ferrispeterchris
Well-Known Member
What is the recommended method of "glassing in" an unwanted hole in the hull below the water line? Peter.
Glassing in hole
- Thread starter ferrispeterchris
- Start date
Talbot
Well-Known Member
Dont know the recommended method, but I like to feather the edge of the hole on the outside, and put a plywood pad covering it on the inside, then lay up some glass cloth. Finishing with an epoxy covering on the outside.
simonfraser
Well-Known Member
pad on the outside, stops it all falling out of the hole
William_H
Well-Known Member
Typical hole is where a log paddle was removed. I suggest lots of thick glass and or woven rovings and epoxy although polyester will work ok. You need to chamfeer the edges both inside and outside to a distance of at least twice the hull thickness and deep enough so only 25% of the hull thickness is not chamfered. (after cutting from both sides.
(You started with a 50mm hole in 10 mm thick hull. Grind the edge of the hole on the outside until it is 20mm larger in diameter at the surface going to zero when 4mm deep. Do the same on the inside.)
On the inside you place a sandbag in one of those shopping plastic bags or covered in cling fil. Hopefully you can press this down so it goes into the hole about half way.
Starting from the outside you cut fibreglass circles firstly the diameter of the hole and then getting larger until you have 5mm thick glass for a 10 mm thick hull. For the commonly available fibreglass this will be a lot of layers but for thick woven rovings not so many. However you should only use a few layers of woven rovings. (woven rovings are like pieces of rope of fibreglass strands woven into a mat that is quite thick like 20 times as thick as fibreglass as a cloth. Of course both vary in thickness known as weight) Whatever you can get is good.
You saturate with resin each piece and put into the hole. Hopefully they don't fall out again. The trick is to totally saturate the fibreglass cloth as shown by colour change while not having too much resin. roll the cloth or stipple with a brush to get it fully saturated and right into position with no air bubbles or gaps. ( If you have never done this before it is worth trying a few layers on a piece of plastic to see how much resin is necsssary and observe how itt hardens.) The whole job needs to be done at least at 15degrees temp or more. In winter you will need heat lamps or blowers and a tent over the job.
When the patch is fairly stiff but perhaps a little tacky it is time to remove the sandbag and build a similar patch on the inside. The two patches being not fully cured will bond together well so even a poor bond onto the hull itself won't matter as it is locked in with glass bigger than the hole on both sides.
Once the outside is hard you can add more resin with a filler or grind it down to the correct level until finally you can paint over it. Grinding is difficult if it is not hard (it just clogs your sand paper or grinder) and sometimes cutting with a sharp knife, chisel or even a power pllaner will do better. It might take a week to get really hard and a week gap between inside and outside won't hurt.
Don't worry too much there is no chance of a leak and the hull will be a lot stronger than it was with the hole. Highly stressed fibreglass wings on aircraft are repaired this way often with a shamfer only on one side but that relies on bonding to the original material,
I repaired a log hole on my boat long ago and couldn't even find the spot now unless I went probing. Polyester requires a small amount of hardener like 10 drops for quantity of resinabout 1 cup full while epoxy is mixed at definite rate of from 1to1 to 1to 2 of resin to hardener. The polyester can be speeded up in cold conditions or if you are in a hurry with double the amounnt of hardener while epoxy can only be speeded by a little gentle warmthh. Good luck do a trrial rubn first it is a lot of fun. olewill
(You started with a 50mm hole in 10 mm thick hull. Grind the edge of the hole on the outside until it is 20mm larger in diameter at the surface going to zero when 4mm deep. Do the same on the inside.)
On the inside you place a sandbag in one of those shopping plastic bags or covered in cling fil. Hopefully you can press this down so it goes into the hole about half way.
Starting from the outside you cut fibreglass circles firstly the diameter of the hole and then getting larger until you have 5mm thick glass for a 10 mm thick hull. For the commonly available fibreglass this will be a lot of layers but for thick woven rovings not so many. However you should only use a few layers of woven rovings. (woven rovings are like pieces of rope of fibreglass strands woven into a mat that is quite thick like 20 times as thick as fibreglass as a cloth. Of course both vary in thickness known as weight) Whatever you can get is good.
You saturate with resin each piece and put into the hole. Hopefully they don't fall out again. The trick is to totally saturate the fibreglass cloth as shown by colour change while not having too much resin. roll the cloth or stipple with a brush to get it fully saturated and right into position with no air bubbles or gaps. ( If you have never done this before it is worth trying a few layers on a piece of plastic to see how much resin is necsssary and observe how itt hardens.) The whole job needs to be done at least at 15degrees temp or more. In winter you will need heat lamps or blowers and a tent over the job.
When the patch is fairly stiff but perhaps a little tacky it is time to remove the sandbag and build a similar patch on the inside. The two patches being not fully cured will bond together well so even a poor bond onto the hull itself won't matter as it is locked in with glass bigger than the hole on both sides.
Once the outside is hard you can add more resin with a filler or grind it down to the correct level until finally you can paint over it. Grinding is difficult if it is not hard (it just clogs your sand paper or grinder) and sometimes cutting with a sharp knife, chisel or even a power pllaner will do better. It might take a week to get really hard and a week gap between inside and outside won't hurt.
Don't worry too much there is no chance of a leak and the hull will be a lot stronger than it was with the hole. Highly stressed fibreglass wings on aircraft are repaired this way often with a shamfer only on one side but that relies on bonding to the original material,
I repaired a log hole on my boat long ago and couldn't even find the spot now unless I went probing. Polyester requires a small amount of hardener like 10 drops for quantity of resinabout 1 cup full while epoxy is mixed at definite rate of from 1to1 to 1to 2 of resin to hardener. The polyester can be speeded up in cold conditions or if you are in a hurry with double the amounnt of hardener while epoxy can only be speeded by a little gentle warmthh. Good luck do a trrial rubn first it is a lot of fun. olewill
philip_stevens
Well-Known Member
Look at http://www.westsystem.com/, go to "projects", "index", "Repairing machined holes in fiberglass", and look at diagrams 6 and 8.
twisterkai
Well-Known Member
Been offline for a bit but finally replied to your post on log transducers etc.
ShipsWoofy
Well-Known Member
This might be helpful
GRP REPAIR MANUAL
It is a 450kb pdf document, best right click and save as so you have it on your hard drive...
hope this helps.
Incidentally, I recently filled a 42mm hole under the water line, the principle is simple and I am very pleased with the results. PM me if you are unsure and I will send my telephone number if you want to chat about how to tackle it...
GRP REPAIR MANUAL
It is a 450kb pdf document, best right click and save as so you have it on your hard drive...
hope this helps.
Incidentally, I recently filled a 42mm hole under the water line, the principle is simple and I am very pleased with the results. PM me if you are unsure and I will send my telephone number if you want to chat about how to tackle it...
ferrispeterchris
Well-Known Member
Thanks everyone, Peter.
