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Catalina/Capri 25/250 Sailor's Forums

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Plugging a Transducer hole

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existentialsailor
Master Marine Consultant

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USA
1180 Posts

Initially Posted - 01/13/2005 : 18:27:51

I am removing my non-operative transducers. I will not be replacing them until next winter and they will be relocated to in front of the keel.

What would be the best way to permanntly plug these holes? Please note, the hull will be receiving a bottom job in a few months, so the "finishing" is not what I'm interested in at this point.

Thanks.

Rick

Edited by - on

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 01/13/2005 : 20:06:06

Hey Rick,

I did this very thing last spring when I finally removed two obsolete transducers leftover from the previous owner. I patched the two round holes pretty much as instructed in West System's softcover [url="http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?keyword=318485&resultCt=1&storeId=10001&catalogId=10001&productId=28521&y=5&x=25"]Fiberglass Boat Repair and Maintenance[/url] booklet ($2.99 West Marine).

This booklet describes in excellent detail the procedure to repair holes in the hull. The procedure is essentially to bevel the holes from the inside, put a temporary backing on the outer hull, then laminate epoxy and fabric from the inside. Once the epoxy has cured, remove the temporary backing and fill and finish the outside.

So Rick, spend the $2.99 for the above mentioned booklet. You'll be glad you did.

Edited by - on

Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 01/14/2005 : 07:40:44

Those used to be available for free on the website. I should've downloaded them when I could.

By the way, the $2.99 price is a bargain....MSRP is $3

A good temp backing by the way is waxed paper

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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 01/14/2005 : 08:22:42

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Duane Wolff
 ...A good temp backing by the way is waxed paper
<hr height="1" noshade id="quote"></blockquote id="quote">

Wax paper is exactly what I used, along with some stiff foam, a piece of plywood, and some 2x4's.

As for the booklet, it is money well spent.

Edited by - dlucier on 01/14/2005 08:25:32

existentialsailor
Master Marine Consultant

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USA
1180 Posts

Response Posted - 01/14/2005 : 09:30:48

Thanks Don,

I ordered the pamplet you recommended.

Appreciate the pointer.

Edited by - on

Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 01/14/2005 : 18:01:53

Rick,

I moved a thru-hull hole in my C-25 below the waterline. Here's what I did to permanently eliminate the old hole.

Using a 5" right-angle grinder, I beveled the outside of the hole at a 12:1 taper. That is, to repair a 2" round hole in 3/8" fiberglass, grind an 11" diameter shallow cone, with the edges of the original hole ending up knife sharp. (2x(12x3/8"))+2"=11", right?

I then lightly ground a few inches around the 2" hole on the inside of the hull to prepare the interior surface for bonding.

Both before and after all that grinding of the old fiberglass, I washed the repair area with acetone.

I applied two laminations of 14oz cloth and epoxy resin to the inside a few inches larger than the hole to form a backing for the real repair on the outside.

Once the inside patch was firm, I started laminating circles of 14oz cloth on the outside. Each disk of cloth was slightly larger than the remaining depression, so that the ragged edges ended up outside the final finished hull surface. In other words, I started with the largest disk first, a bit bigger than the ground out bevel. Some books say to start with the smallest disk, but WEST and I suggest doing it the other way around.

When the patch got too hot or lumpy to continue laminating, I took a break until it cooled and/or hardened enough to grind. I then ground the ragged patch to about the final profile before deciding what size and shape pieces of cloth to cut for the next few layers.

Any time after the first few outside layers harden, you can grind and/or sand smooth the interior part of the patch. (It has no structural significance to the finished repair.)

Once the whole patch was within a 1/32" or so of final thickness, I switched to epoxy based filler putty (WEST w/high density filler and/or microfibers). I then faired the area using 60-grit sandpaper on a longboard.

After final fairing, I applied a few more coats of epoxy to protect the fibers from water.

Got all that? Make Sense? Got questions?

-- Leon Sisson

Edited by - on

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 01/14/2005 : 18:37:29

Leon, question...What's the advantage to applying the patch from the outside? Working upside down with epoxy can't be all that fun.

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Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 01/14/2005 : 21:29:02

dlucier,<blockquote id="quote">quote:<hr height="1" noshade id="quote">What's the advantage to applying the patch from the outside? Working upside down with epoxy can't be all that fun. <hr height="1" noshade id="quote"></blockquote id="quote">The outside patch rule might be a hold over from the days of making repairs with polyester resin, when "secondary mechanical bond" was more wishful thinking than reliable expectation. With the patch on the outside, water pressure is pushing it tighter against the hull, whereas water pressure would be trying to creep under and pry loose a patch applied from the inside. Also, sometimes there are obstacles to easy access inside the hull, such as the liner. (With the method I described, if the liner is in the way, just skip the inside steps of the repair, but otherwise proceed as described. One less mess to clean up!

)

Working upside down with epoxy resin isn't all that hard. I've literally spread gallons of WEST on overhead surfaces while laying on my back. The only times it was really agrevating were in tight quarters where I had trouble seeing what I was doing or moving freely. There are a couple of ways to reduce and cope with the potential for drips. On large jobs, I chill the mixed resin in an ice water bath. I started doing this to extend pot life, but it also thickens the epoxy until after it's spread, where upon it warms up and thins out briefly until the cure resumes. By then it's off the applicator and in a thin enough layer that it's not so likely to drip or run. (And if it does drip, you're less likey to be under it by then!

) One caviat is that in a warm humid climate, the chilled resin tends to collect condensate from the air, so small batches and speed are still important. When applying messy and/or toxic glop overhead, I wear gloves, full face shield, and old long sleeved clothes. For the truly concerned, there are disposable Tyvek bunny suits. (And they look so presidential!

)

-- Leon Sisson

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Oscar
Master Marine Consultant

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USA
2030 Posts

Response Posted - 01/14/2005 : 21:50:28

<blockquote id="quote">quote:<hr height="1" noshade id="quote">on the outside, water pressure is pushing it tighter against the hull<hr height="1" noshade id="quote"></blockquote id="quote">

Like a plug type door on the airplane....never thought of that, good point!!

Oscar
C42 # 76 "Lady Kay" (Ex. C250 WB #618 )
Georgetown MD/Fort Lauderdale FL

Edited by - on

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 01/15/2005 : 10:01:16

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Leon Sisson
 The outside patch rule might be a hold over from the days of making repairs with polyester resin, when "secondary mechanical bond" was more wishful thinking than reliable expectation...<hr height="1" noshade id="quote"></blockquote id="quote">

My through hull patches are sort of locked in place. The old flush mount transducer holes had a tapered opening from the outside and when I beveled the area from the inside for the patch, I left some of that outside taper. This gave the opening a slight hourglass shape, with the majority of the bevel on the inside.

My theory was that with this slight hourglass shape, there was no way that the patch was popping out in any direction.

Edited by - on

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 01/15/2005 : 10:05:28

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Oscar
 <blockquote id="quote">quote:<hr height="1" noshade id="quote">on the outside, water pressure is pushing it tighter against the hull<hr height="1" noshade id="quote"></blockquote id="quote">

Like a plug type door on the airplane....never thought of that, good point!!

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

But Oscar, at altitude, isn't the pressure being exerted from the inside of the cabin? Which would mean that the door should open inwards so that this positive pressure can hold the door in place.

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existentialsailor
Master Marine Consultant

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USA
1180 Posts

Response Posted - 01/16/2005 : 14:02:21

Thanks Leon,

This sounds a lot like doing my stitch and glue kayaks, however, I've not yet had to plug a hole in a kayak and the hull material is okoume plywood, so there is only one layer of fiberglass used, except at joints.

I appreciate the detailed instructions.

Edited by - on

Oscar
Master Marine Consultant

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USA
2030 Posts

Response Posted - 01/17/2005 : 15:00:20

Don, I was referring to the overwing exits on older airplanes..(727/DC-9/older 737)..I shoud have been more specific. They came out one way...inward. Nowadays most doors are held in place with movable/mechanical means. Then again, some of the 767 doors come in, and then go up into the ceiling....Anyway, as someone said, the point is not to just create a plug and glue it in place, but to create a solid object which fills the hole, but won't fit through it. A mechanical bond, not just chemical. In fact you could make a plug, with a tapered head on it, stick it in the hole, no "glue", launch the boat and it would stay in place...held there by water pressure. Never thought about it in these terms, but learnt an important way to look at it......

Oscar
C42 # 76 "Lady Kay" (Ex. C250 WB #618 )
Georgetown MD/Fort Lauderdale FL

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