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Good points, Bob.
While aligning the windvane rudder yesterday prior to drilling the mounting bracket holes, I happened to pound on the transom with my fist. No, not in frustration. More like a manly man’s kind of “see how solid my boat is” pounding. Only it didn’t feel all that solid. Actually, it felt kind of thin and springy. Hence the question I posed to the group. I already knew what I had to do, but wanted an excuse not to do it. Only thanks to Don it didn’t work. Also, as you sort of pointed out, that rudder is sure to hit something hard some day. So, I am going to lay on some extra roving as he suggested. Now’s the time, hauled out in the yard with the lazarette empty. A little grinding, a little itching and the worst is over.
As for the backing, I do sometimes use 1/4″ aluminum for plates and probably will in this application. As you point out, it’s pretty easy to work using ordinary tools. But to really spread the stress over the broadest area, 1/2″ or 3/4″ plywood between the reinforced hull and the backing plates makes sense to me. Yes, I’ll remember to bevel the hull-side edges, and I always double-coat plywood with epoxy resin for this kind of thing, and make epoxy sleeves for the bolt holes to preclude water intrusion. None of it is rocket science, just time consuming.
I do not agree with using 5200. There doesn’t seem to be a need for that kind of adhesion here – the thru-bolts will hold things in place – and we all know what a bear that stuff is to remove if & when.
Tor
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Silver Heels, P-424 #17
http://www.SilverHeels.us
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You will only need to remove the plywood when you install the sugar scoop transom with the built-in swim platform. That's my criteria for 5200. Will I ever need to remove the thing? No? 5200 rules.
That said, everyone has their own way and the mere fact that all boats float indicates that there's more than one way to skin a cat. Or attach backing plates. If you're going to all the trouble of encapsulating plywood then 5200 is not even on the radar. If you're just going with backing plates, then it's a good solution.
Neither is better than the other – just different. Both are accepted ways of doing this.
So, Tor, do it your way and know you've done the best job possible!
Bob
On Mon, Mar 23, 2009 at 9:13 AM, Silver Heels < ([email][/email])> wrote:
Quote:Good points, Bob.
While aligning the windvane rudder yesterday prior to drilling the mounting bracket holes, I happened to pound on the transom with my fist. No, not in frustration. More like a manly man's kind of “see how solid my boat is” pounding. Only it didn't feel all that solid. Actually, it felt kind of thin and springy. Hence the question I posed to the group. I already knew what I had to do, but wanted an excuse not to do it. Only thanks to Don it didn't work. Also, as you sort of pointed out, that rudder is sure to hit something hard some day. So, I am going to lay on some extra roving as he suggested. Now's the time, hauled out in the yard with the lazarette empty. A little grinding, a little itching and the worst is over.
As for the backing, I do sometimes use 1/4″ aluminum for plates and probably will in this application. As you point out, it's pretty easy to work using ordinary tools. But to really spread the stress over the broadest area, 1/2″ or 3/4″ plywood between the reinforced hull and the backing plates makes sense to me. Yes, I'll remember to bevel the hull-side edges, and I always double-coat plywood with epoxy resin for this kind of thing, and make epoxy sleeves for the bolt holes to preclude water intrusion. None of it is rocket science, just time consuming.
I do not agree with using 5200. There doesn't seem to be a need for that kind of adhesion here – the thru-bolts will hold things in place – and we all know what a bear that stuff is to remove if & when.
Tor
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Silver Heels, P-424 #17
http://www.SilverHeels.us
~~~~~~~~~~~~~~~~~~Quote:
Original Message
<.. snip>Post generated from Pearson424 Forum using Mail2Forum
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Bob,
5200 rules, but ruthlessly. I’m not encapsulating the plywood. That’ll go on between the extra roving and the aluminum backing plates. The plywood is just to spread the bolt stress more widely and evenly across the roving-reinforced surface. Since I’m going to bed the windvane mounts on the outside (of course), and waterproof the inside plywood with a double epoxy coating and bolt sleeves, pray tell why I would want to bed the interior plywood backing at all, let alone glue it permanently to the fiberglass. I’m wide open to a better fix, but just don’t see the value in that one – probably because I’m a neophyte repair guy talking to a real engineer.
And now that you mention it, a sugar scoop transom with built-in swim platform might be just the thing.
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Silver Heels, P-424 #17
http://www.SilverHeels.us
~~~~~~~~~~~~~~~~~~Quote:
Original Message
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Hi Tor,
One or the other – either 5200 and bare aluminum plates or epoxy and plywood. Not both.
Bob
On Mon, Mar 23, 2009 at 8:17 PM, Silver Heels < ([email][/email])> wrote:
Quote:Bob,
5200 rules, but ruthlessly. I'm not encapsulating the plywood. That'll go on between the extra roving and the aluminum backing plates. The plywood is just to spread the bolt stress more widely and evenly across the roving-reinforced surface. Since I'm going to bed the windvane mounts on the outside (of course), and waterproof the inside plywood with a double epoxy coating and bolt sleeves, pray tell why I would want to bed the interior plywood backing at all, let alone glue it permanently to the fiberglass. I'm wide open to a better fix, but just don't see the value in that one – probably because I'm a neophyte repair guy talking to a real engineer.
And now that you mention it, a sugar scoop transom with built-in swim platform might be just the thing.
~~~~~~~~~~~~~~~~~~~~~~~
Silver Heels, P-424 #17
http://www.SilverHeels.us
~~~~~~~~~~~~~~~~~~Quote:
Original Message
<.. snip>Post generated from Pearson424 Forum using Mail2Forum
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