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Old 16 June 2016, 08:20   #21
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What advantage is there cutting a hole on the outside Officer ?

I do appreciate I can access that area easier from the inside if I do.. but so far.. I feel its not required..however you do this for a living..so I will listen

I think with a patch like this on the inside..and its really just a backup to the exteral patch which will be large and has plenty overlap to seal it properly

I will cut another hole if I think it worth while..but dont want to cut one for the sake of it if this one works ?
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Old 16 June 2016, 08:22   #22
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Originally Posted by office888 View Post
Why not? That's the right way to do it.
Its your way.. and it could be considered the correct way..but why ? ..do you think this method will fail ?

I hope Im not sounding arrogant by asking as its not my intention..Im just wondering why ..if I get a leak..do I have to make another to repair the first..then have to repair the one I just made..if that makes sense ?
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Old 16 June 2016, 08:58   #23
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Originally Posted by The Gurnard View Post
Its your way.. and it could be considered the correct way..but why ? ..do you think this method will fail ?

I hope Im not sounding arrogant by asking as its not my intention..Im just wondering why ..if I get a leak..do I have to make another to repair the first..then have to repair the one I just made..if that makes sense ?
Not at all!

Glue is very weak. It is probably one of the worst ways to assemble something.

In order to maximize chances of success, you need to pave a road to success. Your method may work in the short term, but there are a lot of variables. You are mixing two different chemicals together which could yield mixed results... they operate by two completely different curing mechanisms.

PVC boat glue is nothing more than ~25% solids suspended in a lot of solvent. Typically, it is some kind of synthetic resin It is applied to the material, then, the solvents evaporate. This drives the solids in to the material, enhancing the bond strength. The problem is, is that if it is applied too thickly, it will skin over. The solids at the surface will dry, will the solids at the bottom will remain wet because the solvent is trapped with no way to escape. Then, when the part is laid up, the surface skin will break, releasing the solvents, which will then deactivate the bond you just tried to make.

Mixing with sikaflex may entrain solvents, which may weaken the bonding of the PVC glue, of the Sikaflex, or both.

Ultimately, if the repair fails, you'll be stuck removing that globby mess as well which may permanently damage the material.

By going from the inside of the boat, it allows you to:
Apply thin, even coats of glue to both the patch and the boat
It allows you to maximize your patch overlap, which will increase the holding strength of the patch.

Best of all, it is a known working method! By applying a patch from the inside, it also makes for a stronger patch than from the outside. Instead of pushing UP the patch, trying to make it bulge, instead the air pressure is trying to push that big patch through the tiny hole. The chances of the patch peeling free ever are non-existant. Since the patch is on the inside, it is no longer affected by chemical exposure, UV, and there's no mechanical wearing motion to possible cause an edge of the patch to lift.

My 2 quid. Take it as you please. I understand why you're hesitant. For the first 2 years when I apprenticed fixing inflatables, I tried to avoid doing inside outside patches at all costs because I was very bad at them...
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Old 16 June 2016, 09:04   #24
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G,

Do you need to prep the inside of the tube for the the internal patch as you would the outside? How sticky is PVC glue - do you get the chance to put it in and add your second bigger internal patch before it sticks to the wrong place inside the tube? Is your big internal patch robust enough to seal all round with just a 1cm pulling area?

Given your quick fix patch in a wet boat seemed to hold I can certainly understand your reluctance to get new holes - each of which is a potential leak. Of course I know nothing as I don't have these headaches!
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Old 16 June 2016, 10:10   #25
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Thanks for the guys..and I do appreciate what you are saying and it makes total sense even to me. If I were doing it for someone else and my reputation depended on it .. making another hole is the certain way to go.

I have just applied the patch to the boat this minute though..possibly because Im a stubborn old git ..but to explain some of my thoughts..

I wouldn’t have though the glue/ sikaflex mix will be under much pressure on an internal tube?.I would have thought when the tube is blown up..the air will push against the patch.. not like the external patch which will be pushed off. The boat is kept on its trailer and never deflated.

I often mix glues and had no problems..in fact have had great success sticking things with sikaflex then running cyano around the edges to hold in position until it sets. Perhaps it weakens the glue..but those things are still stuck down and some for quite a number years ..and they still withstand stress. I have also used PVC one part glue and Sikaflex mixed before with great success..but I cant say how much it weakens the glue.

For the external patch ..I will use two part glue..and have the area spotless before applying

Correct too Poly..I have no idea what the internal surface is like..it could be greasy as hell for all I know..but Im willing to give it a try..and have just done so..in theory .. it worked a treat. The external patch will be well cleaned and prepared etc. Im banking on internal pressure assisting the glue mix to hold the patch in place when under way.

Perhaps the title of difficult to access is misleading as I had no problem accessing the leak..and now the patch is in place.. I have a wooden board applying pressure to it from the outside ..through the flattened tubes..as well as the gut being held taunt.

If I had a puncture in a bike tyre..which I have had often..I would never dream of putting an internal patch on or cutting another hole so I could repair the first..but I appreciate PVC boats are different. Its not a high pressure tube either,.. around 250 milky bars is all..not like an airfloor

If it holds another four or five years ..Im happy..its a 12 year old boat remember. Possibly only used around a dozen time a year now too..as Im using the Frib far more

But as you guys say..time will tell. I will be honest..and keep you all informed ..etc

Thanks for taking the time to write it out too Officer it is appreciate ..it will help others decide how to repair leaks on their boats etc.

The second patch before going through the hole..it all went easy enough..but I got slippery fingers..which was expected

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Old 16 June 2016, 12:01   #26
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I am glad Im a stubborn old git..as it saves me a fortune.

The mix of sikaflex and PVC glue will be no where near cured yet.. its only an hour since I installed the patch.. however I have pumped the tube up almost to full pressure but not quite. The pressure is now holding the internal patch firmly in place and ensure it conforms to shape of the tube.. until it all cures properly.

All the wet..is a mix of fairy liquid and water flung over it..not a bubble in sight either..and that is only the internal patch.. the hole chaffed in the black layer has also just been built up flush with sikaflex once I knew the internal patch was airtight



After that ..an external patch once everything is cleaned and dried .. and its bobs yer uncle...or more correctly.. back to sea next week.

IMO Repairing leaks is not a rocket science .Those that hesitate are often folks that get hung up on the scientific gobbledygook of it all ..but thats only my opinion.. so could be wrong.

How you guys sort your leaks ..is your own business ..but I hope you found this method interesting .. if not as an easy alternative to the professional way.

I will give an update on my external patch and floor board mods as I do them
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Old 16 June 2016, 12:56   #27
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Just my two pence why would you want another hole?
When you normally repair from the outside anyway not that I agree or disagree with the mixing ot two components purely because I never tried it but what I have tried is applying marine flex under water onto a ground piece of steel achieving 200 psi pull off since the repair is being pushed on by air it mearly needs to stick as for contaminated surface the internal repair fluids stick so why shouldn't gurnard's cocktail since he has proved the mix. Once he has the inside set and he's happy he then is reverting to a normal repair.
The main reason I suggested the mushroom was they are intended for internal repair they are shaped in such away that the air flattens the outer lip to form a seal if the glue doesn't dry air tight but it's the same thing as gurnard's way in a different format hope it works for you mate.

Cheers
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Old 16 June 2016, 13:03   #28
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Oh... No.1 leak testing fluid in the glass... thought it was a somewhat frothy gin & tonic to celebrate success!
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Old 16 June 2016, 13:22   #29
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Hi Jeff.. I have complete confidence it will work. I would have used those tyre plugs if I had one..but it wasnt worth me buying a whole kit.

The external patch will be the main one for the leak. The internal is only for a plug...and a bit of backup

Personally there is no way I would cut a big enough hole to do a nice internal repair in that position.. that is the area that takes the pounding from the transom and outboard.. so even if I still have a wee leak..its still a small hole.. an access patch on the outside would weaken the whole structure..especially .. if as officer said "Glue is very weak"

Im not so sure its so weak though ? .. I had a devil of a job trying to get the accessories off the PVC seago I scrapped..they were glued on with chinese glue..sixteen years old.. It tore the PVC laminates rather than glue separating. Makes me wonder if Chinese glue is as folks think ?
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Old 16 June 2016, 13:59   #30
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Originally Posted by The Gurnard View Post
if as officer said "Glue is very weak"
"Specs on" Gurnard - he's called Office888. Your repair is very novel and I'm confident it will hold. I've done a couple of "off manual" repairs myself over the years but I'd credit luck with their success. I've surprised that you feel a patch on your tubes would weaken them appreciably - after all, your entire boat is glued together, surely?

And IMO, you're a good enough engineer to know why "glue is weak" - you wouldn't be weiming that poor laminator, would you?
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