Amt of epoxy to be used?bottom OD18

podfather · Post by **podfather** » Fri Sep 27, 2002 11:05 am

Looks like others were as confused as I, in trying to estimate how much epoxy I will need for each step in the process. Jacques most recent reply cleared my head....somewhat...At least now when applying epoxy you´ll have a better idea if you´ve squeezed out enough so that you use about what the formula calls for. (I THINK)

Post by **jacquesmm** » Fri Sep 27, 2002 11:49 am

This is how we calculate for our kits, BOM and weights: for each boat, during the design, we must calculate weigths, areas etc. anyway. That data, extracted from CAD, is in a spreadsheet. That spreadsheet is quite elaborate: at least 6 pages for a small boat! We calculate how much resin you need - to cover all the plywood two sides - to build the fillets - to fiberglass All plywood areas are calculated. All seam lengths too, for fillets and tape seams. All fiberglass weights are extracted from there and we apply factors. For plywood priming (saturation), we use the System Three figures for Okume. For the fillets, we use our own formuila, for the glass, we use the glass weight at 50%. Waste and overlap factors are used plus, at the end, a total 15% safety margin. Then, because of packaging, we round up to the next resin jug. This works fine in most cases but some builders use more or less than others. We must average.

podfather · Post by **podfather** » Fri Sep 27, 2002 12:46 pm

What I had meant about the formula was...If 1 1/2 gal is what you should use on the 12oz Biax area of the OD18 than if you use 3/4 gal per half you´ll know that you´re somewhat on target of 40% to 50% glass to resin that is desired. Knowing how much resin should be used for gives you a better idea if you are stayiing close to the strength that has been planned.

Edward · Post by **Edward** » Fri Sep 27, 2002 9:30 pm

Yipes...this looks confusing. I am builduing the OD18. I just did this step and I am mixing it this way: I mixed a cup and a half at a time. I used four of that mix. That makes 48 oz total to wet it out and get it down well. I have so far used three of that mix atop it ....36 oz. The finish is where I want it now so that is a total of 84 oz =10.5 cups total so that is just over one gallon of the mix. I am a first time builder so I did maybe use more epoxy than needed yet I doubt it. I am a quick study and the resin was very well squeegied from the inital lamination so it was as little epoxy as was needed to do the job. The second coat took care of the inital weave that was showing and got it to the point that minimal faring is needed.

podfather · Post by **podfather** » Sat Sep 28, 2002 6:27 am

Edward of Danvers ..Mass. Building the OD18.. Please contact me directly at my posted E-Mail address. I´m just a little behind the stage of construction that your in ...need to pick your brain!!! Podfather

almus · Post by **almus** » Mon Sep 30, 2002 7:18 am

Just as a follow-up, I emailed system-3 regarding their quoted coverage for epoxy on biaxial tape. Their reply was that the 32ft^2 per gallon was for the following fiberglass: "The tape is DBM 1708. It is 17 ounce double bias stitched to 3/4 ounce chopped strand mat for a total weight be square yard of about 25 ounces." Strange, I thought glass, glass-tape was not typically done with epoxy. -Almus

Post by **jacquesmm** » Mon Sep 30, 2002 9:36 am

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD>Quote:<HR></TD></TR><TR><TD><BLOCKQUOTE> On 2002-09-30 07:18, almus wrote: Just as a follow-up, I emailed system-3 regarding their quoted coverage for epoxy on biaxial tape. Their reply was that the 32ft^2 per gallon was for the following fiberglass: "The tape is DBM 1708. It is 17 ounce double bias stitched to 3/4 ounce chopped strand mat for a total weight be square yard of about 25 ounces." Strange, I thought glass, glass-tape was not typically done with epoxy. -Almus </BLOCKQUOTE></TD></TR><TR><TD><HR></TD></TR></TABLE> I don´t know who emailed that but it is 100% wrong. First, glass content has nothing to do with resin brand. There is no need to call System Three about it, see any text book about fiberglass. To give an amount of resin per area is also very unusual in our industry: nobody calculates that way. In open layup, one can reach glass contents of 33 to 50%. This means, 12 oz. of glass = 12 oz of resin at 50% or 24 oz. at 33%. 1708 is biaxial with matt: we do not sell it , we do not specify it. To my knowledge, System Three does not sell biaxial with matt. Our System Three kits contain exclusively biaxial tape 12 oz. without matt, part number DB120 from Hexcell (Owens-Corning). Calculations based on 1708 would double the amount of resin!!! Anyway, the real question in this discussion is "how much resin does one need for a particular job"? The answer is: at least as much as the weight of the glass used, probably more if this is a first boat. We calculate all BOM´s based on 50% content plus a 15% safety margin.

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