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        Build Log Nico Hobbies Su-47 Berkut Profile Pusher w/ Simple TV

#1 crxmanpat Jun 12, 2010 10:36 PM

Nico Hobbies Su-47 Berkut Profile Pusher w/ Simple TV
 
10 Attachment(s)
So I've been a real big fan of pusher jets every since I first flew a tomhe Mig-29 almost 3 years ago. So much a fan in fact that I bought Nico Hobbies from a friend of mine in order to keep the mini pusher jet business going.

In order to create some new planes, I learned QCad. So here's my very first plane that I drew from scratch. I chose the Su-47 Berkut because I hadn't seen a profile mid-motor one done here before. Come to find out just the other day that birdofplay had also done one. :p I didn't find it in my search because it is over in the Scratchbuilt forum.

I started with the larger airframe first. I've found that a bigger all 6mm plane is easier to design, build and tweak before creating one in a smaller size. Here are my stats:

Wingspan - 31.35"

Length - 42.15"

Controls - Tailerons with airlerons tied in

Build material - 6mm depron

Motor - Suppo 2212-6 2200kv outrunner

ESC - Suppo 30A

Servos - 2x HXT900 9gr

Prop - EMP 6X4E (APC 6X4E works too)

Battery - 3S 2200mAh 20C (needs the weight to make CG)


Dry Weight - 10.5oz, 297 grams

AUW - 16.7oz, 473 grams


Attached are the Full, Tiled Letter and Tiled A4 plans. Decals are currently being created and will be added to this post when completed. If there is any interest in cut kits with hardware, I'm sure I could come up with something for the website.

These plans and decals are for personal use only and may not be copied or altered for commercial use.

A complete build log follows this post.

Pat
www.nicohobbies.com

#2 crxmanpat Jun 12, 2010 10:47 PM

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OK, here's the full build instructions (I'll do these in a series of posts).

First, prepare the wing spar channel by laying a piece of blue painters tape over the entire channel. Then flip the wing over and frame out the channel with blue tape.

Next, mix up enough 5-minute epoxy to fill the entire channel. Fill the channel with epoxy and insert the CF rod (I use 5mm OD tube). Press the CF firmly into the channel until the epoxy runs out, then scrape off the excess with a straight edge, like an old credit card.

Allow the epoxy to start setting up. Once it is sufficiently hard, but BEFORE it cures, peel the tape off both sides.

Pat

#3 crxmanpat Jun 12, 2010 10:57 PM

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Next, prepare the control surfaces for hinging. I find it's easier to hinge now versus after construction.

First, you will need to add supports to the elevons as they have a weak spot. I used some 1mm x 6mm CF stick. Epoxy the CF stick as indicated in the pics.

Next, use a sharp knife or sandpaper to cut angles into the leading edges onf the control surfaces. I use scrap flexible plastic packaging for hinges. Packing tape also works well.

After hinging the elevons, move on to the ailerons.

Pat

#4 crxmanpat Jun 12, 2010 11:03 PM

7 Attachment(s)
Now glue the body pieces together. Allow it a little time for the glue to set up. Then glue on the intake sides. Next glue on the bottom fuse section. These pieces will help support the joint in the body pieces.

Next glue on the upper fuse section, the belly pan, and the upper and lower rear fuse sections.

Pat

#5 crxmanpat Jun 12, 2010 11:12 PM

5 Attachment(s)
Now it's time to glue on the intake dividers. Before gluing them on, you need to cut angles in the foam where it will glue to the airframe. See the pics for more info.

Then glue on the vertical stabs. They need to be at a slight outward angle, so sand or cut angles in the foam where it glues to the body. Also sand the tabs to assist with the fit.

Now you will need to decide how you want to attach the belly pan hatch. I like to add tabs to the front of the hatch, and glue supports onto the belly pan to keep the hatch in place. Then you can use velcro or magnets to keep the hatch securely in place.

#6 crxmanpat Jun 12, 2010 11:22 PM

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Now you need to prepare and install the motor mount. You need to cut a ply mount from 1/8 lite ply to match the foam backer. Prepare the ply mount by taking the X mount from you motor and marking the screw holes. Then drill the holes with a 1/16 drill bit.

Now take your mounting screws and tap the holes. This will make it easier to install the screws later.

Now glue the ply mount to the foam backer. I use hot glue for this. After the glue cools, retap the holes with the screws. Then glue the motor mount assembly onto the plane. Make sure the ply is to the prop slot. I use hot glue here as well.

Finally, glue in your control horns.

This completes the assembly.

Pat

#7 crxmanpat Jun 12, 2010 11:34 PM

4 Attachment(s)
Final steps.

Now that the plane is completely assembled, all that's left to do is some shaping and installing the electronics. The intakes on the full size bird are quite rounded. In order to make the plane look a little more scale, I sanded the edges round as much as possible. You can get a greater rounded effect by adding foam doublers on the interior of the electronics bay.

Prior to installing the electronics, I masked off the areas that were to remain white, and then spray painted the entire plane with Testors flat black. In order to keep the paint from bleeding under the tape, I brushed on a thin layer of WBPU and allowed it to dry.

For the electronics, I put the ESC on one side and the RX on the other. The lipo goes all the way forward in the electronics bay, and I put it sideways. This required that I remove some foam from the lower fuse piece right at the front of the bay.

I will be adding decals as soon as I have them created.

Maiden is scheduled for tomorrow morning depending on the winds. For the CG, I am starting at the forward edge of the wingtips.

Pat

#8 Dark Angel Jun 12, 2010 11:37 PM

She looks sweet! Good luck on the maiden.

#9 crxmanpat Jun 13, 2010 02:13 PM

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Success!

Well, sort of. Got out to the field this morning and the weather was perfect. Very light winds right down the runway. Installed the lipo and did the final checks before maiden. All looked well.

Throttled up and launched. The plane immediately wanted to dip down, and I have too much throw on elevator. Need to turn that down some. Dailed in several clicks of up and she was flying hands off. No aileron trim needed at all.

I did two laps at 3/4 throttle to make sure she was trimmed and to check the roll rate. Rolls are nice, but not too fast. Feels good where it's currently at. This plane looks fantastic in the air! You can hardly tell it's a profile bird.

On one of passes it looked like I had a little wiggle in the wings, but didn't think much of it. So at the end of the second pass I turned in to the runway for a WOT pass. The wingtips fluttered and promptly departed the airframe! I forgot that forward swept wings need support all the way out.

So I immediately cut throttle for an emergency landing out in the weeds. But as soon as I did, she set up into a nice glide. So taking a chance I throttle back up to half to see how she flew. Amazingly I was able to get her right back to me with no further damage!

So I will glue the wingtips back on and add some CF for support. I'm updating the plans and will put the revision up when done.

Pat

#10 crxmanpat Jun 13, 2010 03:10 PM

Updated plans added to the first post.

Pat

#11 crxmanpat Jun 13, 2010 07:13 PM

Damage has been repaired and ready for more flights!

Pat

#12 birdofplay Jun 13, 2010 08:11 PM

Winds here were BUSTIN' all day.
20 - 30 mph !!!

Sorry for your Clipped wing experience.

Allz well that endz well, eh :-)

See this pic from my su-47 thread ...
http://www.rcgroups.com/forums/attac...mentid=1672185

#13 kwinters Jun 13, 2010 09:18 PM

Pat,

My second SU-47 had constant chord ailerons of 1.25" - very lazy roll rate. I increased the chord to 1.60" on my third and current plane and I'm VERY pleased with the roll rate.

Yeah, definitely need cf running wingtip to wingtip...

Your SU-47 looks great!

KW

#14 birdofplay Jun 13, 2010 11:21 PM

Pat, I was just comparing "our" versions and noted that ...

Your version might be easier to balance than mine was as your motor/slot
is further forward.

#15 crxmanpat Jun 14, 2010 09:05 AM

Yeah, I wanted to get it as far forward as possible just for that reason. Once I find the good CG on mine, I may be able to balance with a 1350 up in the front part of the bay. Using a 2200 right now.

I'm going to fly it again on Friday and try to have Jim and Tina get pics and video.

Pat


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