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Thread: Commander 147

  1. #106
    Join Date
    Sep 2001
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    San Rafael, CA
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    3,617
    Jerry, Excellent,
    spiffy companion way there!

    And the new proposal for the compression beam and bulkhead is obviously a vast improvement.
    It'll be a perfect upgrade.

  2. #107
    Join Date
    Sep 2001
    Location
    Northern MN
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    1,100
    Nice work, Jerry! She is looking F I N E!! Having the wood prefinished before final install ought to really speed things up in the assembly phase. And I can't say enough that your expert craftmanship shows in your work.

    What's the plan with your mast beam and main bulkhead? Solid beam? Laminated beam? Laminated beams are easier, in my opinion, but solid may have less integrity concerns when it comes to glue choice, water intrusion, etc.. And how about the bulkhead shape? Honestly, I kind of like the shape you got in the photo with the pieces, that I assume are braces, meeting the existing Commander style bulkheads.

    P.s. 'Glad you have the surgery behind you. Post procedure recovery really throws me of kilter for a while.

    DOH! I just saw the yellow overlay on your photo. Looks fantastic!
    Last edited by Tony G; 09-10-2010 at 09:28 AM.
    My home has a keel.

  3. #108
    Join Date
    Sep 2008
    Location
    Brooksville, FL
    Posts
    720

    Thanks everyone

    Tony

    I would love to get your input on my plans which by the way is an open invitation to everyone else also. The best part of this or any forum is getting insight and ideas from others on what you are trying to accomplish.

    My plans currently are to vertically laminate white oak for the strong back. I'm using resorcinol glue to eliminate water and glue issues. I've kind of drawn in the new bulkheads in the photo below to better illiustrate the new look with the new bulkheads. Then I drew in some sections so you can more easily understand the plan of what I'm planning to do. Please feel free to offer suggestions.

    I plan to use 1/2" marine ply for the bulkheads and cover it with 1/4" mahogany ply for looks. For the trim material on the edge of the bulkhead I plan to glue up thin strips of mahogany (as thin as 1/16" if necessary to make the curves) that will end up 3/8" thick and follow the curves of the bulkhead.
    Attached Images    
    JERRY CARPENTER - C147
    A man can succeed at almost anything for which he has unlimited enthusiam.

  4. #109
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    Sep 2001
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    Northern MN
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    Jerry,

    My input is start right now. What you have planned is fantastic. Clean and functional and why ask for anything more? Maybe Ebb has some wisdom on the vertical laminated beam he can add but it seems a ok to me. I never thought of laminating in that orientation... And resourcinol is the glue to use. (I wish I had used it so that nagging fear would go away)

    I am already envisioning the pictures. She is going to be saw-weeet.
    My home has a keel.

  5. #110
    Join Date
    May 2008
    Location
    Excelsior, Minnesota
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    325
    Looking great Jerry! Your companion way looks first rate. I wish I had the old style. My strong back is of similar dimensions and also white oak. I used West sys. and stainless dowels. Its only been two years but it hasn't busted yet, knock on wood. I like the look of your bulkhead.... but dude.... chicks dig doors!
    Mike
    C227

  6. #111
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    Sep 2008
    Location
    Brooksville, FL
    Posts
    720

    You might be right Mike...

    But the three "chicks" that matter most to me are the admiral and my two grown daughters who are all OK with the curtain as long as there is a mechanical means of keeping it closed when in use. And the admiral has a custom window treatment business and already knows how she plans to make it. So I guess I'm lucky this time.

    I spent some time today making templates for the new bulkheads. So far they are just partial templates, I need to do some demo tomorrow to make the bottom part but tonight I want to start bandsawing the strong back. Here is a picture with the partial templates in place with the template for the strong back. I tried in the second picture to stitch two pictures together to get a more complete view of the whole area but it only "kind" of worked.

    The layout did not work out quite like I thought it would. I tried to make the upper portion of the bulkhead slant parallel to the cabin side. And I wanted 10" of support under each side of the strong back. What you see is the result of those efforts.
    Attached Images    
    JERRY CARPENTER - C147
    A man can succeed at almost anything for which he has unlimited enthusiam.

  7. #112
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    Sep 2008
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    Brooksville, FL
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    What a difference an inch makes...

    I just was not happy with the look of the bulk heads yesterday so today I took another inch off both sides and I'm much happier with the look of the layout. See for yourself below.

    My biggest concern is that now I have 2 more inches of unsupported distance between the bulkheads. The total distance unsupported is 35-3/4". I know the beam will be stronger when glassed to the deck tying it all together but I still feel the need to find some way to test the strength of the beam. I would like to see it capable of handling 2500 lbs. Do any of you have any suggestions?
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    JERRY CARPENTER - C147
    A man can succeed at almost anything for which he has unlimited enthusiam.

  8. #113
    Join Date
    Sep 2001
    Location
    San Rafael, CA
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    2 cents worth.
    Early on in A338 I decided to replace the original sawn beam with a laminated one out of white oak and epoxy. Not the best choice.
    On the last current page in ebb's gallery thread you can read what I later decided to do
    because I really don't think that white oak can be glued.....totally, including with resorcinol.

    If I was to do it over again and I couldn't find the scantlings in a piece of oak to band saw the single piece out like the original
    I would definitely do the beam with vertical pieces as you suggest.
    BUT also mechanically lag the pieces together with BRONZE screws.
    Iron is a notorious enemy of oak, so I would not use even 316.

    I really can't imagine the arch being bent by the downward pressure of the mast.
    If the arch is non-bendable even when supported by partial bulkheads then the arch must be made immovable.
    Gluing it to the roof is a good idea. So to the bulkheads with thru fastenings.
    You might think about adding gussets on the inside, on the other side of the beam.
    This can be done by adding a piece of solid oak as a strut along side the cabin down to the hull.
    The struts would completely immobilize the ends of the support beam.
    Imco I would not depend on the bulkheads alone to hold the beam in place.
    If you do you are only adding support off the side of the beam even if you thru-fastened it to the bulkhead.

    Since you are band-sawing the vertical beam pieces out you don't have to have a parallel sided
    lamination. You can increase the thickness of the beam as goes toward the ends. Yousometimes see bridge structures that do this.
    In other words the exposed part of the beam would LOOK like it got skinnier in the center of the span. But you could keep the scantling you are happy with but increase the height of the beam as it goes toward the bulkhead supports - essentially loosing no head-room.

    Could also add extra width to the beam, an extra vertical lamination.
    Last edited by ebb; 09-12-2010 at 11:55 PM.

  9. #114
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    Sep 2008
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    Brooksville, FL
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    Ebb

    I always appreciate your 2 cents worth.

    I will take your advice and use bronze screws to lag the beam together. I already bought some #12 x 2" screws that I had planned to use for the combings. I can drive them in from both sides and they will overlap a 1/2" in the middle.

    Did you notice my plan to use a double bulkhead with lumber spacers between in post 288? In the area under the beam ends I will use white oak spacers between the two sides as posts to transfer the load all the way down to the hull.

    BTW what were the final width and height dimensions for your strongback?
    JERRY CARPENTER - C147
    A man can succeed at almost anything for which he has unlimited enthusiam.

  10. #115
    Join Date
    Sep 2001
    Location
    San Rafael, CA
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    3,617

    gluing white oak

    another half cent.
    There have been reports in forums of failures with both resorcinol and epoxy gluing white oak.
    Each report does not go into full depth of what happened, Moisture, clamping pressure, actual kind of white oak, temperature, loads, weatherability (UV, shrinking, expanding).
    Failures could be due to anything - lousy glue or not carefull measuring of Parts A & B. Resorcinol has a shelf life as well. There have also been many triumphs and total success.

    All woodworkers agree that laminations should include redundant mechanical fastening.
    Especially horizontal load bearing laminations.

    It is the acid in quercus alba that the epoxy doesn't like.
    One worker says he has had success rough sanding faying surfaces JUST PRIOR TO GLUING.
    Not allowing the wood oils to come to the surface. As we might suppose there may be an adverse oxidation on the wood surface that acts as a debond. This rings true to me - unscientifically.

    Your vertical glueup won't pop off veneers when weight is put on it - which is what happened to laminations I've done.
    The glue-up pressures in curved veneer lamination can be severe and glue can be squeezed out of the joint.
    If you are laminating with epoxy you might consider a layer of cloth in the glue to preserve the glue line. The horz-lam beam in A338 is done that way. The vertical mode won't require enormous pressure.

    You will probably be building up a baulk and cutting it out on a bandsaw.
    You be able to see the insides of your glue lines to see how well you did.
    You also will be encapsulating the beam in epoxy, which will go a long way to stabiliizing it.

    For resorcinol you'll want freshly milled surfaces to start and perfectly sustained temps. Lots of clamping pressure.


    Why not use trenails instead of screws - expensive screws - to marry the glue-up together.
    Drill holes through the completed lamination and glue in white oak DOWELS. 5/8" D comes to mind. Drill the holes thru face to face.
    Ebb would skew the holes slightly in various directions so that there would be no way the laminations could come apart. You'd never be able to drive a sharp chisel into a glue-line to see if it would pop loose.
    Wouldn't happen. Trenails, better than screws. whatdoyouthink?

    Have to turn your own dowels probably. Or 8 side square stock and hammer through a die plate. I think the key to using epoxy successfully on white oak is freshly prepared surfaces and 100% solids epoxy. NO solvents. No solvent prep of the wood.
    Since there are so many variables there is no guarantee that it will be successful.

    Bronze screws will look better in those coamings!
    __________________________________________________ __________________________________________________ ___________________
    Have to add: I glue many pieces of wood together using laminating epoxy.
    Saturate surfaces, then wipe them 'dry'. The glue is epoxy mixed with fumed silica. Use the wet out brush to apply the fairly stiff gel. You can get pretty even coverage by smooching it around.
    You cover both faying surfaces. When you press them together it is impossible to squeeze out all the gel glue.
    You have a glue line and successful bond. In other words you can't glue with plain jane liquid epoxy.

    I have never had a failure (but never used it for curved lams) with Smith & Co's All Wood Structural Epoxy. (google this: Oak and Teak Epoxy Glue - You Can Depend On It ---smithandcompany.org) It is a 2-part viscous thick material formulated for gluing wood to wood. There is a Steve Smith style tutorial immediately available on the website telling you how to use his glue. It's probably expensive - don't know about S&H.
    Won't recommend System 3 - T-88.
    Last edited by ebb; 09-13-2010 at 12:16 PM.

  11. #116
    Join Date
    Apr 2008
    Location
    Forsyth GA
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    396
    Jerry, The companion way looks great, the hatch handle is a great two function bit of work, handle and splash guard. Thanks again for your old companion way trim it worked perfectly for my Electra, an odd note, all but one screw hole lined up with my original holes.
    I seen somewhere you wanted to test the strength of your laminated beam to the tune of 2500lbs. How about the same way the strength of fiberglass layups were tested in the 60's, lay the beam in your driveway and drive your pickup on it and measure the flex. Carl

  12. #117
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    Sep 2008
    Location
    Brooksville, FL
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    Carl

    You're the second person to tell me to drive a vehicle up on the strongback. I might have to give that serious consideration.

    Glad the piece worked out for you, how amazing is it that the screw holes lined up????
    JERRY CARPENTER - C147
    A man can succeed at almost anything for which he has unlimited enthusiam.

  13. #118
    Join Date
    Apr 2008
    Location
    Forsyth GA
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    396
    Jerry,
    I guess the one guy with the tape measure may have built our boats!!!!! LOL
    I wasn't kidding about driving on it, although you could try jacking the truck up with a floor jack and then lowering the tire on the strong back so you can monitor the flex if any.

  14. #119
    Join Date
    Sep 2008
    Location
    Brooksville, FL
    Posts
    720

    Strong back update

    Well...after feeling unsure of the actual design specs needed to support my mast and knowing I did not want a problem down the road I decided to enlist the help of a professional.

    I started off by sending an e-mail to Jim Taylor who designed the entire Precision line including boats up to 28 feet that used strong back designs. He has also been involved with the design of the Sabre Spirit a 36'-8" daysailer along with 5 other Sabre boats. And that just touches the tip of the iceburg for what Jim has worked on. When I contacted him he put me in touch with Steve Koopman who is the marine structural engineer that Jim partners with on his designs. Steve's business is SDK Structures and he has been involved in projects like Alinghi, and Speed Dream - the quest for the fastest monohull on the planet. So I feel very comfortable with his ability to produce sound structural design work.

    The cost to have Steve provide me with an engineered design that would allow me to safely support my mast turned out to be in my opinion quite reasonable. So a deal was struck and Steve has designed my strong back for me. Unlike most Ariels and Commanders my strong back has a pretty wide unsupported area that is designed to be as wide as 39". I wanted the more open feel that this would give me in the small commander cabin.

    Steve tells me the loading on this beam came in higher than either he or I had first suspected. He told me the compression loads are maxing out in the 7000 lb range. So to manage the load with my 39" wide unsupported span I will be using carbon fiber caps top and bottom on the laminated mahogany beam. Here is the design I will be using see the first picture below.

    As of this last weekend the old bulkheads are out and the old tabbing ground down a lot to allow for the installation of the new bulkheads and beam.
    Attached Images      
    JERRY CARPENTER - C147
    A man can succeed at almost anything for which he has unlimited enthusiam.

  15. #120
    Join Date
    May 2008
    Location
    Excelsior, Minnesota
    Posts
    325
    Jerry,
    How goes your project?
    I have not been able to even start anything on my winter project list and am getting worried that I won't find a slot to get her into the shop before spring. I guess its good news we're so busy but I would like to get The Princess into the shop for a week or two.
    I think my experimental battery bank (4 group 27s) has served its purpose after two years and the voltages are starting to vary between batteries by upto a volt. They are still good enough to serve as house batteries on some other boats, so I'm planning on replacing them with a more substantial bank. I think I'll mount most under the cuddy sole where I took out the 500lbs pig and leave some in the chain locker to help balance the boat. I was pretty happy with the range of the 77 ah pack but I think perhaps I was biting too deeply into the depth of charge and shortening the life abit. Also I had to send my charger in to be checked and adjusted as it was failing to go into float mode and boiled the batteries a couple of times.
    I'm just starting the process, have you done much research? What have you been looking at as far as brands and types? Have you landed on anything yet or found anyone you would deem a clear leader in the field of the Lead Acid batteries? Have you abandoned the idea of Lithium ion? I don't know if I could swallow the cost.
    Mike
    C227

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