual building techniques.

[Don Case]

6 hours ago, wefalck said:

The rabbet is there to keep the garboard plank close to the keel, even if the ship is flexing and twisting in a sea. So most larger seagoing vessels are constructed with rabbets in the keel and the stem.

 

When the garboard sits more less vertical on the keel, theoretically, you have two options for the rabbet, you can cut a square groove (or square notch, if there is a keelson sitting directly on the keel) or you can cut a triangular groove, as usual, but then have to sharpen the edge of the plank to fit. The square groove/notch arrangement would be difficult to get water-tight, as the slightest variation of thickness of the plank in the groove can cause it work loose and the caulking to fall out. If you have a triangular groove, you will be wedging the garboard plank into that groove and it cannot move in any direction.

 

However, whether it is worth to replicate this on a model is another question. One cannot see this, once the planking is finished and you can arrange the rabbet in the way that is easiest to make - that is when you only care about appearance and don't want to reproduce actual building techniques.

Thank you. I think I've got it now.