Fibreglass sheathing required for large schooner in Lesvos, Greece

[s/v Jedi]

In the US biax can come in +/-45 or +/-60 or 0/90.

I recommend to use altering layers of 1708 and 1808 stitched materials. The result is like a quadaxial with fibers running in all 0/45/90 directions.

1708 is a +/-45 and 1808 is a 0/90 orientation.

Wipe with denatured alcohol just before glassing.

Yes, do vertical panels, I think it will be easy. Don’t coat the wood before you start glassing… coat 10 minutes before the dry glass goes on but check for dry spots just before putting the glass on.

Use rollers for adding epoxy (West System sells roller that don’t immediately fall apart) and use finned thin rollers to work the air out. These thin rollers are what makes it stick instead of delaminate down the road.

[Spot]

I was doing some math for my current repair last night and liked using the 'compare' function for fiberglass reinforcements at this website:
https://compositeenvisions.com/
Their datasheets have oz/yd and grams/GSM units and a resin usage figure starting point of 40% by weight.

My vendor sells a mat compatible with epoxy, some are not having a styrenated binder that does not dissolve in epoxy.

Same vendor suggested 2 layers 1708 (-45/45 biaxial with mat) with epoxy for my repair (based on small cell phone pics and my descriptions). Running the numbers through Vectorlam:
https://vectorply.com/vectorlam-4/
indicated I would need 3 layers 1708 with one layer rotated 45 degrees to be 'axial' (0/90) to achieve similar basic mechanical properties of the thicker chopped strand mat and polyester resin I removed. Now if I could only remember my login/password to find out 'which' layer...

All the best to the OP and thanks everyone for all of the added information.

[Franziska]

Originally Posted by Benz

Not to drift the thread, but nobody calls the 0-90 cloth "biaxial"; it is plainly called "cloth" or "woven roving", because it has one axis, 0, with the warp travelling along the axis and the weft going at 90 degrees to that.
The "biaxial" is so called because the strands are going at plus or minus 45 degrees to the axis of the cloth, but meet each other at 90 degrees.
There are also twill weaves and harness weaves which are not biaxial, even though strands cross each other, but 'Biaxial' is a very specific thing.
I would use biaxial cloth for the sheathing, but first I would ask whether the juice is worth the squeeze: it's going to be a huge and expensive and difficult job, and pre-wetting panels big enough to be worthwhile with epoxy is usually done on an impregnator: doing it by hand outside will be tough, even with professional help.
Is the rest of the boat worth the work on the hull, and is the budget substantial enough to cover the inevitable cost overrides?

Nope. 0:90 is a stitched biaxial not "cloth".

Cloth is a woven material and always 0:90.

The difference is the reduced level of crimp, because the fibers in the stitched material lie flat already and can take load directly, while woven materials tend to stretch before they take the load.

Hence multi axial fiber complexes are superior in load bearing than simple woven cloths, or worse chopped strand mat.

Multiaxials are best when used with vinylester or better epoxy.

Sent from my MHA-L29 using Cruisers Sailing Forum mobile app

[s/v Jedi]

Originally Posted by Spot

I was doing some math for my current repair last night and liked using the 'compare' function for fiberglass reinforcements at this website:
https://compositeenvisions.com/
Their datasheets have oz/yd and grams/GSM units and a resin usage figure starting point of 40% by weight.

My vendor sells a mat compatible with epoxy, some are not having a styrenated binder that does not dissolve in epoxy.

Same vendor suggested 2 layers 1708 (-45/45 biaxial with mat) with epoxy for my repair (based on small cell phone pics and my descriptions). Running the numbers through Vectorlam:
https://vectorply.com/vectorlam-4/
indicated I would need 3 layers 1708 with one layer rotated 45 degrees to be 'axial' (0/90) to achieve similar basic mechanical properties of the thicker chopped strand mat and polyester resin I removed. Now if I could only remember my login/password to find out 'which' layer...

All the best to the OP and thanks everyone for all of the added information.

The three layers with one rotated to reorient the fibers: you can simply do two layers of 1708 and one layer of 1808 without the need for rotating and wasting material.

Try to balance the layup, so the 0/90 layer goes between two +/-45 layers

Check my carbon fiber beams thread with lots more info on layup schedules, fiber orientation etc.

[catsketcher]

Jedi

I like the idea of mixing up the laminates - +-45 and across the grain unidirectional (or quadraxial really). In my world of reducing weight in laminates the thought is that running fibres along the path of the planking is redundant, because of the high strength of the planks.

So, I use +-45 (what I call double bias) and also unis run across the grain - and not run any fibres along the planking direction.

I understand the OP is not at all interested in reducing laminate weight, but I don't get why fibres should run parallel to the strong planking, whereas it is vital in the cross grain direction.

In the OP's case, a combination of +-45 and uni or 0/90 should be good. It will be way overspecced anyway.

cheers

Phil

[s/v Jedi]

Originally Posted by catsketcher

Jedi

I like the idea of mixing up the laminates - +-45 and across the grain unidirectional (or quadraxial really). In my world of reducing weight in laminates the thought is that running fibres along the path of the planking is redundant, because of the high strength of the planks.

So, I use +-45 (what I call double bias) and also unis run across the grain - and not run any fibres along the planking direction.

I understand the OP is not at all interested in reducing laminate weight, but I don't get why fibres should run parallel to the strong planking, whereas it is vital in the cross grain direction.

In the OP's case, a combination of +-45 and uni or 0/90 should be good. It will be way overspecced anyway.

cheers

Phil

You have the wood fibers aligned but fiberglass is about four times as stiff as wood, so you greatly improve its properties with fiber in every direction.

Of course, to keep it together, the other directions are more important and making it better comes after that

[Benz]

Originally Posted by Franziska

Nope. 0:90 is a stitched biaxial not "cloth".

Cloth is a woven material and always 0:90.

The difference is the reduced level of crimp, because the fibers in the stitched material lie flat already and can take load directly, while woven materials tend to stretch before they take the load.

Hence multi axial fiber complexes are superior in load bearing than simple woven cloths, or worse chopped strand mat.

Multiaxials are best when used with vinylester or better epoxy.

Sent from my MHA-L29 using Cruisers Sailing Forum mobile app

Have it your way. Around here if you ask for "biax" you will get +/- 45. For long runs (with epoxy, at any rate), we just use unis--they come in stitched rolls of varying widths, but the bulk of a glass/epoxy boat will be plain biax, with woven cloth outer skins.
1708 and 1808, because they're stitched to CSM, are used only for poly/vinylester construction. I've never seen anyone use 0/90 stitched biax for epoxy construction, but my experience is limited to a dozen boats or so.

[catsketcher]

I have used a fair bit of 0/90 for foam boats. It is a pretty common schedule for weight conscious multis built in foam. 0/90 is also used almost always in Duflex sheets as well. Monos may be different but in cedar strip we use the timber to take the fore and aft loads and use uni across the planking or what we call double bias (+-45)(Usually uni inside and +-45 outside). In cedar strip the planks are usually about 12-18 mm thick, so even though they have a lower modulus of stiffness and tensile strength, the timber is still more than equivalent to few layers of fibre running parallel to the grain (the glass being about 1-2mm), hence the use of +-45 double bias instead of 0/90 on lightweight multis.

But as we don't know the load conditions on the OPs boat, the laminate should have a bit of a mix, ensuring the laminate is strong in all orientations - so a mix of 0/90 and +-45 would be a good idea.

[Spot]

Our 'local' biax with mat is -45/45 and OK for epoxy. There is not a 0/90 option listed. My 15 pieces are only 38" and 50" (1 and 1.27 meters) long and max 14" (.35 meter) wide so not much to cut and some of it is already slit tape.

https://www.expresscomposites.com/db...-45-w-ltwt-mat

The listing has the classic oz/sqft/sqyd confusion thing on the mat ...

[s/v Jedi]

Originally Posted by Spot

Our 'local' biax with mat is -45/45 and OK for epoxy. There is not a 0/90 option listed. My 15 pieces are only 38" and 50" (1 and 1.27 meters) long and max 14" (.35 meter) wide so not much to cut and some of it is already slit tape.

https://www.expresscomposites.com/db...-45-w-ltwt-mat

The listing has the classic oz/sqft/sqyd confusion thing on the mat ...

Unfortunately, your local shop has it mixed up. I’m pretty sure they are selling 1708, not 1808. 1708 has a +/-45 degree orientation and 1808 has a 0/90 degree orientation. Your shop claims 1808 is +/-45 which is in error. See attachment.

Edit: and Google is wrong too; 1708 is not woven. The levels of ignorance are amazing and it will become so much worse… half of group 8 students is analphabetic hmmpfff.

About the use of 1708 and 1808: they have an 8 ounce chopped strand mat stitched to one side of the biax. For a new build this isn’t required and the weight does not make up for the benefit. But for repair and especially sheathing it is a very good option because the csm buffers surface irregularities so that the biax strands are better oriented and supported.

Also, these products are fully compatible with epoxy as well as polyester and vinylester. They are stitched, there is no binder like in normal CSM.

[yourskipper]

Wow, thanks for all the information folks!
I am trying to digest it all, but very helpful.
(The pictures were taken before the edge was tapered.)
There is no question that we are going ahead with the work, the rest of the vessel is in good condition and she is less than 25 years old...
Will try to remember to keep posted / come back with any further questions as we progress.

[aqfishing]

Whats wrong with just putting back what was there? Cannot really see much benefit to what the OP suggests? Why mix different resins and different cloth?
It worked before, and would still be fine had the wood underneath not rotted.
FYI, fisherman used to glass chop strand over old wooden boats to stop leaks and hide rot. The local authority all but put a stop to this by insisting every 4 years it must be removed, and with good reason.

[De.windhoos]

Originally Posted by yourskipper

We are refitting a 90ft schooner in Lesvos for a Christian charity.
She had some quite large areas of rot in the wooden planks, which have now all been replaced.
She is sheathed with polyester resin and chopped strand mat.
We want to replace this with epoxy with biaxial cloth, or similar, preferably using a vacuum to install.
There are approximately 20sq meters to be done to a thickness of about 10mm.
Do you know someone in Greece who might be able to help us?
Please let me know!
Thanks

What help are you looking for? Hands to laminate, adressen to source material, consulting?

[s/v Jedi]

Originally Posted by aqfishing

Whats wrong with just putting back what was there? Cannot really see much benefit to what the OP suggests? Why mix different resins and different cloth?
It worked before, and would still be fine had the wood underneath not rotted.
FYI, fisherman used to glass chop strand over old wooden boats to stop leaks and hide rot. The local authority all but put a stop to this by insisting every 4 years it must be removed, and with good reason.

What is wrong is that it was bad. Polyester simply is the wrong resin and chopped strands … I dunno, tell me what good it does?

[dalemann]

What on earth does a Christian Charity need with a 90 ft. schooner ?? Sounds pretty dodgy to me.