Glassing a hole in the boat?

graham

graham

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I have two holes about 1.5 inch diameter which had redundant impeller and transducer in.

I am going to glass up the hole with epoxy and woven roving on the next dry day.

I am thinking of grinding the hole inside and out to increase the outer diameter by about an inch glassing it with small circles of woven roving so the final epoxy repair is rivet shape if you know what I mean with extra layers on the inside as well onto freshly ground or sanded area of hull.

HoleRepair.jpg


Is this the way to do do it,any tips? I recently helped a friend do a similar job so am aware of temperature issues with curing epoxy.
 
Graham

Had this done on A22 Sea Moon recently with three holes filled; appeared to have been done with a lot of fibreglass matting on inside rather than epoxy.

Can't you let the next owner do this?

IanC
 
I would prefer to see just one taper (internal)as there could be a problem with voids, and having something hard to wet out /stipple against, unless you laminate one side at a time. Use circles of mat increasing in size, ending up with a 50mm overlap in excess of the ground section on the inside
As you are aware temperature and cleanliness of the repair site are essential
 
There is a chapter on this in Pat Manley's book 'simple boat maintenance' which gives details of materials and techniques. Jolly good book to have and quite cheap.
Regards,
Pat Manley (only kidding)
 
I think that's exactly how Jake Kavanagh showed how to do it in an article in PBO last year. He covered the outside with a few layers of parcel tape, applied a thickened epoxy mix (using microballoons) first, and then laid up a series of glass cloth circles on a sheet of polythene. This can then be lifted as one and applied to the hole. Stipple into place with a bit more epoxy.
 
I have done many similar jobs ranging from altering the housing for a transducer, blanking off a redundant exhaust hole, right up to the manufacture and glassing-in of an entire stern tube on new inboard installations. I never bothered with epoxy; plain polyester resin and CSM were more than sufficient.

The main thing to ensure is to really grind back to the existing fibres, using a coarse disk. Epoxy won't break the bank, of course. However, in my opinion the hassle of accurate mixing and temperature control, besides the added expense of epoxy is just not justified - especially on a simple blanking-off job like you describe.
 
I second Grajan's advice about keeping the taper mainly to the upper surface of the repair. I carried out this type of repair and found sagging and voids very hard to avoid, (sorry! ) when working "overhead". A small taper here is OK, but nothing too ambitious. Be sure to use a glass mat suitable for use with epoxy.
 
Thanks for all the advice people. Forecast for cold and wet tommorow,sods law /forums/images/graemlins/grin.gif
 
G'day Graham,

Tips as requested:
Only use epoxy resin when working below the water line because it's stronger and is more water resistant than other resins.

Start after any dew has dried off indicating the humidity is dropping, it should be below 73% and the temperature above 20*C during curing. a light will help maintain temperature if left on.

Start by running heat gun over and around the area as it's most important that no moisture remains in the exposed laminate, you can also use this to speed up the curing process later.

Cut an old plastic container and tape it to the outside of the hull then use a prop to hold it in place, this will avoid working overhead and reduce the risk of voids, as well as reducing the amount of sanding later.

Start by mixing a small amount of resin and hardener then adding some 'closed cell' micro balloons, they will be easy to sand back later.

As the holes are small you should be OK with roving's but I would advise bi-directional cloth and a layer of roving's after each 2 or 3 layers of cloth. Use roving's for the first layer and take care when placing it not to disturb the micro balloon layer.

When you have built up past the sharp edge of the two angles left by grinding from both sides, use a small grooved roller to remove any excess resin, this will add strength to the repair, you are looking for a one to one ration by weight of cloth and resin.

The last layer should also be roving's, this will help to contain any stray strands close to the surface, finish by adding 4 coats or resin only wet on tacky to avoid sanding between coats, this will provide a good seal and chemical barrier.

Allow this to cure, I would expect you will not have to stop because of heat build as the holes are small. When cured, remove the plastic on the outside and wash the area with a running hose and and Scotch brite plastic scourer till it it no longer forms beads, this removes the residue left by curing. Now you can sand it without spreading the contamination.

Sand smooth with the hull then using the paper and a couple of fingers, remove a small amount inside the repair area, clean off with a little Acetone and apply 4 or 5 coats of epoxy wet on tacky to seal the repair, after curing wash as above and sand with a 200 grit to remove the gloss finish. Apply some epoxy primer and the paint of your choice.

More tips:
Pre-cut all the glass before you mix any resin. Use Latex gloves, clean uncured resin off with white vinegar, mixing containers should wide and shallow to keep the resin cool, work area should be well ventilated.

Hope this helps.

Avagoodweekend......
 
The double chamfer (ie inside and outside) means that provided the 2 patches are pressed together in the middle to bond you have a patch that is locked in and can not fall out even if completely disbonded.
I would suggest you start from the outside build up the patch then hold it in place with a circle of plastic or wood covered in cling film. The closer this pad resembles the hull contour the less filling/sanding.
Then before the outer patch has gone completely hard put on the inner patch making sure that it is well bonded to the outer patch.
I did one on my boat about 10 years ago using polyester and I am not sure I could even identify where it was now- no probs.
olewill
 
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