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Nov 12, 2009, 09:20 PM
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kepa's Avatar
Build Log

110 cm Depron Avro Vulcan with plans & Blue Steel nuclear missile


Hi,

After building a couple of models out of balsa and seeing some of the simple and not so simple free foamie plans, I decided to give it a try. At first I was going to build the easy build Vulcan posted by davereap ( https://www.rcgroups.com/forums/showthread.php?t=595706 ). So I bought some Depron. 6 mm was all they had and since the plans called for 3 mm, I decided to make it bigger. And after making a bigger (110 cm span, or ca. 43") delta wing triangle I looked at it and it looked too flat and flimsy. So I had to build a "real" wing. I found some 3-views and started measuring, cutting and fitting. I'm not going for "scale" but will build what I think I can easily do. Remember, this is my first foamie.

So, because I started with the easy build plans I had already made a big triangle. After looking at the 3-views I cut it shorter, closer to scale, and added the extra parts for the Vulcan shape. If I had started with nothing but the 3-view, I could have cut the whole wing in one part. I then made the ribs. I took the Clark Y airfoil and mutilated it to fit. And now I have glued some spar structure and the ribs onto the bottom plate. Oh, and I put some 2 mm CF rod near the elevon hinge line.

I'm using Uhu Por as adhesive.

-kepa

Edit May 16, 2010: I posted some plans in post 17, https://www.rcgroups.com/forums/show...0&postcount=17

Edit Dec 28, 2010: Blue Steel missile project starts in message 112, https://www.rcgroups.com/forums/show...&postcount=104
Last edited by kepa; Dec 28, 2010 at 10:08 AM.
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Nov 14, 2009, 05:06 AM
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Here are some pictures of my yesterday's progress. Oh, and I forgot to mention in my first post that this will be a one-motor pusher.

-kepa
Last edited by kepa; Nov 14, 2009 at 06:52 AM.
Nov 14, 2009, 06:46 AM
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Mark Winstanley's Avatar
Looking good so far. Keep the build photos coming. Are you going to post plans when you are complete?

Mark.
Nov 14, 2009, 10:41 PM
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kepa's Avatar
Quote:
Originally Posted by Mark Winstanley
Looking good so far. Keep the build photos coming. Are you going to post plans when you are complete?
Thanks! It would be nice to have plans to share but at the moment I don't have any drawings, except for the 3-view from http://www.airwar.ru/other/drawe.html . I measure, think, cut and fit. And I don't even know if this thing will fly.

Here's what I have done tonight:

I cut and glued together three layers for the vertical stabilizer. I guess fewer would have worked too, but I decided to go for scale thickness and some airfoil shape. After sanding I glued the fin to its proper place. The lower parts of the fin sheets extend forward and back to anchor it rigidly and to stiffen the whole tail end. There will be no rudder control.

I then routed (as in from A to B) the flex rod tubes through the wing structure.

As I worked on and through both ends of the wing center section I noticed that there was a completely empty bay between the vertical fin and the radio compartment. What use could possibly be found for an empty *bay* hopefully near the center of gravity of a model *bomber*? So I cut open the bottom of the bomb bay. Between this bay and the radio compartment in front there's a short section left over from the plus-shaped nose skeleton, and I had glued a wall behind it. A perfect place to put a micro servo for operating the bomb drop! I experimented with the linkage and found suitable geometry for opening the door. And that's not all! I stuck a peg (CF rod) through the front wall of the bomb bay and forward into the wall of my servo tray. I then glued a strip of thin plywood to the wall to take some of the stress induced by bombing operations. I'm also planning to make the bomb bay door easily removable. So the servo, with its arm positioned just right, and the peg, and a rubber band enable me to carry external payload too. Just like the real Vulcan! I'll just have to be careful with the pusher. I'm already regretting not going for EDF...

-kepa
Nov 14, 2009, 10:59 PM
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Quote:
Originally Posted by me
I'm already regretting not going for EDF...
And next I'm going to regret not building undercarriage. Maybe even retracts.

-kepa
Nov 18, 2009, 10:26 AM
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Hi,

I've been so busy building that I haven't had a right moment to report my progress until now.

After discovering my bomb bay, I furnished it with a bomb rack/chute. And there are balsa arches located at each end of the door opening. These are for keeping external loads aligned.

While I was working in the bomb bay, I routed the motor wires from there to the tail. I then put my ESC on another vacant shelf in the plus-shaped structural bulkhead.

The shelf where I put the ESC is quite small so next I got to thinking how I could keep the ESC cool. Well, the shelf is open to the radio compartment in front and the bomb bay in the back. A natural direction for air flow. After this I kind of went overboard. The simplest solution would have been to add a simple intake scoop somewhere in the radio compartment. But no. I constructed an air duct from the cockpit, which will act as a scoop, down next to the battery. Then there's the ESC between the radio compartment and the bomb bay. I also opened a route for the air to flow into the tail and through holes in the firewall right in front of the propeller. Only I don't know whether the ram air will blow the bomb door open, or if the propeller pulls a vacuum there so that the door won't open.

Now the internal structure was ready and it was time to cover the whole top side. My Vulcan is basically a big wing with the fuselage parts added as decoration.

Next, I bent some sheet to go around the tail end and the nose, and glued it on. Oh, and I made a cowl/tail cone to cover the motor.

I've also cut a radio compartment cover, and right now I'm building the round parts of the fuselage on top of the cover and the rest of the wing.

-kepa
Last edited by kepa; Nov 18, 2009 at 10:32 AM.
Nov 20, 2009, 05:17 AM
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As I mentioned in my previous post, I was then making the round fuselage on top of the wing. After completing that, I then made and glued the fin extension.

Yesterday I cut the correct windshield line on the cockpit, and then glued on some CF strips to divide the windshield. There won't be any actual window "glass" there because of my air scoop idea. Then I installed the cockpit on the fuselage.

Next, it was time to make the final version of the bomb bay door. I wanted to be able to remove the door for carrying external load and I didn't think repeatedly pulling tape off the depron would be good in the long run. So I used two small flat hinges, and put in balsa reinforcement for the hinge line. The removal of the door is made easier by using one piece of wire to pass through both hinges as a pin.

Unfortunately the geometry of the door linkage is such that quite a modest load in the bomb bay will overpower the micro servo. I'll have to see if I can make the servo arm go over the top center and still somehow also release the rubber band used for external loads.

-kepa
Nov 20, 2009, 08:48 AM
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Coming along nicely,looking forward to a video Kepa.
Nov 21, 2009, 03:33 PM
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You have really good building skills. Great work.
Nov 21, 2009, 04:35 PM
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Looking good
Nov 24, 2009, 10:15 AM
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kepa's Avatar
Thank you, guys.

As I said, this is my first foam build. It seems that with balsa, I have to cut a thousand parts and glue them together, whereas with depron it's more like cutting out the pieces that don't belong in a model airplane.

I made the elevons, and hinged and linked them. I had to put thin CF strips in them as spars because I managed to put a bend in them while gluing the two layers together. I also added small pieces of balsa for the control horns to attach to. I used three flat hinges per side.

I then sanded the leading edges, and made the nose cone.

The Vulcan is now basically ready for test flights. I rigged the elevons with reflex, but after testing I'll sand the underside of the trailing edge. So I don't want to paint her yet either.

The AUW at the moment is about 630 g (between 22 and 23 oz) and with a CF2822, 8x4 prop and 3S she should be able to get airborne.

So now it's just a matter of waiting for a perfect weather. I would much prefer having either long grass or lots of snow to soften the likely maiden mishaps but at this time of year we have neither.

I'm also working my way into Sketchup and using this Vulcan as a learning project. If all goes well, I might upload the plans sometime in the future.

-kepa
Dec 25, 2009, 07:37 AM
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Vulcan finally flew!


I had been waiting for my private airfield (a lake in front of my parents' house) to switch into its winter mode (i.e. freeze), and then for a calm day. As a bonus, we also got some 10 cm (4") snow for a cushion.

I was a bit apprehensive about the maiden flight. After all, this is my first delta wing model, and a scratch build. How about the CoG? Would this be too much plane for me to handle?

Anyway, after careful measurements of my Vulcan, I finally got the several CoG calculators, both on line and an Excel sheet I downloaded, to agree. The initial CoG was/is 28 cm (11") behind the point where the leading edge meets the fuselage, or 31 cm (12.2") in front of the trailing edge at the root, or, most conviniently, right at the middle of the front hinge of my bomb bay door.

I was also conserned about the amount of reflex needed. I was worried that I might have left the pushrods a tad too long, becuse even with full up trim, the elevons were deflected only 1 or 2 mm upwards. And how about the control throws?

And one more thing: How would I launch this thing? There's nothing on the bottom to get a good grip on!

So, here I was, standing with the Vulcan resting on my fingertips, and my other hand on the throttle. I was going to do a test glide first, but I needed the power to get the bird moving forward. So I hit the throttle, took a step or two forward and pulled my hand away from the model to handle the other stick. The Vulcan started with a shallow descent, leveled off and started to climb. I let it. My test glide had turned into a real test flight. And what a test flight it was. Everything was spot on! No pitching up or down, regardless of throttle setting. Power off glide is stable and flat, hands off even. I'm not an aerobatic pilot (yet) so I can't comment on that side of the flight envelope, except that at one time I was heading too close to the shore of the frozen lake and the plane-eating trees, and I moved the stick a bit quicker and more than I would usually do. Wow! It really turns, and rolls, too. With my current set up (CF2822 motor, 8x4 prop and 3S pack) it should go vertical too, but I found out that this wasn't the case. Perhaps my cheap Chinese LiPo performed even worse than usually in the cold. It was -20 deg. C (-4 deg F) after all.

Anyway, this is a good aircraft and I like it!

Now, depending on the weather, it's either more flights or a paint job...

-kepa
Dec 25, 2009, 07:45 AM
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Congrats, can you get a video?

Have a good Christmas.

Jim
Dec 26, 2009, 06:17 AM
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Quote:
Originally Posted by JimW
Congrats, can you get a video?
Thank you! Unfortunately there were no cameras present on this occasion. I'll make sure we get some footage next time.

Quote:
Originally Posted by JimW
Have a good Christmas.
Thank you! Family, good food and a bit of drink, funding for new radio gear, and a succesful maiden flight. I'd say it's been perfect so far. I hope yours (and everyone else's) was and is a good one, too!

-kepa
Dec 28, 2009, 08:38 AM
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Success and a failure


I flew my Vulcan again today. Before the flight I had sanded the bottom of the trailing edge to eliminate the need to trim the elevons for reflex. I already had built in a flat piece of wing behind the tail ends of the ribs. So, I launched with up trim just to be safe, and after leveling the Vulcan started a steep climb. I centered the trim on my transmitter, and everything was spot on again. Success!

Unfortunately I got a bit carried away, complacent and "behind the aircraft", and managed to put the bird nose first in the snow. The nose section broke off at the point where it joins to the wing. But it was a relatively clean break, so after adding a bit of UHU Por, it's almost as good as before.

Still no video, but here are a couple of snapshots from today.

-kepa


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