rhumlady
Well-Known Member
When glassing in bulkheads using West epoxy and 360gm cloth, how many layers would be advised? I am quite able to get a 1 to 1 ratio glass to resin.
Glassing in bulkheads
- Thread starter rhumlady
- Start date
Rum_Pirate
Well-Known Member
I would suggest not thicker than the bulkhead thickness, possibly down to half thickness on each side of the bulkhead. Mind you this all depends on the reason for the bulkhead : watertight and structural to a simple partition type from one area to another.
30boat
N/A
With epoxy resin and roving of that weight a single layer will do and two will be very good.Make sure the plywood is scored in the area to be laminated or else remove the outer veneer to improve adhesion.
electrosys
Well-Known Member
Personally I wouldn't use West Systems epoxy for that job - it's too viscous to wet-out mat throughly (or to penetrate plywood to any depth) - indeed I don't know why people rave about it.
Suggest Epiglass, or General Purpose LayUp Resin from ABL Stevens www.resin-supplies.co.uk which as well as being ideal for use with woven mat, has a much more user-friendly 2:1 mix ratio.
I suppose you could thin the West stuff with acetone, but it's not a practice I would recommend.
Suggest Epiglass, or General Purpose LayUp Resin from ABL Stevens www.resin-supplies.co.uk which as well as being ideal for use with woven mat, has a much more user-friendly 2:1 mix ratio.
I suppose you could thin the West stuff with acetone, but it's not a practice I would recommend.
oldsaltoz
Well-Known Member
To ensure a good lay up and wet out, start by running a grinder with a cutting disc over the area to be treated.
Then mix up some micro-Fibres and resin and apply using a small round object (I like the little fish past jars) this will give a neat radius to lay up on and avoid hard corners.
Hope this helps.
Good luck.
status
Well-Known Member
I was under the impression, when glassing to the hull, the wooden bulkhead should not touch the hull, the joint is made by 'fillets' of laminate. This is to stop hard spots in the hull causing problems during natural flexing.
With regards to number of layers, 300g CSM gives a layer thickness of 0.7mm according to my tables (so 360g will be marginaly thicker). I would recomend CSM to get around the bend of the joint. Based on nothing more than gut feel I would think you want 2-3mm of laminate so a minimum of 2 probably 3 layers both sides.
Right, thats my opinion for the day, please dont rattle my rock untill Monday!
Stuart
With regards to number of layers, 300g CSM gives a layer thickness of 0.7mm according to my tables (so 360g will be marginaly thicker). I would recomend CSM to get around the bend of the joint. Based on nothing more than gut feel I would think you want 2-3mm of laminate so a minimum of 2 probably 3 layers both sides.
Right, thats my opinion for the day, please dont rattle my rock untill Monday!
Stuart
rhumlady
Well-Known Member
Thanks for the reply's guys. CSM is out as I am using epoxy and as Oldsaltoz says I have radiused the corners using a mix of resin & filler and a mixing stick with a 15mm radius to give a fair turn for the cloth. The bulkheads are trimmed back from the hull and 12mm foam slab is inserted which has been cut at about 45 degrees along both edges which also eases the amount of fairing that is required. I have decided to go with 6 layers of resin/cloth as I don't believe I need too much due to the fact I am using epoxy at 1:1 not polyester at 3:1. So far I have done 2 half bulkheads and have my first full height one ready to go once I have sorted out some issues with the hull/deck join and the glassed in bolts for the rubbing strake.I am mainly using 18mm ply just now as the 12mm stuff is ****, not that the 18mm is much better.
Graham_Wright
Well-Known Member
snowleopard
Well-Known Member
I don't think you said whether the bulkheads were GRP or wood - that will affect which type of resin you use.
I did all my bonding a ±45° stitched glass fabric with a thin layer of CSM pre-bonded to the underside.
One important point when using any glass fabric is to have both sets of strands crossing the join at 45° rather than one at right angles and one parallel to the join. This prevents the springiness of the fibres opening up a gap along the angle of the join.
I did all my bonding a ±45° stitched glass fabric with a thin layer of CSM pre-bonded to the underside.
One important point when using any glass fabric is to have both sets of strands crossing the join at 45° rather than one at right angles and one parallel to the join. This prevents the springiness of the fibres opening up a gap along the angle of the join.
rhumlady
Well-Known Member
The bulkheads are marine ply. I was not aware of the 45 degree bit as I assumed strength would come from the direction of the fibres and at 45 degrees the strength would be reduced. I have the epoxy and am happy using it. I don't want to go over to polyester again.
Last edited:
Tranona
Well-Known Member
Think maybe all this discussion is a bit of overkill. I suspect that the original bulkheads were bonded in with CSM and polyester, simply because that was in an era when boats were "overbuilt" in the sense that extra strength was assumed to come from just using more volume of cheap materials.
Epoxy/glass cloth is clearly superior is strength weight ratio and has the added advantage of creating a better bond on existing polyester. However there are thousands of boats surviving nicely with the "inferior" method of construction.
Repairs on more recent boats may be more critical because of the trend toward designing structures to take the loads without using excess materials.
oldsaltoz
Well-Known Member
Using epoxy resin alone as a glue is not a good idea, epoxy resin alone is very brittle so any movement can break the bond, particularly if the layer of resin is only thin.
Adding some Micro-Fibres to the resin and leaving the joint material at least 1 mm thick will result in a very strong bond, making removal all but impossible without breakage.
Hope this helps.
Good luck.