Logo
Builders' Plan Gallery  |  Hip Pocket Web Site  |  Contact Forum Admin  |  Contact Global Moderator
November 13, 2019, 10:20:25 AM *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with email, password and session length
 
Home Help Search Login Register
Pages: [1] 2 3 4   Go Down
Print
Author Topic: SR-71 Blackbird  (Read 6972 times)
0 Members and 1 Guest are viewing this topic.
Tyrannt
Bronze Member
***

Kudos: 3
Offline Offline

United States United States

Posts: 43

Topic starter


Ignore
« on: December 08, 2015, 03:32:21 PM »

Hello everyone.

I decided to post my blackbird.  I admit to being scared to do this because of the excellent work by everyone else. I haven't build a free-flight model in years. (Mostly scratch builds, with comets and sterling kits thrown in.)

I drew the plans using a ruler and a circle template.  They are what I call working plans. Good enough to build on but not complete.  There is some mistakes in the plans, that I haven't fixed yet. The not completed parts, are parts I haven't quite figured out yet.

The model.  I am building it like the moon bat.  Flat on the building board. One Problem is that 3/4 of the blackbird is on top.  When doing the engines you can't just cut the circles in half, they are now at 3/4 circles.  This changes where the keel goes.  I admit to doing them five times. I saved the engine exhaught pipes for the end, so I could get them centered.  Getting the set up and the notches right was the hard part.  I did one engine first, then the fuselage, then the other engine. Then i built the wings into the fuselage and engines.

I included two shots with my 12" ruler for size comparison.

Main info:

Wingspan 13"
Fuselage 25"
Fuselage height 1 1/2"
Wing area approximately 54" to 56". ( I used, that looks like a square and divided it in half for the triangle's.)
Engines are 1 1/2" in diameter and ten inches long. Not including the nose cones.
Wings are cracked ribs. Main spars runs in the fuselage and into the engines.
Pusher prop with the rubber running through the fuselage.  Prop size unknown. I have a six inch red prop I am considering.
I also enlarged the rudders.
Attached files Thumbnail(s):
SR-71 Blackbird
SR-71 Blackbird
SR-71 Blackbird
Logged
Tyrannt
Bronze Member
***

Kudos: 3
Offline Offline

United States United States

Posts: 43

Topic starter


Ignore
« Reply #1 on: December 08, 2015, 03:40:22 PM »

A few more random photos
Attached files Thumbnail(s):
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Logged
Tyrannt
Bronze Member
***

Kudos: 3
Offline Offline

United States United States

Posts: 43

Topic starter


Ignore
« Reply #2 on: December 08, 2015, 03:44:06 PM »

A few more.
Attached files Thumbnail(s):
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Logged
Tyrannt
Bronze Member
***

Kudos: 3
Offline Offline

United States United States

Posts: 43

Topic starter


Ignore
« Reply #3 on: December 08, 2015, 03:54:49 PM »

The two rudders. The weight right now is 17 grams. I am worried about the weight. Still have the bottom and the tissue to go.
Attached files Thumbnail(s):
Re: SR-71 Blackbird
Re: SR-71 Blackbird
Logged
faif2d
Platinum Member
******

Kudos: 31
Offline Offline

United States United States

Posts: 1,192


Sun came up I was here to see it = good day



Ignore
« Reply #4 on: December 08, 2015, 04:27:11 PM »

I have absolutely no idea why you were being shy about your build!  I think it looks wonderful, both the plans and the construction.  Thanks for sharing with us!!!
Logged

I used to like painting with dope but now I can't remember why!    Steve Fauble
Wout Moerman
Gold Member
*****

Kudos: 22
Offline Offline

Netherlands Netherlands

Posts: 620


WWW

Ignore
« Reply #5 on: December 08, 2015, 04:31:36 PM »

That is a ambitious project, and it really looks great! About the weight, I have no idea how much lift the body will generate. It might work out OK. At least you won't be needing nose weight, I guess! Do you have an idea where the center of gravity has to be placed on a free flight Blackbird?

I noticed that the wing has a normal airfoil without elevator. This might be a problem resulting in very little stability. For flying wings often a reflex airfoil is used, in which the rear of the profile is bent upwards.

I think the rudders will be stronger when the spars are one long part and the ribs are in smaller parts. But I think this is OK because they have little chance of being damaged.

Keep up the good work!

Wout
Logged

Rubber FF scale:
www.zininmodelvliegen.nl
Crabby
Titanium Member
*******

Kudos: 132
Offline Offline

United States United States

Posts: 2,176


I never met a modeler I didn't like



Ignore
« Reply #6 on: December 08, 2015, 04:38:18 PM »

FWIW remember this thing is a supersonic jet designed to fly fast. Remember to wind up and throw it like a baseball.
Logged

The Threadkiller!
DavidJP
Titanium Member
*******

Kudos: 45
Offline Offline

United Kingdom United Kingdom

Posts: 2,891




Ignore
« Reply #7 on: December 08, 2015, 05:26:27 PM »

That is rather exciting and congratulations on the workmanship and the whole choice of project.

I think it is one of those models which will need quite a bit of experimentation but will be quite fun. Possibly you could make the construction a bit lighter but there is a very good chance that it will have to fly quite quickly anyway so your flights might be a little short but impressive?

Await more please!
Logged
Sky9pilot
Titanium Member
*******

Kudos: 50
Offline Offline

United States United States

Posts: 2,733


WWW

Ignore
« Reply #8 on: December 08, 2015, 06:47:24 PM »

WoW... I love this model!  I've got quite a lot of pictures of the real bird when I lived in Sacramento and traveled up to Beale AFB their home base!  This is a great project.  I'll look forward to following this build!
Sky9pilot
Logged

Best Regards,
Sky9pilot
    "If God is your Co-pilot, consider switching seats!" 
http://www.stickandtissue.com/cgi-bin/yabb2/YaBB.pl
http://freeflightarchive.com/index.php/homepage-2
Don McLellan
Titanium Member
*******

Kudos: 63
Offline Offline

Canada Canada

Posts: 2,387




Ignore
« Reply #9 on: December 08, 2015, 08:44:30 PM »

What Sky9pilot said!  This is a great project and am also looking forward to more pics of your progress.
Logged
Tyrannt
Bronze Member
***

Kudos: 3
Offline Offline

United States United States

Posts: 43

Topic starter


Ignore
« Reply #10 on: December 08, 2015, 08:50:10 PM »

Thank you everyone for the kind words. I am my own worst critic.

Thanks for the heads up on the elevator. I will probably be adding small plastic trim tabs for elevator. Been out to long on this and totally forgot about them.

For the center of gravity. I don't really know.  My plan is to cut out a flat piece of cardboard, the size of the model. Add the rudders and fly it untell I get a good glide. Then start from there on the model.

One of the reasons for posting is I am going to need some help. Start thinking of a good propellor and rubber size.  This is one area I have always struggled at.  I have learned a lot from this website.

My son said he would teach me how to throw a baseball again. He throws over the top, and I'm a sidewinder.

I have loved this plane since I was little.  Their is just something about it.  I really love the story behind this plane. What the engineers did to solve all the problems, just amaze me.
Logged
Tyrannt
Bronze Member
***

Kudos: 3
Offline Offline

United States United States

Posts: 43

Topic starter


Ignore
« Reply #11 on: December 08, 2015, 09:12:18 PM »

Forgot to add. From prop hook to nose hook is 20".  I haven't bought any rubber yet, but plan on it soon.

Also the best way for the engine cones. Balsa build up, and hollow out. Foam. Or tissue, soaked in CA.
Logged
Wout Moerman
Gold Member
*****

Kudos: 22
Offline Offline

Netherlands Netherlands

Posts: 620


WWW

Ignore
« Reply #12 on: December 09, 2015, 02:17:16 AM »

Any idea how you will hold the plane when launching?
Logged

Rubber FF scale:
www.zininmodelvliegen.nl
DavidJP
Titanium Member
*******

Kudos: 45
Offline Offline

United Kingdom United Kingdom

Posts: 2,891




Ignore
« Reply #13 on: December 09, 2015, 06:23:04 AM »

A cross bow? Wink
Logged
Bulldogger
Gold Member
*****

Kudos: 4
Offline Offline

United States United States

Posts: 254



Ignore
« Reply #14 on: December 09, 2015, 08:30:53 AM »

Very cool.  Looking forward to following this build.  Thank-you for sharing it!
Bulldogger
Logged
Wout Moerman
Gold Member
*****

Kudos: 22
Offline Offline

Netherlands Netherlands

Posts: 620


WWW

Ignore
« Reply #15 on: December 09, 2015, 09:09:27 AM »

A cross bow? Wink
good one! I was thinking catapult.
Logged

Rubber FF scale:
www.zininmodelvliegen.nl
Copbait73
Gold Member
*****

Kudos: 10
Offline Offline

United States United States

Posts: 582



Ignore
« Reply #16 on: December 09, 2015, 09:40:21 AM »

Neat subject and excellent build.

Regarding your C/G, go to your scale side profile and locate it just forward of the main gear. Do a lot of glide testing without the prop and rubber to get this right. Make sure your evelon adjustment and C/G location give adequate pitch stability. Error to a forward position or you will have a lawn dart.

You will need evelons on your delta but your oversight will help you out. Adding clear tabs of adequate area will effectively give more wing area. Pure jets are sensitive trimming the elevens but your addition of a prop (large stabilizer) makes this much easier.

If you make this a pusher you will need noticeable nose weight. A practical solution is to place the prop at the nose. I find this unsightly and "cheating" however it is fully legal in FAC scale modeling competition.
Logged
Tyrannt
Bronze Member
***

Kudos: 3
Offline Offline

United States United States

Posts: 43

Topic starter


Ignore
« Reply #17 on: December 09, 2015, 11:42:10 AM »

The mental image of me having a cross bow was great. Loved the idea. But, no I plan on launching it like a baseball fastball.  The plane is quite sturdy in front of the leading edge. So one hand on the leading edge the other holding on to the prop.

Thanks for the help on the center of gravity.  I still want to keep it a pusher.  That way it kinda disappears in flight.  Thought about painting the prop black for that reason

What's a good kind of plastic for the trim tabs?

Logged
tom arnold
Gold Member
*****

Kudos: 30
Offline Offline

United States United States

Posts: 692


Casper Wyoming



Ignore
« Reply #18 on: December 09, 2015, 12:10:17 PM »

I would not put too much faith in the fastball launch. I ran into that problem with a ducted fan model I had in which needed a fast launch. The only problem was that the harder I launched it, the more my hand would roll like a baseball pitcher's and I succeeded in snap rolling it into the ground constantly. My solution eventually became an overhead launch like a thrown soccer ball but even that was a poor solution.
Logged
Sky9pilot
Titanium Member
*******

Kudos: 50
Offline Offline

United States United States

Posts: 2,733


WWW

Ignore
« Reply #19 on: December 09, 2015, 04:26:22 PM »

Found this I think on RCgroups... it's a ball park location for CG.  Wishing you great luck with this project!
Sky9pilot
Attached files Thumbnail(s):
Re: SR-71 Blackbird
Logged

Best Regards,
Sky9pilot
    "If God is your Co-pilot, consider switching seats!" 
http://www.stickandtissue.com/cgi-bin/yabb2/YaBB.pl
http://freeflightarchive.com/index.php/homepage-2
Big Dave
Bronze Member
***

Kudos: 1
Offline Offline

United States United States

Posts: 56




Ignore
« Reply #20 on: December 09, 2015, 04:31:48 PM »

A good fast launch Tom, takes practice, and guts.  Our arms were not designed to throw model airplanes the correct way, without a lot of training.  And a pusher would be even more difficult. 

This is an amazing project, I hope it flies like a dream.

Dave
Logged

Two minutes is a long time!
Crabby
Titanium Member
*******

Kudos: 132
Offline Offline

United States United States

Posts: 2,176


I never met a modeler I didn't like



Ignore
« Reply #21 on: December 09, 2015, 05:21:36 PM »

I would not put too much faith in the fastball launch.

I would put nothing but faith in your launch its your best bet!
Logged

The Threadkiller!
jym6aw6
Gold Member
*****

Kudos: 11
Offline Offline

United States United States

Posts: 378




Ignore
« Reply #22 on: December 10, 2015, 02:24:35 AM »

Some years ago saw a FAC Nats video with Dennis Norman launching his B-52 scale glider using the hi-start catapult method. He had an assistant hold a tall pole upright. One end of a very long length of rubber strip was attached to the top of the pole and the other end was slipped over a hook on the model. The effect was like a gentle slingshot. Not sure that he had the model trimmed but the flights were of short duration.

Maybe someone with some hi-start launching experience can comment? Looks like it might have some potential with smaller jet models like the Blackbird.


Jim (6aw6)
Logged
DavidJP
Titanium Member
*******

Kudos: 45
Offline Offline

United Kingdom United Kingdom

Posts: 2,891




Ignore
« Reply #23 on: December 10, 2015, 05:08:16 AM »

This becoming a very entertaining topic!
Logged
Copbait73
Gold Member
*****

Kudos: 10
Offline Offline

United States United States

Posts: 582



Ignore
« Reply #24 on: December 10, 2015, 07:11:49 AM »

Don't know where all this concern regarding launch is coming from. Rubber powered models with their high static thrust are basically motor sticks at launch. This one even more so. It's ducted fan models of very low relative thrust that have these issues at launch.

 I found my  XB-70 - a long nosed delta - to be a baby to launch. Use typical two handed over head.
Logged
Pages: [1] 2 3 4   Go Up
Print
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Valid XHTML 1.0! Valid CSS!