Some hints on building composite hand launch gliders
Foam Cutting and Template Holder
Safety First
Epoxy allergies and sensitization. This site suggests nitrile rubber or nitrile butatoluene gloves only... it says Vinyl gloves are less effective than Nitrile and latex gloves are almost useless.
http://dermnetnz.org/dermatitis/epoxy-allergy.html
Phil Pearson Encore HLG building sequence
ftp://ftp.avvanta.com/users/
RCGroups:
http://www.rcgroups.com/forums/showthread.php?t=634176&highlight=tabooish
http://www.rcgroups.com/forums/showthread.php?t=246671
Lighthawk assembly guide (good info on supergeeish building and great RDS how to)
http://rcbuilder.com/lh_guide/welcome.htm
Taboo Build Guide
http://www.olgol.com/TabooGT/build1.html
Have Plug now what (Shawn Porter)
http://www.rcgroups.com/forums/showthread.php?t=534484
Have Mold now what (Shawn Porter)
http://www.rcgroups.com/forums/showthread.php?t=534484
Supergee II
http://www.charlesriverrc.org/articles/supergee/SuperGeeII.htm
Shopping list from composites store CST
Wire cutting:
http://www.cstsales.com/tekoa_hot_wire.html
Here's the Feather cut that I used...If you wanted to get fancy, you could get one of the metal folding bows that they sell for the feather cut. Get the span to match your design. Don't be afraid to cut smaller span panels, there is much less drag on the wire if they're shorter spans... you can join them together after you're done cutting... just need to square the edges and glue them with something that won't make a hard spot... like Fast Guerilla glue
Vacuum Bagging:
Nylon Bagging Tube
18" wide , 10+ yds.
Price per yard when ordering 10+ yards V115
http://www.cstsales.com/vacuum_bag.html
The bag that I had was 18" wide nylon and whatever span you need... looks like you might as well get the 10+ yards for the $, you'll probably mess up one or two... Also, I don't know if you'll get to a wider chord, maybe 27" would be better? probably just take up table space.
Bag Seal Clip 20 inch length
Reusable mechanical seal
Designed to close the end of a 18" bagging tube. V192 $4.95
http://www.cstsales.com/vacuum_bag_seal.html
Definitely worth it... its not obvious from the website if that is 1 clamp for $4.95 or 2...
Breather Strip
2" wide x 12 ft V300 $1.95
http://www.cstsales.com/breathers_bleeders.html
This is the felt like stuff... your guys indicated you may have some of this already...
Mylar 0.014" Thick, 24" wide, RT - 10+ ft.
Price per foot when ordering 10+ ft. V225 $1.30
http://www.cstsales.com/release_film.html
I think you'll be happiest with the 14 mil mylar for the bagging. What I used last week was 10 mil, and it just isn't quite as nice of a surface as the 14 mil gives. Get the width/length you'll need for at least an inch of run-out both front and back... ie a 12 inch chord should have 1"+ 12" + 1" = 14" of chord.
Polyester Peel Ply, 60" wide
RT to 250º F, 2 yd. pkg.
Tightly woven. Textured surface for secondary bonding. V246 $11.95
http://www.cstsales.com/release_film.html
Wow, this seems really expensive for peel ply. I don't remember spending anything like this much on my peel ply... which means I probably got it at Boeing Surplus back in the day.
Partall Paste #2 Mold Release Wax
24 oz. Tin
Color green, Working Temperature Room Temp. V201 $13.95
http://www.cstsales.com/mold_release.html
Here's the wax I used... There's others out there, but this is pretty universally used in R/C. The sprays on this page are good for some molds, but will not be satisfactory for wing mylars.
Composite Materials:
Aramid Fabric, 1.7 oz., 1-9 Ft.
38" wide. 195 denier, 34 x 34 Thread Count, Plain Weave, Thickness 0.004".
Price per foot when ordering 1-9 ft. K121 $17.95 per foot
http://www.cstsales.com/aramid_fabric.html
Wow, this stuff is even more than I remembered it was. You can use glass for the LE if you really can't afford this, but I think you're going to want to use the Kevlar. Don't forget to cut at 45/45 (bias). You can use this for Living hinges too, if you want to.
Unidirectional Carbon, 3.7 oz, Webbed, 1-9
ft.12" wide, 0.005" thick, price per foot when ordering 1-9 ft.
This is the same Webbed UniCarbon now available again. CF341 $12.95
http://www.cstsales.com/uni_carbon_fabric.html
I think you may have had plenty of the uni - carbon, but this is what I would get if you're going to get some more.
Fiberglass Cloth 0.7 oz., 50" 25 yds. to full
roll Plain Weave
Price per yard when ordering 25 yards to full roll G01063-50 $3.90
http://www.cstsales.com/e_glass_cloth.html
Here's the 0.7 oz cloth I think you're designing for. There are some other sources for fiberglass if you would like them... I'll have to dig a little though...
3M 924-3/4 Adhesive Transfer Tape Roll for Scotch Tape Gun, 3/4 Wide x36 Yards
http://www.amazon.com/3M-924-3-Adhesive-Transfer-Scotch/dp/B000BNU7T0
For the leading edge Kevlar...
Additional Fiberglass Source
Here is the balanced fiberglass... we use either of these 2 balanced weaves in our DLG's...
http://www.thayercraft.com/index.htm
1.2oz/sq yd super light, for the optimum in lightweight
http://www.thayercraft.com/6060.htm
1.6oz / sq yd slightly heavier, but easier to work with and makes a good solid wing
http://www.thayercraft.com/1280.htm
The 3/4oz like what we've used in the past is here. Usually done in 2 layers, can be challenging to work with:
http://www.thayercraft.com/Style%20106.htm
The Epoxy I've had the most success with is the MGS also from Aircraft spruce. Its nice in that it offers several cure times... although I always use the 2 hour for any wing lay-ups. Its become very expensive when you include shipping.
http://www.aircraftspruce.com/catalog/cmpages/mgsresin.php
Resin Research is something that's become available recently...
http://www.resinresearch.net/id8.html
And here's one of my other acquaintance's (Don Peters who makes the Icon) candid assessment of that epoxy:
I've been using the 2000 resin with 2100 hardener. Its the best system I've ever used - very similar to MGS.... except its half the price. The resin is a bit thick, but the mixed system is about right for laminating. I keep it in a heat box at about 80 degrees, which helps thin the resin to make it easier to pump. I've tried the 2080 resin (higher modulus), but its just too thick to handle for such a small increase in stiffness. The fast hardener is acceptable for surface coating; the slow and extra slow have too much surface tension, so they won't maintain a cohesive film. "Additive F" is supposed to alleviate this, but it doesn't really work any better, so save your money. I've used 2050 resin with 31200 hardener. I think that's the Composite Pro stuff. Its really intended for resin transfer molding where they pump it through matched molds. Its water-thin, and it wets out instantly, but it also drains instantly so its really hard to get the right amount into your layup. The parts are always starved for resin, so they look like dog doo.
Foam Cutting and Template Holder
I used an old Feather cut...
available here:
http://www.cstsales.com/tekoa_hot_wire.html
A Wiki on Foam cutting:
http://www.eflightwiki.com/eflightwiki/index.php?title=Hot_wire_foam_cutting
A nice website with good info from Charles River R/C club:
http://www.charlesriverrc.org/articles_foam_vac.htm
Some do it yourself foam cutters:
http://www.charlesriverrc.org/articles/foam_vac/mrcss_foamcutter.htm
http://www.charlesriverrc.org/articles/tools/brengmancutter.htm
http://www.instructables.com/id/Hot-wire-foam-cutter/
http://www.spacemodeling.org/New/how_to/Foam_Cutter.htm
http://www.nsrca.org/technical/tip_tricks/foam_cutter/foam_cutting_power_supply.htm
Here are the old drawings of the template fixture that I lent you for the feather cut. Note how the templates sketched here are higher off the table than the ones we had on Thursday night. This is more what you want. Additionally, I think we need to attach the feather cut with a block under it that brings the pulleys up in line with the Starting/ending height of the bow on the templates, as they are sitting on the fixture.
I also put on some Template drawings I have for SD7032, although I think they're camber or thickness may have been adjusted from the original, so check them out before you use them. Note also that the ramps into the foam are a little different from what we had Thursday. I would lean towards the ramps in the drawings, I had much better luck with this type of ramp. I would be happy to sketch up the real templates if you like... just send me the dimensions.
Let me know if you have any questions, of if you can't read the .dxf. The originals are in Autocad 2002... I'll attach those as well. I'm not very familiar with Solidworks yet, hopefully it can read one of these file times.
http://www.tgworks.com/TEMPLATE JIG.DXF
http://www.tgworks.com/TEMPLATE JIG.DWG
http://www.tgworks.com/SSROOT.DXF
http://www.tgworks.com/SSROOT.DWG
http://www.tgworks.com/SSTIP.DXF
http://www.tgworks.com/SSTIP.DWG
Sunspot Tip Foils... note the wash-out comes from the sloped bottom of the template.
Foam Core Preparation
Sand foam cores: prepare the foam cores for covering by first removing the strings of melted EPP from the EPP leading edge and the rest of the core. This can best be done by picking them off with your fingers or using tweezers. Next, using the dry-wall sanding screen and a light touch, carefully sand the EPS foam hairs off of the cores. Care should be taken to not leave sanding marks on the surface of the foam. Use the sanding screen to sand the leading edge of the cores. Work slowly allowing the screen to do the work, pushing too hard will cause the EPP to ball up and chunk out. The best low speed performance will result from a relatively blunt leading edge, see wing cross section on the plans for guidance while sanding. The wing tips should be sanded round to match the rest of the leading edge. Avoid sanding the area where the EPP leading edge joins the EPS since these are two rather different materials, they will sand differently creating a step between them. Use 240 or higher grit sandpaper to fine sand the cores. Fill any scratches or nicks with filler. Too much filler may add unnecessary weight, and may cause the markers to be distorted when you color the Chinook.
So, yes the rollers do seem to waste epoxy, there is epoxy in the roller that is NOT coming back out. I'm sure you've tried to rinse out a paint roller in the sink, and it keeps coming and coming and coming!
So, first, lets make sure you're using the correct roller...
I think this might work, but its hard to tell from the picture:
I'll cut these 9" down to fit my 3 or 4" roller:
The beauty of this, is you can roll the epoxy out on the cloth without moving it around. I think that's going to be essential for doing paint on the mylars
You just wax the mylars... (I'm almost certain you'll need wax to get spray paint to work, spray on release and spray paint sounds like a bad mix), lay the fiberglass layer on the mylars... mix up your epoxy, spread it on a paper plate. Roll epoxy into the roller... starting in the middle and rolling out to the left tip roll on the epoxy... go back to the middle, now roll out to the right tip. That will soak into the glass and 'stick' the glass to the mylar. Give that a minute or 2. Now, roll out from this middle strip of epoxy to the LEs and TEs. Then lay down the carbon spars... roll them once and then quickly flip them over and roll again.
Now, roll out the Kevlar LE on the cores. Its already stuck on with 3m 924, right ;-)
http://www.amazon.com/3M-924-3-Adhesive-Transfer-Scotch/dp/B000BNU7T0
OK, so finally lay toilet paper on the glass and carbon. use a hard roller of some sort (mine looks like this)
http://www.tools4flooring.com/gundlach-4s-seam-tile-roller-p-350.html?___store=english_11239125331
to push the TP into the FG and suck up all that extra epoxy. I use my heat gun to warm the epoxy up at this point and get even more Epoxy out.
go over with the roller again.
Toss the TP, lay the cores on the mylars. Use a couple pieces of thin scotch tape to hold the mylars top and bottom. Slide into the breather and junk and stuff and then slide into the bag.
You might get away with some epoxy dye instead of paint...
http://www.tapplastics.com/shop/product.php?pid=50&PHPSESSID=201001211506421629223005
General handbook on composite materials. LOTS of detail from a public military publication
http://www.library.ucdavis.edu/dept/pse/resources/fulltext/HDBK17-3F.pdf
Aircraft spruce's MGS epoxy
http://www.aircraftspruce.com/catalog/cmpages/mgsresin.php
and the specs are in this .pdf...
http://www.tgworks.com/mgs285_epoxy.pdf
There's also Resin Research...
http://www.resinresearch.net/id8.html
Foam Properties
http://ciurpita.tripod.com/rc/notes/compositeSpar.html
Wing Spar Sizing
http://www.tgworks.com/sparsizing.xls
Some information from the early 2000's...
tail booms from the early 2000.htm
Wing
Repair with Syringes
So, I've been where you are before with the syringes, all clogged up, and hardening fast... and I've had my choice words! I've found you definitely cannot use any filler in the epoxy. And I've also found some epoxies work better than others. The MGS is much better than say West Systems... but mostly due to viscosity. There are some syringes that the needle screws on, these would be better if you can find them.
So, here's what I've used the last couple of times because the syringes are a bit of a pain:
here they are at Hobbico
http://www.hobbico.com/tools/hcar3785.html
Here's a similar one:
http://www.woodcraft.com/Product/2020544/22894/WoodRiver-Disposable-Glue-Syringes--5-pieces.aspx
You might even find them at Joanne's fabric or Walmart in the craft section?
It's all plastic. and so the needle doesn't pop off;-) But you can even use the ones you have without the needle! You just need to drill a hole in the wing that is big enough for the whole tip to fit in! Its like 1/8", or more, so what.
So, here's the whole process:
Drill whole in wing for syringe. I often do it right in the spar, where the delam is. You might need to poke some holes at the far end of the delam so the epoxy can flow. Mix up the thinnest epoxy you got. You could add a little alcohol to get it even thinner. put it in a ziploc baggy. Squeegee it down to a corner. cut the corner. use the baggy to squeeze it into the BACK of the syringe (its impossible to suck it up into the syringe). put the plunger in. You might get some air in there, but who cares, its not your arm your putting this into. put it into the whole. Inject until you see the epoxy flowing into the delam. Done.
I've used a sponge or paper towel to dab epoxy on the skin where there's a delam. Dab it on, hit it with the heat gun, it should penetrate, but you might need to punch some pin holes in it. Then wipe off the excess.
Allow to cure in a heat box.
I'd guess the joiner should be 3 inches or less. I'd route out fore and aft slots for the joiners in the left and right wings, then glue in the balsa spars with imbedded aluminum tubes. Glue them in and then fiberglass over. Finally, cut that joint with a fine jig saw blade.
Here's where the pictures are:
http://ph.groups.yahoo.com/group/SALglider/photos/browse/4ce4
Design Software
XFLR5 - Planform and airfoil integrated design
http://xflr5.sourceforge.net/xflr5.htm
Profili - Airfoil performance and plotting software
http://www.profili2.com/eng/default.htm
Plane Geometry - Design parameters in Excel spreadsheet. Plug in the measured parameters of your model and back out the performance properties, or vise-versa. Great for scaling up planes or making small changes in design but keeping the flight characteristics the same
http://www.envisiondesignusa.com/evdusa/Plane_Geometry_Overview.html
Linkage Design - calculate you linkage layouts, calculate torques and moment arms for your servos, etc
http://www.envisiondesignusa.com/evdusa/Linkage_Design_Overview.html