Keel refit

[newbridge]

I have dropped and refitted one of the keels on my Newbridge Venturer. during the refitting I have torqued the bolts up to 75 psi but have not been able to find out what the true final torque should be. Any help on this would be greatfully received.

 

[misterg]

Hello, and welcome!

Unfortunately not an answer, just to ask how you got on dropping the keel, as I have the same job to do this winter on our Venturer.

The keels on ours (bilge keeler) are the later type with flanges on the top that fit into recesses under the hull, and the bolts (8?? of them) are 3/4" whitworth. These have some horrendous potential maximum tightening torque, which seems excessive to me when the head is only supported by a ~2" square washer - I'm not an expert, and unless I hear otherwise, I would just go for "as tight as I can" , once the bedding compound has had a chance to set. Ours were not very tight (maybe why the keels need to be re-bedded!).

Perhaps someone could explain normal practice based on 3/4" bolts & a 2" square washer onto GRP ???

(I'm not sure what the fixing arrangements are for the older keels where they bolt onto GRP stubs, though)

Andy

 

[Jonny_H]

Never dropped the keels on a Newbridge, or a bilge come to that, but this is what I've done on some racing keelboats in the past (e.g. Projection, Squib etc) ...

Host the boat into the air on a lift (around 2 foot off the ground should do it)
Place a large tractor tyre under the keel
Undo the bolts inside
Quick knock with a large hammer to loosen any sealant etc
Wait .... /forums/images/graemlins/shocked.gif

In time (usually a couple of hours) nature will take its course! /forums/images/graemlins/grin.gif

Don't know whether this is the sort of approach others have adopted?

Jonny

 

[newbridge]

Hi Andy - Thanks for your reply. Wizard is also a bilge keeler although she only has four bolts per keel. The dropping was fairly straight forward realy. Like all these sort of jobs - 80% planning and 15% doing and 5% admiring your work with passing human traffic.

As she was being craned out for the winter I made sure she was seated on fairly chunky blocks so I could get a trolly jack under each keel. Then as I jacked her up I chocked her fairly well along her centre line and placed props along the sides and at her bows. She held realy well there. I only felt the need for about four inches of drop to allow me access to both keel and hull surfaces so was able to take the boats weight and remove the blocks beneath the keel. This meant she stayed much at the same angle as she had been craned in at.

Next I removed each bolt in turn repairing and reinforcing the hull with fiber and resin as I progressed. Once each bolt was drawn I replaced it with a length of steel rod that would easily slide as the keel was lowered. That ensured the keel was kept in line with the hull holes at all times so as to make it easier when realigning. Befor the final lowering I made a timber bracing frame behind the keel for it to slide down and keeping its true angle.

As you noted the size of washers is fairly small and I was not very happy with the origional size. I had some more made thicker and slightly larger all round.

Once both surfaces had been cleaned and primed or resined the reasembly was reasonably straight forward. A realy good layer of sealing compund and slowly jacking up keeping in line with the four steel pins I'd used. I then re-bolted each hole and tightened up firmbut not too tight. I then left the sealing compound to go off for a week and then tightened up so as to make a realy good seal and not squirt all the good stuff out.

that leaves me at my current stage - having torqued up to 75psi and not being able to find a definitive torque guide.

regards

Chas

 

[essexboy]

Size and thread of bolts / nuts will be needed for an answer methinks

 

[newbridge]

Four stainless steel bolts - three 3/4" and one 1/2". All aprox 5" in length.

 

[William_H]

Bolts are made to be stretched if they are to provide the greatest resistance against fatigue. Hence the bolt manufacturer soecifies the required torque.
Now if it the cyclinder head of your diesel this is critical as the repetitive stress on the bolts can result in early fatigue failure. A bolt if stretched between 1.5 mm and 2mm repetitively resists fatigue better than if stretched between 0 and .5 mm repetitively.

Now in your keel this is a different story. Repetitive fatigue is not likely to be a problem. But more importantly the structure around the keel is not likely to be able to withstand the pressure required to stretch the huge bolts. The bolts are made oversized to account for log term corrosion factors. ie bigger lasts longer.
So I reckon that the tightening torque should be dictated by the weakest structure in the load circuit ie the fibreglass and if you tighten them up as tight as you can with say a 1 metre bar that will be fine. olewill

 

[misterg]

Thanks for the description - Pretty much what I had planned, just not got around to it, yet.

Cheers,

Andy