The mast beam on my soon paid for A-273 shows no immediate signs of deterioration, but I thought a fun project on an otherwise quiet late afternoon would be to make a door way arch to further strengthen an already strong little ship. This contraption will be bolted on to the vertical members of the doorway, with the ends resting on cut-off pieces of trim. It will also be jacked up snug against the beam, with just a short bronze rod to index it.
It is made of ash, 17 laminations, and measures 1 5/8 square. Should have been one more layer, but when it was all clamped up I saw number 18 lying over in the firewood pile.. It will lower the headroom in the doorway, but at 6'3" I'm already crawling around in there.
So, what's the glue? The big question, right? Subject of many discussions here and elsewhere. Well, contrary to other folks experiences (friends and internet experts) I used Gorilla Glue. Why? Wanted to do this thing right now and besides epoxy it was all I had. Living 65 miles from the nearest city limits your spontaneity.
Since it is strictly not necessary it can acts as an experiment for Gorilla glue without dire consequences.
It will be shellac'ed.
My son did the tops'l schooner (at least that's what he calls it) when he was 9.
Last edited by jan nikolajsen; 03-29-2010 at 10:51 PM.
As I have mentioned before I plan to remove my commander compression post and replace it with a strongback. So today I started reading some of the prior posts to determine the demensions I should aim for on the strongback. Then I started measuring my commander and it seems that there are some differances between the the two boats in the amount of curvature of the deck unless I'm missing something else.
The drawing on page 23 of the manual shows the bottom of the strongback as a straight line from one side of the cabin to the other (or so I assume since the full width is not shown).
ebb said that his original strongback was 4-1/4" tall in the middle and tapering to 2-1/2" tall at the ends and 2-3/4" thick. If ebb's original was straight accross the bottom, that would indicate there was only 1-3/4" of camber from the edge of the cabin to the center.
ephifany said his original was only 3-3/4" tall in the middle but from the picture his does not look like it was flat on the bottom. So I may be making an assumption I should not.
In any case, I have 4" of camber in my deck. I placed a straight edge accross the cabin touching the bottom of the deck on each end and in the middle I had a rise of 4". So I will not be making my strongback straight across the bottom. If I want to end up someplace in the 2" thick area on the ends that means it would extend down 6" in the center. That is a bit much IMHO.
Below is a sketch of the approx. layout I'm looking to do. I plan to make it from 3ea. 4/4 boards of white oak laminated together vertically with resorcinol which will give me approx 2-3/4" thickness. I will butter the top of the strongback prior to putting it in place with thickened epoxy and then tab it to the deck and the bulkhead supporting it which will also be tabbed to the hull and deck. And of course I will have white oak bracing on the v-birth side which will be covered with 1/4' mahogany plywood as will the aft side of the bulkhead.
Any suggestions or comments about the plan?
JERRY CARPENTER - C147
A man can succeed at almost anything for which he has unlimited enthusiam.
Jerry, Just took another look at the old strongback that came out of A338.
It isn't straight across on the bottom as you might think because of the doorway to the forward stateroom. The original door was cased.
In fact the top liner of the opening is often the first indication that something is going on under the mast.
So the strong back definitely looks curved top and bottom - until I sighted along the bottom and saw that the mid part had been flattened (looks like with an AX) obviouisly to square the doorway.
I laminated my 'upgrade' and later decided that it would have been BETTER and SIMPLER to bandsaw the beam out of white oak. And so easy to make the slight chamfer along the top to snug the cabin top.
Commander's have a COMPRESSION POST.
My guess is that the fiberglass of the cabintop can be kept honest with a plain curved beam top and bottom. In other words I think you can skinny the beam depth as long as you still support the center with a post. I might make the beam a little WIDER - to make up for the cheat.
The beam on the Ariel is 4' long.
Not much to get bent even with a point load in the center.
In fact, bet there never has been an actual bent beam in any of our boats.
Yesterday's Alberg Assoc breakfast there was talk of the Triton's beam getting pressed down and the cabin sides getting pushed out!!! Could see the bulging! That just wouldn't happen with our cabins.
Making sure our shortie is married to the cabin top will imco cancel the remotest possibility of that happening in a Commander.
I'd make certain the center post cannot move.
Actually you could scroll into the beam a PAD in the center over the post, to fatten the beam there if you want to skinny it down. You'd do this all at the bandsaw, right? no gluing in anything extra.
That would remove any tendency to bend. In other words, leave the beam deep in the center but scroll out the sides to remove head bangers. Really round the edges, someone's going to head the beam anyway!
In a modern 'engineered' mast compression POST set up they'd probably just have a disk of some material under the mast - with no beam at all!!!!
ebb thanks for the feedback. I'm always interested to hear what you have to say.
So the bottoms were curved also. That explains a lot about the dimensions.
ebb, you may have missed that my whole reason for doing the mast beam is to eliminate the compression post. The unsupported portion of the beam in the center will actually be less than 2 foot wide when my mod is complete.
BTW the Precison line of sailboats made here in Florida are current production models with mast support beams that are made with plywood laminated together and then glassed to the bottom side of the deck. They have only a small portion of the beams ends supported by a plywood bulkhead that is just screwed to the beam. You can see it a little bit in the picture of my old Precision 18.
JERRY CARPENTER - C147
A man can succeed at almost anything for which he has unlimited enthusiam.
Sorry Jerry,
assume is the mother of all foul ups.
The key still is we can have nothing move under the mast.
And each of us has our own unique solution it seems when we stray from the box.
I love the sweet lines of the Commander.
The curve of the cabin roof is particularly pleasing.
Maybe, maybe it's possible to design a kind of 'break water across the cabin under the mast.
Have the beam outside.
If it wasn't a breakwater but a rounded slope sided and gel-coated mound it might just disappear and not mess with the lines.
In discussing sailing Ariel Spirt, one of the possibilities was the idea of sailing her to Puerto Rico. As I considered what I would want to do before undertaking such a journey, the thing that came to mind first was to address the strong back.
I like the idea of the stainless plate sandwich, but getting the stainless bar and having it polished before getting underway was not going to work. I like the earlier post about using large aluminum angle, but hate hitting my head on the doorframe.
Add to that Ariel Spirit has the original bright work trim around the door, which I would not want to mess with that.
Used 5, 5/16" stainless carriage bolts with the smooth sides and stainless fender washers on the cabin side. Not a bad look, and very strong.
I like the angle because the extra angle will prevent the bar from trying to twist. The difference in what I did was that I put the "extra" bit on top. I a very pleased with the way it came out, will post a couple pictures later.
Just learned the person in NC that was buying the boat is going in another direction, so I am getting underway in a bit to sail the ~140 nm across the big bend... Glad to have addressed this before heading off shore.
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