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Lamination schedule and mold release

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Old 12-24-2017, 10:29 AM
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Mms_citrus
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Default Lamination schedule and mold release

2 questions. First, what would you all recommend for the lamination schedule on this model? It’s 42” span. I was thinking that 2 layers 4 ounce might be enough, but I’m not sure...
Second, I’ve been messing around with parting planes. I was going to do a top bottom split, but I’ve been thinking and I don’t think my canopy will release unless I split the top in half? Am I correct in this belief? I also decided to mold the rudder with the top fuse, so I’m looking at a 4 piece top mold, which is fine. I think I’ll be happier with the outcome. Any thought are appreciated.

for clarification, not the lamination schedule on the mold, but on the parts I produce from the mold. I’ve got my mold materials all figured out.
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Last edited by Mms_citrus; 12-24-2017 at 10:31 AM.
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Old 12-24-2017, 12:10 PM
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Mold release wax, and PVA (polyvinyl alcohol) for release. 2 layers of 4 oz. will probably be a good place to start. I really like a "crowfoot weave" or a "twill weave" because they drape, or take contours well. Be prepared for disappointments! Your first attempts won't be perfect. Study molding techniques, and part layup processes. Fiberglast Products has training videos on the net. I've been working in fiberglass for 40 years, and I still make mistakes, and I'm still learning. Thayercraft is a good source for cloth. I just got about 30 yards from Steve last week.
Most modelers split their airplanes vertically. That's what I've always done. That doesn't mean that for your project you can't split it horizontally. It's your choice. Keep in mind the "draft of the part". You don't want it to lock up in the mold. A lap seam is a great way to join the part halves, but it requires more mold preparation up front. It pays off in the long run if you are producing a lot of fuselages, but not so much if you only plan to make one, or a couple of parts. The alternative to a lap seam, and the most common way of joining parts, is with joint tape. In a production environment it's beneficial to join the halves in the mold, which requires access to the inside of the part through the mold (typically the wing saddle) and special tools. The parts can also be joined outside the mold. I tape them together, or spot glue with CA, and then tape the seams internally. Good luck, and let us know how it turns out.
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Old 12-24-2017, 12:39 PM
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THe shape of the fuse is not conducive to a vertical split. The route Iím going now takes any draft into account, itís just a lot of extra molding. Having never done this before I donít know how much of a recess will lock a part in the mold. I originally intended to do only a 2 part fuse, top and bottom. The canopy sides are almost vertical with horizontal recessed panel lines. I assumed the would lock and not pull straight up, hence the split upper half fuse. Basically I donít know how much panel lines will effect the release.
as far as joining the fuse halfís, I had intended to mix up an epoxy putty and glue my bulkheads and fuse parts together as one. Any reason this wonít work? I would be able to seam it after I pull the parts but Iíd prefer not to. Iím counting grams at this point.
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Old 12-24-2017, 09:43 PM
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Small ridges on the canopy probably won't "lock" the part up in the mold, since there is some flexibility to thin layups. If the "plug" came out of the mold, the parts should. Using a blast of air, especially if you only have a slight draft in your mold, helps to pop parts out of the mold. Your plan to build the internal structure, and form the molded parts over it should work. Give it a try, and see if it gives you the results you desire. Keep in mind that most glass fuselages are joined as a unit, and then the internal structure placed inside. The typical model only requires a minimum of reinforcing parts: a firewall, wing hold down plates, stab doublers, maybe a rudder post, and servo rails.
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Old 12-30-2017, 04:21 PM
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My wings are molded and the horizontal stab. Came out good for my first attempt.

Scratch build McDonnell XP-67
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Old 12-30-2017, 05:44 PM
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Great work. I wish I had seen your complete thread before I tried to answer your question on "parting" your fuselage mold. Looks like you have mastered many of the tricks and techniques of molding fiberglass parts. Now that I see that you are incorporating some of the wing with the fuselage, I understand why you wanted to mold outer skins to go over an internal structure. Good job.
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Old 01-04-2018, 09:43 PM
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So I’ve been experimenting with the wing and hor stab layup. I need a little advice. So I’ve been playing around with 4oz, and I’m getting a little trouble on the edges, some voids. I’m just doing wet layup. I’m not vacuum bagging......yet. I may have to tho. If I’m careful with resin application I can keep the weight low enough. I’m looking at full wing skins coming in at around 1.4 ounces, 1.7 with spars and and servo.
So since I’m having some void problems on the leading edge I was thinking that I have 2options. Mix a thickened epoxy and taper the leading edge more, then glass.
Or do several layers of 1oz.

Or or is there other methods I’m missing. I really have very little practical experience here..4 oz is the lightest I can get thru my wholesaler. That’s why I went with it, and I thought it would be the appropriate choice.

also since I’m asking, what is the normal procedure for laying up parts? Do you spray or brush a layer of epoxy on first, let set and then glass or do like I’ve been doing and just layup glass in the mold?

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Old 01-04-2018, 10:24 PM
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Some people start with a "skim coat" of resin (a brushed layer of epoxy) which gives a better external surface, but also is a little heavier then a simple layup. Sometimes I spray paint in my mold. The purpose of either a skim coat, or painting is to reduce the the porosity, or pin holes that have to be filled in the finishing process. It is also a standard procedure to mix resin with filler like cabosil, ( not sure if that is the correct spelling?) One general term is to call it "mud" which is then spread into sharp corners where the cloth won't lay. Nose rings, tail posts, wing fillets, and even sharp leading, and trailing edges. Sometimes a bag, like a cake decorating bag is used to pump the mud into the sharp areas. I make my bags out of poly, or nylon film. A totally different approach to getting your cloth to lay in the mold is to use two layers of say 2 oz. cloth in the mold instead of one layer of 4 oz. I don't know what kind of cloth you are using, but some cloths lay down better then others.
Cloths referred to as "crow's foot weave" and unidirectional are good choices for our models. I get a cloth from thayercraft.com that is 3.7 oz unidirectional, which I recommend highly.
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Old 01-04-2018, 10:28 PM
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Thayer Craft's web site is down. I just ordered cloth from Steve two weeks ago, and he told me to check out his e-bay listings.
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Old 01-05-2018, 10:30 AM
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I just purchased 10y 2.7 oz or something like that. I got some 1 oz coming too. Iíve been using cotton flock for thickening. Iíve used Cabosil in the past with polyester boat repairs. Any difference. I think the cabosil may have been a lighter product.
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Old 01-05-2018, 10:52 AM
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Over the years I've used micro balloons (brown and white) cotton flocking, ground glass, and Cabosil for thickening my resin,(polyester, and epoxy). My preference for most "mud" filling applications is Cabosil. My experience with cotton is that it's harder to smooth out when wet, and harder to sand, but excellent for structural applications, such as fillets behind firewalls, and landing gear blocks.
Don Stegall sells starter kits with different kinds of fillers in small quantities. He has posted on this site before, as well as the NMPRA site. Don has also done some videos on the different fillers, and their applications.
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Old 01-05-2018, 06:50 PM
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Do you think 42Ē needs removable wing sections? Iím thinking now about laying up the wings and fuse as 1.
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Old 01-05-2018, 07:20 PM
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That's sounds like a small airplane. Depending on your estimated all up weight it's certainly seems like an option to make it one piece.
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Old 01-05-2018, 07:58 PM
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Yea i wanted something I could fly at the park first. Iím shooting for 3lbs all up. Itíll be close but I think I can get the bare fuse in at a little over a pound. And Iím estimating with a 5000mah battery which itself is almost a pound, so I can shed weight there at the expense of flight time. Glassing it all at once will make it so much easier. Iíve been having a fit trying to decide how to make the wings removable, I had a clever servo mount figured out, no servo covers and stuff but itís just too small and itís too complicated for something this size. I need to simplify.....
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Old 01-06-2018, 08:47 AM
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For a 3 pound plane I would make it 1 piece. As long as transportation is not an issue, a removable wing will add more weight in the structure necessary for wing mounting hardware, hardpoints for wing bolts, and hardened points in the wing to keep the bolts from distorting it.
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Old 01-11-2018, 12:48 PM
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Talk Tom,e about coring. I was thinking of using balsa sheet. I’m wondering how to prevent The balsa from soaking up too much resin or is that not really a concern. What would u use. And how would you do it. I’m coring so that I can use minimal bulkheads.
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