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Jeff D

Torsion Box Roof construction

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Hello,

 

I am a newbie and a future BJ boat builder/owner. But first I need to finish work on my existing 43' Pearson Portsmouth fuel consumer. My flybridge bimini top is shot and I want to build a hardtop. But it needs to be light so it soesn't change the CG too much and due to the fact that it will need to be lowerable as I have to drop it to get under a 15' bridge everytime we use the boat.

 

In the build pictures I see the pilothouse roof and forward deck are Torsion Box construction. I would like to get more information on this technique. Is it part of BJ standard plans? If I knew for sure which BJ I would build I could spring for the plans and modify for my rooftop. Or does anyone have a reference that I could check out?

 

Thanks in advance and I sure enjoy this and the various builders blogs and pictures. Someday I may join thos ranks....

 

Jeff

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Hi Jeff,

Welcome to the group.

There are in the Bluejacket plans two options for the roofs, one is just two layers of 1/4" plywood glued together and the other is a sandwich made up by a bottom layer of 1/4' plywood, 3/4" ribs about every 6" with rigid insulation in between and a 1/4" top layer of plywood. Some used beadboard plywood for the bottom layer for good looks.

The second is the better option since it eliminates condensation and provides a bit of insulation.

Both types of roofs are built on a rounded form made out of 2x2 lumber spaced 6" apart.

On the Wooden Boat Forum look at the building of a barge by Waltwood. 

http://forum.woodenboat.com/showthread.php?201767-Building-Another-Barge

He used a product called Carbon Core, a lightweight honeycomb sheet.

 

Good luck with picking out a Bluejacket model.  I have a 25 foot version.  https://www.flickr.com/photos/ejds33/

 

Egbert

 

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I guess I should enter this discussion.  On the Bluejackets, I expect that both decks and pilothouse tops will have people walking on them at times.  The foredeck especially may have the occasional jackbooted dockman jumping on it.  Therefore each was designed to suit the expected loads that would be placed on it.  I specify 1/4" ply for the top layer but 3 or 4mm is adequate to handle the tension loads on the bottom of both.  Spacing of internal ribbing (laminated 3/4" beams) is also closer in the foredeck for the above reasons. 

 

In Jeff's application, there will not be any need for supporting heavy or concentrated loads on the structure so it can be designed and built with this in mind.  I would choose 4mm ply for the top and bottom skins and perhaps less interior structure as well.  The foam is not only for insulation although that is a plus.  The blue or pink 3/4" styrofoam also offers rigidity and additional support for the thin skins.  The more curvature that is built in, the more rigid the structure will be.  Depending on the area of the hardtop, wind loading may be a factor and the mounting must be strong enough to handle that when the top is extended.

 

If Jeff sends me an email, I can email a drawing of the BJ pilothouse top with notes of recommended differences.

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Thanks to each for the help. 

 

Egbert - I just consumed 1/2 of boss' time checking out your Flicker. Very nice work.

 

Oyster - Do you have a Flicker? 

 

Tom - Thank you for the drawings.

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I do not have any photo albums like Flicker. I do good to be able to log in on the forum. ;):D  Egbert's album is a great resource though for detailed constructions for the BLuejacket for sure.

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Thank You,  

 

I'm pretty bad at taking pictures.  We are currently floating in the St. John's river with two other Bluejackets  after spending two nights in different campgrounds with the boat what they call boater homing.

 

Oyster, you should put your pictures up somewhere.  It is for sure a build with a lot of different ideas and building methods.  I wish I did it that way for the bottom when I was laying on top of it trying to work on the keel and the area around it.

 

Egbert

 

 

0227171027a.jpg

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Are any of you St John's floaters going to make it to west coast Florida? If yes, home cooking awaits you. We are on the Alafia River of of Tampa Bay and would welcome cruisers.

If you can't make the West Coast, I would love to see some live BJs and could drive to St John's. Any one going to be around for a bit?

Jeff (a wannabe BJ builder)

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"Boater Homing" Now that's a new term that needs to be added to the sales brochure.:D When you get time, tell us about the boarding ladder that's showing. Is it a collapsible one that you carry, and purchased off the shelf?

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The ladder is not collapsible, that would have been nice.  My neighbor welded it together from aluminium.  I put  a couple of lawn mower wheels under it to drag it in the back of the pickup.  It is the right height with the side door to get in and out.  Too stiff to climb over the transom.  

Not all campgrounds take boats so it is advisable to plan and call ahead. The two nights we did  where a good experience.  Cheaper than a motel and you don't have to worry about the boat in a parking lot.

 

Egbert

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On 3/1/2017 at 1:52 AM, Jeff D said:

Are any of you St John's floaters going to make it to west coast Florida? If yes, home cooking awaits you. We are on the Alafia River of of Tampa Bay and would welcome cruisers.

If you can't make the West Coast, I would love to see some live BJs and could drive to St John's. Any one going to be around for a bit?

Jeff (a wannabe BJ builder)

I did send you a message with the details.  

Egbert

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48 minutes ago, ejds said:

The ladder is not collapsible, that would have been nice.  My neighbor welded it together from aluminium.  I put  a couple of lawn mower wheels under it to drag it in the back of the pickup.  It is the right height with the side door to get in and out.  Too stiff to climb over the transom.  

Not all campgrounds take boats so it is advisable to plan and call ahead. The two nights we did  where a good experience.  Cheaper than a motel and you don't have to worry about the boat in a parking lot.

 

Egbert

Thanks, Hope you are having a good trip so far. Post some scenery shots if you get a chance.

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I guess I need to throw my hat in the ring on this subject.. The wife and I did the Great loop with our BJ 28.. in 2014-2015.. The boat did well .. This year we trailer-ed our De De to Florida for 2 months of boat time.. Boga Chitta, St Lucie river.. Okeechobee waterway to Ft Myers and back and then a week with Two other BJ25.5 .  All went well.. Unlike Egbert, the wife and I often overnight in Cracker barrel parking lights or Walmart.. Its free other than buying a meal.. We also do this with the 5th wheel RV when going from one place to another.  

 

www.flickr.com/photos/bluejacket28  for build pictures...

 

Henry

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Here are a few pictures from the Florida trip.

Hontoon State ParkIMG_2765.thumb.jpg.0eec4a0cc87c87f5e21008909a235e45.jpg

Boater Homing

0227171027a.thumb.jpg.d0f86ceadcbe783a05d4df78ecf0d472.jpg

Underway

IMG_1147.thumb.jpg.d827b493351009e0255ca0748d3103c7.jpg

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