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Author Topic: SR-71 Blackbird  (Read 5880 times)
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Crabby
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« Reply #25 on: December 10, 2015, 08:14:11 AM »

I talked about launch because my Mig 15 wouldn't fly unless I launched it at initial power-burst speed, after that it would cruise around really happily. But if I did a gentle push it would do any number of insulting things on its way into the dirt. Not a ducted fan model, just a simple prop tractor...I see the obvious differences in the two. I just wanted to raise some awareness.
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« Reply #26 on: December 10, 2015, 10:11:38 AM »

Really interesting!!! Have you contacted Tobgun? He build a Concord, but aparently didn´t last too long  Undecided. Anyhow, he have experience with a prety similar type of plane (long fuselage, delta wing..) http://www.schauggspace.de/my_hangar.htm
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« Reply #27 on: December 10, 2015, 11:11:42 AM »

Really interesting!!! Have you contacted Tobgun? He build a Concord, but aparently didn´t last too long  Undecided. Anyhow, he have experience with a prety similar type of plane (long fuselage, delta wing..) http://www.schauggspace.de/my_hangar.htm

I miss his work. Very innovative.

He built two Concordes. The second one flew great and there's a video of it in there somewhere.

I think the SR-71 and the Concorde are both excellent FF subjects if built light. One could probably set them up as twin pushers and get great performance and ridiculous bonus points at the same time. Not to mention the cool factor.
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Tyrannt
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« Reply #28 on: December 10, 2015, 11:47:25 AM »

Want to thank everyone for the help.  I have to say I am really excited about this.  I am a slow builder and the only time I can build is burning the midnight oil. Because of this I started to lose interest. You all have rekindled that spark. Thank you.

Last night after reading your comments. I had to find out where the center of gravity is right now. I put a small piece of tape to hold the nose cone in place. Found where my landind gear goes. And balance it.  Just about perfect balance at that point.  I would have never figured on having to add nose weight. I now know its going to need some. ( didn't have the rudders on.)

Next step for me is to use my dremel and sand I little out of each bulkhead in the engines.  I have the bulkheads for the engines cut and notched, along with the fuselage bulkheads.

I always planned on it being a pusher, but entertained the idea of a multi.  Three props. Two in front of the engines.  I also thought about turning the engines in to rubber powered duct fans.  I already am in over my head in this build, so decided to keep it simple for this one. One prop, pusher style.
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« Reply #29 on: December 10, 2015, 03:58:46 PM »

One of the other reasons I decided to just go only with a pusher prop, is that the two front propellers could only be 2 1/2" max.  I thought the weight vs. Usefulness about the same. Launching it would be a whole new set of circumstances.  If you look closely at the engines you will see that it was set up for multi propellers.

When I was a kid. I used a ten foot piece of rebar set in the ground. Had about ten feet of 1/8 rubber attached to the top. Used a paperclip for the hook. Models were around 10".  Flew for three or four seconds at a time. Hours of fun.

I realized that the two attachments with my ruler didn't upload so I am attaching them now.
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Re: SR-71 Blackbird
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Crabby
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« Reply #30 on: December 12, 2015, 09:23:13 AM »

Everything looks straight as a pin. Great craftsmanship going on here!
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« Reply #31 on: December 12, 2015, 09:25:44 AM »

Really interesting!!! Have you contacted Tobgun? He build a Concord, but aparently didn´t last too long  Undecided. Anyhow, he have experience with a prety similar type of plane (long fuselage, delta wing..) http://www.schauggspace.de/my_hangar.htm

 One could probably set them up as twin pushers and get great performance and ridiculous bonus points at the same time. Not to mention the cool factor.

Now I am getting turned on! a twin pusher would be wayy out cool!
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« Reply #32 on: December 14, 2015, 02:05:44 PM »

Really interesting!!! Have you contacted Tobgun? He build a Concord, but aparently didn´t last too long  Undecided. Anyhow, he have experience with a prety similar type of plane (long fuselage, delta wing..) http://www.schauggspace.de/my_hangar.htm

 One could probably set them up as twin pushers and get great performance and ridiculous bonus points at the same time. Not to mention the cool factor.

Now I am getting turned on! a twin pusher would be wayy out cool!


Ain't nuthin' like em. They always fly well, and they fly for a mighty long time, too.
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Tyrannt
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« Reply #33 on: December 14, 2015, 03:11:51 PM »

I want to give a special thanks to copbait73 and sky9pilot for the center of gravity on the blackbird.  That was a great big help.

Crabby, I would love to see a multi.  I would suggest using motor sticks.  The props need a little distance to clear the leading or trailing edges.  Other wise you have to use really small props and spin them really fast.
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« Reply #34 on: December 14, 2015, 07:06:33 PM »

Thank you.
One more thing. Based on my experience with many jet type configurations I believe any rubber motor configuration other than a prop at the extreme nose will make your model too heavy to fly.
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« Reply #35 on: December 27, 2015, 09:03:03 PM »

I have flown a few RC SR71s. They are very sensitive to roll input. Very little aileron will make them roll very quickly so keep those adjustments small. The fuselage makes lots of lift but get the nose up a little too high and it will flip over itself. So my guess is a smaller prop with low pitch and a long loop of rubber may be a good way to go. The CG on the ones I had were more forward closer to the notch by the engines. One ballpark way on a jet CG is to look at the main gear in the extended position then make a 15 degree angle going forward, that will be a approximation of the CG. The reason being that they want the plane to rotate easily for takeoff. Not a hard fast rule but a good way to estimate when the model is complex in shape.
« Last Edit: December 27, 2015, 09:13:04 PM by dslusarc » Logged
Tyrannt
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« Reply #36 on: January 05, 2016, 03:28:21 PM »

I have question for everybody. Have you every had a model you are building and something keeps bugging you. You think about it but just can't figure out why.

This happened to me. Something kept bugging me and I finally figured it out. My cockpit was all wrong.  The window supports run up and down, not front to back. The cockpit also sits a little more forward then the rest of the body blending. I got it fixed and feel a lot better about it now.  It's all the time I have had to work on it though.

After rereading all the many posts.  I am getting a little concerned about having a flat wing,  I am putting on plastic tabs on the end of the delta wing for adjustments. ( still can't believe I missed them in the building). Do I slice and dice my outer wings and  put in a 1/4" of dehydral or rely on the plastic tabs.  Now is the time to fix this. I can still pin it down to the building board flat. I haven't started building the bottom stringers yet.
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Super64
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« Reply #37 on: January 07, 2016, 11:12:22 AM »

Hi Tyrannt,

I will give you my humble, very stale opinion, since I haven't built in ages.

I put together an Me262 and failed to properly build the wings, all she did was roll off to one side or the other.

The wings need sufficient dihedral so that the tips are above the thrust line.

Please continue, this is fascinating.

-Joe  Cool
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Tyrannt
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« Reply #38 on: January 07, 2016, 03:06:01 PM »

Thanks super64.

I am going to put a 1/4" dehydral in the outer wings.  I was looking at it last night and realized that it wasn't as bad as I thought.  I just need to cut a small triangle out of two spars on each wing and push them up. Then add a 1/32" gusset to each side of the spars.  Maybe just the front spar.  I will leave the leading edge and trailing edge alone and just let it curve up with wing.

Made a little progress on the blackbird last night. Put most of the bulkheads and stringers on the bottom of the fuselage and the engine bays.  It really adds a lot to the look to see the bottoms on.

Still have to work on the tail end of the fuselage. Need some more thought on how I am going to do it. Haven't figured out how to bring the top and bottom together and leave enough room for the prop hook.

Thanks for all the kind words and help with this project. I have learned some much from everyone.

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Tyrannt
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« Reply #39 on: February 15, 2016, 06:55:57 PM »

Hi everyone.  Sure have been enjoying everyone's builds lately.  I am amazed at all the great work and lessons I see here.  Haven't had much time for building lately, but, doesn't mean I can't watch everyone's else.  Thought I would give you all a quick update.   Progress has been made. It's moving forward now. More about that later.

The bottom stringers are on as I mentioned in my last post.  I broke off all the stringers I had left long for the tail ends on the fuse and engine bays.  I decided to do the engine exhaught ducts differently than originally planned.

I taped the nose on for the head on shots.  I saw where someone took a picture down the fuselage, I thought it was pretty cool, so I copied them.  The pictures didn't come out as well as I had hoped, but you get to see them anyway.

Oh no here it comes, why I went backwards.  The last picture is the weight.  I have never used a scale in building. I have to admit it's been an eye opener.  I kept watching the weight grow and grow.  The bottom stringers and their bulkheads add 4 grams of weight alone.  I was starting to freak out about the weight.  Thats when I figured out my weight problem.  I have been building this all out of 1/16" balsa, when I should have been using 1/32".  (Why do i, all of a sudden, start hearing laughter and "ROOKIE."). I decided to sand down all the stringers I could, instead of starting over.  After several hours of work with a disposable finger nail file, I have taken over 4 grams of weight out.  I sanded down the outside to where it needed to be, then carefully sanded the inside of all the stringers to around 1/32".  All ready started stripping some 1/32" to finish the rest of the plane.

Next up. Finishing the tail end of the fuselage and install the thrust button.  
Attached files Thumbnail(s):
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
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« Reply #40 on: February 15, 2016, 08:16:30 PM »

Oops. I forgot to mention that is the weight before sanding. With the nose, plane and tail feathers it now weights 16 grams.
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Tyrannt
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« Reply #41 on: August 03, 2016, 02:47:57 PM »

Hi everyone.  Well life has been getting in the way of working on my blackbird. Some good, some bad,  some real bad, but we all just keep moving on.

I have been able to get some work done on it.  Couldn't sleep a couple of nights ago, so decided to mock up the plane.  This is one of the first times I have done this.  Building most of the plane on the building board hasn't really made for a need.  Thought y'all would like to see them.

Attached files Thumbnail(s):
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
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Tyrannt
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« Reply #42 on: August 03, 2016, 02:54:51 PM »

Forgot to mention that I added some dihedral to the wings. The now are even with the trust line. It ended up about 3/8". 

Couple of more pictures.  I really like these ones. 
Attached files Thumbnail(s):
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
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Tyrannt
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« Reply #43 on: August 03, 2016, 03:07:27 PM »

The engine noses cones are made of card stock.  Had fun trying to match the colors to a sample of balsa.  Wanted to match the balsa when I cover it in tissue.  I had a couple of problems making them. ( Posted some of my failed attempts.  There were a couple more in styrofoam.) Due to were they are at, I made them removable using a bamboo skewers.

Now the tail end.  I didn't like the trust button I had, but could not find a good one. So I installed it.  Later I found a good trust button.  When I went to take it out, and build a new one. I found I had glued it to the nose block.  I ripped out the bulkhead trying to get it out.  I am going to use the new trust button and the black propeller.  It was made as a pusher prop.

I am going to need nose weight to balance it.  It balances at the center of gravity with out the prop on.
Attached files Thumbnail(s):
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
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« Reply #44 on: August 03, 2016, 03:36:31 PM »

This is one awesome build. Well done and I know you still have more
coming. Simply Stunning!!

Skyraider
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Tyrannt
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« Reply #45 on: August 03, 2016, 06:41:02 PM »

Thanks skyraider.  This build has really been a challenge for me.

Somehow I missed a picture. I really like this one. Don't know why, but I do.
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Re: SR-71 Blackbird
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« Reply #46 on: November 24, 2016, 08:49:11 AM »

Finally the moment of the reveal.  I have chosen the NASA #844 for my model.

I love it when the history of the plane is posted. (I really learn alot by the history.)  So now, I guess it's my turn.

Facts and time line. ( Just the NASA flights)
Lockhead SR-71A (61-7980/NASA 844)
Retired by air force in 1990.
Given to NASA on Feb 15, 1990.
Placed in storage untell 1992.
Flown by NASA from 1992 to 1999.
Final flight on Oct. 9, 1999.
Placed on static display on Sept. 14, 2002,  at Dryden Flight Research Center.
Flew 734 flights including 56 NASA flights.
Total flight time of 2353.6 flight hours.
Last one of the blackbird's to fly.

Several of the missions for NASA were for sonic boom testing with other aircraft. F-16 xl, f-18, yo-3a.  Testing new electronic systems, and my favorite, the larse system. (Linear aerospike). (Imagine strapping a rocket motor to the tail of the blackbird.  Due to leaks in the oxygen system it was never truly fired off, and they got all the information they needed from the other tests.)

Still have several fiddly little bits to do.  I also am going to try and shrink up the tissue alot more.  This time with water and a hair dryer. First time was with just water, and I left it to air dry.
Attached files Thumbnail(s):
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
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Tyrannt
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« Reply #47 on: November 24, 2016, 05:16:50 PM »

For covering the blackbird I had a few Interesting problems to overcome.  I covered the bottom first.  It went on in eight pieces.  I first covered just were the rear of the fuselage were it starts to taper down to the tail.  Then both engines. Then the rest of the fuselage.  Both outer wings.  Last i did the inner wings.  

The top of the plane was the same except for the leading edge of the outer wing.  I forgot to put a glue joint in.  I ended up just glueing the tissue to tissue.  That ended up being a huge challenge for me.  

Accidentally poked a couple of holes in top. I just added a small piece of tissue and am calling it an access panel.

I covered it dry using white glue and water mix.  Using the hair dryer and more water alot of the wrinkles came out.  Still plenty left but I'm happy with it.

On the rudders, I covered them normally.  For the NASA logo, I cut a strip of copy paper a half inch wide.  I then kept copying the NASA logo untell I had it the way I wanted.  Then colored it in really dark.  I then cut another strip the same size and placed it over the top of the new template.  Then copied it with a red colored pencil.  Using a red colored pencil I copied it.  ( The S is still not right, but, I'm happy with it.) Then glue it in place with a glue stick and trimmed off the excess.

The white strips were made the same way.   The numbers were drawn out several times.  I placed a couple of pieces of copy paper between some newspaper.  Using a brand new knife I cut out the numbers I had drawn.  Then it was a matter of just picking out the best ones and glue them on.

For glueing on the rudders, I made  a jig out scrap foam board.  I traced the pattern off the plans then transfered it to the foam board.  Used two bamboo skewers to hold them in place.  Then glued both rudders in place at the same time.  Worked great.
Attached files Thumbnail(s):
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
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Tyrannt
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« Reply #48 on: November 24, 2016, 05:19:33 PM »

Not sure why the one picture went upside down.  Don't know how to flip it. Sorry.
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« Reply #49 on: November 29, 2016, 10:13:45 PM »

Nice job on the SR.... love this aircraft!  Hope to do one some day!  I look forward to your flight reports!
Tom
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