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georgeblackwood
31 Posts |
 Posted - 07 Aug 2011 : 14:19:45
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Hi everyone.
I have a Norman 17 currently sitting on a trailer in my garage whilst I do a few repairs on it. I've noticed that there is a certain amount of flexing/bending on the keel where it is supported by the trailer roller nearest the bow.
The roller is 150 cm/ nearly 5 feet back from the bow of the boat. There are another two roller supports on the trailer, one about 70 cm from the stern and another roller in the middle of the two other rollers.
If I lift up the bow of the boat so it is clear of the roller closest to the bow then the keel sags down/straightens up.
Are keels designed to have this kind of flexing or should they remain rigid?
If the keel is supported with another roller further forward then this would solve the current flexing problem of the keel whilst on the trailer.
I'm just wondering does the keel need further support from the deck or is a certain amount of flexing ok?
All replies greatly appreciated.
Thanks |
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georgeblackwood
31 Posts |
Posted - 07 Aug 2011 : 19:10:21
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Here hopefully are a few photo's to illustrate the flexing/bending keel.
[img}http://www.flickr.com/photos/66067538@N05/?saved=1[/img}
Hope this helps with the explanation, (a picture is worth a thousand words and all that)
Thanks |
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Deano
United Kingdom
1843 Posts |
Posted - 07 Aug 2011 : 19:38:47
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I'll jump in here, but I'm no expert!!
I would suggest that your boat is designed to sit in the water and be supported evenly over a large surface area. You have taken it out of it's natural environment and point loaded the hull. The sagging you are seeing is normal and is due to the above.
It sounds like you could use a few extra rollers to evenly support the keel. Have a look at a few boat trailers to get the feel of just how many rollers you may need.
BUT!!! If you are planning to strap a 60HP engine on the back and undertake fast coastal drug running, you may wish to strip the insides of the boat out and replace with a super strong structure.
Dean - Boating on the Great Ouse.
Freeman 30 "Silver Gem"
See the photos http://www.flickr.com/photos/54758027@N00/ |
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georgeblackwood
31 Posts |
Posted - 07 Aug 2011 : 20:04:14
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Thanks for the reply Deano, Yes I was definitely thinking of adding another roller up closer to the bow as when I lifted the bow up before, clear of the roller closest to the bow I put some timber blocks in to support the keel further up and it solved the problem.
I just wasn't sure if I was going to do any damage to the keel when it's rolling on and off the trailer as I'm intending to take it out of the water after every trip.
Thanks for the advice and as far as the outboard goes I'd say it will be maximum 15hp.
Anybody else got any thoughts on the matter, I'm a great believer in the wisdom of crowds.
All advice welcome
Thanks
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adi-n-chez
United Kingdom
1980 Posts |
Posted - 08 Aug 2011 : 21:09:13
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Again like Dean I'm no expert (Where is Clive !!!) - Certainly my 22 Keel has never done that in its many lift outs - More support definitely req but I also suspect a little de-lamination , What happens inside the boat when the keel is pushed upwards ? Does the whole floor come with it ore are the keel timbers pushed upwards parting from the GRP ?
Adi
Sewer Tubes ? I'd rather have a D**ncr*ft (Only Kidding) |
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georgeblackwood
31 Posts |
Posted - 08 Aug 2011 : 22:31:34
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Hi adi-n-chez,thanks for the reply. You and Deano are definitely more expert at this boating lark than me. This is my first boat and i've not had it in the water yet. I feel that the roller support closest to the bow is too far back(i.e. at the moment it is about 5 foot back from the bow. So i'll be putting another roller in closer to the bow.
Even looking at the main Norman homepage(two classics side by side), you can see that the roller closest to the bow on that boat is about a foot or two back from the bow and the boat hull shape in my eyes anyway appears to be fairly strong at that point.
The boat has been sitting on the trailer for over a year now that I know about, the guy I bought it off never got around to doing it up.
So I guess the lack of support has weakened the keel somewhat at that point loading on the roller closest to the bow.
Anyway I've put a picture up of the floor inside the cabin to give an idea of the lack of support that the keel currently has. A couple of bits of 2 by 1 fiber glassed in. There appears to be the part of the original center stringer and then another stringer which has been added beside it.
The keel is not moving too much maybe there is a half inch difference once it is straightened up if the bow is lifted free of the roller.
But I guess from what your saying adi-n-chez your keel is rigid all the way along with very little or no flexing when it is on a trailer.
Anyway I better stop waffling on and publish this before you're all gone to bed.
Thanks for the advice, keep it coming
All advice welcomed expert or not. |
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georgeblackwood
31 Posts |
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cliveshep
Thailand
1324 Posts |
Posted - 09 Aug 2011 : 02:41:35
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Hi there George. For what it's worth the chap who said that the hull is evenly supported in the water is perfectly correct and 100 years ago what you have described and shown would have been fairly acceptable in a wooden boat. If you've ever seen the cobles or the Hastings beach boats "work" you'd be amazed. On the beach you could get hold of the transom to one side and twist the hull a good 15 degrees, the bow not moving at all.
However, your boat is grp not wood, and grp doesn't like being "hogged" on a trailer in that way. You'll inevitably get spider-web cracking, that will allow water to start to get in and things go downhill from there on. There is insufficient stiffness in the hog for the weight of the boat, especially when you consider you haven't actually got it fitted out yet. I would make a reasonable attempt to replace or add to the hog or kelson another larger member and glass it in from stem to stern. It is a bit of a chore as you'll have to clean off the inside of the hull thoroughly to get a good bond and cut through the little bulkhead forming the intersection of the vee berths so the new hog can pass through up to the turn of the bow.
I think dnme has done that on his - should be some pics on here I suspect as he loves to post pics which is going to help others. He's done a cracking job for a beginner.
The almost flat area of the bottom does make it difficult to stiffen it, a probable reason for the Callumcraft/Norman 17 hull design being abandoned in favour of the 25deg constant deadrise deep vee hull all later models have. With that in mind you might consider bolting on a hardwood keel outside, bedding it on a decent marine mastic or bedding compound, and glassing that in. That will solve the problem and improve immeasurably the crap steering characteristics as well. Again, look at the pics of dnme's boat to see what it looks like underneath. That would solve both problems once and for all.
It's better to do it now whilst you have a reasonably light hull to manhandle than attempt it once all the fit-out is completed because unless you have a yard gantry etc you are NOT going to lift it up to work on it.
The cost of boating is insignificant compared to costs of a young wife and two teenage kids! |
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cliveshep
Thailand
1324 Posts |
Posted - 09 Aug 2011 : 02:47:23
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quote:
Originally posted by adi-n-chez
Again like Dean I'm no expert (Where is Clive !!!) - Adi
Sewer Tubes ? I'd rather have a D**ncr*ft (Only Kidding)
"Clive" is currently not on-line so much due to getting rid of a psycho other half who was destroying my own and my children's lives. That might sound unfair, overly blunt or extreme but is the whole unvarnished truth. I've been very preoccupied of late - sorry chaps. Too many lawyers and police in our lives.
I will be around more again as things begin so settle down at home and traumatised daughter (son is not so affected - his girlfriend has cushioned and supported him) gets back on an even keel so to speak.
The cost of boating is insignificant compared to costs of a young wife and two teenage kids! |
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georgeblackwood
31 Posts |
Posted - 09 Aug 2011 : 16:37:24
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Hi Cliveshep,
Thanks very much for the informative reply. Great advice. I will definitely try to stiffen up the hog with a larger piece of wood. I'd say it might be quite difficult to get a full length of wood all the way from the stem(most forward part of the boat bow; I just looked it up on google just in case any other novices are reading this post!)to the stern, as the floor rises up closer to the bow by quite a bit.
I think that if I managed to get a new kelson in which started from the current cabin seating back to the stern, then it would make an enormous difference to the overall strength of the boat hull and keel. This would cover the weak point in the keel.
Now all I need to do is convince by business partners (Dad and Brother) that it's a good idea. There even more anxious than me to get the boat in the water.
As far as bolting another keel on, I think that I'll leave that one for another day, not that I don't think it's a good idea,it's just you have to stop somewhere with these boats. I'd kind of like to try the boat with it's current keel to see how it handles, after all it will mainly be used on the canals.
No doubt after I've seen it zig zag from side to side of the canal with my own eyes, i reserve the right to change my mind and take all your advice on board, again I'd say i'm going to have my work cut out trying to convince the business partners to stiffen the kelson. I'll have to start working out more so I'll be able to lift the boat after we add all the plywood fittings! We're going to put in a removable floor so there will be no problem with access to add another hardwood keel afterwards.
I was actually surprised how light the boat is once everything is stripped out of it.
Thanks again for the advice. It's really appreciated.
Just on a personal note, sorry to hear about your current domestic problems. I hope it all works out for you and the kids. Good luck. |
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Keel rigid or flexible?
