Commander 147

[carl291]

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

[Commander 147]

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????

[carl291]

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.

[Commander 147]

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.

[Commander227]

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

[Commander 147]

Mike

First I'll address your question about batteries.

As far as batteries go I have done a lot of reading on the subject and part of that research taught me that in a battery bank like you and I need, not only do the batteries all need to be the same model and age, but they should also be in the same physical location. The reason is that ambient temperature can cause batteries to charge at a different rate and get out of balance with each other. Which could possibly explain part of your issue. Destiny will be a coastal cruiser so I probably need more range from my batteries than you would being located on a lake. But also like you the added 500 LB lead pig is coming out of Destiny and I really like the idea of a similar amount of weight going back in, in the form of batteries. So my batteries will be these….


http://www.odysseysoutheast.com/pc1800-battery.php

Four of these batteries will fit very nicely on the cabin floor under the forward end of the cockpit. They can all fit in the same location with square aluminum tube under and between them for air circulation and heat dissipation. My charger has a thermocouple heat sensing unit that will go in by the batteries which will keep them from overheating. If the heat climbs to high the charger shuts down until the temperature drops back to a lower range and then it starts up again. Because these batteries have a very large inrush capability they can be charged faster than many other batteries. But in this heavy charging mode than can also develop more heat. So I may decide I need to add a temperature sensitive fan to the battery bank area to assist in the heat dissipation.


I also like that for the same dollars I can get close to twice the range with the Odyssey batteries that I could get with the Lithium Ion batteries. Those batteries are just too expensive for me.

The progress on Destiny came to a screeching halt for a while. Business got so bad that I was down to 30% of my normal income and it meant that all non essential expenses were eliminated. So I put all my effort into doing what I could to turn that around. Thankfully things are improving again so I am finally getting back to work on Destiny.

The construction of the support beam has proven to be more of a challenge than I first anticipated. I am actually on the second attempt and this one so far is going well. The first attempt went bad when I tried to use resorcinol for the glue in the mahogany lamination. I did not have enough open time with the glue to make it in one layup and so I was forced to do it in several steps. The resulting beam started to seperate when I applied the first 20 layers of carbon fiber. And this is too important to take a chance with so it was back to the drawing board.

For the second shot at the beam I used a tropical blend epoxy (very slow setting) to give me plenty of time to get glue on all surfaces and everything clamped up. The beam came out perfectly. Then I shaped it to fit the underside of the deck (no small challenge) allowing 5/16" accross the entire top for the carbon fiber that would come next. Then I layed up 20 layers of 9 oz unidirectional carbon fiber on the top of the beam. After it cured I ground the edges flush with a belt sander and to my delight when I test fit the beam I had a very good fit.

Tonight after work I plan to get everything set up and ready for the 20 layers of carbon fiber and two more layers of mahogany that will go on the bottom of the beam. Then tomorrow evening I can hopefully do the laminating.

Here are a couple of pictures of the beam in it's current status.