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mikecaffrey
15 Posts |
 Posted - 10 Jul 2016 : 22:59:46
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Right, first of, hi all... I'm new to the forum!
I have a mid to late 70s 23ft and live on board. This summer I plan on building a new top for the boat which will give me more internal space and headroom while allowing me to fully insulate ready for the winter. Picture a 23ft Norman hull with a narrowboat style top of marine ply.. pictures to follow!
The main frame will be hardwood and SS bolts built up from the gunnels, once built and clad I'll be taking a grinder to the original upper before running cabling and insulation and internal fitting.
I'm wondering, has anyone ever done this to a GRP boat? Everyone I've spoken to seems to think it feasible but still I have some worry regards structural rigidity. I've not been able to find anything to shed light on the construction of the boat and how cutting the top off might affect it.
Any thoughts are greatly appreciated!
Once the job is done the windows, screen, canopy and any other usable items will be up for grabs on here at no cost beyond shipping.
Thanks in advance
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stratford4528
United Kingdom
414 Posts |
Posted - 10 Jul 2016 : 23:50:48
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| My thoughts are if you ever want to sell it. Making it higher it would not go under some bridges and tunnels if ever it was needed. If it was me and I needed to live on board I would a buy boat more suitable. |
Edited by - stratford4528 on 10 Jul 2016 23:51:34 |
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cliveshep
Thailand
1324 Posts |
Posted - 11 Jul 2016 : 02:15:23
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You will render the boat valueless if you hack off the cabin top and replace it with a plywood box.
If you really want to add to the living space build a proper wheelhouse and enclose it - but really a Norman 23 is not suitable for much else.
Rule of thumb for those who build (or used to build) or modify boats - if it looks a crap design - then it is.
Finally living the dream!
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mikecaffrey
15 Posts |
Posted - 11 Jul 2016 : 07:35:29
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Cliveshep - thanks for the reply, though it does seem unjustifiably negative! Your phrasing, 'hack-off' 'plywood box' ' Norman 23 not suitable for much else' etc! Are you always so negative?
First off I've been a carpenter for over 30 years, it won't be a plywood box and nor will I 'hack off' the top! You've not seen the design and so don't know if it 'looks crap'.
Rule of thumb when replying to posts - don't be so presumptuous and outright negative.
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mikecaffrey
15 Posts |
Posted - 11 Jul 2016 : 07:41:41
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quote:
Originally posted by stratford4528
My thoughts are if you ever want to sell it. Making it higher it would not go under some bridges and tunnels if ever it was needed. If it was me and I needed to live on board I would a buy boat more suitable.
I've made a careful study and done my research as best I can and from that have come up with a height that will likely be okay while still giving me headroom.
The reason I live on a 23ft boat and need to make more of it is that I don't have the money for something else, I have to make the best of what I have.
I've spoken with a boat surveyor and an engineer in a dry dock (I won't identify them here) and both seem to think my plan is feasible but were unsure of the construction of a GRP boat. |
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mikecaffrey
15 Posts |
Posted - 11 Jul 2016 : 07:45:19
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To clarify on my original post:
I asked if anyone had made such a modification and also if anyone had information or thoughts on the structural rigidity of the boat, I'd thought that a Norman forum would be a good place to seek such information.
If you have any thoughts or information regarding these questions, either for or against then I'd really appreciate hearing them.
Best to all... |
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trevork
3949 Posts |
Posted - 11 Jul 2016 : 12:45:35
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| Have you spent any time having a look through the main website? There are many examples of projects and adaptations to the whole Norman range. I can think of at least one "careful surgery" example! |
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mikecaffrey
15 Posts |
Posted - 11 Jul 2016 : 14:33:13
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quote:
Originally posted by trevork
Have you spent any time having a look through the main website? There are many examples of projects and adaptations to the whole Norman range. I can think of at least one "careful surgery" example!
Thanks for the reply... a little yes, though I've not looked at everything yet, work stops me!
I'll browse more later. |
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greenmills1314
United Kingdom
27 Posts |
Posted - 11 Jul 2016 : 18:31:23
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Hi
Just a thought on basic ship construction.
Imagine an upside down triangle, the bottom point is the keel of the boat and the two top corners are the gunnels, the forces on all the 3 points are equal and the structure stays rigid. The fibre glass roof section of the Norman is bonded/screwed to the hull, the corners and decking acting as strength points opposing the keel. Remove the top of the triangle and the hull could snap, but with careful addition of gunnel strength members running fore and aft you should be ok.
If you left the side decking in place and added timber bonded in under the deck and put at least two full width bulkheads bonded to the sides you should be ok
Paddy
Clanky tiff |
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mikecaffrey
15 Posts |
Posted - 11 Jul 2016 : 22:24:51
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Hi Paddy
Thanks for that info... sounds sensible to me.
My plan is to leave the gunnels intact and about 50% of the foredeck width, on to the gunnels I plan to bolt 75x50 graded timber to the top and a steel plate under to prevent any risk of the bolts pulling through the fibreglass. Bolts will be at around 450mm centres.
The side timbers, near vertical will be fitted using a half housing type joint with 2 bolts through to prevent and rotation. Atop those will sit another 75x50 running fore/aft...
The roof struts, of 36mm ply will be notched to sit on to the 75x50 and will also have cut-outs to support 3 fore/aft roof beams placed equally across the span. There will be blocks added as required to strengthen various sections and to allow for rope cleats to be fitted etc.
I'd not thought about bulkheads, aside from a full width rear panel in to which the door will be fitted, I'll explore the options...
quote:
Originally posted by greenmills1314
Hi
Just a thought on basic ship construction.
Imagine an upside down triangle, the bottom point is the keel of the boat and the two top corners are the gunnels, the forces on all the 3 points are equal and the structure stays rigid. The fibre glass roof section of the Norman is bonded/screwed to the hull, the corners and decking acting as strength points opposing the keel. Remove the top of the triangle and the hull could snap, but with careful addition of gunnel strength members running fore and aft you should be ok.
If you left the side decking in place and added timber bonded in under the deck and put at least two full width bulkheads bonded to the sides you should be ok
Paddy
Clanky tiff
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IanM
United Kingdom
2238 Posts |
Posted - 11 Jul 2016 : 23:07:02
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Hi Mike
Welcome to the forum. The reason you got some (rather unfair!) negative reactions was probably that we've seen some shockingly bad DIY Norman topsides, some not much more than (bad) garden sheds.
The good news is that, structurally speaking, you'll be fine with a moderate topside modification as long as you use a bit of common sense (which you seem to possess). The bridge/tunnel point is a valid one and mods may affect the re-sale value a little. But unless you build it out of cardboard or go crazy with top-heavy construction it's not really going to cause you any problems.
And it's your boat so you can do what you like with it, even if it offends the purists. Be sure to post some piccies of the build process and of the finished thing. |
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cliveshep
Thailand
1324 Posts |
Posted - 12 Jul 2016 : 03:38:34
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quote:
Originally posted by mikecaffrey
Cliveshep - thanks for the reply, though it does seem unjustifiably negative! Your phrasing, 'hack-off' 'plywood box' ' Norman 23 not suitable for much else' etc! Are you always so negative?
First off I've been a carpenter for over 30 years, it won't be a plywood box and nor will I 'hack off' the top! You've not seen the design and so don't know if it 'looks crap'.
Rule of thumb when replying to posts - don't be so presumptuous and outright negative.
I built/rebuilt boats amongst other things until I retired, the post is not negative in the slightest, what can you build onto a Norman 23' hull in plywood that could possibly inprove it? It has full headroom already, minimal side decks, and a rot-proof top-sides. You can ignore my advice - go ahead, it is your right to disagree, but I stand by my professional assessment.
Finally living the dream!
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mikecaffrey
15 Posts |
Posted - 12 Jul 2016 : 12:33:03
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Hi Ian and thanks for the reply and the welcome :)
I'm sure there have been some rather grim looking 'designs' pass by, I've seen a good few on the canals myself! I'm very aware of the potential height issues, I've got a small stove on board and the pipe extends a fair way above the roofline and it's led me to having to remove it on occasion, especially on the Nene to get under a bridge or 2. I've learnt from that and now have a fair idea of how high I can go without an issue, I accept that there may be one or two places where there will be an issue still but they'll be very rare...
So far as resale goes I'm happy to risk it, if it goes well (As planned) then to some buyers it will add value, to others not. Right now I have no mind to ever sell anyway :)
Thanks for the compliment! After 30 years as a carpenter (not a house builder with a nailgun type!) and electrician I feel confident in my design and ability to carry it through, my concern is my lack of knowledge when it comes to GRP construction, hence my post. I don't want to undermine the boat!
Once the work begins there will be plenty of before and after images as well as under construction ones... I'll be sure to post them on the forum.
quote:
Originally posted by IanM
Hi Mike
Welcome to the forum. The reason you got some (rather unfair!) negative reactions was probably that we've seen some shockingly bad DIY Norman topsides, some not much more than (bad) garden sheds.
The good news is that, structurally speaking, you'll be fine with a moderate topside modification as long as you use a bit of common sense (which you seem to possess). The bridge/tunnel point is a valid one and mods may affect the re-sale value a little. But unless you build it out of cardboard or go crazy with top-heavy construction it's not really going to cause you any problems.
And it's your boat so you can do what you like with it, even if it offends the purists. Be sure to post some piccies of the build process and of the finished thing.
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mikecaffrey
15 Posts |
Posted - 12 Jul 2016 : 12:42:02
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Clive - how can you say it's not negative? You're STILL being so now!
You're coming across as some kind of elitist snob! What's your issue?
The 23 does NOT have headroom, it's very low such that I cannot stand upright anywhere except under the canopy, and that's with a curved floor! Seems you don't know the 23 at all. As you state your advice and assessment to be a professional one, perhaps you'd care to share what it is that qualifies you to make such a statement? What makes it professional Clive?
My proposed modification will give sufficient headroom throughout as well as allow a level floor, provide a means to insulate and thereby avoid the condensation that is inherent in the GRP design, be completely watertight and with proper maintenance be rot proof as well.
Do you have anything to add?
quote:
Originally posted by cliveshep
quote:
Originally posted by mikecaffrey
Cliveshep - thanks for the reply, though it does seem unjustifiably negative! Your phrasing, 'hack-off' 'plywood box' ' Norman 23 not suitable for much else' etc! Are you always so negative?
First off I've been a carpenter for over 30 years, it won't be a plywood box and nor will I 'hack off' the top! You've not seen the design and so don't know if it 'looks crap'.
Rule of thumb when replying to posts - don't be so presumptuous and outright negative.
I built/rebuilt boats amongst other things until I retired, the post is not negative in the slightest, what can you build onto a Norman 23' hull in plywood that could possibly inprove it? It has full headroom already, minimal side decks, and a rot-proof top-sides. You can ignore my advice - go ahead, it is your right to disagree, but I stand by my professional assessment.
Finally living the dream!
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trevork
3949 Posts |
Posted - 12 Jul 2016 : 15:48:06
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OK. so the two of you obviously disagree! Lets leave it at that please!
The luxury of forums is that we can ignore what we don't like. There is no golden rule at having to bite at every point you may not agree with.
Mike, yes, can I repeat the warm welcome to our forum. carry on and post the details and pictures of the work as it progresses, that is what we love to see on here.
Clive, please desist form having a go at further posts. Just ignore them if you don't agree.
Being that I have the power, I will simply delete any further posts that I think return to this popintless squabble from either of you! |
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jud
United Kingdom
113 Posts |
Posted - 12 Jul 2016 : 21:22:27
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Hi Mike.
Your project makes interesting reading, and I'm looking forward to watching your progress and seeing the end result, but is it going to add much weight to the boat?
My 23's on a canal and if I'm not careful she's chewing mud.
Hope all goes well for you,
Jud.
p.s. not trying to put your fire out Mike, just curious |
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Topic |
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Boat mods
