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dnme
Ireland
110 Posts |
 Posted - 27 Jul 2011 : 15:33:20
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Dearly beloved,
I am restoring an old Norman 17. Recently I went to the trouble of ripping up and replacing the floor stringers. The floor in that boat is flat, there is no bilge and the stringers are only about an inch high. I copied exactly the recreation of the original stringer system, but now looking back, I realise I should have implemented a drainage system.
Here's a pic of my newly clothed and epoxied floor with the new stringers.
Here's a vid of what I'm talking about
http://www.youtube.com/watch?v=THJLytRiRpo
So as you can see, the stringers on the flat floor form compartments. I am thinking now of cutting a 1cm notch into each stringer where it meets the central stringer, then placing a small plastic tube down in the notch and epoxying back over that to allow a through drain. Also considering placing a sump plug at the back on the bottom of the transom. I might also try and find a 12v pump with an intake pipe that I can lay on the floor to add a bit of added water removal functionality.
Bear in mind I am going to cvover the floor with a raised marine ply floor. I will leave a hatch or opening for inspection and what have you but it means drainage is all the more important.
What do you think?
What ywould you do here?
Would cutting into these stringers weaken them?
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My Norman 17 restoration thread (pics and vids)
http://www.boards.ie/vbulletin/showthread.php?t=2056217528
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Edited by - dnme on 27 Jul 2011 15:37:21 |
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Revolvor
United Kingdom
75 Posts |
Posted - 27 Jul 2011 : 16:02:15
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I WOULD NOT cut a notch in the stringers, By cutting a notch you will basically lose all the stiffness that was being supplied by the GRP at that point. The stiffness in what is essentially a "Box-section" is derived from the top and bottom webs. In order to retain stiffness, you would have to drill holes close to the hull, maintaining the GRP above it - or cut a notch, and then cap it with GRP to regain the strength.
People that "notch" floor timbers in their houses for central heating pipes are losing stiffness there too - they should ideally drill through on the centre-line.
Cheers, John |
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dnme
Ireland
110 Posts |
Posted - 27 Jul 2011 : 16:58:17
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quote:
Originally posted by Revolvor
I WOULD NOT cut a notch in the stringers, By cutting a notch you will basically lose all the stiffness that was being supplied by the GRP at that point. The stiffness in what is essentially a "Box-section" is derived from the top and bottom webs. In order to retain stiffness, you would have to drill holes close to the hull, maintaining the GRP above it - or cut a notch, and then cap it with GRP to regain the strength.
People that "notch" floor timbers in their houses for central heating pipes are losing stiffness there too - they should ideally drill through on the centre-line.
Cheers, John
Well I did say "epoxy back over" each notch. How would you go about drilling through the stringers close to the hull? I simply cant get a drill that will drill flush like that. Any other tool that might do it?
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My Norman 17 restoration thread (pics and vids)
http://www.boards.ie/vbulletin/showthread.php?t=2056217528
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Revolvor
United Kingdom
75 Posts |
Posted - 27 Jul 2011 : 18:43:02
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| Thinking more about it, drilling holes would probably result in bare wood being exposed, so is not such a good idea. The objection to notching would be that the GRP would be weakened, but if you glassed over the bare wood, and more importantly laid GRP tape across the notch to regain the bending strength then it would probably be OK. I'm new to this, with no practical experience of GRP in boats, but am just applying common sense and a reasonable knowledge of strength of materials. I'm sure you will get some other advice too. Good luck. John |
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cliveshep
Thailand
1324 Posts |
Posted - 27 Jul 2011 : 20:38:33
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DNME - no holes and no notches my friend! You've done an outstanding job there - well done. Now create the bilge with beams across the stringers you have, use treated timber and the minimum of stainless screws to anchor down. When I say beams all you really want is say a 50mm thick batten with a packer in the middle. You can of course go larger creating more height for the cockpit floor if you want. In the cockpit you can go across the cockpit side to side and simply have a packer off the hog - you do after all have some vee or curve however slight. If water gets in yes, it will lay in the little squares but with loose floor boards you can always mop it out. Just make sure you treat the beams and I suggest s dollop of mastic under the ends before you screw them down.
Likewise in the cabin - this time you are only doing the middle between furniture and you really want the minimum to keep that important headroom. Treat the ply underside with a suitable rot-proofer first, Sikkens or similar, and I suggest you glass in a runner all the way down in the angle of the vee-berth to hull for the floor board to sit on. If you fix that to the front of the berth it can act as a support when you glass it in, unless you already have a GRP moulded vee berth.
The cost of boating is insignificant compared to costs of a young wife and two teenage kids! |
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dnme
Ireland
110 Posts |
Posted - 27 Jul 2011 : 23:32:06
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Ì am putting in a marine play floor. I dont want to have to mop out the underfloor at all. plus I would often forget. I do not want water sitting down there as it wil cause mould and rot. I have got to add a drainage solution.
If you consider that I intend to add new stringers to hold my floor, these will be ply pieces on their side moulded to the floor and presenting a flat uupperside to screw the floor to. So these will add even more stiffness to the hull. Having spoken to a few others tonight, I think I am going with V notches cut into each stringer re-sealed with epoxy. I will install a drainage hole and plug at the transom and leave an inspection hatch or door in the floor.
I will also add drainage holes to the new floor stringers. Eater will then be able to drain freely to the transom and drain. So when I take th eboat out after a day oin the water, I can just park it up at home, raise the bow and open the plug at the transom, it'll allow drainage and air in.
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My Norman 17 restoration thread (pics and vids)
http://www.boards.ie/vbulletin/showthread.php?t=2056217528
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Deano
United Kingdom
1843 Posts |
Posted - 28 Jul 2011 : 21:03:30
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Where is all this water coming from???? It is a grp boat, not wood!!
Seal the windows well and you will not have all this water in the bilge that you worry about!!
Do not cut the stringers!!!
Dean - Boating on the Great Ouse.
Freeman 30 "Silver Gem"
See the photos http://www.flickr.com/photos/54758027@N00/ |
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adi-n-chez
United Kingdom
1980 Posts |
Posted - 28 Jul 2011 : 21:57:48
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Agree with Didnt have to lift the floor for yrs , then we had a prob with condensation over the yrs accumulating bailed that out & it was fine - Next prob with bilge water was due to a leaking transducer (now fixed)
You should have a dry boat all the time if you are planning launch / lift cruises
Adi
Sewer Tubes ? I'd rather have a D**ncr*ft (Only Kidding) |
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dnme
Ireland
110 Posts |
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canalboy1949
United Kingdom
115 Posts |
Posted - 29 Jul 2011 : 08:30:22
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Why not simply drill some holes in the bottom to let the water run out? Oh, no, that might not work very well, would it!  |
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Knighty
United Kingdom
654 Posts |
Posted - 29 Jul 2011 : 13:39:26
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| Shame you didn't think about drainage before glassing it all over. You could try a drill with a flexi drive to get some holes and maybe line the holes and try and seal them somehow. Or leave lift out panels in the floor to mop it out if water gets in. |
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Deano
United Kingdom
1843 Posts |
Posted - 29 Jul 2011 : 15:48:49
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if you drill holes, they will only clog with bits of leaf, fluff and weed and then you will be no further forward.
No bilge pump in the world will ever remove all the water, far from it. they usually leave behind about an inch of water. The only way to shift that is with the sponge and bucket method.
I like your idea in principle, but from some one who has been there in a number of different boats, you ain't ever going to achieve it. I think that is what other people are trying to tell you.
It is a 17 foot boat, you will have to mop the bilge .... it is just the way!!!
Dean - Boating on the Great Ouse.
Freeman 30 "Silver Gem"
See the photos http://www.flickr.com/photos/54758027@N00/ |
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dnme
Ireland
110 Posts |
Posted - 29 Jul 2011 : 22:09:01
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The point is that the boat has no bilge. Its a flat floor with an original design of criss cross stringers. terrible design, all it does is retain water. I have added holes, and am adding a drain plug at the transom. I'll leave a lengthways door openable in the new ply floor for inspections and cleaning of the drain holes. I am not envisaging much dirt down there as it will all be covered by said floor. Being simply able to open the drain plug and tip her up on the trailer when I get home appeals to me.
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My Norman 17 restoration thread (pics and vids)
http://www.boards.ie/vbulletin/showthread.php?t=2056217528
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Topic |
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A question of drainage
