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.

 

The density of Okoume BS 1088 plywood is around 450–500 kg/m³. If you're unable to get Okoume in India, alternatives like meranti, sapele, or mangium plywood (all BS 1088 rated) can be used. These materials are denser than Okoume but still suitable for boat building. The density will affect the weight of the boat, potentially making it heavier, which may impact performance and the amount of fiberglass required. However, as long as the plywood is BS 1088 rated, you should be able to adjust your build accordingly.

 

The wood being described as Okume is known as Gaboon in parts of the world.Which may be why you will have difficulty locating BS1088 Okoume plywood,it isn't a designation that really exists.The BS is an abbreviation of British Standard and the 1088 refers to the specific standard for marine grade plywood.To conform to the standard the species of wood should be classed as durable and the bonding should be resistant to a period of boiling.As gaboon isn't classed as durable,it can't actually conform to the standard but there is a sub category known as BS1088(gaboon) which requires glue that conforms but recognises that the wood will not and is stamped accordingly.



For the purpose of building a kayak,1088(gaboon) has the advantage of being light and sufficiently durable as he boat is unlikely to be afloat for weeks at a time.If it can't be located,any other 1088 ply will be OK but at the penalty of a bit more weight to lift when launching.It may not add up to much more than the weight of an extra water bottle and a couple of sandwiches.If the plywood doesn't have reddish,brown glue lines be suspicious.

 

Here is the stamp ( I like the artwork) from the 6mm plywood I am using on my current project, described as a medium density Meranti from the vendor:

 

BS 1088 Okoume plywood typically ranges in density from 480 to 500 kg/m³, which is favored for the Chesapeake 16LT to ensure the finished kayak remains lightweight and easy to car-top. In India, your best local alternative is likely Gurjan (often sold as Marine Grade IS 710), but you should be aware that it is significantly heavier, often averaging between 750 and 800 kg/m³. If you find you have to use plywood from different material to fit a taxi service or simply to accommodate local availability, the density will not prevent the panels from fitting together since the geometry of the plans remains the same; however, the higher density will make the hull much stiffer to bend during assembly and will result in a finished boat that is noticeably heavier to transport and sits slightly lower in the water.