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Old May 23, 2010, 03:19 PM
AndyKunz's Avatar
Illinois
Joined Sep 2001
22,326 Posts
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Shrike Build

Two years ago I had put together a Shrike 400 kit, powering it with a Mega 16/15/4 and 3S. It was FANTASTIC - even the jet jocks in the club liked it. Our club has a paved runway, and I've been battling shoulder problems for several years, so I gave the plane to a friend rather than punching a hole in the ground with it.

Our club had to postpone our Builders Contest for two weeks due to wind. GREAT! I suddenly had an excuse to build something I've been wanting to since I gave the Shrike 400 away.

I took the plans for the smaller one out, traced the outline into TurboCAD, and re-scaled it to 35" span. I then set about reducing profile drag on the fuselage, and changed the airfoil to a NACA 0015 for stability without too much drag. I also added retracts and a new internal structure and changed the construction techniques in several places.

First, the fuselage was built. The round holes are where Dave Brown pushrods will go through it (the wing is built using them as a wing jig like we did in the 70's). The square hole is where the LE of the stab goes through. The motor mount was set up for an E-Flite Power 25 Heli, but I'm cutting it back to a Power 10 on 4S to save weight and not give up much speed.

Andy
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Old May 23, 2010, 03:28 PM
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Illinois
Joined Sep 2001
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The wings were built using Dave Brown pushrods as a wing jig. The LE was sheeted top and bottom, as well as the top of the center area. In this photo, you can see I have installed E-Flite electric retracts in the wing. The servo is mounted on a removable plate. The paper tube is Estes BT-5 serving as a conduit for the retracts and aileron leads.

On the right wing you can see a faint outline where the wheel wells will go. They are made by boiling 1/16" sheet for about 5 minutes, then wrapping around a 2" rattle paint can and allowed to dry overnight. They are trimmed to length, then glued into the top sheet.

Andy
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Old May 23, 2010, 03:35 PM
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Illinois
Joined Sep 2001
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Meanwhile, the stab is built from 3/8" square balsa. The LE was not glued on, but it pinned firmly into place to keep everything together. After the glue dried, all the corners were drilled out to accept 1/8" dia birch dowels for pinning them together. I prefer pinning then this way, much as furniture is done, because it seems to be stronger and lighter than gussets. It can't be used everywhere, but at this thickness it's very good.

In this photo you can see the stab positioned beneath where it will be on the fuse. You can also see the nose gear in its well. The battery access is behind the nose wheel, in the 6" space between the DB pushrods. You can also see the 1/32" x 1" ply doubler that runs from the rear spar up to the firewall.

You can also see the cowl in place. It was built from four (top, sides, bottom) of 1/2" balsa sheet with a 1-3/4" nose ring. The motor is installed and a plastic spinner to serve as a sanding guide. This is a good use for plastic spinners - sacrificial sanding templates!

Andy
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Old May 23, 2010, 03:41 PM
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Illinois
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This photo shows the view inside the nose gear bay. It is mounted on a sheet of ply (1/8" thick x 2" long, with the front section doubled up for 1/4" x 1"). If I had been working with laser-cut parts, I would have keyed these all together. There is also triangle stock on the top side of the plate to ensure maximum gluing area. The ESC will be on the top of the fuselage, getting air from the firewall on its way out the back end. You can see a small hole in the firewall in the first fuselage photo. This will be opened up to promote breathing. Smaller size permitted me to get the wires out of the way and have a pilot hole for later.

You can see I left the leg long so that I can adjust the length later. This will be used to ensure I have adequate prop clearance. In the top right corner of the bay you can see the nose steering servo. There's a ton of room in here. I will be making a doors for all wheels. That's always the hardest part of them for me.

Andy
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Old May 23, 2010, 03:45 PM
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Illinois
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In this photo you can see the wheel wells for the main gear. Nothing special here, just to show the next step. The area around the mechanism is built up with soft balsa, then sanded back to give a smooth surface when sheeting the bottom.

Andy
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Old May 23, 2010, 03:52 PM
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The wing bottoms were sheeted, then the excess sheeting on the LE, root, and tip was removed.

Aside from the messy workbench, in this photo you can see the DB pushrods in the wing. These will not be glued in until after covering and final assembly. The cowl is held on by socket head screws that are countersunk into the cowl. They screw into a tapped hardwood block, with a 1/32" ply backing epoxied into the cowl. The cowl is also hollowed out to about 3/16" thick.

The fins were built in the same manner as the stab from 1/4" thick hard balsa. I used toothpicks to pin the corners together (pre-drilled, of course).

If you look at the TE of the wing you will notice that it's much taller than the sheeting there. This will be sanded off eventually. First I need to cut the ailerons to shape and tack-glue them to the TE in the correct place. Then some aggressive sanding will make a smooth transition for the wing there. That will help keep the drag down while preventing flutter and erratic flying.

Andy
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Old May 23, 2010, 04:01 PM
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Illinois
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So then Saturday we held the rescheduled Builders Contest. I was up until 1:00 in the morning working to get it presentable. The Shrike won first in the combined
Designer/Plans/Kits category. BTW, the abundance of E-Flite and Hangar 9 products is because they have the products I need for something like this, but is helped along by being a Horizon employee.

The Shrike will be finished in the same orange/white/black scheme as my Kaos 40 beside it. The Kaos took first in the BARF category, so it must be something appealing about those colors Actually, they're very visible in the air and should be good for my eyes to track.

Andy
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Old May 23, 2010, 05:57 PM
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Great looking Shrike Andy!
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Old May 23, 2010, 08:16 PM
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Illinois
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Thanks for the comment.

Tonight I show the ailerons tack-glued in place. I will be doing a little carving (just a little) to remove big chunks of wood, then sand until the wing and aileron meet (also doing the wing tip at the same time). The TE of the wing portion is thicker than it needs to be so that I can safely sand for a perfect fit.

BTW, this thread is my answer to the other thread "How do we bring model building back?" Basically, show how to do it, and how much fun it is. It will end with how much fun it is to have something different than the rest of the guys at your field

Andy
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Old May 24, 2010, 09:21 PM
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Tonight I sanded the TE and wing tip. A little filler will be needed in a couple places to ensure the covering is smooth. You can also see the tools I used - a knife to carve the big stuff away, a coarse sanding block to make things straight and do the rounding of the tip, and a flexible block to make everything smooth.

Andy
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Old May 27, 2010, 06:12 PM
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Covering starts tonight!

Andy
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Old May 27, 2010, 11:14 PM
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Old May 29, 2010, 03:59 PM
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Illinois
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I've been away working on the plane and not taking as many photos as I should have. Covering is just about complete. I wanted to show a little trick I use, which is especially important on the Shrike.

We all know you can't glue to covering and expect your model to stay together, and we always do most of our covering before assembling components. So how do you make nice edges and remove the covering where it normally gets so that you can make a strong glue joint?

On the Shrike, this would be the wing roots to the fuselage and the vertical fins to the sides of the stab.

Here's my trick. I make a template the size of what I want to glue using masking tape. It is about 1/16" to 1/8" smaller than the surface (larger surface area is better). In these photos you can see (if you look closely, it's hard to see) where I put masking tape on the side of the stab before covering. I then covered the stab normally, and then cut the film away using the masking tape as a guide for the tip of the knife blade.

In the second photo, I have removed the masking tape and covering that went over it. You can see a nice glue surface left behind. You can also see the 1/8" dowels that peg the stab together.

My goal is to have the Shrike ready for a Memorial Day maiden flight.

Andy
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Old May 31, 2010, 02:45 PM
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Illinois
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Well, it's flyable! The only thing I need to do is attach the main gear doors. Being a holiday, a bunch of the guys from work showed up at the field to get some fun flying in. David Payne had the honors of the first flight, not only because he's great on the sticks but he's also flown a Shrike in the past. I set up the rates on the DX8 to give three range settings for him to get me in the ballpark. After some more tuning flights I will put the finalized throws on the plans.

Unfortunately, my friend wasn't able to keep up with the plane with the camera, so all the pix are on the ground.

If you look closely at the wingtips, you can see I installed LEDs from the E-Flite light kit. They aren't visible in normal daylight when flying If I'm ever up at dusk (not likely with a hot rod like this!) they may help. Otherwise, they're just for the "cool factor."

First flight was 5 minutes on 2200 mAH 3S 30C Thunder Power cells (E-Flite Power 10 with APC 8x8E). When I took it over to the charger, it was still at 45%, so I put another 2 minutes on the timer for the next flight.

Shortly after he landed, a cold front came through with some heavy rain, so I packed it up and came home so I could post these.

Andy
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Old May 31, 2010, 02:53 PM
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United States, IL, Riverwoods
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Shrike build

Love the plane. I think I will build one. Can you show how the hatch for the nose wheel works?

Thanks, Jim
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