Build Thread-Scratch built for 8s
 

I have been out of pattern for several years. I have been building “virtual pattern planes” on my laptop for a couple of years. Now that I finally have a workshop, something solid is taking shape.

It started as a set of plans for the Pattern Giles I got from Gator, must have been six-seven years ago. I took the basic dimensions and drew them up in AutoCAD. Then I tweaked it a little. I double tapered the wing and made some other changes. I got the fuselage framed up, then was forced by illness to put it on hold. It is still collecting dust in the garage.

Two years ago I resurrected the idea as a .110 (8s) e-pattern, and over that time the design has gone through a significant evolution. The latest pressure on the design was the drop in battery prices making a 10s setup within my budget, but dang, I had already worked it to death, so 8s it is.

The pictures are snap shots taken during various stages of development.

Last week I sent my cut files to a laser guy I found. As I write this, I have the fuselage framed up. It went pretty quickly and the parts fit was really good. The only changes to laser parts v0.2 is reducing the number of breakout tabs.

RE: Build Thread-Scratch built for 8s
 

The first step was to cut the fuse stringers. Rather that try to splice balsa, I decided to use some 1x2 birch from Home Depot that I milled down to ¼” x 3/16” . Then I built a fixture to cut the cross braces. The fixture is made from a piece of ¼” a/c plywood.

The first picture shows the bottom of the fixture with a key made from 1/8” plywood glued to the bottom. The key fits into the miter slot then the fixture is fed into the blade. This makes a zero gap blade slot which I find useful when cutting thin pieces. Having a small chunk of material sucked into the works is a pain that I like to avoid.

The second picture shows the fixture clamped to the table with a guide bar made from a piece of 1x1x1/8 aluminum angle.

The third picture shows the cut being made. I have found the secret to this is to use the widest blade that will fit your saw (3/8” for my little Ryobi), and the finest pitch. The wide blade helps eliminate drift, and the fine pitch gives a relatively smoother finish. Another important element in eliminating blade drift is that the blade be sharp. The second I see any drift, the blade gets changed. This blade was brand new when I started this project.

Pictures #4 and #5 shows the jig I built for cutting the diagonal pieces. I cut these from the birch stock I had just cut. After assembling the fuselage sides I came to regret this choice since they seemed a little heavy. On v0.2, the bracing will be made from balsa. (I have a scale on order, but have not gotten it yet.)

Picture #6 is the finished cross braces.

RE: Build Thread-Scratch built for 8s
 

The parts as they came back from the laser cutter.

RE: Build Thread-Scratch built for 8s
 

Before starting on the fuselage sides, I assembled the elevator servo mount.

RE: Build Thread-Scratch built for 8s
 

The top stringer is pushed up against a straight edge, the cross braces, side plates then bottom stringer are placed over the plan and weighted down. The gusset plates are glued to the stringers and cross braces. Doublers for the wing tubes were then glued in place. Then CA was used to securely glue the entire structure.

The sides were then test fit over the plan.

RE: Build Thread-Scratch built for 8s
 

Hit the first snag. The hole in the elevator servo mount was over sized. I had to build it up, and change the hole size on the cut file v0.2. Then when I went to mount it to the fuse side, the servo crashes into the diagonal brace in that bay. The solution was to replace the diagonal with a 1/8” balsa plate with a cutout for the back of the servo.

In the original design the sides were made from balsa sheets spliced together. There was provision in those fuse sides for the elevator servo to stick through to just short of the Monokote. That got missed in the redesign.

RE: Build Thread-Scratch built for 8s
 

The elevator servo is mounted to one fuselage side. I decided to do it this way for two reasons. First, it gets the servo further back mainly to keep the pushrod short. I mounted it on its side so that the axis of the servo arm is parallel to the axis of the elevator hinge. It makes for a cleaner linkage. To get it that far back I went to a low profile servo, a JR 9411.

RE: Build Thread-Scratch built for 8s
 

Next came planking the bottom of the fuselage. I glued in a small number of trapezoid bulkheads, then ran three sheets of 1/8” planking. This is the one bit of structural design that survived pretty much intact from the original Giles, except for the lightening holes, and lack of pipe tunnel. I used a sharpened 3/8” brass tube to make holes at the corners of the lightening holes, then I cut between them. As I often do, in the middle of building something and a better way occurs to me. Rather than use solid planking, Run ¼” wide strips at the corners, then cap strip the bulkeads. In the next version this will require 3 additional bulkheads, but the reduction in waste material, makes it worth while, especially since it might also save some time. You can see where I added a “fake” bulkhead about midway through the aft section of planking.

RE: Build Thread-Scratch built for 8s
 

dreadnaut,
Very nice work so far. I'll be looking forward to your updates. Have you decided on the power train yet ?
Ed

RE: Build Thread-Scratch built for 8s
 

AXI 4130
CC ICE 75 ESC
ZIPPY 4000mAh (2x4s)

RE: Build Thread-Scratch built for 8s
 

After a short interruption tot he schedule, I have started working on the plugs for the canopy/cowl/turtle deck as I had to get the fuselage framed to this point to match things up. I am also going to attempt laying up my own CF landing gear. To do this I first need to decide on the prop. Searching the web, it looks like something in the 16"-17" range. I can worry about pitch later, just want to size the legs right now.

Ed, do you have any experience with this?

RE: Build Thread-Scratch built for 8s
 

Hi Dave,
If you are talking a 4130/20 ..... then something in the 18x12 area would be what you need. Alternately, an APC 3 blade 15.75x13 pattern prop will get you a bit more clearance .... but is not as efficient.
IMHO .... stay away from CF gear, either self made or purchased. Either it delaminates or is too stiff and launches you back into the air on a less than perfect landing. Just go to TNT and they will make a custom aluminum gear for you. I did this for my Inspire 90 and have been using that gear for 2 years now without an issue.
Ed

RE: Build Thread-Scratch built for 8s
 

It is the -20. I appreciate your views on the CF gear, but I already have a mold I made when I was working on a 2m glow back in '04 when I dropped out. I had (still have in fact) a Webra 1.45 that swung an 18" prop, so I will try to use those. If it doesn't work I have a lot of experience working with 6061. I will probably wind up with several 17"-18" props to try out to see what works for me.

Thanks for the input.

RE: Build Thread-Scratch built for 8s
 

Finally able to get back to the build. I had to get the motor mount cut, I had left it off the original cut file :eek:.

I decided to make the canopy and turtle deck from fiberglass, so I started to build a plug. I cut two pieces of white foam insulation with a hot wire. I did it by hand, as you can see from the rough finish at the tail. No big deal. I soaked some balsa sheets then formed them over the foam forms and let them dry to the rough shape, the glued them on with contact cement. The shape was a little distorted near the tail, so I will have a little bit of a job filling and shaping. The built-up area will be blocked out with flower shop foam and shaped.

I hope to get all the plugs done by next weekend so I can start on the wings, stab and rudder.

RE: Build Thread-Scratch built for 8s
 

I decided to make my own CF gear from a mold I made several years ago. The layup was 1 later of 5k woven fabric, 16 runs of 20k tow and 1 layer of 5k fabric, because I think it looks cool. I’m not really happy with the results, but I will use them for now, and make a better mold later. Why make my own? I have had the material sitting around, so I may as well use it.

RE: Build Thread-Scratch built for 8s
 

That glossy finish on the gear looks terrific!

RE: Build Thread-Scratch built for 8s
 

Thanks.

There are some flaws if you look close, but that was a first try using that method. If you look close, there are pin holes and bubbles. The way I did it was to cut a strip of 2mil painters drop cloth 5" wide x 2" longer than the layup. I taped that to my building board then laid a strip of the carbon fabric. Mixed 15g of West System and squeegeed it on then laid 4 strips of tow, then 1 strip of 2 oz fg. The 2oz fg was used to prevent ripping the cf tow while squeegeing in the next 15 g of epoxy. One more layer of tow, one more of 2oz fg, 15g more epoxy squeegeed in.

Then I did another lay up just like it then mated them face to face, put them in the form, bagged it up then vacuumed it.

I am pretty sure that the pinholes came from putting breather on only one side. On my next pull, I plan to use breather on both sides, but that will sacrifice the high gloss finish.

I use paper towels as breather, but it leaves a texture on the part like they put into the towels; flowers and such. I am going to try to score a roll of "institutional" paper towels, like those used in public restroom dispensers. They are untextured.

Tonight the wife has a "girls night out" so I plan to get the wing, stab, and rudder jigs built, and work on the cowl plug.:D

RE: Build Thread-Scratch built for 8s
 

Dreadnaut, how much vaccuum were you pulling?

you might be better off using peel ply on the outer surface, then a breather, to really get the thing hauled down. After that you could probably sand and laqueur to your desired finish.

I am a bit curious as to why you're using cloth, considering bolly and a lot of the other manufacturers dont.

RE: Build Thread-Scratch built for 8s
 

Rendegade,

I'm pulling just 8"hg. I'll pull more next time. I had considered peel ply, but am trying to get them so that I do not need to do a secondary operation. As far as the fabric goes, that is just the outer layer, and is mostly for looks. I like to lay up on plastic sheet, and even if I did not use CF, I would use some kind of fabric. I find it easier to squeegee resin to fabric, then place a layer of tow, then a thin (2oz) layer of fabric so I can squeegee another coat of resin. I repeat until I have the buildup I want.

Got the wings framed up this weekend, will post pictures soon.

RE: Build Thread-Scratch built for 8s
 

Yeah, sounds good, but I think you're a bit down on vacuum.

Honestly I can't see a way of getting a one-motion (cure? action? job? you know what I mean!) part out of the mould and have a decent finish without some pinholes. Sure more suck will make them samller but I think they'll always be there.


Carbon looks cool anyway. As long as they stop your prop touching, they're doing their job!

RE: Build Thread-Scratch built for 8s
 

Time to start on the wings. I had parts laser cut for a wing jig. I am starting with 0 dihedral for this mid wing plane, so the wings will be 100% symmetrical, so I can use the same jig for both sides. If I have to add dihedral on v0.2, I could still use the same jig, just having to pay attention that the holes for the wing tube are assembled so as not to wind up with two lefts, or two rights.

I started by gluing the bottom spar to the leading edge sheeting, using a straight edge to insure that it is totally straight. I positioned this on the jig, and then used the root rib, and tip rib to position it in the jig. Then I glued the root rib, then the first shear web, followed by the second rib then the second shear web etc. all the way to the tip. Years ago I built a sailplane kit from Airtronics called a Sagitta, that used this technique, and it works well. This was a beautiful machine cut kit that was an American equivalent of MK quality. You do not worry about the ribs coming out aligned perfectly over the plan, because if the webs are accurately cut (these were, and mine were lasered), the two wings will come out the same.

RE: Build Thread-Scratch built for 8s
 

The wing tube is 22mm CF tube I got at a LHS, and then I made my own FG sleeves. Next I glued in the aileron sub ribs using a 1/32” shim. Then I stick an x-acto knife through the sheeting in several spots to mark the location to be cut out later. The next two pictures show the aileron hinge line knockouts in the ribs. The last shot is of the aileron hinge spars, and control horn hard point.

RE: Build Thread-Scratch built for 8s
 

Now the wing tube sleeves are glued in with lite ply doublers on the inboard and outboard ribs. Then the wings were test fit to the fuse, and I was pleasantly surprised that the tip to tail measurements came out right on, and needed no adjustment.

RE: Build Thread-Scratch built for 8s
 

The last thing I did before calling it quits for the day was to start working on the plug for the molded wing tips. I tack glued a piece of 1/8” balsa sheet to the wing tip, then sanded it to match the wing profile. Then I glued a 1/16” profile plate to that, then top and bottom pieces of flower shop foam using 45 min epoxy thickened with cab-o-sil.

RE: Build Thread-Scratch built for 8s
 

I'm back, two funerals, a wedding and a long list of honeydoos later. Sad to say that since I am pushing hard to catch up for lost time, the documentation got a little sketchy.

I started on the stab by gluing the plan to a flat piece of mdf, then gluing the jig to that, then setting a pre-cut piece of sheeting. The pencil marks fro the ribs don't show in the pictures. Then I stared laying in the ribs, starting at the root, and working out, using the webs to set the spacing.