RE: Bridi UFO Build (all wood)

RE: Bridi UFO Build (all wood) (Full Version)

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rainedave -> RE: Bridi UFO Build (all wood) (6/1/2006 10:06:21 PM)
This stage was a lot of fun. I cut and fit the wheel wells and glued them in the wings. I did this after checking the wheels one last time by placing a level on the fuselage. The nose is set slightly down. The openings for the retracts still allow a good 1/8" of adjustment each way for the wheels, so I can still make minor adjustments. I temporarily hooked up the air lines and checked the system. It all works great. Next I will sheet the center of the wing. The nose wheel retracts completely into the fuselage with no part exposed. I was very happy with the way this turned out. This was the first time I've ever installed retracts and I think it went very smoothly. I'll admit I'm pleased! The only part that was a bit tricky was making sure I cut the gear legs to the proper length.

rainedave -> RE: Bridi UFO Build (all wood) (6/2/2006 9:12:52 PM)
Instead of driving 45mins to my LHS for a $2 bit of hardware, I decided to fabricate my own tiller for the nose gear steering setup. I took a Hitec servo arm and cut off two of the arms and put a piece of brass tubing in it as a bushing. Then I slid a bolt through that and soldered a nut underneath tight against the bushing so that the servo arm spins freely. The bolt then goes through a piece of ply that will be glued inside the fuselage. For the cable connectors I soldered pieces of brass tubing onto lengths of threaded rod, flattened the ends of the tubing and drilled holes for the cable. The cable is Dubro pull-pull rudder cable looped through brass tubing which was crimped and covered with heat-shrink tubing. The other ends of the cables will be hooked up similarly to the tiller arm on the nose gear. Then, a regular adjustable nyrod pushrod will run from the homemade tiller back to the rudder servo. It was necessary to use cable since the distance from the nose gear tiller changes when the gear is retracted. The cable simply goes slack when the gear is up.

rainedave -> RE: Bridi UFO Build (all wood) (6/3/2006 3:36:38 AM)
I got the nose gear linkage hooked up. It's not the prettiest job, but it works. I had to make a number of adjustments and modify a few things to get it to retract and lower correctly without anything catching or binding. The cable has to be taught enough that there's no slop, but just loose enough that it won't prevent the spring-down mechanism from locking. Since I'm new to installing retracts I decided that if it worked correctly 90% of the time it might as well not work at all. So, I added a piece of balsa over the retract since one time the cable snagged on the pin that secures the air cylinder. It might not happen again in a thousand cycles, but it will when something like a deadstick occurs. You see, I'm basically Murphy's poster child. I'm sure I'm boring you all with this minutia. All in all, it wasn't any more tedious than installing a steerable tail wheel. I really enjoyed fabricating the little tiller assembly, I like the stuff where you have to do a bit of basic engineering.

8178 -> RE: Bridi UFO Build (all wood) (6/3/2006 4:54:31 PM)
rainedav The detail info is great! Can you show the retract sequence with the balsa cover installed?

Jagdgeschwader 26 -> RE: Bridi UFO Build (all wood) (6/3/2006 5:28:01 PM)
Dave, Still neat as a pin! I might suggest you harden the balsa under the cables with epoxy or CA so the cables do not carve into it under tension. Also, why not clip off the outer portions of the steering tiller on the nose gear strut and fill in the bottom block accordingly? Just a couple of ideas. Keep up the good work.

rainedave -> RE: Bridi UFO Build (all wood) (6/4/2006 1:45:12 AM)
Thanks y'all! 8178, I've uploaded a pic of what I think you wanted to see. j26, those are both good ideas. Thanks. It's great having someone "proof" my work since I can get so lost in the details that I miss the practical improvements that another set of eyes will notice. I didn't show it in my last post, but I cut away a lot of the underside of the balsa block so that the cables clear everything. One of the pics below tries to show how thin it is in places. The reason the red tiller is so far back is to allow room to get the tank in and out. Ideally, I'd rather have it up closer to the gear to shorten the cable runs. I took three pieces of threaded pushrod, wrapped them tightly with copper wire and soldered them together, then covered it with heat-shrink tubing to make the elevator pushrod. I can still use a cf or fg shaft if I feel it's necessary. I had been scratching my head about how to route the servo leads and air lines through the wing. I needed a way that would allow me to remove and replace them if needed after the wing is sheeted. I've seen giant-scale models with cardboard tubes in the wings for this purpose, but I had nothing around the house like that small enough. No worry, I soaked a sheet of A-grain 1/16" balsa with Windex and taped it around an aluminum pole and put it in the sun to dry. I'll admit the result looks a bit odd with the 90° bend, but it actually works very well. To remove and replace the wires and air lines I just have to tie a length of monofilament on the end before pulling them out. Then I use it to pull the stuff back through again. Installing these balsa tubes should have been done before the wing halves were joined. If you look close you can see how I had to cut the ribs and then replace part of them on top of the tubes. It's no less strong and it will all be covered with sheeting anyway. You can also see where I needed to cut out a curved section of the ply tongue that holds the wing to the fuselage. The nose wheel was hitting it before. I just put the wing on my postal scale and I was sort of surprised. With the retracts, servos and all that extra "woodworking" I did it weighs 1lb., 13oz. The bottom sheeting and ailerons will add another 2 1/2 oz., but that's lighter than I thought it would be. Lots of pics!

Paternguy -> RE: Bridi UFO Build (all wood) (6/4/2006 4:10:56 AM)
I would go with the dave brown carbon fiber push rods, I think you may get to much flex with that set up. Remember this bird is fast. If that push rod flexes, you may end up with flutter. Just my 2 cents. Looks great. I realy like the blsa tubes used for the air lines and servo leads.

rainedave -> RE: Bridi UFO Build (all wood) (6/4/2006 4:47:06 AM)
Paternguy, I was just looking at those today on the web. How would you modify them for dual elevators? Would you run one cf rod to the back of the fuse and then use heavier wire - like 4-40 - to branch off to the horns? Or is there a better way I'm not aware of. Pics would be great. I'm using Dubro HD horns. I've already glued the end-grain blocks into the elevators, but I still need to drill them out and glue in the hardwood dowels. Thanks, David

Paternguy -> RE: Bridi UFO Build (all wood) (6/4/2006 8:31:36 AM)
They come with an end cap for the rod that uses 2 4/40 rods in a "Y". I used them on my Tipo and it worked great. The carbon rod is very stiff, and with the end cap you can get away with running fairly short pieces of rod. There is very little slop in this set up. I am sure some of the other guys here have used them over the years, I first found them in the early 90's, and I use them on every plane I build. I don't like the nylon rods, they seem to get a little soft in the heat and change the trim of the aircraft from flight to flight. I have never used them for control surfaces, but I have flown other people’s planes with them, you can feel the slop in the air, again just my 2 cents.

rainedave -> RE: Bridi UFO Build (all wood) (6/5/2006 2:13:29 AM)
Thanks, Paternguy. Well, I re-order all new control hardware today.: GP deluxe 4-40 pull-pull system, Dubro 4-40 Safety-lock Kwik-links, threaded 4-40 rods and the Dave Brown fg pushrods. It could end up being the best $26 I spend on this plane. I also ordered a 6v 1200mah Nimh rx pack. It actually weighs less than a 4.8v 1200mah nicad pack. This will add a little oomph to my servos (from 44 to 57in/oz). Elvis Costello once said that every musician is a Magpie and a thief and he meant it in a good, complimenary way. I know I've borrowed my share of techniques and ideas from the better modelers. The Central Hobbies web site has a good how-to on installing MK horns. I basically followed their method for the Dubro horns I'm using. I cut out the surfaces and glued in balsa blocks end grain facing out. Then, I used a paddle bit (man, I need to buy some Forstner bits the next time I'm at Harbor Freight) to cut 7/16" holes in the blocks with a drill press. I drilled out some 1/2" dowel in the drill press and glued segments into the blocks. Then I sanded everything flush. The UFO plans say to slant the elevator horns 15° forward for differential. The Dubro horns I'm using extend past the hinge line as is, so I think I'll go with the way they are. Does anyone know if needing more down than up is due to the anhedral stab, or was elevator differential common practice on all pattern planes?

fireman7875 -> RE: Bridi UFO Build (all wood) (6/5/2006 1:52:04 PM)
Beautiful work, rainedav! I especially like the formed balsa servo lead tubes- MITRED no less!!! You and 8178 must have some kind of competition going on to see who can build the prettiest airframe. Keep it coming- I love it! Brian

rainedave -> RE: Bridi UFO Build (all wood) (6/6/2006 4:29:49 AM)
Thanks Brian! I really enjoy making little specialty parts and things like the balsa tubes. I sheeted the bottom of the wing tonight. If I forgot anything it's too late now. It looks like measuring ten times and cutting and glueing once paid off. The tires are nice and centered in the wells when retracted. I still need to relieve two small places when the coil springs touch the sheeting. I weighed the wing again, this time with the Dubro HD horns installed in the ailerons; it's at 31.75oz. I still need to build up the fairing thing that sits under the front center section of the wing and blends into the bottom forward part of the fuselage. I'll epoxy glass tape around the center joint before attaching the fairing. Since I ordered a new 4-40 pull-pull system I used the 2-56 hardware I already had to redo the nose gear cables. It's much neater now and it works a lot more smoothly than the clunky brass cable connectors I had made.

FLAPSDOWN -> RE: Bridi UFO Build (all wood) (6/6/2006 4:27:09 PM)
What a beautiful job! I'm so inspired I ordered my plans yesterday. I've never built a UFO, I was always a Dirty Birdi fan. I have 4 complete fiberglass kits I'm stashing away. Right now, I need to get away from the warbirds and get back to my roots. Thanks for the inpiration.

rainedave -> RE: Bridi UFO Build (all wood) (6/6/2006 11:49:22 PM)
Thank you, FLAPSDOWN! What a coincidence. I was just studying some photos of the UFO from the magazine construction article for the sake of inspiring myself to get this thing in the air. From the September, 1977 RCM:

rainedave -> RE: Bridi UFO Build (all wood) (6/7/2006 1:23:29 AM)
A few pics of the wing fairing. The wing has also been glassed top and bottom around the center section.

aerobatixkid -> RE: Bridi UFO Build (all wood) (6/7/2006 4:56:28 AM)
That is some of the best wood work I've seen. What kind of knife do you use to get clean cuts like that? Shane

rainedave -> RE: Bridi UFO Build (all wood) (6/7/2006 8:04:56 PM)
Thanks, Shane. You'd be surprised how many parts I shape using various grits of sandpaper wrapped around various blocks, dowels and other objects.

rainedave -> RE: Bridi UFO Build (all wood) (6/8/2006 4:41:39 AM)
Elevator pushrod, Take Two. I followed Paternguy's advice and used a Dave Brown fg pushrod. The "Y" end cap that came with the rods was apparently made for 2-56 wire so I strayed from the instructions. I glued the end cap in first and then drilled out the holes slightly smaller than a piece of threaded 4-40 rod. It was a real chore threading the two wires inro the end cap as it was pretty tight. As a result I was worried that the end of the pushrod might split so I wrapped a strip of fg cloth around the end with epoxy. It's now extremely strong and many times stiffer than the nyrod. The next thing to do is mount the rudder servo so I can install the pull-pull system. I read an interesting article on this thing known as Ackerman. Supposedly, as a result of placing the horn connection slightly back from the hinge line, the cables are the most taught when the surface is at neutral. According to the article having the horn connection directly over the hinge line causes the cables get tighter as deflection is applied. Which is the way all the instructions I've read say to do it.

rainedave -> RE: Bridi UFO Build (all wood) (6/9/2006 4:38:50 AM)
I started the part I probably enjoy the most tonight, although I love every part of building. Shaping the fuselage. I've still got a ways to go, but I like to bring down the corners in stages so I can get a uniform radius all along the fuse. 8178 used a technique on his Cold Duck that allows you to view a cast shadow to compare the right and left contours which works great. I won't bother with templates, I'll shape it by eye until it looks right. The canopy arrived this week. I went with the Great Planes Dirty Birdy 17 3/4" one. Ever take a look at a Tower ad from the late '80 and early '90s? Great Planes had some really awesome kits. It's a shame that sneakers, I mean arfs, can be mass produced so cheap in Asia and then marked up ten times for such amazing profits over here. Anyway, the canopy will work fine, even though it's a couple of inches shorter that what's drawn on the UFO plans.

8178 -> RE: Bridi UFO Build (all wood) (6/9/2006 1:17:57 PM)
Looking wonderful rainedav! You are going to have a blast rolling that baby into a split S, getting it on the pipe for terminal velocity and doing a slow roll from horizon to horizon. Almost as much fun as shaping the fuselage and finding yourself buried in a pile of balsa shavings. It is magical the way the sculpture comes out of the assembled pieces of balsa.

rainedave -> RE: Bridi UFO Build (all wood) (6/11/2006 5:49:46 AM)
Thanks, 8178. It's getting to that point when you start "seeing" it flying. I've started planning the radio layout. With most planes I don't really plan this, I just mount the servos where they help in balancing. But because I'm using pull-pull for the rudder and a Y-pushrod for the elevator - and have never done either before - I wanted to get both servos connection points centered in the fuse. I put the model together as much as possible with the engine, spinner, prop and all controls surfaces temporarily in place. The good news is that everything, minus the fiberglassing, paint and covering, weighs 104oz (6.5lbs). The bad news is it's nose heavy. Since most of the glass/resin on the fuse will be behind the CG I'll get some tail weight there. But I'll have to place the servos, rx and battery as far back as is practical. I built a little box to hold the battery just behind the former at the TE location to get some more tail weight. In the pics the servo closest to the tail is the rudder servo and is centered for the cables. I'll be using different servo arms and the cables will run down either side of the battery box. If you look closely at the pics you can see that the elevator servo is about a 1/4" higher than the rudder sevo. The arm I will use will place the connection point in the center of the fuse so the pushrod can run straignt back over top of the rudder servo. I'll either put the throttle or retract servo opposite the elevator servo. The air tank will just have to go directly behind the battery. Nothing's glued in place yet, so I might come up with a better layout.

Paternguy -> RE: Bridi UFO Build (all wood) (6/11/2006 5:55:24 AM)
You should have made it a tail dragger. LOLOLOLOLOL But seriously, its looking realy good, you will have a blast flyying it.

fireman7875 -> RE: Bridi UFO Build (all wood) (6/11/2006 3:09:36 PM)
Oh my GOSH! You even built a little box for the battery! I can't believe how organized you are![:D] Even I can see it flying. Brian

FLAPSDOWN -> RE: Bridi UFO Build (all wood) (6/12/2006 4:15:26 PM)
rainedav, I was curious what engine setup you decided on. I went through the thread but didn't see it. My plans arrived Saturday, I'm eager to get started. My pattern days are 15 years behind me since I was hooked by warbirds. I'm still an old school builder though. My semi-retired Dad has owned a hobby shop as a hobby since 1974. That's where the 4 glass and foam Dirty Birdi kits came from. I have 4 Enya 60X's and pipes that I put away when I threatened to get into competition pattern flying. It changed everything when I got my drivers license. Oh, one more thing. Have you thought about carving the canopy since you're so good with the knife, plane, and paper. It really will have the right lines. The length, profile and curvature of the canopy just doesn't seem to look right with the great planes canopy. Don't miss understand me, the plane will be spectacular with it or without.

rainedave -> RE: Bridi UFO Build (all wood) (6/13/2006 3:32:00 AM)
Thanks, FLAPSDOWN. I considered doing a carved canopy in one of the posts. Since the fuse will be glassed and painted a wood canopy would work pretty well. Ultimately, I just decided on the GP canopy. The issue of what engine to use has been an ongoing point of indecision since this project started. I have a NIB Tower .61 which is a very good, powerful and well made engine. And they have a great reliability reputation. If there's a drawback it's the weight. It's heavier than the sixties this plane was designed around. K&Bs, for example, are probably seven or eight ounces lighter. I keep hoping I'll come across a good deal on a nib or good condition older engine, but with three reservations: noise, reliability and parts. I'm not going to try and join a new club these days with a '70s screamer. And as much as I enjoy tinkering with my antique engines, I want something that's easy to run, repair and get spares for with this project. If it lasts a while I can always put something else in the nose down the road. Maybe you'll find that you don't really need four Enyas after all![:)] Brian, trust me, I'm not organized! The reason for the battery box is so I wouldn't have to make an access hatch in the fuse behind the wing for the battery. Just to prove it, here's the card table I've built this and the last three models before it on. BTW, I started keeping my CA in a rubber seal, airtight glass jar with a couple of packets of silica gel thrown in, and I haven't had a clogged tip since.

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