Weight of Materials

Hi, I have spent ages searching but I am sure I have missed it because it must have been done by now!

I am trying to locate the weights of sheets of ply. (6mm & 9mm) And also how much each weighs (approx as obviously the epoxy will vary depending on who did it and their skill) once epoxied with 2 5oz layers of woven mat. And also the weight per metre of pine 2x1 (20mm x 40mm)

Any pointers would be much appreciated! (I realise these will only be guesstimates but that is sufficient for the time being!)

 

The ply will weigh about what the source wood weighs per cubic foot or meter. The weight of the wood you use is easily looked up.
The manufacturer of the ply can give you exact weights.
Insofar as the solid wood goes, again see what the wood weighs either per cubic foot of cubic meter. Pine is generally about 26-28 lbs per cubic foot, so a 1"x2" is 1/12 (of a foot high) x 1/6 (of a foot wide) or (1/72) of the cubic weight per foot.
A 1 x 2 is then a bit less than 1/3 lb, maybe 5 oz. per ft.

A.

 

Marine plywood available in Australia is most commonly made from Hoop Pine.
From the web it is given a density of around 600kg/m3.
http://www.australply.com.au/about_hoop_pine.html
This makes a standard 1.2m x 2.4m sheet of 6mm weigh around 10.5kg, and a 9mm sheet about 15.5kg. If you can get okoume (or gaboon) marine ply it is around 70% of this weight. It is imported from Europe or Israel but is stocked in Australia. The use of epoxy and fibreglass mat seems a bad idea for a few reasons. (1) Adds a lot of weight for limited additional strength
(2) Epoxy and mat are not very compatible because of the binder in the mat.
If light weight is important then woven or knitted fibreglass with epoxy is much better.

 

frosh is on the ball with the weights as these are the weights that i have weighed the ply that i purcahsed for my boat out at, china has also started exporting gabboon ply and it can be pruchased at quite good prices now, however there is a tradeoff and that is it is not as rot resistant as hoop pine, i also second the call for woven glass, matt takes more resin and is harder to wet out
hows the design coming along?
ive now sketched mine up and am now in the technical aspects state like yourself
sean

 

Here are a few scraps I have, for what the're worth. Not metric.
This is untreated plywood
A full sheet of 1/2" AC plywood weighs 42# or 1.312# per
sq. ft.

There fore, 1/4" weighs 21# per sheet, 3/8" weighs 28# per sheet,

5/8" weighs 52# per sheet, and 3/4" will weigh 63# per sheet
.
http://www.e-wood.com/ref/weights.asp .
. http://www.websterchain.com/graphicsreduced/approx.htm .
Ted,

 

Plywood weights per meter square;

6mm = 4.8kg
12mm = 7.5kg
15mm = 10.2kg

check this site for anything plywood: http://www.worldpanel.com/Marineplywoods.htm

 

Knowing the exact weight quickly, without a scale:

A stick of any size and length is upended and allowed to float in fresh water in a bucket (a simple pair of wire hoops will hold it upright loosely. Wax the wood first, all surfaces.
The proportion of the wood unsubmerged relative to the submerged portion yeilds the exact ratio of wood to water, so if the wood is exactly half submerged, it weighs exactly 31 lb. per cubic ft., half that of fresh water at 62 lb ft/3. A strip of plywood can also be done this way (but seal it with floor wax). The nice thing is that the wood need not be measured at all, as would be vital to do accurately for a scale to indicate its density. The stick only needs to be parallel-sided.
Very dry wood will take up moisture in use, another question mark. I suppose a moisture meter would help in that area.

Alan

 

I'm not sure what you are talking about with 'woven mat'. Cloth and woven roven are woven, mat is made from chopped strands and is also called CSM. In the U.S., the weight of CSM is per square foot while for cloth and woven roven (WR) it is per square yard. A common weight of mat here is 1 1/2 oz., which equals 13.5 oz. per square yard. A common weight of cloth here is 10 oz., which equals 10 oz. a square yard. Sam

 

There is a chart of the weights of various laminations in the 3rd reply of this thread. Sam

http://www.boatdesign.net/forums/showthread.php?t=8686&highlight=fiberglass thickness

 

Thanks everyone for your quick replies!

Sorry my bad I am meaning the woven cloth, not chopped matt type.

Does anyone have an approximate weight of glass with 10oz of cloth and faired. ( I know it is a bit of a how long is a piece of string!)

I am calculating rough weights, eg 4 sheets 6mm ply = 42kg + Resin & Cloth (10kg?)

 

Northerncat Yeah have made a m couple of models (small scale) just to check proportions and general lines. Have made a couple of small changes and now back recalculating things.... As $$$ are an issue (aren't they always!) I am thinking I might go back to the 2 engine layout as it is easier and cheaper for me to get two 25 - 30 hp engines than one 60 ish. Of course then comes the fun of making sure they have charging circuits and not many have hydraulic tilt/trim. But that is down the track! (I am hoping to launch for next summer) This would also give me a bit of extra safety as I will be buying old motor(s) and at least then I have a backup! (If I do go single engine then I'll get a smaller 7.5 or something as an auxillary anyway for safety... can't see me being able to row it!)

 

1 remember that when you go two motors you need to factor in a20 percent increase in hp
2 10 0z is i think similar to 200gsm, now this needs to have 200gsm resin to wet it out so you get a weight for glass and cloth of 400 grams per square metre
sean

 

Ok thanks!

 

As I understand it, if the cloth is in ounces it is ounces per yd^2.
10oz/sqyd = 10ozx28.4gms/ozx10.76ft^2per m./9Ft^2peryd. = 340gm/m^2

Therefore at 55%/45% resin to glass a sq m of laminate would weigh 340x100/45=755.55gms + sq m wt of ply.

I.E. 340gms cloth + 415.55gms epoxy = 755.55gms total lam./m^2. Chk. 415.55-340=75.55/755.55= 10% off the 50/50
of vacuum bagging. (55%- 45%)

http://www.boatdesign.net/forums/showthread.php?t=16928
Thanks Frosh!

 

i stand corrected your 5 oz then must be similar to our 200gsm, so 2 *5 oz layers is a pretty heavy layup just for waterproofing, in aus when people build large ply cat <35ft its standard practice to cover all exposed surfaces with a layer of 200gsm, this basically seals off the ply from the water and adds a small! amount of strength, any areas that you then want to add a bit more strength you just throw over a few heavier layers,
for comparison the duflex core that has become popular over here has a 600gsm layer on either side of the core and this is considered to be very strong
sean