RE: Scratch Designed/Built Sailplane Fuselage
[quote]ORIGINAL: soarrich If you have the wheel behind the CG it wouldn't bounce, as long as the wheel touches first. [/quote] That is exactly the problem. If the wheel is behind the CG on this fuse shape it can't touch first.
Posted on: 9/13/2012 9:21 PM by Author "wyowindworks" in the forum "RC Gliders, Sailplanes and Slope Soaring"
http://www.rcuniverse.com/forum/fb.asp?m=11227955

RE: Making a glass cowl from the inside of a plastic one ?
PVA stands for polyvinyl alcohol. It's primary job is to create a barrier that prevents any chemical reactivity between the release surface and the layup resin. I like to use Part-all Paste #2 release wax and Part-all Film #10 (PVA). I've never tried to release off of ABS so I'm giving you the safest release combination. Wax alone may work but I think you might run into problems depending on your chosen resin. You should test your chosen combination on a scrap first.
Posted on: 9/11/2012 12:54 PM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11225290

RE: Making a glass cowl from the inside of a plastic one ?
Wax AND PVA would be the most reliable release. You should test the release on a scrap of ABS first.
Posted on: 9/11/2012 12:35 PM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11225272

RE: Vacuum Bags
Back in the day when I used to produce a lot of bagged wing I used the tube bags from ACP. I would attach the breather to the inside of the bag so I didn't have to fuss with it each cycle. I was often able to get 20 to 30 uses out of a single bag. You can see this setup with the attached breather in this very old video that I made: https://vimeo.com/2357551 I also use poly tubing for several application. You can get it in rolls in various thicknesses. I used the 4 mil for multi-use and the 1.5 mil for single use. I used an 24" impulse sealer to seal the ends and an ACP vacuum port through the bag. I would cut the bag longer than I needed and then cut one end just inside the seal with a scissors to open it. I could then reuse it by just sealing the open end again with the impulse sealer. The bag will get slightly shorter with each use. You can also heat weld your own with poly drop cloth plastic using the technique shown in the video. This video shows it's use for bladder fabrication for molding but you can use the same technique to seal bags. You can go directly to minute 3 to see the sealing method. https://vimeo.com/35648020 If I'm bagging molds then I often use the caulk method. Wing molds can be rather heavy and difficult to slip into a tube style bag. If you are doing vacuum infusion then the poly plastic and Stretchlon 200 is notorious for being slightly permeable and fouling the infusion. I'd recommend making your bag from Stretchlon 700 or 800 for infusion.
Posted on: 9/9/2012 1:36 PM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11222951

RE: Large volume hotbox
[quote]ORIGINAL: T_om Thanks Adam, do you have a source on the controller? Tom [/quote] http://www.etcsupply.com/ranco-etc111000000-digital-temperature-controller-p-86.html
Posted on: 9/8/2012 2:39 PM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11222029

RE: Large volume hotbox
Extruded polystyrene insulation foam isn't very stable about 165*F. I would frame the box just like you would a wall. I would line the interior with fiber cement tile underlayment. You should be able to get it from Home Depot or Lowes. You can insulate it with regular house insulation. I would heat it with a 120 volt baseboard heating unit. You can get 30" ones for around $20. You will will have to jump/disable the heat protection circuit breaker or put a breaker with a higher temp rating into the unit. If you want to get to 180*F then you want to use at least a 200*F breaker. You'll want to install a fan to the inside that can circulate the air to eliminate hot spots. You will need a fan that uses bearings that can handle the higher temps. You can control the heating unit with a Ranco controller. These wire up very easily and already contain the relay and temp sensor. There are other heat controllers out there on ebay but you will need to wire them up to a relay to turn the heating element on and off. Adam
Posted on: 9/8/2012 2:17 PM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11222006

RE: Fuselage Nose Repair Ideas
[quote] If your fuse is polyester (smells like a boat factory) use polyester, if epoxy, either resin will work. [/quote] I would use epoxy to make the repair regardless of the resin used to make the fuse. Polyester makes very poor mechanical bonds. Epoxy will stick to cured polyester better than polyester will stick to cured polyester. Polyester sticks to epoxy very poorly.
Posted on: 9/6/2012 10:18 AM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11219606

RE: Wind speed limits?
You can get the record holding planes HERE and HERE. They range from $350 (40") to $3800 for the 100" Kinetic (last I heard). You can get several 80" DS planes in the $1400 range. The larger birds usually require $500 in servos...often more.
Posted on: 9/2/2012 9:26 AM by Author "wyowindworks" in the forum "RC Gliders, Sailplanes and Slope Soaring"
http://www.rcuniverse.com/forum/fb.asp?m=11214477

RE: Blue foam fuselage
You can sand West Systems resin. You can fill larger blems with bondo or a mixture of epoxy laminating resin and micro-balloons. Little pin holes can be filled with a mixture of micro-balloons and primer (single component stuff like Dupli-color Paint Shop)
Posted on: 9/1/2012 8:19 AM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11213493

RE: Blue foam fuselage
I think leaving as much foam in place is a good idea. The foam can really offset the buckling of the skins. If the weight is equal, between leaving the foam or taking it out, you would use a little less glass to offset the weight of foam. The skin would be less pucture resistent but the structure will be stiffer. If you glass the inside of the foam structure it will become even stiffer.
Posted on: 8/31/2012 10:33 PM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11213266

RE: Blue foam fuselage
You can also just melt the foam out with solvent and then peel the packing tape out. This way you don't have to make a seam. There are some new foams that are water soluble. I was just a testing lab that CNC cut the foam blank, ran it through a braiding machine, vacuum infused the braid, and then poured water in through an opening to melt out the foam.
Posted on: 8/30/2012 8:48 PM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11212218

RE: Blue foam fuselage
Polyester resin will eat Dow extruded polystyrene foam. What epoxies have tried before to do laminating? A good epoxy laminating resin is very easy to use.
Posted on: 8/30/2012 6:09 PM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11212090

RE: Carbon fiber cloth supplier?
If the tail is strong enough for flight loads but flexes on impact then you have the ideal situation. The bending, but not breaking, of the fuse on impact is absorbing the impact forces. If the fuse is flexing during flight loads then you would want to stiffen the tail. Carbon is great for increasing the stiffness but it can also decrease the strain properties of the fuse. This means that the tail won't be able to bend as far before failing. Carbon also performs poorly if the rate of strain is high (impact). Lastly, if you add carbon to one area the areas immediately adjacent to the carbon will under go more stress. This requires one to think through how the carbon will be used. Typically the best way to increase the stiffness/strength for the least amount of weight is to align fibers with the forces involved. Fibers parallel to the length of the fuse and on the side will increase the side-to-side flexing of the tail (like a dog wagging it's tail). Fibers parallel to the length of the fuse and on the top and bottom will prevent the tail from wagging up and down. Fibers that are +45 to the length of the fuse will increase the torsional stiffness of the tail. Adding any fiber in any direction will increase the stiffness in all directions. Meaning that adding fiber that is parallel to the length of the fuse will also increase the torsional stiffness. It's just won't be as effective as putting in on 45*. If the bending stiffness is primary then add the material parallel to the length of the fuse. If torsional stiffness is primary put the fiber on both 45* axis (+/-45). The downside to carbon veil is that the fibers are oriented in random directions which is rather inefficient. Veils also yield a low fiber volume fraction (Vf) which means that a majority of the added volume (and weight) will be resin rather than fiber. Fiber is more efficient than resin. Some ways to handle the problem would be: 1) Use cheaper uni-directional fiber rather than woven. This allows you to strategically orient the fibers. UD materials also yeild a higher fiber volume fraction...more fiber for less resin. You cut this into narrow strips if you need to cut down on weight. You can also add strips in hoops around the fuse. This will help prevent the walls from buckling inward. You can buy UD for CST, ACP, and soller composites for very little money. Most of these places sell it by the linear foot. 2) An even cheaper method (and potentially lighter) is use raw carbon tow. This is the raw fiber bundles that are used to make fabrics. 12K is a common size (12,000 filaments). Tow can be dipped into resin, squeegeed through your finger and positioned in the fuse. You can add a few and then if you need more stiffness you can just add a few more. 3) Don't use carbon at all but rather add a balsa web between the walls of the fuselage. This will prevent the wall from buckling and shearing against each other which will increase stiffness. 4) Use a carbon fabric. The light two ounce stuff will cost as much at $60 for a linear foot (39" wide) while the heavier 6 ounce stuff can be acquired for $40 for a linear yard (1 meter wide). The added advantage to woven is the fibers that encircle the cross-section of the fuse will increase the stiffness further. 5) Use a lighter kevlar fabric as a cheaper alternative than carbon. You can get a square yard of 1.7 ounce kevlar for $20. Kevlar isn't as stiff as carbon but is stiffer than glass. It also handles impacts well. Whatever you add you want to taper the ends (like a fabric dart) to more evenly distribute the added stiffness. If the ends are squared off then the fuse will break right at that edge (stress riser). Lastly, if stiffness is the objective then using a stiffer resin will make a difference. Alcohol thinned bonding epoxy (5-10-15-30 minute epoxy) wouldn't be a very good choice. A true laminating resin will do the best job.
Posted on: 8/29/2012 9:27 PM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11211139

RE: Carbon fiber cloth supplier?
What aspect of the tail are you trying to improve? Strength? Toughness? Stiffness? Bending or torsion?
Posted on: 8/28/2012 8:06 PM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11209797

RE: elevator mixing for chuck glider.
Why do you need to secure the elevator halves? You just need to use the V-tail mix on the radio. Rudder/aileron input would split them (cause each half to go opposite directions) and elevator input would move both servos the same direction to move both surfaces the same direction for pitch control. I don't think that this plan will work very well though. Ailerons work well because you have have a long moment arm (to induce roll) due to the span of the wing. A rudder works well because you have a long moment arm (to induce yaw) from the length of the tail. If you try and use the elevators to induce a roll you end up with a very short moment arm. Put another away, you have very little leverage to change the attitude of the airplane. The roll response will be far from "sporty".
Posted on: 8/27/2012 10:13 AM by Author "wyowindworks" in the forum "RC Gliders, Sailplanes and Slope Soaring"
http://www.rcuniverse.com/forum/fb.asp?m=11207744

RE: composite Fuse Joint
The mold for the DLG fuse is made from carbon fiber, MDF, and a partial casting of epoxy and sand. You can see the mold construction in this thread on RC Groups: http://www.rcgroups.com/forums/showthread.php?t=1514414
Posted on: 8/24/2012 5:59 PM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11204956

RE: composite Fuse Joint
[quote]ORIGINAL: yankee samurai Wyo, what is you mold made of? [/quote] Which mold are you referring to?
Posted on: 8/24/2012 9:03 AM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11204488

RE: How Much Glass Cloth to Use for Various Size Fuselages
Multiple layers of fabric is typically stronger. You often need fibers going in varying direction to make a part that has enough torsional and bending stiffness/strength. Also putting the layers at varying orientations (0/90, +/-45) increases the toughness of the fuse. If you put all the layers on the same orientation then the thin laminate is prone to "zippering" along the weave.
Posted on: 8/24/2012 8:58 AM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11204483

RE: Hysol and Polyester Fiberglass Resin Compatibility
You will get a good bond to the polyester. In fact, it will bond to the polyester better than the polyester will. Scuff the bonding surface with 80 sandpaper, clean with acetone, and bond away. BTW, polyester will cure just fine over epoxy....it's just a very poor adhesive.
Posted on: 8/17/2012 8:23 PM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11197452

RE: composite Fuse Joint
to. The reason I ask is because looking at Wyowindworks wing section, and is a great joint... by Wyowindworks to wait til the layup gels and then trim away the excess material and then carry out
Posted on: 8/14/2012 10:05 AM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11193137

RE: Sailplane Wing Design Round II
BFoote, Young's Modulus (tensile modulus) IS a measure of the modulus of elasticity. Elastic modulus is the stress divided by the strain. Shear, tension, compression, bending, and torsion are all conditions in which the modulus of elasticity can be tested. So when you say "modulus of elasticity" what are you referring to? What kind of stress are you applying to the fiber to measure it's elastic deformation? The modulus of elasticity of kevlar 49 in terms of its tensile, shear, and bending properties is higher than glass. Can you show me some tests that show differently? Adam Who cuts kevlar fiber everyday.
Posted on: 8/13/2012 9:45 PM by Author "wyowindworks" in the forum "RC Gliders, Sailplanes and Slope Soaring"
http://www.rcuniverse.com/forum/fb.asp?m=11192355

RE: composite Fuse Joint
Here is an example of the internal construction of a hollow molded glider wing.
Posted on: 8/13/2012 5:44 PM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11192296

RE: composite Fuse Joint
I should amend my statement: Most glider wings use a bog joint on the LE and TE. This works well because the wings are very thin compared to power wings. The bog gets a lot of bite on the LE because of this. Often twisted lengths of carbon tow or glass roving are also used in the LE to increase their strength. The "blunt" leading edge of thicker power sport wings makes the bog seam much weaker. A joggle like SCALECRAFT is using would be the way to go on the LE of thicker wings.
Posted on: 8/13/2012 5:26 PM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11192269

RE: Sailplane Wing Design Round II
[quote]ORIGINAL: BFoote 2) No need for the kevlar spar wrap at all not to mention its a PITA to cut. If shear delamination is going to occur, said kevlar certainly won't help unless one used a VERY elastic glue between the shear member(balsa) and the CF. Gets back to deflection. Kevlar has a very low modulus add in the pittiance of kevlar used and well... better off buying a lottery ticket. Would have been better off wrapping with S-glass or better yet, carbon fiber. Of course neither of these is needed either. If you are so worried about said stress to begin with then the shear web shouldn't be balsa... [/quote] A common failure mode of a spar of this construction is that the top spar cap buckles away from the balsa shear web when the wing is positively loaded. This buckling initiates a bond failure. In my spar tests the wrapping of the spar can make a significant difference in the strength of the spar. Kevlar works better than glass and carbon in this scenario becasue the tenacity of the kevlar is much higher. The tight bends as the wrap goes around the sharp cornes of the spar create high levels of localized stress. Kevlar handles this better and carbon performs the worst. Kevlar fibers are also the easiest to wrap with because they lay down nice due to the suppleness of the fibers. A balsa shear web is fine if the caps or interface bond fail first. Increasing the web strength will only increase the strength of the spar if the web is the weakest component in the system. In my experience the bond between a balsa web and the carbon caps is the most common problem....thus the wrapping. BTW, the tensile modulus of Kevlar 49 (structural kevlar) is higher than s-glass.
Posted on: 8/13/2012 11:36 AM by Author "wyowindworks" in the forum "RC Gliders, Sailplanes and Slope Soaring"
http://www.rcuniverse.com/forum/fb.asp?m=11191645

RE: composite Fuse Joint
Keith, almost all model wings are joined via a bog seam at the LE and the TE. If you send an email to compvideo@wyowindworks.com I'll add your email to a list. When the videos are ready I'll send an email letting you know. I'm closing down the kit fabrication portion of my business. I'll work on the videos again when I get the kit stuff wrapped up.
Posted on: 8/13/2012 8:50 AM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11191595

RE: composite Fuse Joint
[quote]ORIGINAL: moggyman64 Hi All, Can somebody please point me in the direction for information of how to join/bond the two halves of a composite fuselage, and composite wings etc. Regards Keith [/quote] Are you talking in the mold our out of the mold? There are 4 primary techniques that are used for in mold seaming for fuses: 1) Bog joint, 2) Tape Joint, 3) Joggle gasket using joggle tools, 4) and the wet seam (co-cured). These are also put in order according to their toughness. If you are seaming out of the mold you can use a tape joing or a joggle gasket seam...although both are easier to do in the mold. Most model wings are joined with a bog joint. Some larger ones may use a jogglle gasket joint on the LE and a bog joint at the TE.
Posted on: 8/12/2012 5:02 PM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11190337

RE: composite Fuse Joint
Here are some illustration for using joggle tools.
Posted on: 8/12/2012 4:23 PM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11190781

RE: composite Fuse Joint
Bog Seam When making a bog seam the layup is trimmed flush with mold flange on both halves. Typically you wait until the layup gels and then run a sharp razor blade long the flange. A bead of bog, a mixture of resin + thickener + chopped fiber, is run around the edge and the molds are closed. This is the easiest seam to make cosmetically but it is the weakest in respect to fuses. It works well for wings because the surface area at the bond is larger. Tape Seam The fabric is trimmed flush just like the bog seam but a strip of fiberglass tape/fabric is positioned so it spans the joint. You can also use a little bog as well. The seam is stronger than a bog seam but typically heavier and not as strong a wet seam. This technique requires openings in the mold so the tape can be pressed into place. Joggle Gasket This seam is made by using some additional molds/tools that are clamped/bolted to the mold flange. These joggle tools create a step in the layup. The layup is allowed to fully cure, the tools are removed, and the joint is made with some bonding resin/bog on the joggle flaps. This is the most common technique if the fuselage is going to vacuum bagged. This technique does not require any mold openings. Wet Seam See the attached illustrations. This is typically the strongest and lightest seam. It is the most difficult to make cosmetically. This technique requires mold opening to press the flap into position unless a bladder is going to be used. This is the most common technique for bladder molding. Here is a short video clip that breifly shows these seams being constructed Here is another video that may be of some help. & Part 2
Posted on: 8/12/2012 3:54 PM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11190746

RE: GLASS OR CARBON TUBES
[quote]I just read this hilarity. Thanks for making my day. I had a good laugh on the bolded part. Think you meant 5-6g's or higher. =)[/quote] That wasn't a typo. Dynamic soaring gliders are flown in circles at over 400 mph. The record DS glider (Kinetic 100DP) has done laps that have gone 498 mph. Here are some accelerometer readings for a 468 mph flight done by an onboard Raven data logger containing two accelerometers: http://www.rcgroups.com/forums/showthread.php?t=1382898&pp=25#post17294421 You can see that there were several circuits that were near 90 g's and many that were above 60 g. This specific glider has a 100" span and is flown around 12-17 lbs (depending on ballast). Here is an older but fun video of dynamic soaring at 399 mph: http://vimeo.com/8356047 In this video the lap times are right aroung 3 seconds. If the speed is 399 then the circle radius is 279.41 feet. If the circle was perfect the g-loading would be 38.09. In reality the circuit isn't a perfect circle but oblong which means that the top and bottom turn are tighter resulting in a higher loading. PS - You don't need a vacuum bag to get good results with composites.
Posted on: 8/10/2012 4:47 PM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11188602

RE: GLASS OR CARBON TUBES
SidGates, what kind of resin did you use to make the tubes?
Posted on: 8/8/2012 11:12 AM by Author "wyowindworks" in the forum "Composites Fabrication And Repair"
http://www.rcuniverse.com/forum/fb.asp?m=11185726