Pattern Biplane
09-23-2017, 06:21 PM
#76
My very first glass and epoxy job was a Hal DeBolt Caudron 1/4 midget (all wood). It was painted with automotive acrylic lacquer. The rules stated minimum weight was 2 1/2 pounds. I had to use a 500Mah battery to make weight when everybody else was using 250 packs. IIRC the epoxy was "Safe T Poxy" and i think I got it from Aircraft Spruce & Specialty.
So ever since I have always held the belief if done right glass and epoxy can be as light as plastic cote. You just have to pay attention to the amount of paint and epoxy you use.
Ken
So ever since I have always held the belief if done right glass and epoxy can be as light as plastic cote. You just have to pay attention to the amount of paint and epoxy you use.
Ken
09-23-2017, 07:05 PM
#77
I agree with that Ken. I was originally thinking about applying the glass cloth with Klass Kote clear. The plan was going to be mixing it up in my usual manner which is one part clear, one part catalyst, wait 1/2 hour and then add one part reducer and then load it up in the gun. I was going to spray a small area and squeegee the cloth out and repeat as nesessary. When dry I could sand smooth with 320 grit and then apply another application of clear to fill the grain. That however is going to add another 60.00 to the airplane so I may just use thinned epoxy resin.
The other thing to consider is the quality of cloth. Just because it was super cheap I once ordered some .5 oz cloth from Hobby King. The weave was so bad that I immediately tossed it in the garbage. There were 1/16" gaps in the weave. Think of how much resin or primer it was going to take to fill the weave. Sometimes the end result does justify the additional cost of quality materials. I consider myself fairly talented when it comes to building on a budget and still get good results but sometimes you just have to start off with top shelf supplies. A couple good examples of saving money on this project. The foam for my cores came from Home Depot. For a 4'x8' sheet it runs 22.00. So the wing cores and stab cores cost me 22.00 plus 3 hours labor. Most of the wood for the fuselage plug came from Michaels craft store after I got a 20% off entire purchase coupon. I tend to pick up materials when I find a good deal even if I don't need then at that exact time. That was the case with the balsa being used to sheet the wings and stabs. It was purchased a good 4 months ago and placed on a shelf until needed.
The other thing to consider is the quality of cloth. Just because it was super cheap I once ordered some .5 oz cloth from Hobby King. The weave was so bad that I immediately tossed it in the garbage. There were 1/16" gaps in the weave. Think of how much resin or primer it was going to take to fill the weave. Sometimes the end result does justify the additional cost of quality materials. I consider myself fairly talented when it comes to building on a budget and still get good results but sometimes you just have to start off with top shelf supplies. A couple good examples of saving money on this project. The foam for my cores came from Home Depot. For a 4'x8' sheet it runs 22.00. So the wing cores and stab cores cost me 22.00 plus 3 hours labor. Most of the wood for the fuselage plug came from Michaels craft store after I got a 20% off entire purchase coupon. I tend to pick up materials when I find a good deal even if I don't need then at that exact time. That was the case with the balsa being used to sheet the wings and stabs. It was purchased a good 4 months ago and placed on a shelf until needed.
09-23-2017, 07:22 PM
#78
Shawn, I usually cheat when I drill mounting holes in carbon/divinicell laminate. Drill the pilot hole, then drill the composite with a clearance hole about 1/16" larger than the fastener. Put some clear tape on the back side and fill the hole with resin - carbon nanotube mixture. Redrill the clearance hole and you have a 1/32" "Tube" around the fastener.
Scott
Scott
09-24-2017, 08:53 AM
#81
Well.....sometimes I have to stop to catch a breath.
Got up and fabricated the stab root ribs this morning. Got the incidence adjusters in place. I used CA to gue them to the composite root ribs and pinned them in place with CF tube instead of using the #4 sheet metal screws that they come with. CA actually works pretty well on nylon provided you don't use kicker. The blue tubes are guides for the Allen driver so that the holes in the stab surface will be nice and clean. I think 10 grams for both ribs is pretty darned good!
Got up and fabricated the stab root ribs this morning. Got the incidence adjusters in place. I used CA to gue them to the composite root ribs and pinned them in place with CF tube instead of using the #4 sheet metal screws that they come with. CA actually works pretty well on nylon provided you don't use kicker. The blue tubes are guides for the Allen driver so that the holes in the stab surface will be nice and clean. I think 10 grams for both ribs is pretty darned good!
09-24-2017, 09:43 AM
#82
Got the last wing panel in the bag and root ribs glued to the stab cores. That will end my building for the day before I find myself in the dog house. Next weeks goals will be to get the stab tube sleeves aligned and installed and the wings mounted to the fuselage. I would love to be glassing the fuselage plug next weekend.
10-01-2017, 09:42 AM
#83
Time for another update, not too much going on with the build this past week. We have our last local pattern contest of the year and the one I enjoy the most next weekend so I have been busy getting ready/practicing. I was able to get the tube sleeves into the stabs and the stabs all prepped for sheeting. I decided to go into a bit more detail on my sheeting process simply because the process works so well and I think it will be of value to some of you.
The first step is to prep the shucks. This entails getting some 1/4" pressboard and cutting it to match the shucks outline. Then the pressboard is attached to the shucks with thin pressure sensitive tape.
The first step is to prep the shucks. This entails getting some 1/4" pressboard and cutting it to match the shucks outline. Then the pressboard is attached to the shucks with thin pressure sensitive tape.
10-01-2017, 09:49 AM
#84
The next step is to mix up some epoxy laminating resin. For sheeting both stabs I mixed up a batch of 45 grams. That actually was a bit much as when finished I had about 10 grams left over. Then the epoxy was spread out on the sheeting. The goal with this is to use just enough to get a sheen on the sheeting. Any high gloss areas just means too much resin has been applied.
10-01-2017, 09:56 AM
#87
Then the sheeting goes onto the cores and the cores get placed into the shucks with some 1 mil plastic between the sheeting and the shucks. This is done so that if there is any epoxy bleed through it will not glue the shucks to the sheeting. The whole deal then goes into a vacuum bag with paper towel used as breather material. When vacuum bagging, breather is nesessary to get consistent pull over the entire surface. I pull about 5" HG in the bag and let them cure for the next 12 hours under vacuum. 24 hours would make me feel better but unfortunately I am building in the house these days due to a lack of having a garage. I just can't have the pump going off in the middle of the night while we are sleeping.
10-01-2017, 10:42 AM
#89
Another mock up after sanding the LE and TE of the upper wing. Also shown is the tip template. That makes the span and length right at 77". Once the LE stock and tips are glued on and shaped, I can concentrate on getting the match to the wings and fuse perfected. Then onto glassing the fuse plug. On a side note, a few weeks ago a club member dropped off a box with some landing gears. These ended up being the perfect size. I'm pretty sure I know who it was, if so. Thanks Don!
10-01-2017, 04:30 PM
#92
Shawn, in your case 12 hours under vacuum is plenty. I keep mine in the bag for 24 hours, but it is a matter of convenience. You bag on a sheet of marble, I use a sheet of glass. After 12 hours the resin has past initial cure. While still soft, it is well past the gell state where the vacuum will debulk the matrix by removing excess resin. All you have to do is put enough weight on the top of the stack to keep it flat on the table while the resin continues to cure.
Since I know you already know this, it is more for the sake of readers just getting into sheeting wings. Keep up the good work.
Scott
Since I know you already know this, it is more for the sake of readers just getting into sheeting wings. Keep up the good work.
Scott
10-01-2017, 06:10 PM
#94
Shawn, in your case 12 hours under vacuum is plenty. I keep mine in the bag for 24 hours, but it is a matter of convenience. You bag on a sheet of marble, I use a sheet of glass. After 12 hours the resin has past initial cure. While still soft, it is well past the gell state where the vacuum will debulk the matrix by removing excess resin. All you have to do is put enough weight on the top of the stack to keep it flat on the table while the resin continues to cure.
Since I know you already know this, it is more for the sake of readers just getting into sheeting wings. Keep up the good work.
Scott
Since I know you already know this, it is more for the sake of readers just getting into sheeting wings. Keep up the good work.
Scott
10-01-2017, 06:15 PM
#95
Thanks both of you, I wasn't quite happy with what I had ordered and really didn't want to go about making a plug for the gear mold as well. I was a bit surprised that nobody was out practicing on Saturday, I took advantage of the situation and logged 10 flights. Another 30 practice flights and I may be ready for the weekend.
10-08-2017, 05:59 PM
#96
Has anybody ever vacuum bagged mylars over the glass/epoxy on a balsa sheeted wing?
I know the DLG guys do and they get a very nice surface. Might save a bit of sanding/prep for paint time????
Ken
I know the DLG guys do and they get a very nice surface. Might save a bit of sanding/prep for paint time????
Ken
10-08-2017, 06:20 PM
#97
Ken, I have thought of that but with a difference. I would do a glass skin in a mold and then add the foam core. This however comes close enough to a fully molded wing so I would just go that last step. The DLG guys get OK results bagging the skin onto the foam core for a couple reasons. One is they use a more dense foam and two, there is nothing added to the cores prior to bagging.
10-11-2017, 06:08 PM
#98
Back to the sanding stage. I didn't get much done due to getting ready for the final local pattern contest of the year. Now that is over I am back working each evening.I glued all the LE and tip blocks on the wings and stabs. Tonight's task was to get the stabs sanded out. At this point I will sand everything with 150 grit and leave them until it's time to glass everything. Then I will finish sand everything down to 400 grit. Here are the stabs after the first sanding session. I'm reasonably happy with the weight, 176 grams with the stab tube.
10-11-2017, 07:38 PM
#99
Well........How did the contest go?? If you brought home another second place I am going to drive to Sac and slap you. If you did better than that I will drive to Sac and give you back your hat you left at my lake house.
Scott
Scott
10-12-2017, 03:59 AM
#100
I guess you are going to stay home. I took 3rd place. Not too happy about it as it was determined after 4 rounds and not the typical 6 rounds with 1 throw away. The first place guy after his 4th round broke a motor mount landing. He was going to come up 1 round short and I was right behind the 2nd place guy and had a chance to catch him. We woke up to gusts of 30 mph on Sunday and they called the contest.