# Calculate resin req't for hull infusion

Discussion in 'Fiberglass and Composite Boat Building' started by KnottyBuoyz, Aug 8, 2014.

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### KnottyBuoyzProvocateur & Raconteur

I'm planning to infuse the inside of the hull of my boat project. I've done a fw small scale infusions before but tackling something as large as a 31 1/2' x 10' boat is a whole new ball of wax for me. I'm trying to calculate the resin requirement for the pull based on these numbers (rounded up).

......................glass........wt.......total
Bottom Panels...30 sq yd...45 oz...85 lbs
Side Panels...... 21 sq yd...20 oz...27 lbs
Bulwarks............5 sq yd...20 oz...6.5 lbs
Transom............2 sq yd...44 oz...6 lbs
Keel Sides..........7 sq yd...45 oz...20 lbs
Keel Bottom........2 sq yd...45 oz...6 lbs

Fiberglass weight...........150 lbs
Waste in lines etc. .........10 lbs

Pounds per gallon approx. 9 would be 18 gallons resin assuming a 50/50 resin/fiberglass ratio.

Am I close?

Last edited: Aug 9, 2014
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### latestarterSenior Member

Apart seeing a video, I know nothing about infusion, however 15% of 150 would be 22.5.

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### KnottyBuoyzProvocateur & Raconteur

Sorry, it was a long day in the boat shed.

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### groperSenior Member

Type of reinforcement? Dbl bias, csm, uni etc
What vacuum pressure will you infuse at?
Is there any core materials, flow media, or peel ply? if so, need areas and resin absorption of each or the type and will have a ballpark figure.

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### KnottyBuoyzProvocateur & Raconteur

Thanks for looking in groper. I'll try to answer all your questions. Here's the types & weights of th reinforcements.

Bottom Panels...30 sq yd...1x 33oz triax w/8oz mat, 1x 12 oz biax 0/90
Side Panels...... 21 sq yd...1x 1708 biax, 1x 12 oz biax 0/90
Bulwarks............5 sq yd...1x 1708 biax, 1x 12 oz biax 0/90
Transom............2 sq yd...1x 33oz triax w/8oz mat, 1x 12 oz biax 0/90
Keel Sides..........7 sq yd...1x 33oz triax w/8oz mat, 1x 12 oz biax 0/90
Keel Bottom........2 sq yd...1x 33oz triax w/8oz mat, 1x 12 oz biax 0/90

The boat is currently upside down and the exterior was hand laminated. The project is so big I couldn't work wet on wet so sanding was required between each layer, not ideal. The core is 1/2" Meranti BS1088. The infusion is to laminate the inside of the hull once it's flipped.

http://i237.photobucket.com/albums/ff166/KnottyBuoyz/GOPR0004-corrected-1.jpg

These are the two fabrics I'll be using. 33oz Triax & 12 oz biax.

http://i237.photobucket.com/albums/ff166/KnottyBuoyz/KBIII/GOPR0041-1.jpg

I don't have any figures on resin absorption for any of the fabrics I'm using. I could do a test on some scrap to see how well it performs. Say a strip 15 cm wide by 1m long? Something like that.

I currently have a Robinair 15500 that'll pull a near perfect vacuum. It's located about 15' away from the boat. I intend to buy a second pump as backup that'll be similar in performance, volume etc. My last resort is a vacuum generator. Likely all three would be required to debulk the layup.

http://i237.photobucket.com/albums/ff166/KnottyBuoyz/KBIII/IMG_1582.jpg

My portable vacuum generator.

http://i237.photobucket.com/albums/ff166/KnottyBuoyz/KBIII/IMG_1561.jpg

Flow media: Airtech Greenflow 75, 100% surface area coverage. 68 sq yds.
Peel ply: Airtech Econoply J or similar, 100% area coverage. 68 sq yds.
Resin fill & vacuum lines: 1/2", approx. 200'

Starting to think now I'll need a bit more epoxy. Currently looking at getting this: Resin Research Composite Pro 2070 but open to suggestions. This is a low budget project. I'm building totally out of pocket so cost is a major factor in my decisions. What I'm trying to save is the amount of sanding & mess of hand laminating the interior of the boat. It's not a cosmetic part, none of it will be seen unless you pull the deck hatches up. It took me the better part of two building seasons (abt 7 months ea) to hand laminate, fair & prime the exterior.

Thanks, I appreciate your help tremendously.

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### KnottyBuoyzProvocateur & Raconteur

A little more research and I've refined my weight figures a bit. All numbers rounded up so approx.

......................glass........wt.......total
Bottom Panels...30 sq yd...45 oz...85 lbs
Side Panels...... 21 sq yd...20 oz...27 lbs
Bulwarks............5 sq yd...20 oz...6.5 lbs
Transom............2 sq yd...45 oz...6 lbs
Keel Sides..........7 sq yd...45 oz...20 lbs
Keel Bottom........2 sq yd...45 oz...6 lbs
Peel Ply............68 sq yd....2 oz...8.50 lbs
Flow Media........68 sq yd....2 oz...8.50 lbs
Lines...............200 ft........48 oz...3 lbs

Approx. 168 lbs or 19 gallons of epoxy.

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### TungstenSenior Member

The flow media green 75 will use about 40-50 grams a ^ft where the peel ply will be about 5-8 grams.At least this is what my tests showed.

What about the plywood? will this be pre coated.

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### KnottyBuoyzProvocateur & Raconteur

Yes I'll precoat the ply. There's fillets & tape to go on the seams so that's pretty much gonna guarantee a mess anyways!

I read the tech sheet on the Greenflow and it showed it's weight at 98 gm/sq meter. That's what about 4 oz? Your test showed something like 18 oz sq/yd?

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### groperSenior Member

Quick question, why are you using the 8oz mat? Is this CSM? If so, I can't see any reason to put it in when you are using epoxy...

If you precoat all the timber first, then we can assume a minimal resin consumption into the substrate, say 50 grams per sq meter.

All your stitched reinforcements are similar to what I have experience with, and provided you can achieve absolute vacuum pressure around 50pa or better ( I don't know your altitude) and you don't have any significant leaks, your reinforcements will use around 32% of their weight in resin.

Green flow 75 should use around 550grams per sq meter.

Peel ply about 7grams per sq meter.

Resin in your feed line, simply use pi*radius of ID hose^2*hose length for the internal volume that will be wasted. Say your 1/2in hose, every 10ft is going to use 368mls. Need to account for your strategy and work out the total feed volume, the vacuum lines dont need to be accounted for.

Also allow an amount appropriate to what's going to be left in the bottom of the resin bucket, so the hose will not draw air. This is important as when your near the end, you may need to mix a little more to finish it off. If you let the hose become exposed, you will suck a huge air bubble into the job when you open the line again to finish it off. Ruins your day...

So for your flow media and peel ply, I get 34.72kg of resin.
You can do the rest I'm sure for your panel areas using the above info.

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### KnottyBuoyzProvocateur & Raconteur

That's the backing on the 33 oz Triax. I wasn't including it as an extra layer.

I'll adjust my estimate lower, say 40:60 to be on the safe side.

Holy Sh*t! That's almost 9 gallons (\$450) of epoxy left in the mesh & peel ply! Zoinks!

I figured my rounding up and fudge factors would look after what's left in the lines & buckets. Now I've got some real life figures to work with. The amount of resin that'll be left behind in the flow media & peel ply has me a little concerned.

I'll go crunch some more numbers.

Thanks groper.

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### KnottyBuoyzProvocateur & Raconteur

73 meters (240 feet) above sea level.

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### groperSenior Member

I don't work with fudge factors. You shouldn't either on a job like this or you will end up wasting a lot more than you could otherwise if approached meticulously. 30-32% by weight is what you will get with a near perfect vacuum at sea level. At 80% vacuum it will be more like 36-38% by weight. This gives you a range depending on what vacuum you acheive.

With infusion, what you loose in the flow media, you can partially or completely gain back what you lost from the savings in the laminate resin. But this is also why I choose flow media such as 30% shade cloth as the resin consumption is nearly half that of green flow 75.

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### KnottyBuoyzProvocateur & Raconteur

I have to assume the gauge on my vacuum setup is relatively accurate. I've pulled 29" Mercury or 97.8 kPa. I think that works out to 98%.

I knew of using shade cloth. Haven't tried it yet. I'll have to figure that scenario out as well. It would be a real shame to leave \$450 in resin behind in the consumables. I'm not a rich guy, I gotta squeeze the beaver & make him **** (Canadian saying for a cheap skate) on this project.

Very interesting stuff! Makes ya think.

Thanks for sharing your expertise groper. I appreciate it.

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### groperSenior Member

Your vac pump is similar to mine. All good on that front, but with a large setup like this, not in a proper commerical mold, you will get vacuum leaks and it will be difficult to acheive the same vacuum you get on a small job which is easy to get vacuum tight.

Thats the biggest issue you will have to solve with this entire job, getting the whole thing as vacuum tight as possible, the rest is pretty straight forward...

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### KnottyBuoyzProvocateur & Raconteur

Yeah, I know that's going to be an issue. The sheer size of the thing has me a bit worried hence why we're here talking about it.

What do you use for a vacuum film? I've got a sample of Diatex PO120 coming from France. They make it in widths up to 10 meters.

There's really only 1 hole drilled in the hull so far and that's to locate the rudder post!

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