Dist: While waiting for the next step on my Fwd deck fglassing operation I hae started another attempt to figure out how to make my cowl header tank.
I have obtained (2) 8 in. dia. x 2 in. thk. foam disk and a piece of 22 in. x 28 in. pc. plastic material that they have for making custom dry erase boards. I have made that in to an 8 in. ID cylinder 18 in. long and secured it to the foam disk wit a 2 in wide plastic Tape tape from Big lots. After that I used (2) spiral lead tape wraps, (1) each hand to hold the cylinder to brevent uncoiling. This will be my mold. What should I coat the outside with as a mold release? I was cosidering mounting the mold on its longotudinal axis and turning it carefully while pouring molton parafin wax over its surface until fully coated. After it was coated I was goin to mount a straight edge to use as a scraper and thenrotate the mold and apply heat with a heat gun to scrape the wax down to a uniform thickness. Next when the wax was fully cooled I would apply a "Gel Coat" using the scrapper set up that I used for the wax to get a uniform distribution of the coat. (more or less). Then when that had nearly cured I would take and apply a non-woven fiber glass mat thouroghly wetted out. Following that would be another lawer of woven fiberglass. I have looked on the Kr-List and Kieth Eberhard in his discussions of mold making mentions using "Red Pigment" and adding "Cabosil" 10% by volume to epoxy used instead of fiber glass resin for making Molds but this will be the tank itself. (see below from the internet list) My intent would be to fonish with a cylender of about 8 inche ID of sufficient length to make into a header tank of not less then 3 gallons but not more than 3-1/2 Gallon. After the Filler neck, tank transfer lines that return to transfer pump suction Engine feed line with finger strainer and sight glass connection to the tank were made the I would close the tank ends with fibergas sandwich ends and leak test. I may consider usinm a Gems fload swich system to start and stop the fuel pump rather than have the continuous over flow back to pump suction. The idea for the continuous pump operation is that I would have a visual that the main tanks had gone dry by when the header tank level began to fall tha that could serve as a warning that I had to get the bird on the ground and would still have plenty of time to get the job done. Can anyone advise or even blow what I am trying to do full of holes? This is a stage where we can easily fix ill cocieved notions. Thanks in advance. Don Lively Burlington IA 52601 ------------------------------------------------------------------------ List-Post: krnet@list.krnet.org Date: Oct 16, 2003 7:12 AM From: Steven Eberhart <newt...@newtech.com> Subject: Re: KR>molds Here is a quick run down of how I make most of my molds. 1. Start with a good finish on the plug you are going to make the mold from. 2. put a minimum of three coats of good old Johnson's paste way. Apply each wax coat in a different direction and use old flannel bed sheets to buff out. 3. Spray on one or two coats of polyvinyl alcohol (PVA) 4. All of my molds are epoxy/glass and I use West Systems epoxy with the fast hardener. 5. Mix up the epoxy for what will be the mold surface. I start out with a batch of West systems and add red pigment and about 10% by volume of Cabosil. The pigment makes a nice uniform color mold surface and the Cabosil thickens the epoxy somewhat and makes it stick to vertical surfaces easier and also hardens the surface somewhat. 6. brush on your red jell coat and make it a fairly heavy coat. Let cure before continuing. 7. Scuff the jell coat with a scotchbrite pad so the following layers will make a good bond to it. 8. All of the fiberglass used in my molds is fiberglass matte. I don't use any woven cloth. Doesn't matter where you put it in the lay-up if there is any woven cloth in the mold it will eventually "print through" and show show up in the surface of the mold. 9. I tear the fiberglass matte into manageable squares and carefully pull it apart so that each piece is half of its original thickness. Any cut edges have a tendency to show up as fine lines in the final mold surface. I know epoxy isn't supposed to shrink but "print through" is a problem. That is why I always work with torn edges and very thin sections split from the original matte. 10. Buy a box of 1" throw away chip brushes at Harbor Freight Aircraft Supply and start applying the torn sections of matte and saturate with epoxy using the chip brushes stippling out the air bubbles. It is fairly easy to see the air bubbles against the red gel coat. Tear the pieces as necessary to fit around sharp corners, etc. Keep applying matte until you get at lease about an 1/8" lay-up over the complete surface. I generally don't go much thicker that 1/8" to 3/16". 11. I generally trim the excess matte from the mold when the glass has reached the leather stage. Leave the mold alone until it has cured at least twice as long as you think it needs to be completely cured. 12. To pop the mold from the plug start with some wooden wedges and work them between the mold and the plug. Compressed air does a great job of helping to separate the mold from the plug. If you waxed the plug well, and have a good coat of PVA, you should be able to pop off a beautiful mold. 13. After you have your mold separated wash it down well with dish washing detergent. If the phase of the moon was correct you should have a mold ready to lay up parts in. If not, sand the mold surface finishing up with 2000 grit wet or dry sandpaper and polish out with rubbing compound finishing up with white polishing compound. 14. Wax the he** out of the mold using the same Johnson's paste wax. When you think you are done waxing think about how you are going to feel if you ruin it by sticking a part in it and put on some more wax. 15. Be sure to spray a coat of PVA on your waxed mold before you do your lay-ups. Remember a green mold is a lot easier to stick a part in than a well used one that has been waxed many times. Wax and PVA are your friend here. THis is just to give you an idea of how I make my molds. THere is no substitute for experience. Dive in and try it on a smaller part and don't be afraid to experiment. Some things will work and some won't but you will be learning. Steve Eberhart
