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Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

How to get coax through a rubber grommet.

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Initially Posted - 12/31/2007 : 20:16:08

I struggled with this today and then came upon a good solution that I thought I'd share:

Here's the scenario, running new coaxial antenna cable through your mast. You need to run the cable through rubber grommets to prevent chafe. The grommet's ID is the same as the cable's OD.

First make sure that the hole in the mast is slightly bigger than the OD of the grommet's groove. In my case the groove's OD was 11/32", so I drilled out the original hole to 3/8" and then used a Dremel tool to round over the edges. I used a small conical stone which I could fit through the hole to get to the burrs on the inside. This made the hole in the mast slightly over 3/8".

Next, insert the grommet into the mast making sure it's seated all the way around.

Then, to get the cable through the grommet from the inside of the mast you have to do some prep work on the end of the cable. Cut the end of the cable flush, then spend some time tapering the sheath with a razor knife but w/o cutting into outer metal mesh of the core. Once you've got the outer sheath tapered back maybe 1/4" along the cable, "milk" the sheath out leaving the core back maybe 1" inside the sheath. So now you've got a hollow tube which is easily compressible making it easy to pull it through the grommet.

Next, tape the end with good duct tape ( I like Gorilla tape) wrapping from just forward of where the core is back inside the sheath, out to about an inch or so past the end of the sheath so you have a nice tapered piece of tape that's easy to get through the hole.

Next, insert the cable down the mast watching for the tip to go past the grommet. Once you can see it, grab the tapered tip of the tape with a pair of needle nose, or forceps. Pull the tip out through the grommet while feeding the coax from the other end. Gently pull the tip of the tape and then the empty coax sheath till you can use the sheath to pull the cored cable through the grommet.

David
C-250 Mainsheet Editor

Sirius Lepak
1997 C-250 WK TR #271 --Seattle area Port Captain --

Edited by - delliottg on 12/31/2007 20:36:31

PZell
Admiral

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USA
548 Posts

Response Posted - 01/01/2008 : 09:47:38

Hmmmm. I wonder if you could have just slid the grommet down the coax far enough, then poked the coax in from the outside. When you had eveything right slide the grommet up to the hole and use a slotted screwdriver to get the grooves in the hole.

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 01/01/2008 : 12:59:22

Nope, tried that in both directions, ruining one grommet, and gave up before ruining the second one. Since I only had four to work with I wanted to preserve the other ones for the connection at the foot of the mast. I think doing the one in the foot of the mast won't be as hard, since I can reach inside the mast with my hand, where at the top of the mast, there's only a narrow slot to work in so it all had to be done with tools. I'll probably skip the tape part since I'll be able to simply pop it out of the inside of the mast through the grommet with my hand with just the milked sheath.

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Renzo
Admiral

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USA
621 Posts

Response Posted - 01/01/2008 : 13:32:27

Another little tip that can make the job easier is to grease the coax with vasaline or hand cream after you get it started. it makes the pulling go a lot easier and reduces the chance of damaging the cable.

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delliottg
Former Mainsheet C250 Tech Editor

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4479 Posts

Response Posted - 01/01/2008 : 13:42:50

Excellent point, I forgot to mention that.

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Alan Clark
Captain

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406 Posts

Response Posted - 01/02/2008 : 07:59:54

Instead of Vaseline, I would use liquid soap..like a hand soap that is degradable in a relative amount of time.

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Champipple
Master Marine Consultant

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6855 Posts

Response Posted - 01/02/2008 : 14:24:04

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Alan Clark
 Instead of Vaseline, I would use liquid soap..like a hand soap that is degradable in a relative amount of time.
<hr height="1" noshade id="quote"></blockquote id="quote">

I agree with Alan on this one...I seem to remember a high school health teach mentioning potential maladies that might occure when using petroleum jelly in conjunction with polymers of that ilk.

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GaryB
Master Marine Consultant

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USA
4303 Posts

Response Posted - 01/02/2008 : 15:02:38

I'd recommend using electrical wire lubricant that electrician's use to pull wire through conduit. It's made for that purpose. I've seen it at Home Depot and I'm sure it's probably available at Lowe's or most other hardware stores.

GaryB
'89 SR/WK #5862
Kemah,TX

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Renzo
Admiral

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USA
621 Posts

Response Posted - 01/02/2008 : 16:56:07

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Champipple
 <blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Alan Clark
 Instead of Vaseline, I would use liquid soap..like a hand soap that is degradable in a relative amount of time.
<hr height="1" noshade id="quote"></blockquote id="quote">

I agree with Alan on this one...I seem to remember a high school health teach mentioning potential maladies that might occure when using petroleum jelly in conjunction with polymers of that ilk.
<hr height="1" noshade id="quote"></blockquote id="quote">

If you are that worried about it use KY Jelly

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Nautiduck
Master Marine Consultant

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3704 Posts

Response Posted - 01/02/2008 : 19:19:55

<blockquote id="quote">quote:<hr height="1" noshade id="quote">If you are that worried about it use KY Jelly<hr height="1" noshade id="quote"></blockquote id="quote">

Dude, you CAN love a boat too much!

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Renzo
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621 Posts

Response Posted - 01/04/2008 : 09:12:09

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Nautiduck
 <blockquote id="quote">quote:<hr height="1" noshade id="quote">If you are that worried about it use KY Jelly<hr height="1" noshade id="quote"></blockquote id="quote">

Dude, you CAN love a boat too much!

<hr height="1" noshade id="quote"></blockquote id="quote">

Yeah! But not too often!

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ilnadi
Captain

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452 Posts

Response Posted - 01/07/2008 : 11:29:38

You coax it through gently

(sorry, this has been hounding me since I saw the subject line)

BTW, use vaseline, etc if you want the coax to be able to move in the grommet. If you want it to stick, use rubbing alcohol. It will evaporate and the two will pretty much stick to each other.

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delliottg
Former Mainsheet C250 Tech Editor

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4479 Posts

Response Posted - 01/07/2008 : 12:31:20

If it makes you feel any better, I've been wanting to change the title to Coaxing coax ever since I first wrote it. Simply didn't occur to me when I first posted it.

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Gambit
Navigator

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USA
160 Posts

Response Posted - 01/08/2008 : 07:52:03

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Renzo
 <blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Nautiduck
 <blockquote id="quote">quote:<hr height="1" noshade id="quote">If you are that worried about it use KY Jelly<hr height="1" noshade id="quote"></blockquote id="quote">

Dude, you CAN love a boat too much!

<hr height="1" noshade id="quote"></blockquote id="quote">

Yeah! But not too often!

<hr height="1" noshade id="quote"></blockquote id="quote">

All good tips here, you might also start out by buying your boat a drink or two as well.

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