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Nov 07, 2012, 09:32 AM
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Build Log

Another Shrike Build - 40" span electric

This build actually began in June 2011. It's one of those projects that started great, then other things came up. Well, I'm hoping that having a build thread will keep me going at it more until I reach the finish line.

When done, this will be the 5th Shrike I've built (although it started as #3). It was sized to take an E-Flite Habu 32 fan which I still have in the box. The wing panels are almost exactly the same size as the Habu 32's - if you wanted to build a quick one, that would be a neat place to start.

Later on I decided to stick with a prop, as the added expense of new battery packs and a charger for them (I have several 4S chargers, intentionally to limit my model size/cost), it would be better to stick with a conventional power system for now.

Construction began around the nose gear. I made a ply box which included the steering servo and the E-Flite electric retracts. The nose retract box would have been needed for the EDF version. It turned out handy for this one, though probably a bit overkill in both strength and weight.
Last edited by AndyKunz; Nov 07, 2012 at 01:08 PM.
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Nov 07, 2012, 09:42 AM
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The next thing was to get started on the wings. The ribs are NACA 0012. On the other Shrikes I used a 15% airfoil, but with the expected higher speed I went with 12% for this one. The holes are for the wing joiners.

The root rib gets a ply doubler between the joiners to keep them from ripping out. There will also be small disks to spread the load on rib 3. That gets added later, but it could have been done now.

Wing assembly is very straightforward. The spars are poplar because it's what I had on hand, the TE and LE are hard balsa. The ailerons are built up, and will be joined to the wing when it is sheeted (it gets fully sheeted). The hardest thing was to make a tapered TE - next time I think I'll laser cut it
Nov 07, 2012, 09:51 AM
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While the wing glue was drying I started on the tail components. The horizontals are all made from 3/8" square medium to hard stock. The corners are pinned together with 1/8" dowels after the initial glue dries.

The verticals are built from 3/16" thick and are pinned with toothpicks (5/32" dia).

The fins plug into slots in the elevator, and the slots are angled to 10 degrees to match the Shrike look. You can see I've put some extra stab outside the fins, a difference from the stock Shrike. I did this because I wanted to increase the elevator area to be able to increase the angle of attack during landing. The elevator behind the fuselage is virtually useless because of the blanking, so I planned to extend it to the outside. It would look cooler, too
Nov 07, 2012, 10:03 AM
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Back to the wing, now to sheet it. The TE was sheeted first so I could add the ailerons. They will be built onto the lower sheeting. Note that the supports for the retracts aren't in there yet, although they should be. The reason is that I'm designing as I build. That's what happens when you don't want to finish the drawings first!

While that dries, I started sheeting the fins and rudders. Yes, I actually did plan the sizes using the width of the wood as a constraint. That's 1/32" sheet.

The extended stab is sheeted, to side first. This will make it easy for me to cut the slot from beneath so the fins plug straight in. After sheeting the rest of the surface, I had to make hatches for servo access. Because I was planning on an EDF, there wasn't any room in the fuselage to hold the servos. My plan is to mount them inside the stab, both elevator and rudder.
Nov 07, 2012, 10:09 AM
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Here you can see the entire wing top side has been sheeted, the landing gear mounts are installed, and the servo access panel immediately behind it is ready. The straw is from McDonalds and is the perfect size to use as a conduit for the wires.

The aileron ribs are 1/8" sheet cut to triangles. These are sanded to match the taper for the wing, and the sheeting at the TE is beveled at the same time to accept the other side's sheeting. The two thick ribs (3/8" sheet) are where the aileron control horns will be mounted., and where the wing will be trimmed back to fit the stab that is right against it.

Finally you can see all the flying surfaces together. The ailerons still need to be cut off the wing panels, and the rudders need to be hinged. The elevators have not been made yet. Somehow in all my building, I forgot to do them! Just plain forgot!
Last edited by AndyKunz; Nov 07, 2012 at 10:16 AM.
Nov 07, 2012, 10:26 AM
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Now let me take a little detour.

As I said, my original plan was to build this for the Habu 32 fan. To that end, I actually did some work on the fuselage while I was working on the flying surfaces as described above.

The fan is bolted to two hardwood rails that run much of the fuselage length. They form a sort of keel. To this keep I attached a 1/16" ply that defines the edge of the wing/fuselage interface.

Alignment holes are made in it for the wing joiners and for the straw "conduit."

None of this will be used in my prop-driven model, but I still have the parts in case I ever decide to change or build another set of wings.

The nosewheel assembly would be mounted to this, and the rest of the fuselage made of foam blocks, then sanded to shape and glassed over.
Nov 07, 2012, 10:33 AM
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The prop fuselage is the same simple balsa box that we all know and love. This one is sized a bit larger than normal because I wanted room inside for extra goodies. This photo was taken when I had the model together for the first time so that I could set the length of the mains to match the nose.

Because it was originally intended to be an EDF, the nose strut is a bit short. My prop is limited to 9" diameter. Inside those blocks of wood is a Power 25, and one of the higher Kv versions should be perfect for a 9" prop on 4S.

This catches me up to the minute on status. I need to start carving the cowl now so I can post some more photos.

In the last photo in the bottom left corner you can see a box for a Speed 400 Shrike kit. That will hopefully assemble itself this winter too.

Nov 07, 2012, 02:59 PM
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Opening up the wheel wells and servo hatch were straightforward. The initial servo hatch cuts were to match the internal sides of the hardwood edges. Next, they were opened up a bit more, just to remove the sheeting. This makes it easy to have a ply plate that fits down flush.

The ply cover it then cut to fit snug, and lightly sanded to make room for the covering that will wrap over the edges later. Holes are located on the plate, then drilled. The plate is put in place and the matching holes in the wing are drilled and then tapped for 2-56 bolts.

This is the same series of steps used to fabricate the plates for the tail. The servos will be mounted to the plate with the arm extending. Removing the hatch will thus give unfettered access to the insides which will hold remote receivers and telemetry gadgetry.
Nov 07, 2012, 03:05 PM
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Those wing steps were done while the glue in the cowl corner triangles was drying. This will give a bit more strength to the cowl which is needed while working it, as well as provide a little more meat for trimming and streamlining the shape.

I use the spinner as a centering reference, with a pencil trace to show the position. Taping up the spinner protects it while sanding.

In order to work on it easily it's necessary to glue the cowl on temporarily. I will be carving the cowl and rounding the corners on the rest of the fuselage to blend everything together.

After that we will pop the cowl off and hollow it out more to remove weight. But that's getting ahead of ourselves...
Nov 07, 2012, 04:07 PM
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OK, I'm finishing up my vacation with one last photo. A little work with a knife, followed by some real coarse sandpaper and then finer and then the soft sander. Quick work, looks great, feels nice and silky smooth.

Can I inject a plug here for a second? Last year I was given a Craftsman dust collector like this one.

What a difference it makes in my shop! Yes, it's loud, but the belt sander, table saw, and sanding bars no longer coat everything with a patina of dust. It's also helpful by reducing the coughing.

I'm back to work tomorrow, no playing during the day.

Nov 07, 2012, 04:20 PM
Surface, Air & Water Rc Toys..
Nice, I need to start building or atleast continue/finish my B17.
Nov 07, 2012, 04:50 PM
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Wait until you see some of the other projects sitting on my bench. My goal for this winter is to clean the bench off by (re-)building the models on it.

Some haven't been touched in a long time. One was started by my father when I was a little kid. You'll enjoy it - it has a slight French connection to it

Nov 08, 2012, 05:03 PM
Mustang Fever
Nice work, Andy

I have an Extreme Flight Outlaw with a 25 size outrunner in it, on 4S, turning a 10x6. It has an unlimited vertical and a top end of about 75 mph. I think if you use a 9x10 or a 9x12, your Shrike will maybe go supersonic.

I'm currently building, with lots of breaks, a Dan Savage F4 (90mm EDF). I keep telling myself I'm going to finish it. I'm going to finish it. I'm not going to buy any more plans for any more airplanes until this is flying. Right. The 10' Martin mars awaits.

Nov 08, 2012, 10:56 PM
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Hi Bob,

Electricalc says only about 110-120 depending on motor, but that's under 40A.

I had about 3 hours to play tonight, so I worked on the fuselage hatches.

These hatches were built by creating rails (essentially a frame) that matched the inner edges of the fuselage. Anywhere I didn't want glue to stick them together I used thin cellophane tape to mask the wood. Tape was applied to the fuselage between the side and the rails, around the top edge where the top sheeting would go, and between the sheets that defined the front and rear of each hatch. The frame was inserted and pinned into position. I glued the top sheeting on taking care not to get too much onto the tape, and then pinning the top sheeting to the fuse sides, not the rails. During my sanding time last night the hatches were held in place by friction and by the small amount of glue sticking to the tape. Separating them was easy by just sliding a knife under and gently twisting. They popped right off.

To remove the cowl, I first unbolted the motor so it wouldn't break the cowl as I gently whacked it with my palm to pop it free. Next step was to remove the excess wood from the cowl (I left a generous 3/16").

The nose gear bay was simply cut open. I will be making a separate door for it using similar technique to what was done above. It's much easier to make a new one than try to exactly find the edge of the wood for cutting it out.

After that, I made corner blocks for the front hatch back edge and embedded magnets in them. This will be my battery hatch and needs to open quickly. The rear hatch will be for my rx and electronics, so it won't be opened very often. The front edge is held in by dowel pegs, and the rear by a 4-40 into a small block of wood.

Tomorrow I plan to make the connect points for the cowl.

Nov 09, 2012, 09:34 AM
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