Now I have been slowly but surely getting tired of all this manual sanding so out came my trusty Einhell (Dremel look alike). Fitted to this was a DIY router base, the idea coming from, I think, Gert Nieuwoudt.
The working end of the setup.
With the right bit inserted and a sturdy guide it made for a perfectly routered slot for the fibreglass tubes. As the tubes aren't there for structural strength, a couple of dabs of foam safe CA keeps the tubes in place.
All that remained was to add a balsa cap to finish things off.
In my quest for some decently priced servos for the F18 Project I came across these little beauties. They are HD DS929MG ball-bearing metal gear digital servos weighing in at 12.5 gram from Heli Direct, supplied by Sandy Sutherland from XHeli @ R188 a piece + postage. Not bad compared to the close on R300 most hobby shops want for the plastic geared HS85. Unfortunately he only had three in stock, so I opted for two for the ailerons.
I'll probably end up with standard servos for the elevator as space is no problem inside the fuselage. Here they are shown sandwiched between a HS85MG and a HS55. It is the same width and thickness of the HS55 and only about 2mm higher. The 2.2kg.cm torque should be ample for the application. Time will tell if they withstand the Volksies Test....
Reports on the progress of the various projects are looking good. Paul has made some inroads on his flying "canoe" and Herman has also progressed on his Provost. Tomorrow being a holiday will probably see most of us behind the workbench instead of behind the transmitter on the field.
Time to "slice and dice" the wing. Always use a sharp exacto blade for this otherwise you get chunks torn out of the foam. 
Next use a sanding block to lightly sand the bonding surface. Once again plain old wood glue was used to stick on the balsa leading edges.
After shaping the leading edges I added some wing tip blocks.
Then while the glue was drying I marked out where I want the ailerons. The stock was actually 45mm wide, not the 35mm I mentioned earlier. "Look Right" engineering determined the control surface should be 35mm wide. I will cut these free when once I've glassed the wing.
...and this is what the tips look like after shaping.
I decided to add the aileron stock before doing the bottom spar tonight. The only decent aileron stock I could lay my hands on was 8x35mm stock from Mad Models. Probably a bit wide but I will be cutting the ailerons about 25-27mm wide leaving a sub trailing edge of 5-8mm. After measuring it off the wing, a sharp exacto blade takes care of the rest.
The aileron stock was too thick by about 2mm. Nothing a bit of creative shaping can't solve.
So out comes the hand planer. The masking tape is there so I don't accidently start ripping chunks out the foam. One slip and you have to start some unsightly patch work.
After removing the bulk of the excess balsa with the planer, the finer shaping is done with a big sanding block to ensure true flat surfaces. A quick eyeball on the end result and I'm happy.
I used polyurethane wood glue to stick the balsa to the foam. Masking tape held everything in place and while that was drying I could enjoy my dinner.
Looking good so far. The bottom carbon spars and balsa cap came next and I won't bore our blog readers with more pictures of that. Unfortunately I will now be going away for the weekend and will only be able to continue work on the project Monday evening, when I intend stripping off the foam leading edge and replacing it with a balse one, so expect an update by Tuesday.
Cheers, and enjoy the weekend!
I did not have a huge amount of time tonight but managed to lay up the top spars into the wing. I decided to use 12K tows for this as it is less "ropey" than the 60K tows I have and it is easier to get the epoxy to properly penetrate the carbon strands without making one moer-of-a-mess ;o)
First step is to decide how many tows to use. As I have always used spruce spars in the past in all my slope models I had no clue as to how many is enough. I just cut some small pieces and stacked them together until I got to about what I thought "looked" strong enough. Based on the "long-term" Allegro build I am also busy with, which used 4 layers of uni-directional carbon to get to the prescribed 0.7mm thickness I opted for six of the 12K tows. In hindsight If I had enought time I would have opted to use the same technique to make pre-pregnated strips (as described here) from UD carbon and just epoxy them in afterwards.
The depth of the groove was just right as the 1.5mm balsa cap I put on top stood just proud of the wing top surface.
The last bit of epoxy mix was thickened to a syruppy consistence slurry with microballoons and used as a filler to close up the tiny gaps. A maxed-out useless credit card took care of the excess epoxy to prevent too much sanding afterwards. To prevent the wing "negatives" sticking to this beautiful piece of handiwork I cut two narrow strips of Mylar which I put over the spars.
And the last task of the evening before I get some much needed sleep was to weigh the whole setup down. This is where those old UPS sealed lead-acid batteries come in very handy. Tomorrow evening I do the bottom spars.
Using a straight edge the sanding bar makes light work of the task and in less than 30 minutes I had some perfect grooves, top and bottom, ready to accept the carbon tows.
Before I start epoxying the spars in I wanted to join the wings so the spars can be continuous across the join. Seeing as the joing will draw it's strength from the carbon spars, glass wing skin, trailing and leading edge balsa stock the join can be done with plain old Alcolin cold glue. From previous experience I have found if you use epoxy for this join, you battle to cut through this join when routing your aileron servo wires.
While the wing join was setting some more shaping of the fuselage followed. It is getting to the point where I am almost happy with the result. 
The top aft section is going to have to wait until I've made the root templates for the fins. I need to "picture" how the fins are going to blend in with the fuselage.
To do the full size plane justice I am trying to get most of the contours as close as possible to the "real thing" that I can with this technique.
The result I am looking for is to have it slightly better than just stand-off scale. The only area where I am cheating a bit is on the wing. Here I've played a bit with the scale and aspect ratio to, hopefully, get a model that is a bit more versatile and does not need a galeforce wind to fly. I can never resist the urge to do a mockup prop to get an early idea what the end result is going to be.
It's been AGES since I posted on the blog and this opportunity is as good as any resume posting. With the upcoming ETB PSS Fest in October I had to decide on a project to put together. To me the choice was easy, I have always wanted another F18 Hornet. Here's what the previous one looked like that I got from Paul.
With the help of Paul we quickly bashed out all the foamy bits. The fuse is from 20dv foam and the wings from 24dv. Somewhere in there is an F18 hiding away.....
Ahh! There it is.... With the templates already having been made with the previous model it saved me a lot of time behind the drawing board and behind the workbench. Now someone must just invent a foam cutter that can do all the compound curves as well ;o) Mind you, I saw some awesome CNC machines at last week's Electra Mining Show at Nasrec that could pretty well do the trick. Pity about the price tags on these marvels of technology :o(
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