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-   -   Drilled Hole in Hull Repair (http://www.sailnet.com/forums/general-discussion-sailing-related/56790-drilled-hole-hull-repair.html)

weephee 08-04-2009 11:00 AM

Drilled Hole in Hull Repair
 
My sailboat came equipped with a water depth indicator. There is a 1 inch hole drilled through the hull about 2 feet below the waterline where the transmitter or whatever it is called exited the hull. I have remove all this old equipment and now need to fill in the hole. Question is how do I do it. The thickness of the hull at this point is 3/8 inches thick. Do I try and fiberlass in and over it or plug it with something. Both sides are accessible. Thanks

speciald 08-04-2009 11:19 AM

You don't need a depthfinder?

weephee 08-04-2009 12:02 PM

Drilled Hole in Hull Repair
 
The boat also came with a 178C Garmin which has a depth sounder. The remote unit is glued to the inside of the hull and the old one which was thru the hull was no longer being used.

Sabreman 08-04-2009 12:17 PM

I had a similar arrangement on my last boat.

You need to fill the hole:

1. Taper the inside and outside of the hole so that it's no longer a 90 degree edge. Sort of like a sink drain.
2. Remove all traces of paint on the inside and outside. Wipe with acetone
3. Obtain fibreglass roving cloth. Cut several pieces the size of the hole
4. Tape over the outside of the hole with masking or duct tape to temporarily seal the hole.
5. Mix up some West Epoxy or equivalent, soak the roving, and insert in the hole. Repeat once more. Tamp gently to remove air bubbles (This is really important). Let stand until hardened
6. Remove the tape from the outside
7. Repeat #5 until desired thickness is achieved. Make sure to remove all air bubbles.
8. Cut and epoxy a larger cloth piece to overlap the edges of the hole by about 1" and apply to the inside of the hole.
9. Mix collodial silca to thicken the epoxy and fair the outside of the hole.

weephee 08-04-2009 12:34 PM

Drilled hole in Hull repair
 
To Saberman: With the thickness of the hull being 3/8 inches do I fill the hole at one time with the epoxy and roving cloth or do I do it in stages and once it is full do I apply a larger piece on the inside as I should do on the outside. Thanks

Sabreman 08-04-2009 01:00 PM

I would do it in stages. Put in a couple of of layers of cloth, get rid of the air bubbles, let it harden, then a couple more, repeating untill all 3/8" is filled. When all is done, apply the last layer of roving on the inside.

I hesitate to put a layer on the outside because fairing it will be a real pain and you'll probably sand it all away anyway. That's why I suggested using collodial silca as a fairing. You can usea a lower density West fairing compound, but the silca is really strng stuff and this is an important repair.

To put the repair in perspective, it's a small hole and not in a load bearing area, so ther really isn't a need to cover the outside with cloth. After you fill with all the layers of roving (NOT mat) and the final layer inside, the repair will be as strong as the area around it. MAYBE if you pounded a hammer on the exact hole, MAYBE it would give, but I doubt it. There may be some disagreement on this, but I would feel confident with this repair on my boat.

All things considered, this is a simple repair and can be completed in a couple of days (most of the time is spent waiting for the epoxy to cure). A note of caution - don't cheap-out and use fibreglass resin. Use epoxy.

DwayneSpeer 08-04-2009 02:25 PM

Quote:

Originally Posted by Sabreman (Post 511022)
I had a similar arrangement on my last boat.

You need to fill the hole:

1. Taper the inside and outside of the hole so that it's no longer a 90 degree edge. Sort of like a sink drain.
2. Remove all traces of paint on the inside and outside. Wipe with acetone
3. Obtain fibreglass roving cloth. Cut several pieces the size of the hole
4. Tape over the outside of the hole with masking or duct tape to temporarily seal the hole.
5. Mix up some West Epoxy or equivalent, soak the roving, and insert in the hole. Repeat once more. Tamp gently to remove air bubbles (This is really important). Let stand until hardened
6. Remove the tape from the outside
7. Repeat #5 until desired thickness is achieved. Make sure to remove all air bubbles.
8. Cut and epoxy a larger cloth piece to overlap the edges of the hole by about 1" and apply to the inside of the hole.
9. Mix collodial silca to thicken the epoxy and fair the outside of the hole.

Following this repair method will result in a very week spot in your hull that could pop out under severe weather conditions. Don't do it! Do it right or hire it done by a professional! Doing it right involves grinding the hole back at a 12 to 1 ratio. That means that for your 3/8 inch thick hull the outer edges of your ground out area will be 4.5 inches away. Then gradually build up with larger and larger pieces of fiberglass roving until the final piece is the full 10 inches diameter. Actually Ferenc Mate says in his book "Shipshape, The Art of Sailboat Maintenance" that if the hull is greater than 1/4 inch thick then the ground out ratio should be 15 to 1 but everyone else that I've read recommend only a 12 to 1 ratio.

The rest of Sabreman's recommendations are quite good. That is cleaning the area very well, etc.

baboon 08-04-2009 02:32 PM

One option to consider is to leave the transducer in place. It is a solid plug and has no moving parts. Many feel the depth sounder is the most important instrument, and having a back up ready to go is not a bad idea. A through hull transducer will also be more acurate, although I understand the newer surface mounts are pretty good. It seems different manufactures of displays use the same transducers so you may have options as to how to read the depth.

scottyt 08-04-2009 04:33 PM

here are the west systems video's on basicly what and how you want to do it

now you dont need to cut the hole bigger like they, also for a 1 inch hole you wont need the piece backing the hole up. i would use 7 OZ glass not roving, roving is hard to wet out with resin. the big trick i dont think they show on the vid is when you have the glass in place cover it with a piece of a trash bag then squeegee as much resin out as you can. the glass is the strength the resin holds it together

part one

part 2

Sabreman 08-04-2009 05:12 PM

DwayneSpeer is correct. In my defense, in Step#1 where I indicate that a taper is to be made, Dwayne's suggestion is what I was getting at but did not adequately describe. I didn't have an exact ratio in mind, either 12:1 or 15:1 but something along those lines. Either way, it's easy to draw a 4.5" "target" circle and grind to the circle.

I really don't think that roving is that hard to wet. Using gloves, dip it into a tray or similar container with epoxy until wet. I suggested roving because it is stronger and builds quickly.

I wouldn't leave the transducer in place. I did that on our last boat and it was a mistake. The o rings will eventaully dry out and a leak is waiting to happen. Much better to do the job right and debate these details, IMHO.

Thanks guys, for the suggestions. This is what makes Sailnet great. I was not aware of the ratios even though I've done this job and other similar jobs in boatyards and my own boats for nearly 30 years. We always made a taper, but not to a specified ratio. In retrospect, we were pretty close but relied on eyeballing it.

Thanks.... learned something new again. :)


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