 |
|
| Author |
 Topic  |
|
|
dnme
Ireland
110 Posts |
 Posted - 10 Jul 2011 : 21:56:40
|
Folks, as you know I am attempting to restore an old Norman 17. My latest nightmare is to uncover all the original stringers which are rotten. Would you mind having a look at these videos I shot and tell me what you think?
http://www.youtube.com/user/Ballymullaney
Particularly this one - http://www.youtube.com/watch?v=6gJOx5mJ_Xc
(excuse the sniffles, dust dust and more dust)
I'd be very grateful for any advice, particularly as to the architecture of the centre stringer in relation to the keel and what to do there next.
Many thanks in advance |
Edited by - dnme on 10 Jul 2011 22:04:04 |
|
|
Jimbo
United Kingdom
585 Posts |
Posted - 11 Jul 2011 : 08:21:21
|
Hi Dnme, Sorry to see the problems that you are having. First question is the boat out of the water; if not it needs to be because you need to find out where this water is coming from. Secondly, I have just had a very similar problem with my 25ft wide beam Birchwood on which I had to remove and replace the complete transom and some of the stringers.
You will find that water , which has been trapped by the roten stringers will continue to come out for several days if not weeks. This it needs to do before you can do anything. All rotten wood must be removed as well. I am not sure how the keel stringer is installed, but most cruisers are a single skin hull construction , and are made the right way up; so to speak, with the gel coat first and then stiffening up with chopped strand or a coarser woven glass cloth. The stringers are then laid in and glassed over. Copious amounts of saw dust will help to mop up the water. After I had reached this stage it was then a case of getting hardwood stringers cut to size, laid in an glassed over. I prefer hard wood to softwood for this job. However it is not a quick or easy job but can be done single handed; but you must find out where the water is entering from and seal it up well. |
 |
|
|
cliveshep
Thailand
1324 Posts |
Posted - 11 Jul 2011 : 09:16:55
|
I'll enlarge on what Jimbo has told you.
If the water is not dripping out when the boat is out of the water it was probably rainwater and not a hull leak. If it's seeping out from underneath there is hull damage and you will obviously repair that.
Next, the longitudinal member that is rotten is the hog, or kelson, and it's function is to stiffen the hull so the boat can safely sit on the bottom. In the old days of wooden boats it married all the frames or ribs together and carried the garboard strakes (1st planks either side and the keel.
First and most important job is to chock the boat up all down both sides and under stem and transom - NOT the keel yet. Use a spirit or water level to make sure it is level side to side and preferably down it's waterline.
Now eye up the line of keel from underneath at the transom looking down it's length to make sure it is not "hogged" or has an upward curve in the middle, if it has wedge posts from the cabin roof to force it straight keeping the posts clear of where you need to lay the new hog or kelson. You don't want to fix a hull shape that is twisted.
You need to clean it all off and especially clean and well roughen the hull at least 3 inches or 75mm either side of where you intend to fit the new one. Preferably a bit more! Frankly I'd have wanted something wider, perhaps 4 inches or 100mm rather than what looks like 2 inches or 50mm as that doesn't impart an awful lot of stiffening. Force it into shape if necessary by wedges off the roof or piles of stone.
Softwood or hardwood - it makes little difference as it is the profile of the glass fibre layup over it that imparts the strength, but cut a timber to fit from transom to the curve of the bow. Lay it down - you'll need to remove the main bulkhead coaming across the doorway to get it continuous, tack it into place to hold it and allow you to remove any weights or wedges, and glass it in with 3 layer of 60gm/m2 chopped strand mat. Finish off afterwards with a coat of resin to ensure it is sealed. Then you can add any transverse ribs or stiffeners which can be 2 x 1 or 50 x 25mm. Also glass in the coaming again and make sure the bulkheads are properly glassed in at least up to the underside of the side decks as they maintain the hull shape..
The cost of boating is insignificant compared to costs of a young wife and two teenage kids! |
|
|
|
dnme
Ireland
110 Posts |
Posted - 11 Jul 2011 : 13:36:15
|
The boat is sitting up on 2 keel chocks and 4 side balancers in a paddock beside my house. It's under a tarp and kept dry since I bought it in March although I suspect this latest water is from a leak in the tarp.
Clive
Firstly, is there a way for me to proceed without this ? Can I perhaps test drill? check for rot? repair ?
Next, When you say "you'll need to remove the main bulkhead coaming across the doorway to get it continuous" are you suggesting that the keel timber cuts/site into the hull ?
Also, this is a Norman 17, I have a bout 2-3mm total of grp to play with on the hull, very thin skin all round. Also wedging timbers from the cabin roof is not an option as it's so thin and flexible.
My Norman 17 restoration thread (pics and vids)
http://www.boards.ie/vbulletin/showthread.php?t=2056217528
|
|
|
|
cliveshep
Thailand
1324 Posts |
Posted - 11 Jul 2011 : 14:10:44
|
Ok, the cockpit coaming is that part of the main bulkhead at the bottom of the door that is notched across the hog in the doorway.
Secondly, you can wedge off the roof, simply put a timber at the top across the roof side to side and wedge off of that. That puts the loads as tension loads trying to lift the whole topsides off the hull and the resistance to that is more than enough to wedge the hog down.
Third - you need to carry the weight of you and the boat on places other than the keel line - apart from at transom which will not deflect -because if it sits on a thin hull along the keel trust me it will hog, or deflect, under the weight and you'll be bonding that deflection in as a permanent feature which I'm sure you do not want. So - the keel should not carry any weight although you can wedge at the bow where the compound curves should stiffen it and at transom as I said.
Trust me,this particular cat only skins one way!
I know your hull is (actually more like 4-5mm thick) thin - that is why you need to glass in the stiffeners in the first place. The hog is vital in keeping the keel line straight and provides a place for any transverse ribs to bear onto. If the hull is hogged not only will it steer like a clapped-out 3-wheeler in a storm but nothing else will be straight either.
Bite the bullet, chock the boat as I told you, rip out the old rotten timber all the way through, get a nice bit of 4 x 1 1.2 inches, bevel the bottom to fit, taper down at the bow, it should go the full length of the hull right back to the transom and if it doesn't it was wrong before. Glass it in properly with at least 3 layers of 60gm/m2 CSM, lapping each layer further out than the first and you'll have a grand job. Get it wrong at this stage and everything else you do will be a waste of time.
Then glass back either the old coaming or a new one across the main bulkhead doorway, make sure the main bulkheads are glassed in and you will be ready to start fitting out.
The cost of boating is insignificant compared to costs of a young wife and two teenage kids! |
|
|
|
Jimbo
United Kingdom
585 Posts |
Posted - 11 Jul 2011 : 14:12:12
|
| Many thanks for the contribution by Cliveshep and I fully endorse all that he has said. Remember for wood to go black and rotte water must have been getting at it for a number of years. You must find the poit of entry for the water and seal it up for good. Best of luck. |
|
|
|
dnme
Ireland
110 Posts |
Posted - 11 Jul 2011 : 19:08:26
|
Clive, let me just get this straight, lets see if I have you here...
1. Choc the boat on its hull sides and transom sides leaving keel hanging down centre.
2. Remove the existing keel. I assume like the side keels, crawl in under boat with dremmel, cut out the grp covering the keel flush to the hull bottom, then prize / drop the keel timber. Ok so far?
3. Get a piece of 1x4 ish as long as the boat. Now surely I need to cut a curve in it to match the profile of the underside, it curves back along the length of the boat. Ok?
4. Get floor topside stringers glassed in.
5. Get keel timber pressed up into place with wedges
6. glass that in
Is this roughly what you are saying ?
My Norman 17 restoration thread (pics and vids)
http://www.boards.ie/vbulletin/showthread.php?t=2056217528
|
|
|
|
cliveshep
Thailand
1324 Posts |
Posted - 11 Jul 2011 : 20:03:41
|
quote:
Originally posted by dnme
Clive, let me just get this straight, lets see if I have you here...
1. Choc the boat on its hull sides and transom sides leaving keel hanging down centre.
and at the bow where it curves up
2. Remove the existing keel. I assume like the side keels, crawl in under boat with dremmel, cut out the grp covering the keel flush to the hull bottom, then prize / drop the keel timber. Ok so far?
No, leave the existing keel (if unusually it actually has one) because when you cut away the kelson or hog it would drop free anyway.
3. Get a piece of 1x4 ish as long as the boat. Now surely I need to cut a curve in it to match the profile of the underside, it curves back along the length of the boat. Ok?
I suggested something a bit thicker so you can cut it to more or less fit the bottom if the bottom is curved side to side. It won't have much if any rocker on that hull I believe (curve in the length) You will taper the width as it gets to the bow and also shape the bottom up until it goes into the curve of the bow rising from the bottom where it dies out.
Edit: I meant to write four by one and a half but I now see it didn't come out that way in my other response above so I understand the confusion.
4. Get floor topside stringers glassed in.
Everything I have said in both posts refers to the 2nd You-Tube vid which shows the hog INSIDE the boat and that is what I am talking about. If you do have an external keel, leave it off for the moment, glass over any bolt holes inside, and glass the hog in properly. Keel if any goes on after all that is done. The hog or kelson is what will hold an external keel which can contribute to the hull stiffness from outside if the boat takes the bottom as it can serve to spread the weight of the boat, but is a bit like a cast on your leg - your bones are supposed to do the real job. Yours is a displacement round bilge cruiser built for canals and rivers, not a deep-sea yacht but still any keel fitted is to improve directional stability, i.e. steering. On your boat or indeed any other grp boat the external keel does not and must not be what you rely upon to stiffen the hull - it's faulty design. Look upon it as the same as a shoe or boot on your foot, your foot needs nothing to support your body, but a shoe prevents you from hurting yourself on a sharp stone.
5. Get keel timber pressed up into place with wedges
No - get hog pressed DOWN inside with props, tack it into place with strips of CSM and resin, when firm remove props and finish the job INSIDE. Leave the outside at this moment in time - 1st things first, ok?
6. glass that in.
Yup, you got that bit right.
Is this roughly what you are saying ?
Now it is. I was not aware that you had an external keel - we'll talk about how you deal with that later when you've got the hog properly sorted out and any transverse (across the bottom) ribs.
My Norman 17 restoration thread (pics and vids)
http://www.boards.ie/vbulletin/showthread.php?t=2056217528
The cost of boating is insignificant compared to costs of a young wife and two teenage kids! |
Edited by - cliveshep on 11 Jul 2011 20:11:07 |
|
|
|
dnme
Ireland
110 Posts |
Posted - 11 Jul 2011 : 23:05:34
|
I'm totally confused.
Do I leave in the keel or remove it? In your reply to #2, you are saying leave it in. So what am I gonna use that big piece of timber for then?
In #4 you say if I have an external keel, leave it off for the moment ???
whats a hog and a kelson?
#5. No CSM, I am using EPOXY!
Here's a few pics from tonight. The string cavity has dried totally which would hint that the keel is dry would it not? if the keel was saturated/rotten, I'd imagine the cabity would take ages to sry.
1. cavity dried out
2. Keel, seems sound to me, the last thing I want to have to do is go removing this and replacing it. Surely a few explorative drill holes first to see if there's any need to go all guns blazing ???
My Norman 17 restoration thread (pics and vids)
http://www.boards.ie/vbulletin/showthread.php?t=2056217528
|
|
|
|
cliveshep
Thailand
1324 Posts |
Posted - 12 Jul 2011 : 10:33:07
|
Right, those pictures make it clear you do have a keel underneath-
Your first picture inside here
http://i1142.photobucket.com/albums/n603/ballymullaney/Img_6623.jpg
shows the hog or kelson which is inside the boat and is what the keel bolts to, Your original complaint was that it was rotten and your earlier pictures showed that clearly.
My responses ignored the keel, mostly because I wasn't sure it actually had one, but also because you'll have to remove the old keel bolts anyway when you remove the rotten hog.
Everything I said about the hog still applies - remove the keel bolts or if they are rusty just cut them off inside and glass over them first. Hacking away a rotten hog will reveal the keel bolts anyway.
You still do not want the weight of the boat sitting on the keel although once the boat is properly supported as earlier post you can wedge up the keel only to take it's own weight and not that of the boat as well.
Do the hog properly - remember it carries the keel later.
Then and only then re-drill and re-fit the keel bolts, well mastic the holes and glass over the bolts in the keel bottom and the hog inside.
It is all becoming clear where the rot has come from - your keel bolts have been leaking so you might after doing the hog consider removing the keel, checking it for soundness, filling the old bolt holes and drilling completely new ones and bolt the keel back on to the hull through your nice new sound hog with a good bed of Sealastic mastic tape and new bolts.
The cost of boating is insignificant compared to costs of a young wife and two teenage kids! |
Edited by - cliveshep on 12 Jul 2011 10:35:31 |
|
|
|
dnme
Ireland
110 Posts |
Posted - 12 Jul 2011 : 17:37:32
|
There are no bolts. I spent the day grinding clean the cabin floor and the stringer channel. There's a deep string of some kind of bondo down there, it's very healthy and strong as a rock. I'm gonna redo all stringers on deck and in cabin.
You might be thinking od the side keels. I have 2 of those and have already dropped them off the boat. Their keel plates and bolts were soaked and rotten. I will be re-bolting and re-glassing these timbers.
Apart from that, I want to keep it simple.
Many thanks
My Norman 17 restoration thread (pics and vids)
http://www.boards.ie/vbulletin/showthread.php?t=2056217528
|
|
|
| |
Topic |
|
|
|
|
© N.B.A.S. 2020 |
|
|
|
Rotten stringers, need advice
