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Don Szczur 01-14-2004 11:25 PM

FOCUS II ARF construction by-the-numbers
Well, I took the FOCUS version II out of the box last night, at the urging of my 4 year old son. Did more in an hour with this kit than two weeks with my FOCUS I. Great kit with lots of little improvements that make it go together so much easier (and the FOCUS I was pretty easy).

First item in instructions is to put in the (supplied) phenolic wing rotation pin support to the wing. The holes are pre-drilled, but the ply doubler rib is not perfectly aligned. I spent about 2 minutes with a small round file to get them to fit, but quickly lost patience and decided to do it the quick way by using a drill. The first one I picked fit well. I have no idea what it was since its worn out, but measured it against either .281 or .29 inches diameter drill. Whatever... I used the first hammer I could find (a metal hammer) and, after putting a little 5-minute epoxy on the sockets, hammered them in. I went back and read the instructions that say "rubber faced hammer". Oh well, they are a little deformed. No fear, I put the wing adjusters pins in and they still fit perfectly. Ok, this whole process took about 15 minutes. Now I play with the son (he likes assembling the pieces together for the plane- particularly the vertical fin, which fits perfectly on the end of the fuselage).

Cut the wing tube to 25 inches, measured 10 inches from each side (fuselage is just about 5 inches wide) and mounted tube in one wing half. Quickly found the dowel hardpoint (could see it by reflecting the bottom of the wing to light) and drilled a 1/16 hole all the way through and into the aluminum tube. Screwed in a #2 sheet metal screw for now to hold it. Done.

OK, next is to put the wings together on the fuselage. Remember how hard it was getting the wing adjusters in that narrow fuselage of the Focus I? Well, this one is so easy now its amazing. Since the top canopy comes off, one has clear access to the wing adjusters, plus the flat top to the fuselage sides provide a nice flat surface to calibrate the smart-level to set the incidence.

After trimming off the covering around the wing tube socket and pre-cut wing rotation pin cut-outs and putting a 1 inch block to prop up the tailpost, I calibrated the smart-level to the fuselage sides, put on the incidence mount, and rotated the wing slightly to give positive half degree of incidence. Slid the other wing half on and did the same for the other wing panel and marked both the leading edge and trailing edge wing root centers marks on the fuselage sides.

Pulled the wings off and "connected the dots" for leading and trailing edges marks (for sanity check on incidence). Extended the incidence lines all the way to the tailpost and marked where the intersected (perfectly) at 1 1/16 inch high from the bottom of the tailpost.

Looks good. Incidence and wing mounting is done. It took longer to type this out!

Two things I saw- the wing tube was a bit tough going thru the first inch of the wing socket. I took a portable dremmel with drum sanding bit and just took the glaze off of the inner wing socket about a quarter inch inward (probably where the socket goes through the ply doubler at the wing root). Wing tube now slides in easily into the wing.

Next thing- the instructions show to CA the metal wing adjusters to the ply adjuster plates- I'll think that one over tonight (gluing the wing adjusters with CA rather than bolting them to the ply plates).

... til next building session...


Doug Cronkhite 01-15-2004 12:39 AM

RE: FOCUS II ARF construction by-the-numbers
I think you just tack them in with CA and then screw them to the hardwood plates. The CA holds them in place.

Jeff-RCU 01-15-2004 02:35 PM

RE: FOCUS II ARF construction by-the-numbers
I'm going to build along with you on this This is my first focus (and my first pattern arf). Some things aren't too clear in the instructions (like why two sets of landing gear and how do you attach the pipe tunnel). But so far, Alls I've been messing with is mounting the engine. It's turned into a trial and error methodologoy! Hopefully You have a better method!

mups53 01-15-2004 02:54 PM

RE: FOCUS II ARF construction by-the-numbers
Jeff how can you build a plane that doesn't have 2 wings or isn't Eliptical? Mike

Jeff-RCU 01-15-2004 03:46 PM

RE: FOCUS II ARF construction by-the-numbers
Man, you try to go main stream, and everybody is on you! I've still got my Jupiter (I just recovered and re-painted it this winter after a landing accident that cracked the body in a couple of spots). THe Dr. Jekyll Bipe has been stripped of components and going to a swap meet saturday. It never quite worked out for me. I had a hard time seeing orientation and never could deal with the roll couple. I'm selling it real cheap if your interested! Actually steve has been on me to fly a pattern plane that's not 15 years old, or cobbbled together out of swap meet parts. So here I am building a FocusII.

Doug Cronkhite 01-15-2004 04:15 PM

RE: FOCUS II ARF construction by-the-numbers
I loved the Jupiter.. what a great break from the routine..

mups53 01-15-2004 08:38 PM

RE: FOCUS II ARF construction by-the-numbers
You know I think the Focus2 is going to turn heads. Good choice man. Mike

Jeff-RCU 01-15-2004 09:22 PM

RE: FOCUS II ARF construction by-the-numbers
Yeah, one of the first Kfactors I recieved back around 1996, had an advertisement for the jupiter and I always thought it was a beautiful plane. So two years ago, I hunted down the guy that kitted them (Dave Stuart) and he made up a kit for me. The glass work was gorgeous. I went to buy a second kit this year, and he said he'd sold the tooling to someone who wasn't interested in selling kits! So I guess I have the last of the line. That's why I went through the effort of refinishing it after the mishap.

Doug Cronkhite 01-16-2004 03:22 AM

RE: FOCUS II ARF construction by-the-numbers
My Focus 2 is currently being built when something is drying on the Supreme.. And in less than 2 hours work, I've got the wing incidence done, stab and vertical fin in place and landing gear installed. This thing is certainly a good bang-for-the-buck airplane. I must say I prefer the composite airplanes from a looks point of view (really pleased with the way the Supreme is turning out.), but this airplane has a solid place in the pattern world for sure.

Jeff-RCU 01-16-2004 07:02 AM

RE: FOCUS II ARF construction by-the-numbers
What's a supreme?

raptor5900 01-16-2004 08:04 AM

RE: FOCUS II ARF construction by-the-numbers
a plane from ZN.

LeeDavis 01-17-2004 09:09 AM

RE: FOCUS II ARF construction by-the-numbers
Thanks, Don.

It seems I always leave out a couple of the obvious things when writing an instruction manual. In this case it's the installation of the canopy deck and the bottom tunnel. The deck installs with the supplied 4-40 blind nuts/screws and the tunnel with the #4 self tapping screws. We'll put an instruction addendum in future kits that go out.

Also, the main wing incidence per instructions and per the generic trimming guide in the back of the manual give different starting numbers. The point is to start a little "off" then dial it in during flight trimming at the field. The Focus generally ends up around a 1/4 degee positive.

I built the Focus II airframe and mounted the engine in 12 hours. This also included the photography and notes I used for writing the manual, so it goes pretty quick. I didn't keep track, but equipment and hardware installation (IOW, ready-to-fly) probably required about the same amount of time. But, I've built umpteen Focuses. Take all the time you need to build and trim it right, and it'll track on a rail.

Lee Davis
[link=http://www.piedmontmodels.com]Piedmont Models[/link]

Don Szczur 01-17-2004 04:00 PM

RE: FOCUS II ARF construction by-the-numbers
Per the instructions, I glued with CA the wing adjusters to the plywood plates, and then CA'd the plates to the inside of the fuselage (after wings were plugged in and aligned to the incidence marks. CA seems to stick very well to the anodized metal brackets. Gave it some good tugs prying and it seemed to be on there quite permanently. I centered the adjusters with about 1/4 inch of threads above and 1/4 inch of threads below for clearance.

Don Szczur 01-17-2004 11:26 PM

RE: FOCUS II ARF construction by-the-numbers
1 Attachment(s)
Attached are the instructions for mounting the wing.

I'm moving to the next step, mounting the horizontal stabilizer. I noticed the pushrod support in the rear of the fuselage. I started to think about perhaps it would be better to mount the pushrod before the horizontal stab. I went to the hobby shop and started to look around at some carbon fiber solid rods, then came across some excellent pushrod kits from Central Hobbies. These appear to be hollow rather than solid, but quite a bit stiffer and they come with titanium mounts for threaded section. I was considering a cf pushrod because on my FOCUS I I'm using the Brown pushrod and found that between flights (morning to afternoon) the trim could change up to 15 (beeps). I was giving some thought to some balsa pushrods. Any case I figured I'd give it some more thought.

I came home and looked in the box and guess what! In there was one of those carbon fiber pushrods (Central Hobbies type). I just keep getting pleasantly surprised with this Focus II. I also looked closer at the rear pushrod support. My first though was that it looked too big for the pushrod (cf) and looked more the size of the standard size pushrod. However, I noticed at the rear part of the support was exactly the right size. Now this means that one can mount the stab and the pushrod mounting later should be easy.

Doug Cronkhite 01-18-2004 05:52 PM

RE: FOCUS II ARF construction by-the-numbers
Hinged up my control surfaces today. Just have to fit the hatch and canopy and then do final install. I don't think I have 6 hours into this airplane yet. Very nicely done. Everything has gone together very straight without any adjustments required for me.

Don Szczur 01-18-2004 11:19 PM

RE: FOCUS II ARF construction by-the-numbers
1 Attachment(s)
Doug's about a day ahead... any case I'm taking it slow. Steve Wall wa right, my 3 year old (4 as of today) is having fun helping put it together.

By the way I may be in San Diego sometime over the next couple of weeks if I can't find someone to go for a meeting in place.

OK, attached is the alignment diagram. I put the stab on and it fit perfectly. First measured the TE left and right, each side was exactly 14 3/8 from each side of the tail post. Next I measured from the outside tip of the stab TE to the TE of the wing (just before the aileron cutout) each side measured 39 9/16 inches. Its a whole lot easier to measure from this point than tip-to-tip. This can be done with a 48 inch ruler, simple.

I did measure tip to tip and found that the ruler measure (straight forward as above) was accurate within 1/16 inch. I could not measure accurately to within 1/8 inch from tip to tip so I think its in the ballpark. I remember one time I spent hours getting tip-to-tip down to 1/32 of an inch then tack glued the stab in place only to find that it slid one way by 1/8 inch. Lesson learned was that accuracy is more important than precision. (I always like to mark a pencil spot on the ruler so when I measure the other side I use the same mark and don't mistake it a few 32nds off (you start to see cross-eyed after staring at 16 marks between each inch for a while).

Don Szczur 01-18-2004 11:45 PM

RE: FOCUS II ARF construction by-the-numbers
1 Attachment(s)
The top of the fuselage where the vertical fin assemply sits is solid sheeted balse. I took an exacto and, slicing an angled in-cut, I removed a wedge about an inch wide and about three inches long. This provides easy access to gluing the top of the stab through the slot from the inside.

Now eyball alignment is a very accurate way to set up the stab so its parallell to the wing. I propped the plane up about 30 degrees and then stood back and looked from the back, checking to see if the stab was aligned with the wing. I drew a centerline on the wing TE and stab TE and at the ends, made sure they were aligned. They appeared to be pretty close and no trimming of the pre-cut out stab slot was necessary.

The key is to put a couple of fine pencil lines on the rear part of the stab at center to align with the back post, and a couple of marks near the LE for tip-to tip alignement (previous post). That way one does not have to worry about changing these alignments while getting the stab parallell with the wing. Double checked incidence with the same measurement technique as I did on the wing (see a previous post) and again no trimming needed from the stock cut-outs. The stab incidence is pretty close to the .25 negative that the plans call for.

One can look from each side to see the light (gap) on the right side of the cutout. The other side seemed pretty tight. I dropped a series of medium thickness Zap from the cutout I made on the top and let it flow forward. Once it flowed to the LE I squirted some accellerator in there which kept it from seeping though to the outside (keeps it looking nice on the outside). Did the same from the bottom (dripped medium CA from each of the elevator pushrod exits and let it flow forward. Then I did the same for the back (tilted the fuselage up and let drops of CA flow back along the joint. This technique (with one exception when I dripped too much in before hitting it with accellerator) kept everying looking clean on the outside. Finally on the top right gap, used some 5 minute epoxy and let it flow to fill the gap nicely. After it set, I checked the rigidity. This stab mounting is so much more stiff than the FOCUS I.

Took this opportunity to cut a couple of half inch pieces of inner nyrod that was supplied with the kit and glued them in place for the rudder cable guides. I found these nyrod exits helped keep the cable from fraying and breaking over time. By accessing from the same cutout hole I made at the top of the fuselage, this made the task easy.

Next I glued back in place that piece of balsa and sealed up the access slot. Glued on the vertical fin with some more epoxy. It was aligned pretty close with the stock setup. I did not have to sand anything to get the vertical fin to align. This kit is precise!

Don Szczur 01-19-2004 12:03 AM

RE: FOCUS II ARF construction by-the-numbers
Cowling mounting.

This took all of about 10 minutes (I remember it taking days on the FOCUS I, since I kept trying to think it through).

Put the cowl on, marked four X's where the screws should go through, drilled four 1/8 inch holes all the way through to the ply tabs.

Next I removed the cowl, cut four pieces of inner nyrod (the yellow stuff) and CA'd them in the 1/8 inch holes that I just drilled in the ply tabs. Then took the #4 screws and screwed them into the nylon "inserts" to thread them. Someone showed me this technique at the Joe Nall about 10 years ago and its one of the easiest and secure way's I've seen to keep the screws from coming loose in the cowling.

Put the cowl back on and screwed it on. Cowling done, time for bed.


Doug Cronkhite 01-19-2004 12:55 AM

RE: FOCUS II ARF construction by-the-numbers
Hehe.. I did exactly the same thing on the stab mounting Don.. Cut a small portion of the fin mount platform out to access the stab/fuse joint from inside. I haven't mounted my cowl yet, but I did get my engine/mount in place with the cowl as a press fit. I had to shorten the motor box by about 5/8" to put the backplate 1/16" from the front of the cowl. This is with the Hyde A mount and Webra 1.45 Aero X. My fit on the vertical fin to turtledeck wasn't as good as you describe.. but it was dead straight.. so I didn't mess with it. I'll put a small piece of covering over the gap to clean it up.

Overall it's a very quick assembly.. I figure I'll be ready to fly this coming weekend. It's going to make a nice airplane to play with until my Supreme is done :D

LeeDavis 01-19-2004 09:48 AM

RE: FOCUS II ARF construction by-the-numbers
The titanium/carbon fiber pushrod assembly is Central Hobbies. Al is "Good People" and gave us a break for purchasing a large quantity of them. This upgrade from the standard pushrods occured during the construction of the kits after the pushrod supports, based on the standard pushrods, had already been intalled in the fuselages. Our contractor, Ma Yang Chu, graciously agreed to go back and install new supports, with a smaller diameter hole, behind the old ones. That's why there's a sort of step in the assembly.

Though I explain in the instructions about adjusting the fuselage stab holes for correct incidence, fact is, like you guys, I've never had to actually do it with any of the Focuses I've built. Ma understands the precise nature and intended use of the plane and is generally right-on with things.

Good idea about enhancing stab assembly access by going through the top at the fin support. Never thought of that.

Don, don't use all of that hollow, yellow rod! We intended that you use it for a radio antenna support.

Lee Davis
[link=http://www.piedmontmodels.com]Piedmont Models[/link]

aerobear 01-20-2004 07:31 PM

RE: FOCUS II ARF construction by-the-numbers
The current owner of the Jupiter molds would like to sell them as well as a couple of kits. Contact Dale Densley 801-571-1177. I don't know how complete the kits are other than they include at least the glass parts and foam cores. If you want to mold your own stuff there is a substantial amount of glass cloth also available left over from production. I have not seen any of this stuff myself and don't have any further info.

larmark 01-20-2004 10:06 PM

RE: FOCUS II ARF construction by-the-numbers
I finished my Focus II last week. I would like to pass along a few more tips. The Tetra 20 oz tank is too tall. A Dubro 20 oz tank fits fine. Check the fit of the rear bushing on the carbon fiber push rod. Mine was too tight. I had to enlarge it a little. My canopy hatch was bowed in the middle. I cut a piece of 1/2 inch square balsa about the length of the canopy hatch then lightly CA glued it to the bottom of the hatch only near the center. An 1/8 in shim at each end between the canopy hatch and the 1/2 inch square will hold the frame in position while it is installed on the fuselage to glue on the canopy. After the canopy glue is cured remove the temporary 1/2 in square piece.

I used Pactra transparent blue on the canopy and it looks nice on the Focus.

It weighs 9 lbs 14 ounces with a Mintor 170 with Hyde ARI-A mount, carbon fiber pipe and a 1700 nicad pack. The pack is forward to balance at the front of the wing tube

Larry Markey

Pro pattern 01-21-2004 08:41 AM

RE: FOCUS II ARF construction by-the-numbers
Hello Larmark,

I'm also building one.
Currently finishing final prep. for covering. A good friend of mine will do this
job for me. He did the covering of this FOCUS I and did a very very good job. Pattern freak

Could you please show me a pic of the inside of the FOCUS II, because I also was
thinking that the tetra 20 OZ tank would not fit.

And for those who fly with the Webra 160 Aero XP, will a 18 oz tank be fine. (Tertra Clunk tank)

I also had to do a bit of an enlargement on the rear bushing so it could pass through freely.
Also any pic of the finished plane?

Thanks in advance,

Pro pattern 01-21-2004 10:00 AM

RE: FOCUS II ARF construction by-the-numbers
1 Attachment(s)
Hello everyone,

I went to look for info of the Du-Bru fuel tank’s and find out that the 20oz tank
could be use with pressurized fuel system.
Is this so??? See link for the info.[link=http://www.shopatron.com/product/product_id=DUB420/101.0]Du-Bro 20oz thank[/link]

I’m planning on using the Webra 160 as I said in the previous post and with the following set up. See pic.

Planning to do some modification on this system and will probably be like the following , (see pic)
In the overflow line I will put a check-valve so air can only enter the tank and in this line I will put a fuel line T and with a fuel dot make this my overflow.

So I would prefer to use a tank that can handle some pressure.
Will this tank do the job??

Thanks, in advance for the info

bla bla 01-21-2004 04:02 PM

RE: FOCUS II ARF construction by-the-numbers
I have had no joy using Dubro tanks and a YS pressurised system.
Tetra, perfect of course but a 20ozKavan has held up very well over a couple of years due to the fact it has a brass ring around the neck. It could be easier to fit as the sides are shorter than the top/botton or the other way round if you see what I mean.
Having said that, I use a 20oz tetra in my Focus 1 and it fits perfectly , OK I opened up the canopy floor to make roon for the bubble on the top of the tank...but it's like, spot on. Is there so much difference with the F2?
With regards to tank size and 2-strokes. I definately need the 20oz with my OS 1.40. With an 18oz I was flying finals on fumes.
God knows about a 1.70.

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