Layering-up matting 12:1 Long sheet first/inside or last/outside?

[Robert Wilson]

Approx 170mm length/14mm thick 12:1 layering down my skeg and into rudder-shoe.
Should I place the 170mm layer on the skeg first or the shorter lengths with the 170mm covering all the other increasing lengths ??
I shall fair-off with filler (of some sort)

I have plenty of height so the 170mm layer could easily be extended to 250 - 300mm, with subsequent layers increasing in length too.

The rudder shoe will be bolted through the layering and through a 8mm s/s plate embedded within the skeg..

For those of you who followed my "What should I expect now" thread last year, I am at last about to repair the skeg/shoe cock-up that I made when removing the rudder.

All advice gratefully received.

 

[sailorman]

biggest last
make a pattern of the area, draw "annular rings" following the shape, place pattern on the matt & cut the largest then the nxt ring until done.
lay -upthe smallest first & the largest last, you then seal in all the fibre ends & end up with correct profile

 

[VicS]

Approx 170mm length/14mm thick 12:1 layering down my skeg and into rudder-shoe.
Should I place the 170mm layer on the skeg first or the shorter lengths with the 170mm covering all the other increasing lengths ??
I shall fair-off with filler (of some sort)

I have plenty of height so the 170mm layer could easily be extended to 250 - 300mm, with subsequent layers increasing in length too.

The rudder shoe will be bolted through the layering and through a 8mm s/s plate embedded within the skeg..

For those of you who followed my "What should I expect now" thread last year, I am at last about to repair the skeg/shoe cock-up that I made when removing the rudder.

All advice gratefully received.

Biggest first.

Then you end up with a series of stepped edges that just need fairing off.

If you start with the smallest and work towards the biggest you end you with a series or resin filled voids around the edge of each layer.

You are using epoxy and biaxial cloth presumably, not polyester and CSM

 

[PlankWalker]

I would start with the second biggest, work my way in to the smallest, then work my way out again to the biggest, working in and then out gives you a bigger overlap on each piece.

 

[Robert Wilson]

Gentlemen!
I await a consensus of opinion !!!

But thank you for your prompt responses, all of which have merit.

I shall be purchasing bi-axial cloth and whatever East Coast Fibreglass Supplies recommend; presumably epoxy

 

[Bobc]

biggest last
make a pattern of the area, draw "annular rings" following the shape, place pattern on the matt & cut the largest then the nxt ring until done.
lay -upthe smallest first & the largest last, you then seal in all the fibre ends & end up with correct profile

What he said.

 

[Davegriff]

Probably doesn't make much difference, but I've always layered from smallest to biggest on the theory that if a layer doesn't "take" for any reason, it'll be held by the next up, thus less chance of the completed patch delaminating in one chunk, and it only has one "edge"! Probably nonsense, but I've never had a patch delaminate.

 

[dave220]

Largest first. Google west system fiberglass repair. Free manual for download and all info in there

 

[sailorman]

Largest first. Google west system fiberglass repair. Free manual for download and all info in there

So our boatyard are doing it wrong

 

[PaulRainbow]

I'd go smallest first, but if done correctly i doubt it makes a massive difference.

Important thing is to do the layup correctly. A consolidating roller or two would be a wise investment.

https://www.ecfibreglasssupplies.co.uk/category/laminating-rollers

 

[VicS]

biggest last
make a pattern of the area, draw "annular rings" following the shape, place pattern on the matt & cut the largest then the nxt ring until done.
lay -upthe smallest first & the largest last, you then seal in all the fibre ends & end up with correct profile

What he said.

No Its wrong largest first ..... read the West system user guides etc

Gentlemen!
I await a consensus of opinion !!!

But thank you for your prompt responses, all of which have merit.

I shall be purchasing bi-axial cloth and whatever East Coast Fibreglass Supplies recommend; presumably epoxy

See the West System user guides which are available in the ECF website, esp the one on "Fibreglass boat repair and maintenance".
Do it the way West advise. Ignore the people who have not read the guides

https://www.ecfibreglasssupplies.co.uk/topic/westsystemuserguides

See also these guides to choosing and using resins and the various fillers.

http://www.westsysteminternational....g-west-system-hardeners-fillers-and-additives

http://www.westsysteminternational....additives-to-west-system-resin-hardener-mixes

 

[VicS]

So our boatyard are doing it wrong

It seems so if they are doing it the way you suggest.

Read the all guides etc in the links I have given.

 

[PuffTheMagicDragon]

It doesn't really make much difference.

You will need to fair the layers when approaching the finished size. When I did a similar operation I used a flap-disk on an angle grinder to smarten up the shape before I put on the last two or three layers. This ensures that the fibres of the last layers are not disturbed (cut) as they would be when you apply a grinder to them. It also reduces the amount of epoxy fairing putty that you will apply before the final coats of epoxy.

Incidentally, for the actual re-build I used alternate layers of woven rovings and CSM with 'normal' polyester resin but epoxy for the final coats over the fairing putty.

The same method was used for the aft edge of the keel where there used to be a trim-tab.

 

[Motor_Sailor]

It doesn't really make much difference.

Oh yes it does (and not in a pantomime way).

And the reason is apparent when you come to sanding and fairing. Now if you've used simple CSM it doesn't make any difference, but if you've gone to the trouble of using biax, you want the fibres to be continuous along the load path. The longest ones do the most work and if they are the surface layer, there's a chance they will be sanded through and either cut or degradated during the finishing process.

The rule with composites is always "bury your load carrying layers and fair the choss on the top".

 

[sailor211]

Oh yes it does (and not in a pantomime way).

And the reason is apparent when you come to sanding and fairing. Now if you've used simple CSM it doesn't make any difference, but if you've gone to the trouble of using biax, you want the fibres to be continuous along the load path. The longest ones do the most work and if they are the surface layer, there's a chance they will be sanded through and either cut or degradated during the finishing process.

The rule with composites is always "bury your load carrying layers and fair the choss on the top".

This makes sense to be . So enough filler and faring material over the biax so no fibres are sanded.

 

[PuffTheMagicDragon]

Oh yes it does (and not in a pantomime way).

And the reason is apparent when you come to sanding and fairing. Now if you've used simple CSM it doesn't make any difference, but if you've gone to the trouble of using biax, you want the fibres to be continuous along the load path. The longest ones do the most work and if they are the surface layer, there's a chance they will be sanded through and either cut or degradated during the finishing process.

The rule with composites is always "bury your load carrying layers and fair the choss on the top".

You should never have woven rovings as the last outer layer and I don't think that I suggested doing so.
I think that we're saying the same thing in a different manner.