RE: Bridi UFO Build (all wood)  
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RE: Bridi UFO Build (all wood) - 6/16/2006 4:30:25 AM   
rainedave



Posts: 5011
Joined: 7/21/2005
From: Greensboro, NC, USA
Status: online 		The elevator pushrod and the pull-pull linkages are more or less done. I need to buy a couple of larger servo arms, mainly so that the cables will be parallel. With that Futaba wheel each cable is about 1/4" too far in to be equal to the width of the rudder horns. The throttle servo is installed, but I still need to put in the retract servo which will go right across from the elevator servo. Thanks again Paternguy for suggesting the Dave Brown elevator pushrod, I mean there is absolutely zero play in that setup.

I'm sure there are several ways to do this stuff. I guess some people glass everything before installing the control hardware. What I'm going to do is leave the plastic flexrods exit guides extending out of the fuselage a couple of inches or so and cover up the ends and cable connectors with tape. Then after everything is glassed I'll cut the flexrods flush with the fuselage sides and everything will already be in place. You've probably seen C/L models being painted with the leads hanging out and taped up; same principle. I don't think I would ever be able to take everything out and then fish it back through again. I don't even want to think about trying to do that.

The next thing to do is glue on the bottom cross-grain planking, sand off the corners and start getting it ready to glass.

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       Post #: 101

RE: Bridi UFO Build (all wood) - 6/18/2006 1:55:35 AM   
rainedave



Posts: 5011
Joined: 7/21/2005
From: Greensboro, NC, USA
Status: online 		I glued on the bottom planking and attached the subfin today. I'll add some pics a bit later.

Neither the plans nor the RCM construction article mention a thing about recommended control throws. I asked 8178 for some help and he gave me the throws for his Tipo and Blue Angel. By measuring the width of my control surfaces and using a protractor I was able to figure out a range of degrees that I think will work as a starting point for high rates. Of course, setting up differential would mean different degrees up and down, but the figures below are for total throws. There's also the issue of different surface widths on the various planes that throw the figures off a bit. Still, I think I have a good idea now of where to start.

8° each way for aileron = 3/8" total; which is the same as the Tipo
13° each way = 5/8" total; equals the Blue Angel
So, 10° each way is between the two at 7/16" total throw which is what I'll start with for high rates.

10° each way for elevator is 3/4" total; same as Tipo
18° is 1 3/8" total; equals the BA
15° is 1 1/8" total, again I'll use that for initial HRs.

18° each way equals 2 3/4" total rudder; same as BA
20° gives 3" total, sama as Tipo
Either one of these settings should be fine to start with.

I'd also like to hear from you all flying Dirty Birdies as to what throws you're using since the UFO is very similar. Thanks.

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       Post #: 102

RE: Bridi UFO Build (all wood) - 6/18/2006 3:40:21 PM   
Paternguy


 

Posts: 628
Joined: 3/9/2002
From: East Berlin, PA, USA
Status: offline 		I have a glass UFO kit in the basemant, I will look and see if the control throws are in the assembly manual, this evening.

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       Post #: 103

RE: Bridi UFO Build (all wood) - 6/18/2006 5:35:34 PM   
FSFLYER


 

Posts: 41
Joined: 4/25/2004
From: Sykesville, MD, USA
Status: online 		I just looked at the plans for the glass UFO kit that I have. It doesn't show any throws, in fact the information is rather sparse, all that came with it was one sheet, 15" x 30". Not much information, but plenty to get the glass/foam version done. They do show an all up weight of 8-1/4lbs. Did you get any more information with your glass kit? Also, they include 3/32 sheeting and fixed tri-gear. Going to substitute 1/16 sheeting & add retracts when I finally get around to building it.

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       Post #: 104

RE: Bridi UFO Build (all wood) - 6/18/2006 9:04:37 PM   
rainedave



Posts: 5011
Joined: 7/21/2005
From: Greensboro, NC, USA
Status: online 		Thanks y'all for checking the glass instructions. The UFO's control surface widths are very close to those of the Tipo, thanks again 8178. So that serves as the best guide:

Aileron: Tipo - 1.375"; UFO - 1.3125" (1 5/16)
Elevator: Tipo - 2.125"; UFO - 2.125"
Rudder (widest point): Tipo - 4.125"; UFO (average width) - 4.5"

So, I think 8° for ailerons - same as Tipo - will be good; 10° for elevator - same as Tipo; and 20° for rudder - which is just a bit more than the Tipo at 3.125" total throw.

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       Post #: 105

RE: Bridi UFO Build (all wood) - 6/20/2006 2:39:59 AM   
rainedave



Posts: 5011
Joined: 7/21/2005
From: Greensboro, NC, USA
Status: online 		There's an issue with wooden fuselages that are rounded on the four corners and have a sheet balsa top, bottom and sides. The taller the sides are, the easier it is to have it develop. It seems to happen because of two things: one, because there is extra wood in the form of stringers along with glue in the corners, and these stringers are usually of harder balsa; and two, the sheet sides, depending on how thin they are sometimes have a tendency to bow inward. I think this bowing is caused by the various pressures and tensions in the fuselage structure, but I'm not an engineer.

At any rate, if you're not careful you can get a fuselage cross section that looks like the drawing on the left when what you want should resemble the right drawing. The concave problem seems to get magnified when light and shadow hit the fuse at certain angles. Glossy paint will magnify the effect even more, so it only takes the slightest bit of concave surface to become visible.

I've worked really hard with the razor plane and sanding blocks to get the UFO fuse to look like the drawing on the right. But, there's a fine line between getting the corners shaped correctly and going too far and getting the wood too thin. The best fix is to add extra stringers that allow you to plane down the sides of the corners further without things getting too thin, leaving the middle area of the sides the thickest. I'll get some pictures up a bit later.

Of course, a glass fuse eliminates the problem all together!

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       Post #: 106

RE: Bridi UFO Build (all wood) - 6/20/2006 3:31:51 AM   
rainedave



Posts: 5011
Joined: 7/21/2005
From: Greensboro, NC, USA
Status: online 		Here are some pics that attempt to show the outward or convex curve to the fuselage sides that I'm after. You can just see me special sanding trousers, mates.

The surfaces don't show up well in the photos, but the joint near the tail where the two side sheets meet gives a good image of the rounded look.

I've got everything masked off with tape like pushrods, connectors and servo rails (I'm sure to drip resin inside the fuse), I just need to clean off the dust and I can start glassing the thing.

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       Post #: 107

RE: Bridi UFO Build (all wood) - 6/20/2006 1:01:35 PM   
8178



Posts: 2941
Joined: 5/25/2004
From: _ , USA
Status: offline 		Looking great! Another solution is to use 1/2“ triangle stock in the corners to provide a larger radius. The triangle also acts as a cutting guide as the corner is rounded down with the razor plane because the glue joints can be faintly seen.

Looking forward to seeing your glassing process.


_____________________________

Builder and flyer of high performance acrobatic R/C aircraft and a proud member of VR/CS.
Made in China = no sale!

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       Post #: 108

RE: Bridi UFO Build (all wood) - 6/21/2006 2:02:33 AM   
Paternguy


 

Posts: 628
Joined: 3/9/2002
From: East Berlin, PA, USA
Status: offline 		rainedav,

You have inspired me, I went down to the basment earlier and pulled out my UFO kit. I am going to finaly finish it. LOL

I ordered a new wing from Dynamic Balsa, the original cores got damaged in my last move. The glass fuse is in great shape. I forgot how good the glass work on the old Bridi kits was. The fuse is actulay pretty far along, I need to mount the firewall and the nose gear, and of course build the wing.

Thanks,
Doug

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       Post #: 109

RE: Bridi UFO Build (all wood) - 6/21/2006 4:01:54 AM   
rainedave



Posts: 5011
Joined: 7/21/2005
From: Greensboro, NC, USA
Status: online 		That's really cool Doug. I've never seen a glass UFO so you'll have to post some pics.

Thanks 8178! 1/2" tri-stock is a great solution, even better than the extra stringers.

I'll probably start the glassing on Saturday. I still need to pick up a few things like some alcohol for cleaning up, a soft brush for smoothing out the glass cloth before pouring on the resin (it always snags and pulls on my fingeritps for some reason), and some mixing cups. I'm using Pacer Z-Poxy finishing resin which I've used before and liked and 3/4oz cloth. I'll glass the fuse, fin, stab, elevators, rudder, ailerons and the wing out over the gear wells.

I haven't talked about finishing much, but here's what I'm going to do. The outer, open sections of the wing will be covered with nitrate dope and SIG Koverall. I went with Brodak primer and dope so after the Koverall is filled with nitrate and shrunk tight the entire plane, fuse and all, will get primed with the Brodak primer. I'll use this to fill the glass instead of extra coats of resin. I have no idea how many coats of primer and putty it will take, but most of it gets sanded off anyway. Then I'll spray the colored dope and finish with clear butyrate. I'm going to keep the color scheme simple; two main colors a little bit of a third color for striping, or whatever.

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       Post #: 110

RE: Bridi UFO Build (all wood) - 6/21/2006 10:23:24 AM   
Paternguy


 

Posts: 628
Joined: 3/9/2002
From: East Berlin, PA, USA
Status: offline 		Try using pantyhose instead of glass cloth on the fuse, its much easier to work with and its lighter. I did this on my DB and it worked out great and it has been very durable. I used CA to tack it down in several places and pulled the slack to the wing sadle as I tacked it in place. Then I used resin to fill in the weave of the nylon.

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       Post #: 111

RE: Bridi UFO Build (all wood) - 6/22/2006 12:08:42 AM   
Paternguy


 

Posts: 628
Joined: 3/9/2002
From: East Berlin, PA, USA
Status: offline 		Here are a couple of pics of the fuse. One is next to my Dirty Birdy fuse, I was trying to show the diferance in size between the 2, The UFO is about 3 inches longer.

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       Post #: 112

RE: Bridi UFO Build (all wood) - 6/22/2006 1:39:09 AM   
rainedave



Posts: 5011
Joined: 7/21/2005
From: Greensboro, NC, USA
Status: onlin