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Old 18-10-2018, 10:47   #1
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Replace port hole dawg.

Does anyone know where I can find replacement port hole dawg. One if mine has corroded and sheared off.

Boat is pacific seacraft 34.

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Old 19-10-2018, 00:33   #2
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Re: Replace port hole dawg.

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Originally Posted by Richfef View Post
Does anyone know where I can find replacement port hole dawg. One if mine has corroded and sheared off.

Boat is pacific seacraft 34.

Any help appreciated Attachment 179173
What's a Port Hole Dawg I googled it and got:

Doghole Ports | Greater Farallones National Marine Sanctuary
https://farallones.noaa.gov/heritage/doghole.html
These “doghole ports,” so named because they were so small and exposed that mariners joked they were barely large enough for a dog to turn around, became ..

Is it a latch for a porthole like the attachment?

Maybe try
https://shop.classic-boat-supplies.c...olt-removable/

https://shop.classic-boat-supplies.c...crew-with-eye/

https://www.google.com.au/search?q=p...2qPIwYyumjZEM:

It looks like the bolt part is the only part that is broken so why don't you by a brass bolt and make one up?

Clive
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Old 19-10-2018, 01:17   #3
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Re: Replace port hole dawg.

These look similar to yours.

But how can they claim they are "Solid Brass" and then claim below "Aluminum / Mirror" ?

https://www.ebay.com.au/itm/G4349-Po...T74:rk:28:pf:0

https://www.ebay.com.au/itm/Solid-Br...ETH4:rk:1:pf:0 (Actually I wouldn't buy off this guy as he only has positive feedback of 96% - shonky)

Clive
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Old 19-10-2018, 02:59   #4
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Re: Replace port hole dawg.

The broken part is called a swing bolt or rod end bolt. Here is a US source.

https://www.mcmaster.com/swing-bolts
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Old 19-10-2018, 03:30   #5
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Re: Replace port hole dawg.

Robinson's Antiques Hardware - mirror swivel screws
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Old 19-10-2018, 04:33   #6
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Re: Replace port hole dawg.

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Originally Posted by Richfef View Post
Does anyone know where I can find replacement port hole dawg. One if mine has corroded and sheared off.
Sure.

Browse Dover Marine MFG. and Supply CO., INC. and download their catalogue. They are in Deer Park, New York state.

If you search the interweb for "portlight dog" you might find a manufacturer closer to you. And perhaps you'll find exactly the same dog nut shape that your other portlight dogs have.

Here's the relevant page from the Dover Marine Manufacturing & Supply Co. Inc. catalogue to help you on your way.

See Dover catalog - Portlight dogs.pdf, about 175 KB.
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Old 19-10-2018, 04:47   #7
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Re: Replace port hole dawg.

Looks like just the bolt portion is broken. Buy a bronze 3/8" (or whatever thread that is) bolt that has a long enough threads, cut the head off and drill a hole through it.
If you don't have a bolt extractor, a local machine shop or garage will remove the broken piece from the dog for very little $ if not for free.
Make a few spares while you are at it.
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Old 19-10-2018, 18:20   #8
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Re: Replace port hole dawg.

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Looks like just the bolt portion is broken. Buy a bronze 3/8" (or whatever thread that is) bolt that has a long enough threads, cut the head off and drill a hole through it.

Note well that dog bolts (the swing bolts used to dog portlights) are NOT usually manufactured using a machine screw thread.

Instead dog bolts usually have a trapezoidal thread or the modified trapezoidal thread called an Acme thread.

Both trapezoidal threads and Acme threads are easy to cut. But they are NOT the same as the triangular machine screw thread you find on a bolt or machine screw.

For the difference between a standard trapezoidal thread and an Acme thread, see: https://www.natool.com/blog/2016/12/...ats-difference
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Old 19-10-2018, 18:30   #9
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Re: Replace port hole dawg.

Acme thread and trapezoidal threads both have flat tops and bottoms, and very steep angles (29/30 degrees). If you look at the photo they appear to be triangular / pointed at the top and have a large angle... no need to make a simple problem complicated.
I would certainly try a standard thread first.
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Old 19-10-2018, 19:14   #10
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Re: Replace port hole dawg.

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Originally Posted by Rowglide View Post
Acme thread and trapezoidal threads both have flat tops and bottoms, and very steep angles (29/30 degrees). If you look at the photo they appear to be triangular / pointed at the top and have a large angle... no need to make a simple problem complicated.
I would certainly try a standard thread first.
Yes, I think you're right Rowglide. On careful inspection of the photo, the OP's dog bolts do look as if they have a standard triangular machine screw thread.

And perhaps that's the source of the problem. Portlight dog bolts traditionally (and still from good manufacturers, such as from Dover Marine Manufacturing) were cut with Acme threads. The Acme Manufacturing Company invented the Acme thread as an improved trapezoidal thread for worm drives and the like. The idea being that the friction between the external thread and its nut was lower than in the case of a standard square-topped trapezoidal thread.

The triangular machine screw thread is designed for lots of friction: that's what keeps nuts fastened to bolts.

So my guess is excess friction between the dog bolt and dog nut, due perhaps to some surface corrosion on the faces of those triangular threads, prompted a user to apply additional force to the dog nut, causing the dog bolt to fracture. Acme threads might not have led to the problem.

So perhaps time for an upgrade all round to Acme threaded dogs from Dover, so the portlights last the life of the boat?
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Old 19-10-2018, 19:26   #11
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Re: Replace port hole dawg.

Did you contact Pacific Seacraft?
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Old 20-10-2018, 00:41   #12
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Re: Replace port hole dawg.

Lots of great info. I called Dover. 1. They don't sell to individuals. 2. They only have larger sizes.

I plan to get threaded rod end and a wing nut from McMaster (i used to work there). Not an identical replacement but should stop the port from leaking.
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Old 20-10-2018, 00:43   #13
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Re: Replace port hole dawg.

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Did you contact Pacific Seacraft?
Yes. Thumper said they don't have it and to get custom made replacement
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