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Oct 24, 2015, 09:45 AM
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Build Log

Avro Vulcan in foam board from Model Aviation

I've recently printed plans for an Avro Vulcan (bat wing bomber) from a file on the AMA site, I followed a link to the current issue of Model Aviation to find the free plans download and an article detailing construction.

It's a 30 inch wingspan, slotted prop version and a lot simpler, using 2 sheets of Dollar tree foam, than others I've seen references to on RC Groups.

I had a little trouble getting the plans printed to right size at the local copy center, but eventually got it done. I had the file on a thumb drive, and it seems that the file needed to be transferred to their computer before the actual size plan came up on their Adobe print screen. The second time I tried, I brought a ruler to make sure. Larry Kruse has the wingspan marked on the plan, so I used that to prove the scale when it printed. It's 14 7/8 inches from centerline to tip at the trailing edge, half the span Larry marked. Made my templates and things are looking good.

There is no 3-view, but the article clearly describes where the pieces go. Once you know that the narrow part of the triangular piece on the bottom goes forward, the rest falls into place. Intakes on the bottom makes it look like a cross breed of XB-70 Valkyrie and Vulcan, but looks like a good flier, so that's what matters.

I've added a sketch of the bottom of the nose with the "front bottom plate" added. I used the "Fuselage Bottom" template to find the dimensions,
Last edited by DuPageJoe; Oct 24, 2015 at 11:27 AM. Reason: add a sketch of nose bottom
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Oct 24, 2015, 11:45 AM
An itch?. Scratch build.
eflightray's Avatar
Not sure what your picture is supposed to be, but this is an Avro Vulcan --
Oct 24, 2015, 01:04 PM
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Thanks for your beautiful drawing of the real thing. My sketch is of the nose section of the foam board model. Just imagine a flat piece of foam board with outline of the top view of the Vulcan, and a foam box on the bottom to protect the electronics during landing, and you've got the gist. Since "Dollar Tree" stores in the US sell 20 X 30 inch sheets of foam, a 30 inch wing span model needs to be in two sections, with a seam at the back of the nose. The sketch indicates the position of the box on the bottom. The box is supported by a nose skid and two rails that extend nearly to the elevons. There are also foam pieces perpendicular to the wing which represent the outline in the vertical plane.

Simple it is, but scale - not really. Check out the Model Aviation article.

I've seen the real thing at an Air Show in Cleveland, Ohio a long time back. I still remember the back blast as it rolled to turn from a low pass to go back out over Lake Erie. I recently got a book called "Profiles of Flight: V Bombers Vulcan, Valiant and Victor" by Dave Windle and Martin Bowman which has lots about these cold warriors.
Last edited by DuPageJoe; Oct 24, 2015 at 01:11 PM.
Oct 24, 2015, 02:10 PM
“There’s no place like Foam”
gpw's Avatar
MA had a construction article for these several years back ... When Flat Foamies were relatively new ...
Oct 24, 2015, 02:23 PM
An itch?. Scratch build.
eflightray's Avatar
The Vulcan is a beautiful plane, sadly the last UK flying Vulcan, (XH558), has also just had its last flight, (5th Oct).

I have a scratch built 49" span version, and have just started on one of the 80" span versions.

The Vulcan will live on.

Oct 29, 2015, 01:02 PM
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Building progress on the foam Vulcan

Thank Larry Kruse for keeping this great plane in the minds of modelers, even in this rudimentary form.

I've finished cutting parts, and am starting assembly. The first picture shows the wing parts, with the nose piece from my sketch attached to the rest of the wing. This assembly weighs 83 grams (3 ounces). It balances 20 inches back of the nose, just near the position of the motor mount. This might be close to the center of lift for this planform. Larry marks the target Center of Gravity for the finished plane about 4 inches forward of the motor mount, That's consistent with the good stability he claims for the Vulcan model.

The fuselage box and nose skid are shown in the next picture. They weigh 40 grams (1.5 ounces) before gluing to the wing panel.

I added a few little right angle pieces to help with alignment when I assembled the fuselage box. I also added some coarse fiberglass mesh (wallboard repair tape) in between the two parts of the front skid when I glued them together with epoxy. I glued the wing parts together with epoxy, and the fuselage box parts together with hot glue, as per the instructions.

My motor is a little longer than the recommended one, so I might need to move the motor mount forward a bit to keep the prop in the same position. I ran the motor with a 7 X 4 Master Airscrew prop, and it drew about 11 Amps at 11,000 RPM with a 3S battery at about 3/4 throttle. I got the motor off a remainder table at a swap meet, but it's a 400 sized outrunner (28 mm body diameter) and should work.
Oct 30, 2015, 11:22 AM
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I've decided to use Otto Dieffenbach's low noise prop slot design in a 7 inch prop size for this project. It's a fairly minor change from the one in Larry Kruse's plan, just a little more relief on the front side of the prop.

I found this through Balsa or Carbon's "Super Easy" build, post # 73
Oct 30, 2015, 04:58 PM
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Vulcan Wing with Dieffenbach slot

I cut the prop slot in the Vulcan wing according to Otto Dieffenbach's template for a quiet slot, adjusted to a 7 inch prop diameter. I also adjusted the location for the motor mount disk according to the length of my motor. After that, I attached the front skid to the wing with hot glue, using three passes as in Kruse's instructions. I tooled the fillets of glue on each side of the skid with the round end of a hardwood stir stick from Starbuck's. I'm not good at tooling hot glue with my fingers. The fuselage box with the two servo supports were attached the same way. This assembly weighs 138 grams (4.8 ounces ) and balances 17 inches back of the nose. This includes about 18-19 grams of hot glue.

Next, the elevons will be cut from the wing, before adding the upper fuselage section and the motor mount.
Last edited by DuPageJoe; Oct 30, 2015 at 05:09 PM.
Nov 02, 2015, 12:22 PM
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Vulcan Airfame Complete

I cut the elevons from the wing with a sharp modeling knife and a straightedge. They weigh 8 grams. Then I attached the front portion of the fuselage top with hot glue, in 3 passes. Weight at this stage was 148 grams (5.2 ounces) and C of G was 15.5 inches from the nose, without elevons.

I cut the circular motor mount (2 inch diameter) out of 1/8 inch thick craft plywood. I drilled holes for a motor X-mount, and a center motor shaft relief. before I glued the mount to the airframe. I needed to cut back the foam parts about 1/2 inch where the motor mount would be attached, because my motor was that much longer than the one that Larry Kruse installed. I glued the motor to the foam with 30 minute epoxy in two passes, making a fillet at the angles between the foam parts and the plywood on the second pass. The motor mount and glue added 8 grams.

Finally I used hot glue to attach the rear skid and the vertical fin to the airframe, also in 3 passes to make a fillet on each side of the joint. I used a left over corner from a foam sheet as a try square to make sure the parts were vertical. At this point the airframe weighs 173 grams (6.1 ounces) and balances 17 inches back of the nose. Adding the 8 grams for elevons brings the weight to 181 grams (6.4 ounces), with a calculated C of G of 17.5 inches back. The C of G target marked on the plans is 16 inches back of the nose, so I need to put the rest of the gear as far forward as possible.
Nov 03, 2015, 11:47 AM
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Adding Paint to the Vulcan

I coated both top and bottom of the Vulcan with Minwax satin polyurethane varnish to waterproof the paper on the Dollar Tree foam sheets. I used the solvent based version from a spray can. I tried to keep the can at a distance where I didn't accumulate a shiny film, so I wouldn't separate the paper from the foam.

I also gave the top side areas a coating of grey primer, using a spray can of Walmart's "Home Shades" (cheap) branded stuff. I sprayed this as a second coat over the polyurethane. I might have held the can too far away as I sprayed because some of the coating was powdery. I needed another coat of the Minwax to hold it down. Total weight of the paint layers was 26 grams, bringing the total weight, including the elevons, to 207 grams (7.3 ounces).

I've been searching for a paint scheme for one of the Vulcans I saw at the Cleveland National Air Show (Ohio, USA) in either 1974 or 1980. The Air Show website has program highlights for those years mentioning the Vulcan flying over. I seem to remember it in a flat fighter plane grey paint scheme, without camouflage. I don't remember anti-flash white.
Last edited by DuPageJoe; Nov 03, 2015 at 06:45 PM.
Nov 05, 2015, 10:03 AM
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Thrust tests for 400 motor

Before I mount the remainder bin 400 sized motor on the Vulcan, I wanted to make a few tests to see if the thrust would be reasonable with a Master Airscrew 7 X 4 prop fitted. I used a 1500 mAh 3S battery and a Castle Thunderbird 18 ESC to power the motor. I used a wattmeter between the battery and ESC, and a hand held optical tachometer to get RPM. An incandescent flood light was the light source for the tachometer, which I checked with a fluorescent light. It reads 3600 rpm on 60 Hz power. The motor was mounted on a lever arm test stand, using a postal scale to determine thrust. It was set up with the prop as a tractor.

The first graph shows the results, which are quite favorable if I can keep the all up weight below 16 ounces. At roughly half throttle, rpm is 8000 and thrust is just over 10 ounces. Near full throttle, thrust goes over 20 ounces. and rpm is not quite 12000. Max current is 12 amps at nearly 120 watts power to the motor. Looks like a good prop & motor combination.

The next graph show results from the AdamOne prop thrust calculator, for a prop of the same diameter and pitch. I did not find my Master Airscrew prop in the database.

I put the same rpm readings I found in my test into the calculator, to see what thrust and power to prop results it would find. Though the power to prop numbers were output, I plotted them on the X axis with Excel, so the two plots would look the same. Thrust was about 20 ounces near 12000 rpm, and 10 ounces near 8000 rpm. Power to the prop numbers were about 75% of the power to the motor numbers I found.

With a wattmeter and a tachometer you can find thrust fairly easily through a calculator like this if you're using a prop that's in the database. It's the prop that makes the thrust after all.

If you go to the home page on the AdamOne site you can find a calculator for motor & prop combinations also. When I tried this, I found a few other motors in the "Park 400" range that might be useful on the Vulcan in the database.

Electrifly RimFire 28-26-1300
With an APC SF 7X4 and a 3S battery, the Adam One motor and prop calculator gives an Input power of 107 watts ( 10A current) and 79 watts going to the prop at 11764 rpm for this 1300 kV motor. Thrust is 20.4 ounces and approx. level flight speed is 49 mph. Full throttle duration is 9.5 minutes.

AXI 2212/20
The same calculator, for the same prop and battery, gives an input power of 91 watts (8.4 A Current) and 72 watts going to the prop at 10998 rpm for this 1150 kV motor. Thrust is 17.7 ounces and approx. level flight speed is 46 mph. Full throttle Duration is 11.2 minutes.

Increasing kV to 1400 for a custom motor with similar parameters to the Axi one in the AdamOne calculator, gives an input power of 132 watts (12.4 A Current) and 101 watts going to the prop at 12168 rpm. Thrust is 21.9 ounces and approx. level flight speed is 51 mph. Full throttle Duration is 7.6 minutes.

This is similar performance to that found by Dr. Kiwi for the Suppo 2212/10 (28-30) 1400kV motor I found on the Altitude Hobbies site. The % rpm versus V x kV is near 80% also.
Last edited by DuPageJoe; Nov 05, 2015 at 10:09 AM.
Nov 13, 2015, 03:48 PM
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Insignia added to Vulcan

There may never have been a Vulcan in RAF service with this combination of grey paint and non-camo roundels, but there is now one like it in my service. I used my ink jet printer to make the insignia, which I coated with a Testor's clear lacquer. I attached the insignia with spray adhesive applied to the paper back.

I need to add the insignia of my Helicopter maintenance battalion from '71 as a squadron patch.
Nov 19, 2015, 01:09 PM
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Adding Servos and Motor

I added the Tower Pro servos to the Vulcan. They fit in the slots I cut using the plans as a guide. I used Dubro micro connectors at the servo arms, so I could adjust the Elevon angles easily. I made the control rods from 0.047 inch diameter music wire, with a z bend at the control horn end. I used some of the poly tubing from a Dubro control rod set as a guide for the rods. I attached the guide tubing to the plane via a pair of foam scraps and Nylon wire ties on each side. I used Bob Smith Silicone foam glue to attach the tubing to the wire ties and foam scraps, and then in turn that assembly to the plane. The servos ended up being a little heavier than 9 grams each. The servos and control set up complete added 30 grams to the plane. At this point, the plane weighs 252 grams (8.9 ounces) and the C of G is 17.5 inches from the nose, 1.5 inches back of the target marked on the plans.

Next I added the motor and prop using 4-40 screws with Allen Socket heads. I used self locking nuts with poly inserts, so they wouldn't loosen. Larry Kruse put the motor on the firewall before gluing it to the plane. That might have been a bit easier to get the screws tightened, but the tradeoff is the possibility of the firewall shifting while the glue sets from the extra weight on it. I made sure that the front side of the propeller faces the front of the plane, since I'm using a tractor propeller and reversing the motor rotation to get the right direction for the prop blast. At this point, the plane weighs 338 grams (11.9 ounces) and balances 19 inches from the nose. The 86 grams added by the motor and prop push the balance point back, but adding the ESC, receiver and battery should bring it to the target without adding extra weight, especially if I use a 1500mAh 3S battery weighing 4 ounces. Total weight with that battery should be about 17 ounces.
Nov 22, 2015, 04:09 PM
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Mounting ESC and Receiver

I attached the Receiver and the ESC to the Vulcan with hook and loop fasteners. The loop strips were attached to the plane with hot glue.

The plane weighed 375 grams (13.2 ounces) after this, and balanced 18 inches from the nose. This is 2 inches behind the target C of G, or about 26 ounce inches of moment to be taken care of by the battery. If the balance point of the wing and nose sheet together at 20 inches indicates the geometric center of the wing, that might be close to the neutral point, so the target C of G is 4 inches toward the nose from there.

I set up my Futaba transmitter for elevon control, so now I need to check to see if the elevons are heading in the right direction. After that, I'll use hot glue to attach the servos.
Nov 24, 2015, 12:41 PM
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Final bits for Vulcan

I added on the last 11 grams to the Vulcan when I glued in the servos, added loop fastener strips for the battery, and put on a foam Radome. I didn't glue in the servos until I programmed my Futaba Transmitter, to see if I had mounted them backwards. After I set the Transmitter Elevon function, I tried the servos and the transmitter did not need the functions reversed. The picture shows the one on the right side of the Vulcan after attaching with hot glue. The shaft of the servo is toward the rear of the plane and the arm points up toward the wing. On the left side of the plane, the shaft of the servo is toward the front of the plane with the arm again pointing up. When I pulled back on the stick, both elevons pointed up, as they should. Aileron function was normal too. The mixing on my transmitter did the job.

Larry Kruse used tape on the side of the fuselage nose to indicate the Vulcan's Radome. I decided to put some soft foam behind the tape to act as a bumper on the nose. I had some soft pipe insulation with a skin on the outside, sort of a pool noodle float, about the right size for this. The bits are shown in the process of forming. I cut the outline with scissors, then scooped out the excess foam on the inside with a single edged razor blade. I left the smooth foam skin on the outside. I attached the soft foam pieces to the nose with white Gorilla Glue, using masking tape along the outer seams to contain the foam from the glue. I covered the Radome with black Duck Tape, as shown in the last picture.

These last bits brought the airframe weight to 386 grams (13.6 ounces) without battery. The airframe balanced 17.5 inches from the nose. That is 1.5 inches from the target, easy to balance out with a 3-4 ounce battery of 1000-1500 mAh.

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