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Seat backs


Al Stead
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Hello everyone,

I have a question about a modification I am making to my weekender.  I have raised the seat back panel in order to make splash commings from the same piece the full length of the cockpit.  I kind of like the look of it, and it provides better back support.  I also made them fairly high.  The front of the piece is about an inch below the roof level and the rear point is about three inches above the deck.  Also I have sealed up the area behind the seat back to provide floatation.  My lazarette is also sealed off from the rest of the boat.  I am concerned about what is likely to happen to the wood in that sealed area behind the seats, as well as any downsides to the structure from doing it this way.  I am also interested in any performance problems with the extra area above the deck. 

I haven't glued anything up yet, so there is still time to undo it if it proves to be a big mistake. 

Al

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I guess your concern is that the enclosed areas will be more susceptible to damage from condensation and subsequent rot, right?

An alternative to enclosed air spaces would be to use styrofoam blocks in those areas, and provide either ports or ventilation slots to prevent condensation.  The Weekender already floats because it is made of wood; flotation behind the seat backs or high in the lazarette is thought to help right the boat if it goes over.  You could have foam blocks high, with free area and storage under it, and provide plenty of air circulation to prevent condensation.

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When I was building my Weekender everyone said that condensation and rot would occur in a sealed space.  I believed them, so I made sure air could flow through the seatbacks by placing air holes at each end.  However I still wanted buoyancy so I glued the tops onto empty milk jugs and secured them behind the seatbacks.  There is a strap that runs through each jug handle and is secured to the underside of the deck.  This prevents rattling.

600710547_97ced574e5_o.jpg

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Thanks Frank and Bill,

I glued up the seat backs today, so they are actually air tight right now.  I intend to cut an access port in the cabin bulkhead to allow for air circulation.  I don't know if that will be enough, but I will at least be able to check if it is.  To provide for floation in questionable conditions I will make a hatch that I can secure over the port.  I painted up all the faces before assembling, using lots of PL premium.  If those joints aren't air tight, I made a big mess for nothing. 

I've had a couple days to look at the high commings and the more I look at them the more I like them.  My weekender will not look like anyone else's that I've seen.  The added back support seems to be about right for my touchy back even if I made them more upright than the plan calls for. 

I'm shooting for launching some time in June: early July at the latest.  This all depends on whether I make any more bad mistakes.  I can't wait to start learning to sail.

Al

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I rebuilt a thirty year old motorhome inside and out.  The walls and ceiling of the coach were supported by steel studs.  When I stripped out the foam insulation, I was surprised to see that the thirty year old steel looked like it did the day it was installed.  This led me to consider whether regular blown in foam insulation, the kind typically used in new home construction might not do the same for wood inside a closed space like the seat backs.  The stuff sticks to pretty much everything and seems to create a water and air tight seal with whatever it is stuck to.  The stuff is kind of spendy, so it might not be worthwhile in a boat like weekender, but it might be worth a sea trial.

Al

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The foam you are referring to is a two part polyurethane and under ideal conditions it works very well. The home builder doesn't usually have these conditions. In the vast majority of cases, the foam does promote trapping moisture in the surrounding wood, which leads to, well you know. The steel studs in the motor home, where very probably zinc coated and fairly tolerant of some condensation. Steel also doesn't attract moisture like wood can, so it's a difficult comparison to make.

In the end, many do use the pourable foams. I have, but no longer in wooden compartments without other accommodations (spacers and poured into a thick trash bag, etc.). The last time I did it in a wooden compartment I used a corrugated cardboard spacer (about an 1/8" thick) all around the sides. I poured the foam into a heavy plastic bag and welded the bag closed when finished. The cardboard was removed and small plastic 1/8" spacers glued to the hull sides in a several locations, so the foam filled bag would "float" in the space. This permits condensation to form and run down the surface, collecting at the low point, without being trapped by the foam block. This takes some planning to do well, but it's effective.

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hello Paul,

Nope, the steel was untreated in any way at all.  In fact after a year of sitting in my pole barn protected from the elements except for atmospheric moisture, the steel had a nice patina of rust over all of it.  That is what got me to thinking about whether  the foam was sealing it up.  I did notice that the bottom of some of the studs had been eaten away by road salt so that I had to weld cripples onto them, so maybe water can mess with it.  Anyway I don't want to take the chance, so the inspection port is going in very soon.

Oh, and thanks for the advice on the epoxy fiasco.  I scraped away alot of wood, but the patch seemed to work pretty well.

Al

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Whaddya know.  Well somehow the image came through.  This is the Jumping Duck.  I named her after our dearly departed Australian Shepard.  I'm going to screw my courage to the sticking place and take another whack at that fiberglassing thing today.  Decks and cabin.  Once I get that all painted up, it should be a quick job to get her assembled and rigged.  I hope. 

You can see the splash commings with the sculpted lamenated fronts halfway cut out.  I'm going to leave those bright, but the plywood will be painted. 

Al

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Yeah, that's what I thought.  I made the cabin a couple inches higher than the plan calls for because of my stiff back.  I also beveled off the main rafter just inside the hatch because I WILL bump my head on it every time I go below.  The higher commings seemed to undo the look of the higher cabin, which is a nice consequence of trying to be more comfortable. 

I glassed the deck and cabin roof yesterday.  The epoxy is still setting up because it didn't get out of the 50's yesterday.  So far no big disasters.  Because it is getting late for her launch, I will not make the port lights this year.  Anything that I can get away without doing now, I am going to leave for later.  It's time to go sailing.

Arrgh! 

Al

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I glassed the deck and cabin roof yesterday.  The epoxy is still setting up because it didn't get out of the 50's yesterday.  So far no big disasters.  Because it is getting late for her launch, I will not make the port lights this year.  Anything that I can get away without doing now, I am going to leave for later.  It's time to go sailing.

I like your attitude!  There will be things you want to adjust and correct after you sail her a few times anyway, and there are only so many sailing hours in a man's life.  You don't want to get a late start!

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