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Jimbo
United Kingdom
585 Posts |
 Posted - 24 Feb 2013 : 18:12:40
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| Hello MIKEB. If you read carefully my post about how to repair and replace the transom it is all there. There are no shortcuts in doing this job. If at all possible cut out the inner transom grp and leave the outer one intact. If you try to shortcut the process you will be doing it again very soon. You are licky because your boat is 6ft10ins wide, mine is 9ft 6 ins wide so a lot more work and wood involved. Best of luck. |
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mikeb
90 Posts |
Posted - 25 Feb 2013 : 09:20:53
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Jimbo, I'm not sure what the structure of your Birchwood is like, but I think that with a Norman 20, it's easiest to tackle the transom from the outside?
I've made an incision across the width of the transom and down nearly to the bottom of the transom, but the outer skin still seems to be well attached? Should I be able to just peel it off, it seems to be bonded to the balsa wood inside? |
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Jimbo
United Kingdom
585 Posts |
Posted - 25 Feb 2013 : 20:41:20
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| Well since you have got this far you must continue. I think that you need to cut all along the sides and bottom of your transom and maybe using a long flat lever try to destror either the balsa wood or its bond to the transom and so remove the transom. Be carefull not to crack or break the grp transom. On my Birchwood, before I could do anything I had to remove the complete drive leg after I had supported the engine, which by the way is a 2lt Volvo petrol car engine. Then remove the engine with a crane, and spend a whole day with a hammer and wide chisel removing a rotten transom. Then I could start the rebuilding. |
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mikeb
90 Posts |
Posted - 17 Mar 2013 : 17:34:57
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Did a little bit more on it this afternoon. With a 2ft long drill bit I've drilled down through the balsa wood to the bottom of the transom, making as many holes as I can. I've also gone sideways as much as I can. All along the bottom of the transom the balsa wood was very wet and rotten. In the middle 3rd it is probably 70% rotten all the way up to the outboard well, but beyond the width of the outboard well, the balsa wood is relatively sound. I've dug out the balsa wood in the top 8 inches below the outboard well completely, but I'm reaching the limits of how much more I can get to this way.
I can't move the out skin at all around the lines I've cut, and I'm not sure how to make further progress? Do I really need to empty/remove the whole width of the transom, or can I just do the middle third of it? If I must do the whole width, I'd like to get it off in one piece as I'm sure it will be easier to put back together that way, but is that too ambitious?
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merlin
United Kingdom
400 Posts |
Posted - 17 Mar 2013 : 20:29:21
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you will need to cut that whole section out follow the hull line from port to starboard along the bottom stay away from the edge at least 4" to 6" connecting the cut at the transom the use a saw to work down behind the skin and remove it in one piece then clean out all the bad stuff
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mikeb
90 Posts |
Posted - 17 Mar 2013 : 21:46:27
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Yes, that's where I plan to cut next - if you look really closely you can just make out the line I've marked on it. But it isn't budging at all where I've made those first two cuts, so I've no idea how I'll get a saw through the gap. And I am a bit reluctant to make more cuts until I've figured out a way to separate the sandwich.
The only place that is open is the top of the transom across the outboard well, I am thinking that I might be able to use a bow saw blade with a handle made up on one end of it? |
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merlin
United Kingdom
400 Posts |
Posted - 18 Mar 2013 : 07:22:42
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Dont worry to much if the stern section skin does'nt come off in one
you are committed now to removing it just costs a bit more at the end of the day you can buy a gelcoat spray gun and spray the whole stern once it is layed up (makes a lovely job)
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mikeb
90 Posts |
Posted - 25 Mar 2013 : 14:56:47
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I've now managed to get the out skin off, you can see the extent of the rot:
Wasn't quite as bad as I had feared, but it was quite rotten in the middle (due to someones clever idea of drilling outboard well drain holes through the transom that helped it to fill with water), and along the bottom 3 inches - seems to be a tiny leak through the inner skin from water in the bilge.
Scraped and chiselled all the balsa wood away, and cut through to the plywood bracing (which was totally rotten as well):
I've now removed all that as well, ready for replacement. Now I need to decide how to rebuild it (fresh balsa wood isn't on the agenda!).
The void where the balsa wood was, is about 12mm thick, and I am thinking to use 9mm marine plywood here instead (I think 12mm will be too thick). Planning to cut it to shape then screw and bond (with epoxy resin?) it into place on the inner skin, then use epoxy resin to fill the void (should be ~2mm) and bond the plywood to the GRP outer skin.
Where the plywood bracing was (3/4 inch thick, I think), I plan to replace with 2 layers of the 9mm plywood screwed and bonded together.
Does this all sound reasonable, or should I be doing it entirely differently? |
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merlin
United Kingdom
400 Posts |
Posted - 25 Mar 2013 : 16:04:06
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your on a roll now remeber and put a schamper edge where you have cut through the gelcoat on the boat and the cutting if you are going to use it. aviod a hairline joint
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df
United Kingdom
5991 Posts |
Posted - 25 Mar 2013 : 18:53:07
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Thoroughly wet up all the wood you use with resin as you do it to keep the damp out in future, I'd be tempted to use some glass matting between any layers of wood as well.
NBAS--The communal colostomy bag of the boating community.
Visit leomagill.co.uk |
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ken cattell
United Kingdom
192 Posts |
Posted - 25 Mar 2013 : 23:25:21
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Nicely cleaned out good job, downhill from now on!
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mikeb
90 Posts |
Posted - 28 Mar 2013 : 03:28:08
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| Any idea how much epoxy resin I'm likely to need for this job? 3.5kg is about £60 or 6kg is £100. |
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merlin
United Kingdom
400 Posts |
Posted - 28 Mar 2013 : 07:18:01
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Bit of a hit and miss that one, not being rude
but if you are not used to working with it you will lose a good deal due to it setting to quick
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Jimbo
United Kingdom
585 Posts |
Posted - 28 Mar 2013 : 08:30:31
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| I think that the prices that you have been quoted seem rather high. Look in Yellow oages for Fibreglass Suppliers, or Fabbrications in Plastic and ask them where they purchase their supplies from, you should make worthwhile savings. |
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merlin
United Kingdom
400 Posts |
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