Cockpit Seats

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mdidriksen
Rough Carpentry Apprentice
Posts: 50
Joined: Wed Nov 12, 2008 5:15 pm
Boat Name: Calliope Girl
Boat Type: 1971 S&S 34

Cockpit Seats

Post by mdidriksen »

I just recently completed building new seats for the cockpit of my S&S34 and thought I would post a log of the effort here. Sorry for the long post, but it was a long project.

Like any good project, it included most of the basic phases:

1. Enthusiasm
2. Disillusionment
3. Panic and Hysteria
4. Search for the Guilty
5. Punishment of the Innocent
6. Praise and Honor for the Non-Participants

Unlike most of my professional life, I seem to have managed to leave off the last phase, at least as it is traditionally done.

The existing seats (shown in an older picture below) had been re-fastened so many times that going that route would have been difficult. Furthermore, I had always been unhappy with the design, for three reasons. First, as you may be able to make out in the picture, there are boards that end in very sharp points, which are not very well supported. I always felt like they were a medical emergency waiting to happen. Second, while the frame was made of ¾ inch teak, the slats on top were ½ inch teak and flexed a fair amount when you stood on them. I was always worried they would break. Third, the only way to get into the cockpit locker on the starboard side was to lift the entire seat up and move it to the other side of the cockpit. This was a pain to begin with, but in a situation where time was of the essence (e.g., I have an emergency anchor stored in there) it complicated things.

Here is how the originals looked:

Image

Phase 1 – Enthusiasm

As is typical for me, when taking on a project like this I decided I wanted to do it better than the original, and learn something along the way. This always seems like such a good point of view at the beginning. So I decided that I would build the entire seat out of ¾ inch teak, and further, I would create the frame using mortise and tenon joinery. Of course, I had never done any mortise and tenon joinery before.

After sourcing the teak (really should put this sentence under “Disillusionment” given the cost), I set about building router jigs, one for the tenons and one for the mortises. After scouring the web, I settled on a tenoning jig design that is pretty ingenious and works very well. Essentially it allows you to clamp a board vertically and then route around the end of it from above. Hard to describe, but here is a picture:

Image

The board is clamped vertically against a fence and the router sits horizontally on the table above, which has a big hole in the middle and allows you to route the tenon using a rabbeting bit.

I cut out the main face of the first seat and got to work on the cross pieces that would have tenons routed out at their ends. Here is the main face of the seat:

Image

The shape of the seat is a bit odd and required some difficult work to get all the angles correct. The cockpit is sloped at about a 30 degree angle, and the seat basically sits on this slope, with one side of the seat being about 6 inches tall and the other, towards the outside of the cockpit, only being ¾ of an inch or so. Plus, it gets shorter as you go aft. So the whole thing is sort of a triangular prism shape. Worse still, the none of the angles are 90 degrees (of course). So this necessitated some real thought about the tenons.

The frame I constructed has the face (pictured above) with four triangular “stringers” inserted into it via mortise and tenon joints. The two on each end are off-set slightly (the tenon is off-set towards the inside of the seat in order to make the outer wall of the corresponding mortise in the frame thicker), and the smaller one is at a compound angle. In any event, after a lot of thought and experimenting, I cut all of the tenons. Because the two larger stringers would have had tenons that were more than 3 inches wide, I made these up into double tenons to avoid problems due to wood movement. Here is a picture of one of the end stringers, with a double tenon and the corresponding double mortise cut into the face of the seat:

Image

I was pretty happy with how things went so far, but it was time for Phase 2.

Phase 2 – Disillusionment

I started out thinking I could cut the mortises using a flush trim router bit in my plunge router. After wasting some time on this, I realized it would not work, as I could not find a small enough bit for the tenons (my existing flush trim bit was ½ and inch in diameter). Eventually I decided to use a templating guide in my router and build a jig to fit it. This provided a great excuse for buying a set of templating guides as well as a new base for my router. By the time I sorted out the templates and started to work on the jig, I was past my scheduled launch date for the Spring and there was no end in sight. Why did I wait until March to get going on this?

Phase 3 – Panic and Hysteria

After sorting all of that out, it took me multiple attempts to create a mortising jig that worked. What I ended up with was a modified version of a dado jig, in this case modified such that the router template rides along an edge cut into the top, while the bit rides flush with the bottom. Here is a picture:

Image

Essentially, this is a giant parallel rule. Once you settle on where the mortise is going, you take the board that has the tenon in it and put it in place where you want the mortise to be. You then clamp the jig to the tenon, tighten everything down, and remove the board with the tenon. At this point, you can use the plunge router to create a mortise that is perfectly sized to the tenon you have already cut. It all sounds so simple now, but I built three of these before I got one that worked consistently. I’ve left out all of the swearing, but it was clearly time to move to Phase 4. It was now mid-May and the boat was obviously going in the water before I finished. I was, at least, smart enough to have only removed one seat at a time.

Phase 4 – Search for the Guilty

It was difficult to know who to blame at this point, but obviously it could not have been my fault this was taking so long (right?). I worked through my repertoire of swear words but it didn’t seem to help. Took a break and got the boat ready to splash. She went in the water with only one seat in the cockpit (an old one at that). Ugh.

Phase 5 – Punishment of the Innocent

Listing this as Phase 5 is really not appropriate, as it doesn’t do justice to the reality. It implies that things occurred sequentially, when in fact this phase probably permeated most of the project. Suffice it to say that I spent an inordinate amount of time in the garage this spring and early summer, to the detriment of time with the wife and kids. Fortunately, I’m not allowing them to see this or contribute to this post in order to protect myself. ;-)

Eventually, I got all of the mortises cut, dry fit all of the pieces, made some final adjustments at the boat, and glued everything together.

Phase 6 – Praise and Honor for the Non-Participants

Traditionally the praise and honor provided at this phase gives credit to the non-participants for the success of the project, at the expense of the folks who actually made it happen. Instead, I’ll just say “thanks for your patience (and for allowing me to monopolize the garage)” to the wife and kids.

When it was all said and done, the seat came out very well. The frame was assembled with mortise and tenon joints using west system epoxy, but I elected to use screws and plugs (and epoxy) for the slats.

Of course, when I finished, that was just the first half of the project. After a bit of break, I started on the second seat. This time around it went much smoother and faster. I had all of the jigs built and had figured out all the difficulties once before. The second seat ended up taking about 3 to 4 weeks total to construct, mostly working on weekends only.

Here is a picture of the final result:

Image

I will say that having the seat on hinges is a vast improvement. I can get into the cockpit locker easily and quickly now. Also, the seats are much stronger than the original.

Much of the work was done by hand. Power tools used included a circular saw, plunge router, random orbit sander and drill. I used hand planes (antique Stanley Bailey planes from 1920s) to size and finish most of the pieces, as well as some hand chisels to clean up the mortises, bungs, etc.

If I had to do it all over again, after clawing myself away from the window ledge I would probably do a few things differently, but not much. Mostly I think the experience would lead to a better product the second time around, but for the most part only I would recognize where all the mistakes are in the final product (which is generally the sign of a decent outcome).

All that just to knock one item off of the “to do” list.
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earlylight
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Boat Name: Early Light
Boat Type: 1982 Sabre 34 MK I
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Re: Cockpit Seats

Post by earlylight »

Wow, what a beautiful job and a wonderful bit of documentation. Congrats on a job well done!
Dick Coerse
Early Light
Sabre 34 MK1
Solomons MD

http://earlylight160.net76.net
Skipper599
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Re: Cockpit Seats

Post by Skipper599 »

Kudos to you. Great job! Are you going to apply a finish, or allow them to weather into a grey natural finish?
What dimension, and how much did you pay for the gold? Ahem I mean TEAK?
I am: Bob of Wight.

s/v 'Ros Na Cosquin'
a 'Passage - 24'

There are good ships, there are wood ships, and these ships sail the sea

But the best ship, is friendship and may this always be! ... ... ... A prayer from Ireland.
mdidriksen
Rough Carpentry Apprentice
Posts: 50
Joined: Wed Nov 12, 2008 5:15 pm
Boat Name: Calliope Girl
Boat Type: 1971 S&S 34

Re: Cockpit Seats

Post by mdidriksen »

Sorry for the delayed response, but I don't check this forum on a regular basis much these days. I did not apply any finish to the seats. People stand on them all of the time, so I wanted to leave the teak au naturel so that it has better grip. The seats are now on their third year and they look great and have held up very well.

It has been long enough now that I have blissfully forgotten how much I paid for the teak, but it was seriously expensive. I believe it was somewhere between $30 and $35 per board foot at the local lumberyard (which actually had a nice selection so I got to hand pick the boards). Compared to mahogany, teak is insanely expensive. I thought it made sense (not cents) for this application though, especially given that the rest of the trim on my boat is also teak.

Cheers,

MD
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