Visit our Popular Forums

otherthan · 18-01-2011, 21:58

,no way you will un do a bolt with out destrying the thread.

just the nut...not the bolt

best/cheapest option is drill new holes and tap in keel,but need a very slow big drill,compressed air to clean holes,then tap.
new plates and 3/4 bar threaded.

thats probably what i will do

thanks

did this on a wooden boat a few months ago,but heavy going[/QUOTE]

**atoll** · 18-01-2011, 22:19

where you gona be in the uk?
might be able to help if near us.

callmecrazy · 18-01-2011, 22:38

I don't mean to create controversy but, I'd still argue that "tapping" into epoxy is entirely different than "bedding" a bolt into it...
Maybe I'm wrong, but my understanding is the load should be carried by the hull itself and not the threads... by bonding a bolt into the keel, then bolting it through the hull, the load is carried by the nut vs. hull structure. not the threads. by simply 'tapping' a bolt into epoxy (or whatever), the threading becomes the supporting structure and the weakest link... there needs to be a thru-bolt applicationn, no matter how you go about it.

beetle · 18-01-2011, 22:39

Quote:

Originally Posted by jobi

its not the same...I said similar!

I'm sorry, I interpreted 'the same way' to mean 'identical to'. Apparently you have a better idea of how it all fits together, and I will bow out of the conversation.

- rob

beetle · 18-01-2011, 22:48

Quote:

Originally Posted by callmecrazy

Maybe I'm wrong, but my understanding is the load should be carried by the hull itself and not the threads... by bonding a bolt into the keel, then bolting it through the hull, the load is carried by the nut vs. hull structure. not the threads. by simply 'tapping' a bolt into epoxy (or whatever), the threading becomes the supporting structure and the weakest link... there needs to be a thru-bolt applicationn, no matter how you go about it.

And what does a nut attach to? I believe the nut creates a tension arrangement between it's internal threads and the bolt's external threads - so you've always got threads running around somewhere.

The problem arises in tapping threads into a material that is not as strong as the bolt threads, such as lead, or epoxy (as suggested in this case). Bolt and nut design is such that the threads the nut catches are as strong as the bolt's solid center such that, in tension, the bolt should fail before the nut shears the threads.

Tapping into a steel keel is not that unusual; a typical steel keel design has a flange at the top which extends outboard of the keel, and bolts are passed through the flange and up into the hull to provide support. Normally one might arrange bolts running up from the bottom with would nuts inside the hull, but if you wanted to make things simpler one might consider tapping directly into a steel keel and running the keel bolts down from inside the hull.

- rob

callmecrazy · 18-01-2011, 23:01

Quote:

Originally Posted by beetle

And what does a nut attach to? I believe the nut creates a tension arrangement between it's internal threads and the bolt's external threads - so you've always got threads running around somewhere.

The problem arises in tapping threads into a material that is not as strong as the bolt threads, such as lead, or epoxy (as suggested in this case). Bolt and nut design is such that the threads the nut catches are as strong as the bolt's solid center such that, in tension, the bolt should fail before the nut shears the threads.

Tapping into a steel keel is not that unusual; a typical steel keel design has a flange at the top which extends outboard of the keel, and bolts are passed through the flange and up into the hull to provide support. Normally one might arrange bolts running up from the bottom with would nuts inside the hull, but if you wanted to make things simpler one might consider tapping directly into a steel keel and running the keel bolts down from inside the hull.

- rob

Well that makes good sense, and validates my concern. The question then becomes, what is the keel really made of? I seriously doubt there is any foam in the keel. maybe laid on top? If it's really steel and there is a proper flange carrying the load to the hull... then go for it. If not, re-evaluate.

(beside the point)
I agree with everything beetle said except I think I would argue the load issue between a thread and thru-bolt structure... the threads don't carry any significant load, which is the entire point of thru-bolting

I'm going to bed...good luck.

**Boracay** · 18-01-2011, 23:40

I would have thought that crossing one of the more unfriendly stretches of ocean in the world was risky enough.

Crossing in a newly purchased small old boat with suspect keel bolts is surely tempting fate...

otherthan · 19-01-2011, 00:20

Quote:

Originally Posted by Boracay

I would have thought that crossing one of the more unfriendly stretches of ocean in the world was risky enough.

Crossing in a newly purchased small old boat with suspect keel bolts is surely tempting fate...

sorry but I have no plans on crossing with a suspect boat...I will do whats nesasary beforhand...I am a mecanic and owned a body shop for 17 years, I sold the shop to do machinery for a trucking company...trust me I understand the concept...re read my post and you will see that epoxy is only a suport aid, never mension threading it in anyway...I also stated about my intent to make sure the original bolts are in good conditions.

cheers

SimonV · 19-01-2011, 03:43

here are some fixes.
keelbolts

Projects: Below Deck: Replacing Keel Bolts | MadMariner.com

Keel Bolt Removal

**Pete7** · 19-01-2011, 04:05

Right the boat is ashore in a boatyard in the UK, well Wales actually.

Since all that is required is the removal of half a dozen bolts and replacing them with new ones why not ask the boat yard to quote for the work, that way its done when you arrive and you can get on with other things.

At least ask to lift a couple of them to see what they are like, afterall the bolts could be like new were they are protected by the hull and keel and on the bolt heads are mildly rusty and needing a coat of paint.

I wouldn't go about drilling 4" holes "2 deep and then try to fill it, afterall the boat is what 1970s? so the original design clearly works, the risk is the bolts may have corroded. So check a couple first rather than masses of extra work not needed.

Pete

otherthan · 19-01-2011, 07:54

[QUOTE=SimonV;599932]here are some fixes.
keelbolts

this is how the keel is bolted...quite simple and an easy fix

thanks for the link

otherthan · 19-01-2011, 08:03

[QUOTE=Pete7;599941]Right the boat is ashore in a boatyard in the UK, well Wales actually.

the boat is in pembrook...I will sail her to gibraltar and let the sun dry her up a little...the dampness is from rain water not salt...stainless bolts dont get much damage from rain water...after a few weeks of sailing gibraltar I will know what needs to be done befor the crossing.

thanks for your sugestions...however iv stoped long ago giving my money when I can do the job myself...in todays world we have access to information and can get educated on any task.

regards

callmecrazy · 19-01-2011, 08:15

Good find.

That is what I meant by 'backwards' thru-bolting. I just wasn't very good at describing it... The only difference is this has nuts on both ends of the bolt instead of a bolt head. but either way it's the same thing.

So the foam the surveyor was referring to is the stuff that's injected into the pockets? or did they still use foam to stiffen the hull? Just curious...