Help in doing the Math! Graphite/Epoxy bottom coat

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Capt UB
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Help in doing the Math! Graphite/Epoxy bottom coat

Post by Capt UB » Tue Nov 07, 2017 8:58 pm

FS14

I am putting down a Graphite/Epoxy bottom coat. Total of 3-4 coats. 1st. coat will tell me what to do. Wet on wet, if it looks good or let each coat cure, then sand between coats.

I bought measuring cups, spoons and digital scale.
I have the strainer shifter.
I have the S3 epoxy and slow hardener.
1 lbs. of graphite.

I need 25 % graphite in my epoxy mix, how do I do the math, graphite is dry and epoxy is liquid?

I know how to put it on, I just need help with the math.
Thanks, Bob.


I'm always lost when building a boat, it's when the boat is in the water, I know my way.

1970? 13' Canvas on frame canoe
2017 Bateau FS14, starting build Oct 2017.
2017 Bateau NC16, starting soon.

narfi
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Re: Help in doing the Math! Graphite/Epoxy bottom coat

Post by narfi » Tue Nov 07, 2017 9:20 pm

The math of your epoxy is the important part.
25% of the powder is arbatrary though you may want to keep it the same batch to batch for consistency.

What I did was easy math for simple minds :P

I use pumps for measuring my epoxy, and each 'squirt' is roughly 1oz (it doesnt matter since they are the same pumps I do 2 squirts of epoxy and 1 of hardner)
Using this simple math, I knew that 2 squirts + 1 squirt roughly equils 3oz
3+1 = 4
25% of 4 = 1
Therefor I mixed at a ratio of 2 squirts to 1 squirt to 1oz of powder.
Planning a head you can know your ratios and have your powder pre-measured to mix in.

3oz of epoxy needs 1oz of powder
6oz of epoxy needs 2oz of powder
9oz of epoxy needs 3oz of powder
12oz of epoxy needs 4oz of powder
etc.....

Edit: thinking back I may have even done it simpler than that and figured out how many heaping plastic spoonfuls it took to make 1oz, that let me stir in a spoonful at a time for a smoother mixture.

Edit #2: I think I used alot more words than needed....
25% is simple when using epoxy that mixes at a ratio of 2-1 because it allows you to mix 2-1-1 and no math is needed.

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Re: Help in doing the Math! Graphite/Epoxy bottom coat

Post by Jaysen » Tue Nov 07, 2017 9:27 pm

Even fewer words...

Use volume measure not weight.

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Capt UB
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Re: Help in doing the Math! Graphite/Epoxy bottom coat

Post by Capt UB » Tue Nov 07, 2017 9:40 pm

Pour your Epoxy and hardener in separate tubs at the correct ratio, add the wieghts and then weigh out 1/4-25% of the total, mix your Epoxy and hardener and then add your graphite.

Thanks Narfi. I got now.... I found so many different mixes and ways to lay down graphite/epoxy...
I'm always lost when building a boat, it's when the boat is in the water, I know my way.

1970? 13' Canvas on frame canoe
2017 Bateau FS14, starting build Oct 2017.
2017 Bateau NC16, starting soon.

narfi
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Re: Help in doing the Math! Graphite/Epoxy bottom coat

Post by narfi » Tue Nov 07, 2017 9:42 pm

volume.... I did volume not weight.
The powder is light, 1/4 by weight would be a lot of powder........

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Re: Help in doing the Math! Graphite/Epoxy bottom coat

Post by Capt UB » Tue Nov 07, 2017 9:45 pm

Just going to say something about that!

oz dry
oz liquid

Not the same !
I'm always lost when building a boat, it's when the boat is in the water, I know my way.

1970? 13' Canvas on frame canoe
2017 Bateau FS14, starting build Oct 2017.
2017 Bateau NC16, starting soon.

tcason
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Re: Help in doing the Math! Graphite/Epoxy bottom coat

Post by tcason » Wed Nov 08, 2017 9:08 am

Make sure your epoxy is warm before mixing in graphite I like 85 or so.

I put my jugs in front of space heater to warm up.

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Re: Help in doing the Math! Graphite/Epoxy bottom coat

Post by Capt UB » Wed Nov 08, 2017 9:27 am

tcason wrote:
Wed Nov 08, 2017 9:08 am
Make sure your epoxy is warm before mixing in graphite I like 85 or so.

I put my jugs in front of space heater to warm up.
Got it setup, tub with hot water, it's in the upper 80's here in Central Florida...
I'm always lost when building a boat, it's when the boat is in the water, I know my way.

1970? 13' Canvas on frame canoe
2017 Bateau FS14, starting build Oct 2017.
2017 Bateau NC16, starting soon.

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Re: Help in doing the Math! Graphite/Epoxy bottom coat

Post by willg » Thu Nov 09, 2017 11:44 am

Capt UB wrote:
Tue Nov 07, 2017 8:58 pm
FS14

I am putting down a Graphite/Epoxy bottom coat. Total of 3-4 coats. 1st. coat will tell me what to do. Wet on wet, if it looks good or let each coat cure, then sand between coats.
I would recommend applying your coats wet on wet so you don't have to sand. I did that with the 3 graphite coats I applied and I like the outcome. With silvertip like I used there is a 72 hour no-sand window.

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Re: Help in doing the Math! Graphite/Epoxy bottom coat

Post by Capt UB » Thu Nov 09, 2017 12:21 pm

willg wrote:
Thu Nov 09, 2017 11:44 am
Capt UB wrote:
Tue Nov 07, 2017 8:58 pm

I would recommend applying your coats wet on wet so you don't have to sand. I did that with the 3 graphite coats I applied and I like the outcome. With silver tip like I used there is a 72 hour no-sand window.
Thanks Will.
Yes, I'm hoping to start late this afternoon, it still in the upper 80's here. I plan on a tub with hot water to keep things flowing and mixed! It's does put a smile on one face at this point!! :)

I saw the Hexagonal Boron Nitrite "white graphite".... Looks cool!
Bob
I'm always lost when building a boat, it's when the boat is in the water, I know my way.

1970? 13' Canvas on frame canoe
2017 Bateau FS14, starting build Oct 2017.
2017 Bateau NC16, starting soon.

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