Marine grade plywood density

Hi, I am a new builder from India & purchased the Chesapeake 16LT plans. I read that the plywood that I am supposed to use should be BS 1088. I am not sure if I get Okoume plywood in India. If I have to use plywood from different material, does the density affect the plans. Just concerned about it.

1. What is the density of the Okoume BS 1088 plywood used in Chesapeake 16LT
2. What are the alternatives that I can use instead of Okoume? (Of course I will use BS 1088 but of a different material)
3. Does the density affect the plans

Please help

 

1. Doesn't matter

2. Whatever is available where you are... ?

3. No, follow the plan.

 

@BlueBell Thank you very much

 

1. 500 kg/m3 +/- 50kg
2. Whatever you find that is rated BWP (boiled water proof), has no voids and bends reasonably well.
3. No, density affects weight. 500kg/m3 4mm plywood weighs 2kg/sqm, 750kg/m3 4mm plywood weighs 3kg/sqm. All that will happen is that you won't meet the plans target weight, it will be a few kg's heavier.

 

Hello Suneeth, I hope you have a fun boat build. Below is taking easily 'googled' information to its end to estimate raw plywood weight.

I googled 'Chesapeake 16LT' to find that Chesapeake 16LT is a kayak from CLC:
Materials List for Plans Builders:
Okoume - Marine Plywood» 4mm 4' x 8' (3 pieces) [4.46 sq m]
Okoume - Marine Plywood» (Half-Sheet) 6mm 4' x 4' (1 piece) [1.49 sq m]

I googled 'density of Okoume plywood BS1088' and found something like :
BS 1088 Gaboon/Okoume Marine Plywood https://www.winwood-products.com/eng/timber-products/plywood/okoume-plywood.htm
BS 1088 Lloyds Approved Okoume (Gaboon) Marine Plywood
Light in weight (average 500kg/m3) <- checks with @Rumars post above
Standard thicknesses:
4mm =2.0 kg/m2
6mm =3.0 kg/m2

according to my local supplier, Meranti plywood is 30% heavier (you can find the density of your available plywood and do the calculations versus Okoume)
Meranti – Midwest Boat Appeal & Marine Plywood https://www.midwestboatappeal.com/marine-plywood-lumber/meranti/

so for raw materials,
the 4mm sheets =4.46 sq m= 8.92 kg in Okoume, or 11.6 kg in Meranti
the 6mm sheet =1.49 sq m= 4.47 kg in Okoume, or 5.8 kg in Meranti

these would be unyielded weights, yielded weight in the boat will be less (no scrap or sawdust), perhaps you can look at the layout sheets on the plans and estimate a percent used for the plywood to estimate yielded weight of the plywood you will be sourcing for the build.

 

Boil test any plywood purchased in your area for minimum 1 hour. There are lots of imposters in the Asian market stamping bs1088 according to a vendor in Florida I trust.

Testing and criteria for suitable plywood https://www.boatdesign.net/threads/testing-and-criteria-for-suitable-plywood.58295/

 

Thanks @Rumars So to avoid making the kayak heavier I will try to stick to something that is close to 500kg/m3. Thanks again

 

That was very detailed with lot of research too, Thanks a ton @Tops

 

Sure, thank you

 

Excellent advice if you are going to be using the boat in boiling water. If you aren't, don't waste your time.

Assuming you will use at least 3 coats of a 100% solids epoxy on all the ply and timber on the boat, a bigger concern is the quality of the veneers and the bond. Check the edges of all your sheets for gaps, tap them to find voids (probably visible as swelling over a large area and weigh them. If you are still concerned, get an offcut and submerge it in water for a few days and try to peel the veneers apart. The wood should let go before the glue.

Ensure plenty of ventilation, especially in sealed compartments, never leave fresh water sitting on plywood (epoxied or not), paint it a light colour, keep it out of the sun when not in use and try not to subject it to below zero temperatures. Maintained properly, it should outlast you.

 

Don’t waste your time submerging it in water for a few days? The owners of a marine plywood dealership here have seen Asian imposters stamping BS1088 on interior rated glues. OP ‘not sure’ if he can get BS1088. A boil test is good advice and takes an hour. He buys his panels, boils an offcut and verifies it doesn’t fall apart. Simple. If it fails the boil test; it’ll fail your test, too.

Otherwise, I am a fan of your work Rob. Not wanting to get into nonsense with you.