PaulRainbow
Well-known member
West is just their opinion. You need to read less and get out more. Real World experience generally trumps Goggled answers to questions about subjects that you have no actual experience or understanding of.
Would you fill a hole below water line with this?
- Thread starter ghostlymoron
- Start date
West is just their opinion. You need to read less and get out more. Real World experience generally trumps Goggled answers to questions about subjects that you have no actual experience or understanding of.
VicS
Well-known member
You need to read more and learn the best way of doing things instead of preaching methods you've taught yourself and bad practices you've picked up from dodgy boatyards youve worked in or elsewhere
I read the West guide ... then successfully did an identical repair to the OP's in the way they suggested. So dont you start telling me what I dont understand or have experience of.
PaulRainbow
Well-known member
You repaired one hole, using information read from a guide written by the manufacturer of one brand of epoxy products. An expert that does not make you.
Kukri
Well-known member
I'd suggest that the simplest and cheapest way to fill a hole left by the removal of a skin fitting is to put a new skin fitting in the hole, and case need find a new use for it.
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ghostlymoron
Well-known member
The hole is now filled with one layer of fiberglass mat plus P40 reinforced filler either side. Planned launch later today. I'm uneasy as I'll be on board but expect it will be OK provided we don't get an impact on the repair.
I'll be wearing my LJ and relieved when I'm off! Friend is planning an Atlantic crossing eventually.
I'll be wearing my LJ and relieved when I'm off! Friend is planning an Atlantic crossing eventually.
Daydream believer
Well-known member
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lw395
Well-known member
Blanking a skin fitting, there is no need to make the repair a proper part of the hull structure. The hull was strong enough with a 2 inch hole in it, it will be strong enough with that hole plugged.
Therefore a good case for not grinding away lots of material from the hole edges, unless there is some big need to have a flush repair on the inside.
fill the hole, then back it up with a few layers of glass on the inside with a tapered overlap.
The only abrading of the original hull needed is to get a clean fresh surface to bond to.
Much less work, integrity of original structure not compromised, shape retained. Slight weight added.
Therefore a good case for not grinding away lots of material from the hole edges, unless there is some big need to have a flush repair on the inside.
fill the hole, then back it up with a few layers of glass on the inside with a tapered overlap.
The only abrading of the original hull needed is to get a clean fresh surface to bond to.
Much less work, integrity of original structure not compromised, shape retained. Slight weight added.
MagicalArmchair
Well-known member
Wow, I came late to the party to this one Ghostly. I would have taken advice from East Coast Fibreglass and David Johnson of Wessex Resins (who is a Jedi of GRP and epoxy repair awesomeness). As others have said, the only safe repair you can do is 12:1 starting with the biggest piece of cloth first. Its not actually hard or expensive to do. Shame you aren't closer, I would have happily wandered over with a grinder and a glint in my eye for promises of coffee and a slab of battenberg...
My own efforts http://www.albinballad.co.uk/how-tos/fix-a-crack-in-your-keel/ - I do have another write up I need to do around patching up a skin fitting.
My late (more cavalier than me) father would have said it'll be fine, go sailing, if you start taking on water, it'll all add to the adventure!
RichardS
N/A
Surely it's incorrect to compare a 2 inch hole with a skin fitting in it to a 2 inch hole plugged with filler?
The skin fitting has a positive physical location on both the outside and the inside of the hole and therefore cannot easily be pushed into the hull by water pressure or a slight impact (or, indeed, pressed out by someone standing on it!)
Presumably the reason for the "saucer" structure described by Vic is to ensure that the filler plug cannot be pushed in? Filling the hole flush and fairing in on the outside doesn't sound like a good idea to me, whatever you do on the inside. :ambivalence:
Richard
lw395
Well-known member
If you fill the hole and then back it up, then the backing obviously needs to be strong enough to resist any force you might expect, plus a good margin.
It's a 2 inch hole, so the water pressure on it is a bit under 5lb for every metre that it's submerged.
Allow a bit for the hull slamming into waves or whatever. Let's design for 100lb or 500N in metric.
A reasonable resin should achieve over 30MPa of strength.
So an area of 500/30= 16sq mm would be strong enough!
Guess the hull might be 5mm thick? that's 785 sq mm.
Provided you clean the edges of the whole and your resin actually works, it should be fine.
I would chamfer the edges of the hole at some angle to at least get rid of the bits that were ripped when the hole was drilled in the first place.
A layer of mat or cloth behind it won't hurt.
I'd probably add a few over a convenient area.
It is very different if you are say trying to repair a hull that's been crashed and you need it to take the loads of the rig. Particularly if you don' t want it heavy and you want the hull to not have a stiff spot, important in a racing dinghy. That's when you take it to the pro IMHO.
Or where the hole is bigger, the forces build up and you have to start considering the effects of propping in the yard and all that.
I'd not use anything intended for car-bodging underwater though.
But if you're going to be amateur, it's maybe better to keep your gloop to the 2 inch hole rather than demolishing acres of perfectly good structure to replace with amateur gloop.
Those of us who don't trust GRP to have some sort of strength can always buy metal or wooden boats.....
It's a 2 inch hole, so the water pressure on it is a bit under 5lb for every metre that it's submerged.
Allow a bit for the hull slamming into waves or whatever. Let's design for 100lb or 500N in metric.
A reasonable resin should achieve over 30MPa of strength.
So an area of 500/30= 16sq mm would be strong enough!
Guess the hull might be 5mm thick? that's 785 sq mm.
Provided you clean the edges of the whole and your resin actually works, it should be fine.
I would chamfer the edges of the hole at some angle to at least get rid of the bits that were ripped when the hole was drilled in the first place.
A layer of mat or cloth behind it won't hurt.
I'd probably add a few over a convenient area.
It is very different if you are say trying to repair a hull that's been crashed and you need it to take the loads of the rig. Particularly if you don' t want it heavy and you want the hull to not have a stiff spot, important in a racing dinghy. That's when you take it to the pro IMHO.
Or where the hole is bigger, the forces build up and you have to start considering the effects of propping in the yard and all that.
I'd not use anything intended for car-bodging underwater though.
But if you're going to be amateur, it's maybe better to keep your gloop to the 2 inch hole rather than demolishing acres of perfectly good structure to replace with amateur gloop.
Those of us who don't trust GRP to have some sort of strength can always buy metal or wooden boats.....
fisherman
Well-known member
My first answer would be to leave the skin fitting and wood plug it, I have one I did 25 years ago. Next would be bolt and sikaflex round patches of suitable material, GRP, S/S, both sides. If a GRP repair is decided on, then fair back both sides, I would have said 6 inches (maybe wrong) and apply mat/resin both sides so it bonds in the hole, cannot peel off.
ghostlymoron
Well-known member
The fitting was removed because it was weeping around the flange. So leaving it was not an option.
vyv_cox
Well-known member
Back to the question. The major reason why polyester resins are not used for this type of job is because their bonding to the existing surface is purely mechanical. In a 2" hole that has previously had a fitting in it it might be assumed that the sides are smooth, or even worse, that a silicone sealant has been used. In the first case there is not a lot of roughness to which the polyester can adhere and in the second the silicone will inhibit curing of the resin adjacent to it. There is a good chance that with a small impact or even some water pressure the plug will simply push through.
With epoxy fillers a certain amount of chemical bonding may also occur, improving the adhesion. My experience is that in virtually every substrate material, including metals, epoxy resins adhere far better.
fisherman
Well-known member
That's why you make a 'H' section repair, it can't push through. Also I scuff the GRP both sides to expose fibres for mechanical adhesion.
Epoxy is better though.
ShinyShoe
Well-known member
I've used P40's before. a 2 inch hole is probably close to its limits for actually managing to fill the hole. Even at that size I've expect to have to use some re-enforcement while it sets. The whole 12:1 thing amuses me. Clearly anyone who mentions 12:1 in this setting has never used P40's! a 3mm thick skin means covering an area of about 36mm - the stuff is so messy you are probably creating an edge of double that!!
HOWEVER - I've only ever used it on sailing dinghies. Some of those did stay on the water, some of those holes were at or below the water line but not 1m below.
All were used two or three times a week and had people around them daily.
The most common places were front bow (hitting a jetty) or transom bottom edge from kids trailing with the transom too low.
It was always a bodge repair. It didn't always last. It was the kind of thing you did because you had a series of courses running over several weeks and then at the end of that would take them out and do a proper repair.
I don't think we had a consistent "big layer first" approach - partly because it sure depends how easy it is to get to both sides of the holes. *BUT* most importantly - we were not sailing across the Atlantic with our repairs. If I was sailing across the Atlantic I might put some P40 in my repair bag because it is pretty simple to work with. But I wouldn't set out with a P40'd repair...
HOWEVER - I've only ever used it on sailing dinghies. Some of those did stay on the water, some of those holes were at or below the water line but not 1m below.
All were used two or three times a week and had people around them daily.
The most common places were front bow (hitting a jetty) or transom bottom edge from kids trailing with the transom too low.
It was always a bodge repair. It didn't always last. It was the kind of thing you did because you had a series of courses running over several weeks and then at the end of that would take them out and do a proper repair.
I don't think we had a consistent "big layer first" approach - partly because it sure depends how easy it is to get to both sides of the holes. *BUT* most importantly - we were not sailing across the Atlantic with our repairs. If I was sailing across the Atlantic I might put some P40 in my repair bag because it is pretty simple to work with. But I wouldn't set out with a P40'd repair...
PaulRainbow
Well-known member
You sure about that Vyv ? I think not.
lw395
Well-known member
That is not true.
It is an oft-repeated myth trotted out by people who shouldn't be working with plastics.
A competent GRP worker will achieve a perfectly good bond to the existing polyester, using polyester resin.
The key is to abrade the surface immediately before applying fresh resin. This leaves open chemical bonds available on the surface.
If left too long, these bonds will be used by bonding to contaminants or air.
RichardS
N/A
vyv_cox
Well-known member
We are discussing body filler, not a skilled worker with fresh resin.
ffiill
Active member
Black carbon fibre bridging filler designed to bond to car bumper plastic work produces far better results but to using it on a two inch hole?
I agree with leaving a skin fitting in or replacing it with a plugged or blanked off new fitting if thats possible.
I agree with leaving a skin fitting in or replacing it with a plugged or blanked off new fitting if thats possible.
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