inner keel casing support Newbridge Venturer

[CharlesSwallow]

Ah, OK.

I'm pretty sure I read an article or articles by Wild Venture's owners in the NAVA newsletter - I passed them all on to the new owners when we sold our Venturer so I can't check.

(Just to clarify the situation re: chopped strand glass mat - you can get "powder bonded" mat that is suitable for use with epoxy, but it will be described as such. Ordinary "emulsion bonded" doesn't wet out with epoxy and probably what you would end up with by default if you didn't specify otherwise. For what it's worth, if I were doing the repair, I would definitely use epoxy.)Andy

NO. You need to use something with the same flexing characteristics(coefficient of restitution etc) as the original opthalic polyester resin used in the original construction. Epoxy eventually cures to a substance much more regid than poly resin and therefore shearing at the interface is much more likely for no particular strength benefit. "Hard spots" should be avoided and certainly NOT be intentionally introduced.

I know every inch of that boat. After all I owned it for many years and I noticed that even some of my original mods were still there. If the original webbing support is just beefed up she will continue well into old age. Since our "rigourous" ownership she seems to have had a relatively quiet life; partly on Rutland Water and now on an inland paradise in SW france.

Chas

 

[misterg]

NO. You need to use something with the same flexing characteristics(coefficient of restitution etc) as the original opthalic polyester resin used in the original construction. Epoxy eventually cures to a substance much more regid than poly resin and therefore shearing at the interface is much more likely for no particular strength benefit.

I will agree to differ on that

"Hard spots" should be avoided and certainly NOT be intentionally introduced.

Absolutely!

I know every inch of that boat. After all I owned it for many years and I noticed that even some of my original mods were still there. If the original webbing support is just beefed up she will continue well into old age. Since our "rigourous" ownership she seems to have had a relatively quiet life; partly on Rutland Water and now on an inland paradise in SW france.

Chas

It sounds like the original poster has landed on his feet, then!

Andy

 

[Ubergeekian]

I bow to your greater knowledge of this design. However chopped strand mat and polyester resin are no good for repairs to existing grp. The bond between new and existing is poor, and if the area is subject to stress (as it obviously is) then the problem is going to reappear.

One solution is to use a single layer of epoxy resin painted on to the old grp, since it bonds pretty well to old polyester and to new polyester.

 

[AEMD]

I had a look at the hull both externally and internally and it's fine - looks like new inside. Nothing has moved or started to de-laminate so it seems it's just this little repair I need to do. I'll order some stuff from the web and hope it's the right thing.

 

[AEMD]

It sounds like the original poster has landed on his feet, then!

Andy

HER feet Andy :lol:

 

[misterg]

HER feet Andy :lol:

Ooh! Sorry!

Good news about the boat - sorry to have been alarmist.

Which ever advice you choose to follow, the CFS website is a handy reference for all the materials we're talking about. Maybe identify what you need there and then try and find a local source?

http://www.cfsnet.co.uk/

(no connection)

Andy

 

[CharlesSwallow]

HER feet Andy :lol:

Pretty feet too as I remember!


Ooops! Sorry Anne!

Chas

 

[srp]

NO. You need to use something with the same flexing characteristics(coefficient of restitution etc) as the original opthalic polyester resin used in the original construction. Epoxy eventually cures to a substance much more regid than poly resin and therefore shearing at the interface is much more likely for no particular strength benefit. "Hard spots" should be avoided and certainly NOT be intentionally introduced.

Some years ago I did some tensile testing of epoxy resin samples - they show a remarkable degree of elasticity. There is no truth in the assertion that an epoxy/woven cloth layup is not flexible enough. But the biggest problem with a polyester resin repair is the lack of adhesion between the old and the new. That alone is reason enough to use epoxy.
If you're worried about 'hard spots' then the standard practice of feathering out the repair area with increasingly larger pieces of cloth in the layup is the correct practice.
As UB suggests, there are ways of using polyester, but as they involve using epoxy anyway then it makes sense to use it for the whole repair.

 

[Ubergeekian]

Some years ago I did some tensile testing of epoxy resin samples - they show a remarkable degree of elasticity.

As far as I am aware the fibres (glass vs carbon vs kevlar vs boron vs ...) have a far bigger effect on elasticity than the resin matrix, which is really just there to stop the fibres getting damaged and hold them in the right place.

 

[30boat]

The subject of polyester on polyester repairs has been discussed here before.Such a repair job can be every bit as trong as one done with epoxy,it just takes a different approach.I would use epoxy in this case but I'd be equally happy with polyester if the former weren't available.If polyester wasn't suitable for high load repairs I'd have lost my mast many miles ago.The tip on my Fulmar'd bow was broken clean off in an encounter with a steel buoy and polyester was used for the repair as epoxy wasn't available where the boat was.It's possibly the most highly loaded area on the boat and after 7 years there's no sign of delamination or stress.