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1 - 19 of 19
Fiberglassing Techniques
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Jon Finley <finley@...>
I have seen layups use both techniques. The Q plans call for the micro to
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be wet (not dry) when you apply the glass. The EZ community has done a lot of experimentation with what they call "hard shelling." They cut the cores, sand them, apply micro, sand it, and then apply the glass. The idea is that the micro can be sanded to achieve a near perfect contour before applying the glass. It also results in an easy layup (generally) and is much, much easier to get all the air out. To be clear: I am not talking about applying micro to low spots in the core or repairing core damage. I am talking about applying a micro shell around the core before applying the glass. I have always understood that the purpose of micro is to provide some "bite" into the foam (like little fingers going into the foam). The foam (if properly prepared) is smooth and contoured already it just has lots of little holes in it. Yes, the quality of the bond was an issue. The conclusion was that the glass to (dry) micro bond is a lot stronger than the micro to foam bond is so it is not a concern. This was tested by quite a few folks with different techniques but the result was always the same. Peeling the glass up always pulled the micro and bits of foam with it. You could reference CSA back issues for details. My personal conclusion (from reading and doing a hard shell layup) was that I would never do another wet micro layout as the "hard shell" layup is so much easier. I just glassed my replacement tail cone and didn't want to have to hangar warm for several days (day or two for micro to cure and then another day or two for glass to cure) so I did a "traditional" (per Q plans) layup. I now remember exactly why I decided to use the hard shell technique! If you are a "follow the plans" guy, disregard everything I have said and FOLLOW THE PLANS!! Jon Finley Q1 N54JF - 1835cc VW Q2 N90MG - Subaru EA-81 DD Turbo Apple Valley, MN
-----Original Message-----
From: Chris McAtee [mailto:Subcanis@...] Sent: December 06, 2000 8:44 AM To: Q-LIST@... Subject: Re: [Q-LIST] Questions questions Dave- Yes, you do need the to sand the micro before you add the glass. The micro, from what I understand, just makes the surface more true in reguards to smoothness and contour, resulting in less post-glass filling in. Chris McAtee ____________________________________________________________________________ _________ Get more from the Web. FREE MSN Explorer download : http://explorer.msn.com eGroups Sponsor To unsubscribe from this group, send an email to: Q-LIST-unsubscribe@... Quickie Builders Association WEB site http://web2.airmail.net/qba321tm/q-page1.html
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Jon Finley <finley@...>
Oh yea, as I recall the weight penalty on large items (wings, winglets) was
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pretty small. Seems like the big items weighed a pound or two more when hard shelled. Again, see CSA back issues for details/confirmation. Jon
-----Original Message-----
From: Jon Finley [mailto:finley@...] Sent: December 06, 2000 11:10 AM To: Q-LIST@... Subject: RE: [Q-LIST] Fiberglassing Techniques I have seen layups use both techniques. The Q plans call for the micro to be wet (not dry) when you apply the glass. The EZ community has done a lot of experimentation with what they call "hard shelling." They cut the cores, sand them, apply micro, sand it, and then apply the glass. The idea is that the micro can be sanded to achieve a near perfect contour before applying the glass. It also results in an easy layup (generally) and is much, much easier to get all the air out. To be clear: I am not talking about applying micro to low spots in the core or repairing core damage. I am talking about applying a micro shell around the core before applying the glass. I have always understood that the purpose of micro is to provide some "bite" into the foam (like little fingers going into the foam). The foam (if properly prepared) is smooth and contoured already it just has lots of little holes in it. Yes, the quality of the bond was an issue. The conclusion was that the glass to (dry) micro bond is a lot stronger than the micro to foam bond is so it is not a concern. This was tested by quite a few folks with different techniques but the result was always the same. Peeling the glass up always pulled the micro and bits of foam with it. You could reference CSA back issues for details. My personal conclusion (from reading and doing a hard shell layup) was that I would never do another wet micro layout as the "hard shell" layup is so much easier. I just glassed my replacement tail cone and didn't want to have to hangar warm for several days (day or two for micro to cure and then another day or two for glass to cure) so I did a "traditional" (per Q plans) layup. I now remember exactly why I decided to use the hard shell technique! If you are a "follow the plans" guy, disregard everything I have said and FOLLOW THE PLANS!! Jon Finley Q1 N54JF - 1835cc VW Q2 N90MG - Subaru EA-81 DD Turbo Apple Valley, MN -----Original Message----- From: Chris McAtee [mailto:Subcanis@...] Sent: December 06, 2000 8:44 AM To: Q-LIST@... Subject: Re: [Q-LIST] Questions questions Dave- Yes, you do need the to sand the micro before you add the glass. The micro, from what I understand, just makes the surface more true in reguards to smoothness and contour, resulting in less post-glass filling in. Chris McAtee ____________________________________________________________________________ _________ Get more from the Web. FREE MSN Explorer download : http://explorer.msn.com eGroups Sponsor To unsubscribe from this group, send an email to: Q-LIST-unsubscribe@... Quickie Builders Association WEB site http://web2.airmail.net/qba321tm/q-page1.html eGroups Sponsor To unsubscribe from this group, send an email to: Q-LIST-unsubscribe@... Quickie Builders Association WEB site http://web2.airmail.net/qba321tm/q-page1.html
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David J. Gall
Jon,
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I must have missed this item. Did RAF ever endorse the hard-shell procedure? If not, did they ever renounce it? Either way, can you narrow down the approximate year in either the CSA or RAF newsletter so I don't have to dig so deep? On a related issue, I do recall the big debate over sprinkling micro on the surface of a still-wet layup to save on post-cure filling and sanding. Do you have an opinion on that technique? Thanks, David J. Gall
----- Original Message -----
From: Jon Finley To: Q-LIST@... Sent: Wednesday, December 06, 2000 12:13 PM Subject: RE: [Q-LIST] Fiberglassing Techniques Oh yea, as I recall the weight penalty on large items (wings, winglets) was pretty small. Seems like the big items weighed a pound or two more when hard shelled. Again, see CSA back issues for details/confirmation. Jon -----Original Message----- From: Jon Finley [mailto:finley@...] Sent: December 06, 2000 11:10 AM To: Q-LIST@... Subject: RE: [Q-LIST] Fiberglassing Techniques I have seen layups use both techniques. The Q plans call for the micro to be wet (not dry) when you apply the glass. The EZ community has done a lot of experimentation with what they call "hard shelling." They cut the cores, sand them, apply micro, sand it, and then apply the glass. The idea is that the micro can be sanded to achieve a near perfect contour before applying the glass. It also results in an easy layup (generally) and is much, much easier to get all the air out. To be clear: I am not talking about applying micro to low spots in the core or repairing core damage. I am talking about applying a micro shell around the core before applying the glass. I have always understood that the purpose of micro is to provide some "bite" into the foam (like little fingers going into the foam). The foam (if properly prepared) is smooth and contoured already it just has lots of little holes in it. Yes, the quality of the bond was an issue. The conclusion was that the glass to (dry) micro bond is a lot stronger than the micro to foam bond is so it is not a concern. This was tested by quite a few folks with different techniques but the result was always the same. Peeling the glass up always pulled the micro and bits of foam with it. You could reference CSA back issues for details. My personal conclusion (from reading and doing a hard shell layup) was that I would never do another wet micro layout as the "hard shell" layup is so much easier. I just glassed my replacement tail cone and didn't want to have to hangar warm for several days (day or two for micro to cure and then another day or two for glass to cure) so I did a "traditional" (per Q plans) layup. I now remember exactly why I decided to use the hard shell technique! If you are a "follow the plans" guy, disregard everything I have said and FOLLOW THE PLANS!! Jon Finley Q1 N54JF - 1835cc VW Q2 N90MG - Subaru EA-81 DD Turbo Apple Valley, MN -----Original Message----- From: Chris McAtee [mailto:Subcanis@...] Sent: December 06, 2000 8:44 AM To: Q-LIST@... Subject: Re: [Q-LIST] Questions questions Dave- Yes, you do need the to sand the micro before you add the glass. The micro, from what I understand, just makes the surface more true in reguards to smoothness and contour, resulting in less post-glass filling in. Chris McAtee ____________________________________________________________________________ _________ Get more from the Web. FREE MSN Explorer download : http://explorer.msn.com eGroups Sponsor To unsubscribe from this group, send an email to: Q-LIST-unsubscribe@... Quickie Builders Association WEB site http://web2.airmail.net/qba321tm/q-page1.html eGroups Sponsor To unsubscribe from this group, send an email to: Q-LIST-unsubscribe@... Quickie Builders Association WEB site http://web2.airmail.net/qba321tm/q-page1.html eGroups Sponsor To unsubscribe from this group, send an email to: Q-LIST-unsubscribe@... Quickie Builders Association WEB site http://web2.airmail.net/qba321tm/q-page1.html
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John Loram <johnl@...>
Hello Jon:
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Boy!, having done only the "wet micro" lay-ups, what you say seems counter intuitive to me... In what way is the "dry micro" lay-up easier/faster/better? You mention the ease of air removal, but it sound to me that the process you describe just adds another time consuming step; that of the sanding the hardened micro shell to contour. Do not the multiple layers of fiber glass, on top of the carefully contoured micro shell, just destroy all the careful contouring work you've done?. Seems to me that once the fiber glass is down, you just have to do it all that careful contouring again. Or, even if the fiberglassing does not change the contour of the micro shell, would you not still have to go through the process finishing the surface of the glass in which you accomplish both the filling and final contouring in a single operation? Please explain, more! I know for your comment, " I now remember exactly why I decided to use the hard shell technique!", that I'm missing something....... thanks, -john-
-----Original Message-----
From: Jon Finley [mailto:finley@...] Sent: Wednesday, December 06, 2000 9:10 AM To: Q-LIST@... Subject: RE: [Q-LIST] Fiberglassing Techniques I have seen layups use both techniques. The Q plans call for the micro to be wet (not dry) when you apply the glass. The EZ community has done a lot of experimentation with what they call "hard shelling." They cut the cores, sand them, apply micro, sand it, and then apply the glass. The idea is that the micro can be sanded to achieve a near perfect contour before applying the glass. It also results in an easy layup (generally) and is much, much easier to get all the air out. To be clear: I am not talking about applying micro to low spots in the core or repairing core damage. I am talking about applying a micro shell around the core before applying the glass. I have always understood that the purpose of micro is to provide some "bite" into the foam (like little fingers going into the foam). The foam (if properly prepared) is smooth and contoured already it just has lots of little holes in it. Yes, the quality of the bond was an issue. The conclusion was that the glass to (dry) micro bond is a lot stronger than the micro to foam bond is so it is not a concern. This was tested by quite a few folks with different techniques but the result was always the same. Peeling the glass up always pulled the micro and bits of foam with it. You could reference CSA back issues for details. My personal conclusion (from reading and doing a hard shell layup) was that I would never do another wet micro layout as the "hard shell" layup is so much easier. I just glassed my replacement tail cone and didn't want to have to hangar warm for several days (day or two for micro to cure and then another day or two for glass to cure) so I did a "traditional" (per Q plans) layup. I now remember exactly why I decided to use the hard shell technique! If you are a "follow the plans" guy, disregard everything I have said and FOLLOW THE PLANS!! Jon Finley Q1 N54JF - 1835cc VW Q2 N90MG - Subaru EA-81 DD Turbo Apple Valley, MN -----Original Message----- From: Chris McAtee [mailto:Subcanis@...] Sent: December 06, 2000 8:44 AM To: Q-LIST@... Subject: Re: [Q-LIST] Questions questions Dave- Yes, you do need the to sand the micro before you add the glass. The micro, from what I understand, just makes the surface more true in reguards to smoothness and contour, resulting in less post-glass filling in. Chris McAtee ____________________________________________________________________________ _________ Get more from the Web. FREE MSN Explorer download : http://explorer.msn.com eGroups Sponsor To unsubscribe from this group, send an email to: Q-LIST-unsubscribe@... Quickie Builders Association WEB site http://web2.airmail.net/qba321tm/q-page1.html To unsubscribe from this group, send an email to: Q-LIST-unsubscribe@... Quickie Builders Association WEB site http://web2.airmail.net/qba321tm/q-page1.html
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Cash, Gene <CASH@...>
I read something ages ago saying that Rutan (RAF) clearly poo-pooed the
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practice of sprinkling microballoons on wet lay-ups because it would tend to pull up epoxy and starve the lower layers of needed adhesive. For the same reason the practice of laying peel-ply over the entire wing surface lay-up was nixed. There doesn't seem to be an easy way out of the surface finish work. Gene Cash
-----Original Message-----
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Jon Finley <finley@...>
Hi David,
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I don't recall what RAF had to say about it, I would certainly think one of those guys asked. It was at least a couple years ago. I will see if I can lay my hands on them tonight and let you know. I use the "bubble sprinkle" somewhat differently than maybe what you are thinking. I use it to eliminate the glossy surface on the layup so that the dry micro applies easier and has a surface to grip. So the only sanding that is minimized/eliminated is that required to remove the gloss and create something for the micro to grip, filling is still required. With this in mind, I believe that the bubbles should be applied just before the epoxy tackiness goes away and that only a very small quantity of bubbles be applied. The goal is is to have the bubbles stick but not absorb epoxy. I usually sprinkle the bubbles on, rub it in with my gloved hand (if this helps understand when I do it - the epoxy is pretty set), and then brush off the excess bubbles (the ones not sticking). I have never done it with a large/structural layup (haven't had the opportunity). I'm of the opinion that if the layup isn't dry and the builder waits until the right stage, it is ok. I can imagine someone pouring a couple gallons of bubbles on a wet layup, obviously this isn't going to work real well (probably result in an extremely dry layup with a ton of sanding needed (before throwing away)). The big problem with doing this is that layup inspection is very difficult after applying the bubbles, you really need to inspect the layup before applying the bubbles. As long as we are talking about stuff that is "wild & crazy".... I also use alcohol to thin my dry micro. I mix up the micro as dry as possible, add a small amount of alcohol (I do it by eye, but it is probably a tablespoon or so for an 8-12 oz cup of micro), and then add more bubbles. The result is an extremely light micro that is easier to spread. Yea, there was a big debate about this too (does the alcohol mess with the chemical properties of the epoxy, etc...). All I know for sure is that all of the airplanes that I know were finished this way and they still look fine. Jon Finley Q1 N54JF - 1835cc VW Q2 N90MG - Subaru EA-81 DD Turbo Apple Valley, Minnesota
-----Original Message-----
From: David J. Gall [mailto:David@...] Sent: December 06, 2000 11:38 AM To: Q-LIST@... Subject: Re: [Q-LIST] Fiberglassing Techniques Jon, I must have missed this item. Did RAF ever endorse the hard-shell procedure? If not, did they ever renounce it? Either way, can you narrow down the approximate year in either the CSA or RAF newsletter so I don't have to dig so deep? On a related issue, I do recall the big debate over sprinkling micro on the surface of a still-wet layup to save on post-cure filling and sanding. Do you have an opinion on that technique? Thanks, David J. Gall
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Dave King <KingDWS@...>
Hi
When I wrote the question I was using my little Tosh notebook, little keys big fingers, slow typing. I'm back on my regular machine so that means lots of typlexia and bad spelling...;-] What I didn't add to the original question was that I was looking at this with an eye towards getting a perfect contour to start with and if this helps with the final finish ie more accurate or less finishing required etc. Oh yea, as I recall the weight penalty on large items (wings, winglets) wasI take it this is Ez sized wings? I don't have CSA but I did a search through my cp's and couldn't find a reference in there (I'm sure it is somewhere). From what I was told it was supposed to result in a lighter layup as the cured micro layer sealed the foam from any fresh epoxy getting into the pores. I can see how it might come out the same weight or heavier but wasn't too sure about lighter. I have seen layups use both techniques. The Q plans call for the micro toI hadn't heard it called hard shelling so I'll do some searching on that. From the info I had the core was finished then micro slurry applied and squeeged normally but allowed to cure. Then any dimples dents etc are filled, ie scuffed land then filled and allowed to cure. Then the micro 'd core gets sanded down using reversed templates to check contour. The rest of the prep is the same as a glass to glass. Then the cloth gets laid up as per normal. From what I saw of this it should give a good base to start with and if the layups are done with care the final finish is more accurate. Yes, the quality of the bond was an issue. The conclusion was that theIf the foam came up then its definalty failing in the right way. Sounds good. To me it seems that it couldn't be any weaker than a glass to glass bond done over time. ie one layer applied after the epoxy has cured. My personal conclusion (from reading and doing a hard shell layup) wasis so much easier.Thats interesting to as I kept thinking it would be a bit more work in the long run. If you are a "follow the plans" guy, disregard everything I have said andPLANS??? We don't need no steenkin plans!! (quickly donning flame proof underwear) Cheers Dave
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If you use denatured alcohol to thin the "dry micro" for finishing, the
foam will not erode. My 2 cents worth. Bruce Crain On Wed, 6 Dec 2000 12:26:46 -0600 "Jon Finley" <finley@...> writes: Hi David,________________________________________________________________ GET INTERNET ACCESS FROM JUNO! Juno offers FREE or PREMIUM Internet access for less! Join Juno today! For your FREE software, visit: http://dl.www.juno.com/get/tagj.
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jtenhave@mets.mq.edu.au <jtenhave@...>
Dave,
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there are a couple of reasons why the hard shelling technique is not optimum. They are: 1. When sanding the shell, the difference in resistance to sanding between micro and foam is so great that the moment you break through the shell you have stuffed the contour and you are up for a repair anyway. 2. You deny yourself the advantage of a chemical bond between the micro and the glass 3. Foam is much, much easier to sand than micro therefore it is much easier to get a near perfect core with bare foam. ( i.e. long sanding blocks and sanding templates) 4 The near perfect contour you go to such lengths to generate is inevitably disrupted the moment you layup any varying thicknesses of glass on the foam surface (unless you read ahead and make the appropriate allowances in the foam) so you are up for surface filling whichever way you look at it. 5 It doesn't make a great deal of sense to make one simple operation into two or more for no overall benefit. Hope this helps John
-----Original Message-----
From: Dave King [SMTP:KingDWS@...] Sent: Thursday, December 07, 2000 8:23 AM To: Q-LIST@... Subject: RE: [Q-LIST] Fiberglassing Techniques
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Hot Wings
Just another opinion and a look at this from a different perspective - It's
left up to the reader to glean the truth. << 1. When sanding the shell, the difference in resistance to sanding between micro and foam is so great that the moment you break through the shell you have stuffed the contour and you are up for a repair anyway. I have not found this to be a problem unless the core was way too wavy to start with. If you sand only until you see a blue (or orange) pattern appear that looks like a dried up lake bed you still have several thousandths of micro left to keep your sanding block from digging into the foam. 2. You deny yourself the advantage of a chemical bond between the micro and the glass This is a moot point as a clean and sanded epoxy/epoxy bond is many times stronger than the foam/foam bond. The foam will ALWAYS fail first. 3. Foam is much, much easier to sand than micro therefore it is much easier to get a near perfect core with bare foam. ( i.e. long sanding blocks and sanding templates) Its so much easier to sand that it takes a really light touch not to damage the foam. I find that it takes me less time to sand a good contour with the "skin" even though it takes more "work". 4 The near perfect contour you go to such lengths to generate is inevitably disrupted the moment you lay-up any varying thicknesses of glass on the foam surface (unless you read ahead and make the appropriate allowances in the foam) so you are up for surface filling whichever way you look at it. Aren't we supposed to "plan ahead"? About the only area where I have found a problem with loosing the contour is on the leading edge of the wing where lay-ups over lap. Other than this after several layers of (carefully laid) glass have cured a long block will still evenly mark the surface just as it did before the glassing. If the lay-ups are done carefully many times all the prep that is needed is a sanding with 220 and a coat of primer/sealer. 5 It doesn't make a great deal of sense to make one simple operation into two or more for no overall benefit. >> Very true - But I do see a 2 very real over all benefits. 1); I think you get a STRONGER wing because as we all know the limiting factor is the compression strength of the materials we are working with and I find the glass fibers to lay much straighter when layed up on a flat and firm surface rather than over some squishy micro which always seems to move around when working the lay-up. And 2); I find it requires less over all work to get to the finished product. If in doubt - do it by the plans. We know they work. "Think outside the box - but fly in the envelope" <A HREF="http://hometown.aol.com/bd5er/Qpage.html">Q-2 page</A> Leon McAtee
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jtenhave@mets.mq.edu.au <jtenhave@...>
Gene,
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This process straight onto the glass was discouraged because the assumption was that the original layup was optimal i.e. the minimum amount of resin was used to just wet out the glass cloth. By definition therefore, anything that drew resin from an optimised layup would result in a lean top laminate. The solution was to wait until the layup had gelled and then spread the minimum amount of micro over that surface, a reasonably wet mix makes the spreading of a thin layer much easier. At this stage you can sprinkle micro to your hearts content which will result in the leaning out of the wet micro mix and a much easier layup. I would like to be able to take the claps for this, but I learnt this technique whilst working with Dave Ronneburg building the prototype Berkut. One caveat is that this process denies you the opportunity to inspect the skin to whatever bonds after cure, but in Berkut's case, the skins were carbon so it was academic. If this is a concern, those sub surface bond areas could be left bare. Peel plying was discouraged for another reason. It was claimed that this would add weight because the added resin would be used to fill the peaks and troughs between each bundle of fibers in the cloth and if used in that way, there is no doubt there is a weight penalty. The original design calcs are based on the assumption that the top skin will be sanded flat, i.e. that half the bundles will be damaged getting down to the required condition for bonding and finishing. Then the micro finishing process is carried out, filling up the remaining texture and the transitions between layers of glass There is however, another way to look at peelplying. If the top layer is applied slightly rich resinwise, and then peelplyed three things happen. The first is that the surface finish requires little or no sanding prior to bonding, microing and much less filler. The second advantage is that any sanding does much less damage to the structural glass. The third advantage is that the glass bundles are pressed flat and by judicious squeegeeing most if not all of the excess resin can be removed from the layup. The savings in sanding when you are at an energetic and resource ebb are significant. One final caveat is to ensure that the peel ply has no untoward coatings which could degrade the final bond. Hope this clarifies the issue. John
-----Original Message-----
From: Cash, Gene [SMTP:CASH@...] Sent: Thursday, December 07, 2000 5:09 AM To: 'Q-LIST@...' Subject: RE: [Q-LIST] Fiberglassing Techniques I read something ages ago saying that Rutan (RAF) clearly poo-pooed the practice of sprinkling microballoons on wet lay-ups because it would tend to pull up epoxy and starve the lower layers of needed adhesive. For the same reason the practice of laying peel-ply over the entire wing surface lay-up was nixed. There doesn't seem to be an easy way out of the surface finish work. Gene Cash -----Original Message----- To unsubscribe from this group, send an email to: Q-LIST-unsubscribe@... Quickie Builders Association WEB site http://web2.airmail.net/qba321tm/q-page1.html
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Pat Panzera <panzera@...>
"jtenhave@..." wrote:
John, not to single out your message, but rather this is to address this entire thread.... Is there any real proof that raw micro balloons spread over liquid epoxy could wick material away from where it belongs, or is this another hanger legend? If I spilled a bunch of epoxy on my hanger floor, the last thing I would use to try and absorb it would be micro... even if it were free. If it were free, I'd reach for flox first. Heck, when I WANT to mix micro with epoxy it's a serious pain in the rear! I would almost be willing to bet (almost) that if you mixed some epoxy and placed a dime size drop on wax paper, then sprinkled micro over the drop, the surface tension of the liquid would support the weight of the micro, and only the balloons which are actually in contact with the liquid would stick after cure. Additionally, I don't think the optimal ratio of resin to glass can be achieved by the process outlined in the plans. I believe that the hand process produces a epoxy rich lay-up, and if a builder ever saw a lay-up with the exact perfect ratio, he'd swear it was dry. Therefore I can't see how dusting micro over a completed lay-up could compromise the structure. In reality, I can see how it can help to maintain the structure, by reducing the amount of potentially destructive sanding called for in the step immediately before filling the weave. BUT!!! If prototype was built with a (presumably) rich mixture, and we are building knock-off's of the prototype and trusting our lives to it's flight test information, then in order to be secure in this information, we need to do it the same way the prototype was done.... or do our own testing. Pat I've dusted plenty of parts with a very conservative amount of micro, and it always seemed that after cure, almost all the micro came back off, except that which was directly in contact with the epoxy.
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jtenhave@mets.mq.edu.au <jtenhave@...>
Pat,
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Single away, a valid assertion should be able to withstand sceptical questioning! let me play the devils advocate here, If no micro sticks when sprinkled on a resin rich surface ( whether or not it contains glass) why bother doing it at all? I am not advocating this as a practice, merely explaining why it was discouraged. I have never done it, why? because I thought it was a dumb idea, and at the time I built my Long Eze I had not heard of the method of wet micro on top of a tacky layup. Quite apart from the fact that at the end of a wing layup, I had run out of puff.... -and I had peel plied the surface....... With respect to optimal layups, I would have agreed with you to a large extent prior to seeing the experts at work, now I know that it is possible to make parts by hand that are much more efficient...resin wise and the best way of all is under vacuum. Incidently, optimal layups do not look like dry layups, they are uniform in colour and the bundles are discrete, hence the difficulty in sanding them to a uniformly scratched finish. A very good video on the subject is Mike Arnold's tape "How Its Made" describing the construction of the AR-5. If you are glutton for punishment, his "Making Fiberglass Molds" will cast even greater light on the subject. Regards John
-----Original Message-----
From: Pat Panzera [SMTP:panzera@...] Sent: Friday, December 08, 2000 12:28 PM To: Q-LIST@... Subject: Re: [Q-LIST] Fiberglassing Techniques "jtenhave@..." wrote: John, not to single out your message, but rather this is to address this entire thread.... Is there any real proof that raw micro balloons spread over liquid epoxy could wick material away from where it belongs, or is this another hanger legend? If I spilled a bunch of epoxy on my hanger floor, the last thing I would use to try and absorb it would be micro... even if it were free. If it were free, I'd reach for flox first. Heck, when I WANT to mix micro with epoxy it's a serious pain in the rear! I would almost be willing to bet (almost) that if you mixed some epoxy and placed a dime size drop on wax paper, then sprinkled micro over the drop, the surface tension of the liquid would support the weight of the micro, and only the balloons which are actually in contact with the liquid would stick after cure. Additionally, I don't think the optimal ratio of resin to glass can be achieved by the process outlined in the plans. I believe that the hand process produces a epoxy rich lay-up, and if a builder ever saw a lay-up with the exact perfect ratio, he'd swear it was dry. Therefore I can't see how dusting micro over a completed lay-up could compromise the structure. In reality, I can see how it can help to maintain the structure, by reducing the amount of potentially destructive sanding called for in the step immediately before filling the weave. BUT!!! If prototype was built with a (presumably) rich mixture, and we are building knock-off's of the prototype and trusting our lives to it's flight test information, then in order to be secure in this information, we need to do it the same way the prototype was done.... or do our own testing. Pat I've dusted plenty of parts with a very conservative amount of micro, and it always seemed that after cure, almost all the micro came back off, except that which was directly in contact with the epoxy. To unsubscribe from this group, send an email to: Q-LIST-unsubscribe@... Quickie Builders Association WEB site http://web2.airmail.net/qba321tm/q-page1.html
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jtenhave@mets.mq.edu.au <jtenhave@...>
Leon,
thanks for your comments, your points raise some interesting issues which extend the discussion beyond the scope of the original query - which is a good thing! In the interests of bandwidth, let me snip that which is not needed to continue the discussion. I have not found this to be a problem unless the core was way too wavy to start with. If you sand only until you see a blue (or orange) pattern appear that looks like a dried up lake bed you still have several thousandths of micro left to keep your sanding block from digging into the foam. No argument here apart from why bother with the extra work? If the core was correct, none of this would be necessary. Its so much easier to sand that it takes a really light touch not to damage the foam. I find that it takes me less time to sand a good contour with the "skin" even though it takes more "work". So, I might add, would using a lighter grade of paper on ones sanding board. We are not talking about a great deal of finesse here, just care. Aren't we supposed to "plan ahead"? About the only area where I have found a problem with loosing the contour is on the leading edge of the wing where lay-ups over lap. Other than this after several layers of (carefully laid) glass have cured a long block will still evenly mark the surface just as it did before the glassing. If the lay-ups are done carefully many times all the prep that is needed is a sanding with 220 and a coat of primer/sealer. I am interested to learn how it was possible to have planned ahead sufficiently to recess a hard shell for each spar cap laminate, to have permitted the uni skin to have joggled up and down the .009" steps required for each ply, ( 9 plys from memory on the Q1 canard) to have accurately predicted and allowed for the tapes which attach the flying surfaces to the fuselage, and to have allowed for the wing tip layups, the elevator and aileron slot layups, the wheel pant attachment layups and still be able to evenly mark the surface with a long block. (I am assuming that the block is being used spanwise?) Extraordinary stuff! >> Very true - But I do see a 2 very real over all benefits. 1); I think you get a STRONGER wing because as we all know the limiting factor is the compression strength of the materials we are working with and I find the glass fibers to lay much straighter when layed up on a flat and firm surface rather than over some squishy micro which always seems to move around when working the lay-up. It is unclear that the limiting factor is the compressive strength of the materials we use. in the case of our composite It is less than the tensile, but so is the peel strength and the bearing strength, so what? That is why different layup schedules are used. The limit is the stress that the part sees, hence the flight envelope and the weight limit. It is quite unclear why one would get a stronger wing because we all know the limiting factor is the compression strength....... Perhaps I am missing something here? I think you will have universal support for the assertion that having the fibers lying straight is desirable, but it could be that there was too much, too soft micro beneath the layup which was too wet which permitted the problems described above. The optimum amount of micro is that which just fills the cells of the foam. Remember that honeycomb cores have gaps of several millimetres between the edges of the cells. All you have to do is to provide a bond sufficient to transfer the shear loads carried by the core - as you rightly pointed out above....it is not a lot. And 2); I find it requires less over all work to get to the finished product. You are right, Leon but the quality of the product may differ. Other than items produced in a female mold it is hard to think of anything which would achieve the finish specified in the plans with a 220 grit sand and a coat of primer sealer. Regards John
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Hot Wings
In a message dated 12/7/00 23:20:38 Pacific Standard Time,
jtenhave@... writes: << Leon, thanks for your comments, your points raise some interesting issues which extend the discussion beyond the scope of the original query - which is a good thing! >> ======================== I am so glad that you did not take my post as an attack on your views - It was definitely not meant as such and I was worried that it would be taken that way given the history of this group. I have done lay-ups both ways and I have just found that I am more efficient doing it the "hard shell" way. Try it, you might like it. Your observations about planning ahead with regard to the .009" thick lay-ups for the wing spar caps brings up a question that someone here might know the answer to. I have always assumed that the factory took the thickness of these lay-ups into consideration when they made the templates for hot wiring. Having never lofted the "real" airfoils and compared them to the factory templates I don't know if this is true or not. While it makes no real difference one way or the other I would kind of like to know one way or the other. "Think outside the box - but fly in the envelope" <A HREF="http://hometown.aol.com/bd5er/Qpage.html">Q-2 page</A> Leon McAtee
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Pat Panzera <panzera@...>
"jtenhave@..." wrote:
<snip> let me play the devils advocate here, If no micro sticks when sprinkled on aIt's not that "no" micro sticks, but it's been my experience that only the thin layer of micro which is in direct contact with the uncured epoxy sticks. Take a mixing cup half full of properly mixed (uncured) epoxy, and fill the balance of the cup with micro, then (with no mixing) walk away and let it cure. Believing the common theory that sprinkling powdered micro balloons over a properly wetted out part robs the part of epoxy, one would assume that when we returned to the test cup, we'd find a large part of the epoxy has wicked up into the micro. Not having actually tried this experiment, I believe that when we return to our cup, we will be able to dump out of the cup, all the micro, save a very thin layer. But to answer your question... this thin layer now makes for a highly suitable surface for applying an additional layer of micro, after a small amount of light sanding, which may or may not be needed at all. Thanks! Pat
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jtenhave@mets.mq.edu.au <jtenhave@...>
Pat,
toggle quoted messageShow quoted text
I agree with you here, indeed I think that you might even be giving the micro a better chance to wet out than would be the case with an optimal layup. I am moving house right now so all my laminating gear and aircraft projects are packed up, but I will do the experiment and report back. A peel plied surface would also provide the same preparation for sanding and filling. John
-----Original Message-----
From: Pat Panzera [SMTP:panzera@...] Sent: Saturday, December 09, 2000 7:29 AM To: Q-LIST@... Subject: Re: [Q-LIST] Fiberglassing Techniques "jtenhave@..." wrote: <snip> let me play the devils advocate here, If no micro sticks when sprinkled on aIt's not that "no" micro sticks, but it's been my experience that only the thin layer of micro which is in direct contact with the uncured epoxy sticks. Take a mixing cup half full of properly mixed (uncured) epoxy, and fill the balance of the cup with micro, then (with no mixing) walk away and let it cure. Believing the common theory that sprinkling powdered micro balloons over a properly wetted out part robs the part of epoxy, one would assume that when we returned to the test cup, we'd find a large part of the epoxy has wicked up into the micro. Not having actually tried this experiment, I believe that when we return to our cup, we will be able to dump out of the cup, all the micro, save a very thin layer. But to answer your question... this thin layer now makes for a highly suitable surface for applying an additional layer of micro, after a small amount of light sanding, which may or may not be needed at all. Thanks! Pat To unsubscribe from this group, send an email to: Q-LIST-unsubscribe@... Quickie Builders Association WEB site http://web2.airmail.net/qba321tm/q-page1.html
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Mike Dwyer <mdwyer@...>
I thought it was pretty easy to lay down the micro then the glass per the
plans. I wouldn't waste the time for the two extra steps of micro&sand. Just my opinion. Mike Q-200 built in 16 months
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Pat Panzera <panzera@...>
"jtenhave@..." wrote:
A peel plied surface would he heavier, as all the void space between the threads would be filled with 100% epoxy. Additionally, sanding would be a serious drag, and would be necessary as there's hardly a good way to lay peel ply on a compound curved surface without it wrinkling and trapping high spots of pure epoxy. On another note, as for placing 10oz bid directly over uncured micro (as the plans call for) I've had a bit of trouble keeping the micro from oozing (even if only a little bit) between the fibers as I wet out the first layer of glass, and therefore micro ends up between the layers of glass. Pat
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