Ampreg 21

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Garry R

Ampreg 21

Post by Garry R » Mon Nov 17, 2008 5:53 pm

I have to sort out the leak on the centreboard case on my boat and saw this stuff which is an SP system laminating epoxy. Its properties as very low viscosity when warm so it penetrates well but with a long gel time with the slow hardener make it prety attractive for this application around the centreboard casing as it will get into the garboard/keel/hog joint and hopefully seal it. It has good compressive properties too. However, it is sold only as a 3.6kg minimum at £84.92 ex VAT so not that cheap when you don't need that much. Is there anyone out there who might like to share some for this type of application as it is also used for sheathing. I'll likely go ahead anyway but give me a shout if interested. If you wanted to find out more info then phone 01983 828000 where the guy at SP Systems was really helpful and clued in. Apparently the way to do it is to drill holes 4-5mm and make a little reservoir using eg pipette tips stuck into the hole. Make sure the wood is bone dry by heating over a period of time and then again just before you start. This allows the air in the wood to expand and then when you fill the reservoirs with the epoxy the wood shrinks sucking the epoxy in. Keep topping up the reservoirs with warm epoxy until it doesn't flow in any more and then apply heat to cure. With luck the epoxy will have penetrated into the gaps and wood and give a good seal/bond. I'll keep you informed.

Chris3543
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Re: Ampreg 21

Post by Chris3543 » Mon Nov 17, 2008 11:04 pm

Hi gary

For what you want Ampreg is no better or more runny than SP106 or 320 when warm and is significantly more awkward to work with as well as very expensive. It's very sensitive to mix ratio and should only be mixed by weight.

I wouldn't bother! You can get a slow hardener for 106 and 320.

Garry R

Re: Ampreg 21

Post by Garry R » Tue Nov 18, 2008 9:55 am

The guy at SP told me that the advantage of the Ampeg21 was that as a laminating epoxy the flow properties are excellent and that heating increased the flow (about 50% decrease in viscosity/5C rise in temperature). The heating apparently in this case does not substantially decrease the rate at which the epoxy will set and so if you want something to creep and adsorb well into the joint you are attempting to sort out this is its main advantage. If you heat the SP106 even with the slow hardener the setting time becomes short so penetration is reduced even though viscosity is lowered with heating.

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Ed
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Re: Ampreg 21

Post by Ed » Tue Nov 18, 2008 11:37 am

Very interesting....

I am almost tempted to go halves with you just to do some experimentation myself.

I was going to post saying pretty much what Chris said....but held back as the case for using Ampreg was well argued....

But agree with Chris....my understanding was that Ampreg was rather 'hard' to use and you need to be much fussier about preparation and curing, including applying some heat afterwards to get it to really cure properly. All of which can be harder in a 'real-world' situation like this rather than in a clean mould in a heated workshop.

But, as I said, I would be really curious about how you get on and how it goes.

I don't use SP Resins. I used to, and I am sure they are fine, but have for ages now used Sicomen Epoxy from Matrix Mouldings in Bristol. Wizz (One of the directors) there has been a wonderful resource for help for me when building in epoxy and taught me tons. Strangely enough, on my last visit we were talking about the possibility of using some of the more exotic 'laminating' epoxies rather than the 'wood' epoxies I normally use, but this was for a more straightforward laminating task.

My gut reaction is to stick to a normal wood or glueing epoxy and just use the slowest hardener and a bit of heat.

You could consider using a diluent in small doses. Some people are very against this, claiming the problems with solvent entrapment cause a loss in strength......but it can make a big difference in places like this where you would be happy for a 10% loss in strength against the advantage of better penetration. This is effectively what the SP300 or SP3000 or whatever is.

The problem with this job, having done it myself more than once, is that unless you open the joint right up, you can't really clean it out properly and it tends to be full of old aerolite glue, often stuck to both sides of joint. If you don't clean out this old glue, it stops the epoxy from making a decent adhesion to the wood. Thin epoxy can help here.....but it does not totally solve the problem.

If you are thinking about going hi-tech with Ampreg.....you might also like to consider setting up a vaccum bag to pull the epoxy into place, which can also work really well. Not so hard to do. An old fridge compressor, some tube, some clamps, some plastic sheeting, some black-tack.....and you are off.

Anyway, tell us what you decide and tell us how it goes.

I don't really want to put you off using Ampreg as I am curious to find out how you get on.

cheers

eib

Oh, Matrix Mouldings are at: http://www.matrixmouldings.co.uk/ and talk to Wizz
Ed Bremner
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Garry R

Re: Ampreg 21

Post by Garry R » Tue Nov 18, 2008 12:03 pm

Thanks for that Ed

The one that I quite like the look of would be the Bx flexible system. This would seem to fit in well with my idea that any small movement of the centreboard case/hog/keel with rig tension would not break the glue line but stretch a little. It also has a low viscosity (to my mind an essential to allow penetration of the gap you are trying to fill) it has a long pot life with 5 hours using the Ultra slow hardener and do wonder if it would do the business better than something less penetrative and rigid. It is also suitable for cold applications and a boat will have that pretty much most of the time in and off the water (in the north I doubt if the water gets more than 12-15C at any time !!!! The old lady (Gannet not Trish) will be pretty flexible anyway and wonder if this is the way to go. I'll give the guy a ring and see if he has some thoughts.

I really don't want to remove the case at this point in time - maybe once I have retired and have loads of time on my hands and also when she needs a refurbish in 2-3 years. I feel that I will have to make a new case then anyway as there are some stains on the mahogany where I have the leak(s) so looking for a reasonable holding measure at the moment.

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Re: Ampreg 21

Post by ACB » Tue Nov 18, 2008 1:25 pm

This is interesting as I have a little flottilla of leaky Fairey centreboard cases to try to sort out. I had already bought some West with slow hardener and I am very much an amateur gluer-up of things so a more user-friendly epoxy is better for me. I was thinking of just warming the affected parts with a hot air gun.

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Garry R

Re: Ampreg 21

Post by Garry R » Tue Nov 18, 2008 3:17 pm

As I said warming up leads to speeding up the hardening cure

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Re: Ampreg 21

Post by Rupert » Tue Nov 18, 2008 5:14 pm

It can be easier to remove the keel than the centrecase (or even just the bit of keel with the slot in it) and mend the boat from the outside, which is, of course, where the water is leaking in from in the 1st place! If the case is rotten, this won't work, but then nor will any sort of epoxy, however hitec and expensive!
Rupert

Garry R

Re: Ampreg 21

Post by Garry R » Tue Nov 18, 2008 5:27 pm

Following on from that Rupert how much strength does the keel impart? If removing the keel from the slot area how far ahead of the slot would you cut? I assume that you would then replace the area with new wood? I think that the leak is coming in from the garboard/hog/centreboard case joint and mostly on the port side and most likely, from what I can see, towards the front of the case nearer to the mast step king post.

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Re: Ampreg 21

Post by Chris3543 » Tue Nov 18, 2008 5:43 pm

We ended up with a load of it that needed to be used because it was near it's expiration date. Trust me it's a real pain!

Other than being very intolerant of low temperatures and fussy about mix ratios we found absolutely no advantage over the standard 106 or 320 resin. It may be a little stronger, but you don't need it. It is probably more brittle. I certainly wouldn't say it's viscosity is significantly less. You need to ensure a minimum temperature of 25 degrees i think otherwise it won't go off.

It's a laminating resin not a glue. Use the products for what they are designed to do and they will perform well. I think it would be an expensive experiment really. As with all things it may be worth a shot, but i'm sure there are better products.

Would Spabond be any good or is it pre thickened?

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Re: Ampreg 21

Post by DavidC » Tue Nov 18, 2008 6:07 pm

I have to go among with Chris here. I have used Ampreg and it is a pain in the ..... Tricky to use and needs very careful handling.

If you have the perfect set up and everything is controlled it is a good laminating resin, but I would never use it for general boat building. I know SP said it is ideal but they have said several things over the years which didn't quite work out. Equally they work in the rarefied air where every workshop is perfect :D Obviously we all have them :D

I would talk to Wizz at Matrix for advice. Having said that nothing is going to satisfactorily going to stick wet wood together in a joint that that is full of rubbish and old glue :cry:

D

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Re: Ampreg 21

Post by Rupert » Tue Nov 18, 2008 6:43 pm

Garry R wrote:Following on from that Rupert how much strength does the keel impart? If removing the keel from the slot area how far ahead of the slot would you cut? I assume that you would then replace the area with new wood? I think that the leak is coming in from the garboard/hog/centreboard case joint and mostly on the port side and most likely, from what I can see, towards the front of the case nearer to the mast step king post.
When I did F665 many years ago, and "before I knew better", I just cut the keel at an angle at the point where it split, did the mend and glued and screwed new bits in after. It worked, as I guess the case imparts alot of strength to the boat at that point. I'm not certain I'd do it again that way without some serious thought as to the structure, but as it worked once, maybe I would. Might find out on Saskia at some point I guess! I suppose one difference is that when I did 665, she had a solid mahogany case, rather than ply, which maybe changes things. I suspect I would bottle out and remove the whole keel now, to see what else is hiding, if nothing else...
Rupert

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Ed
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Re: Ampreg 21

Post by Ed » Tue Nov 18, 2008 7:28 pm

When I did mine.....it was a pretty serious bodge job as they so often are.

I didn't want to pull out the case either.

Strangely enough I didn't have a leak, but I knew that I had a few soft bits of hull and hog....and centreboard case...anyway the boat jumped on the trailer going over some bumps and the support hit the hull right by the keel and went straight through leaving a hole 20mm x 10mm. So I knew I needed to do some repair, I then stripped it and started looking for soft wood. To my dismay (and a real lesson for me) I found rather a lot of rott. In fact, by the time I had finished I had 3 places I could put four fingers through up to the palm and a few others where I could put in a finger or two....all along the edge of c-board case. The edge of hogg was also completely gone, right up to the edge of the bottom support to c-board case, but mainly/only along the edge. I also had a hole through the side of case about the size of the palm of my hand.

I knew that the case....and hogg.....and maybe keel should all come off, but I didn't want to do that.

I dried it up cut the edges clean, really cleaned out as much old glue as I could from all joins, which meant really digging in until I was quite sure there was next to no rotten or soft wood left. Agba can go sort of 'soft' without actually rotting - you can easily tell where this is by tapping with something metal and heavyish - the tone of knock changes quite obviously when you go from the hard to the soft agba.

Anyway once I had a ton of holes, I just scarfed the edges, cut patches and dropped them in. As long as the choice of wood was good, they seem to look pretty OK. Some bits were interesting, like the patches to the centre-board case, but as long as the scarf was done with the female side on the case and the male side on the patch, it was easy enough.

Anyway, it was only supposed to be a 1-2 year fix, but its been 5 or 6 now and shows no signs of failing or leaking.

But, I think my advice would be that if you have had a leak, then there has been plenty of time for water to get in and cause rot or softening of the agba/mahogany/ply, so do reallybe quite ruthless in checking to make sure you get all the soft wood out, because whatever glue you use, it won't stick to soft wood.

cheers

eib
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Re: Ampreg 21 - Firefly board case

Post by Ed » Tue Nov 18, 2008 7:31 pm

This topic could easily get waylaid.....but for Firefly nuts....

Rupert, you mentioned a Firefly with a solid mahogany c-board case.

I have never seen one of these - do you have any more info? What kind of number was this? Was it original? Was it in class?

I am always so happy to see a solid case. Every dinghy I have had with a solid case has been a solid boat. Rozzer, my Int14 and others had solid cases and it just made the whole boat so strong.

Any more info would be interesting

cheers

eib
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Re: Ampreg 21

Post by Ed » Tue Nov 18, 2008 7:36 pm

Oh also....

you mentioned one of the Sicamen flexible resins.....they do sound very interesting and very high tech....and possibly hard to use and expensive to buy.

I would be interested to hear what Wizz says about it....

But I kinda think in the end you will be best off with a standard wood-glue epoxy and a slow hardener, or I think you can get an extra-slow hardener for the Sicamen Resin.

If you talk to Wizz, tell him to drop by the Forum and tell us himself

cheers

eib
Ed Bremner
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Jollyboat J3
Firefly F2942
IC GBR314 ex S51 - 1970 Slurp
MR 638 - Please come and take it away
Phelps Scull
Bathurst Whiff - looking for someone to love it

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