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Scottl0413
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« on: October 15, 2017, 11:05:52 PM » |
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Well, I've been busy developing a new A/B classic model. I've named it "New Hope". It's a 450 sq. in. wing based on the Geodetic Galaxy, pwr. is a .15 Conquest spinning a 7 X 4 Cox gray competition prop. Finished weight ready to fly is 564 grs. (20 ozs.) Testing the engine it seems to be turning around 28K rpm, rpm meter was acting up so couldn't get a solid reading!!! Hope to fly it soon!
Scott
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FF Bruce
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« Reply #1 on: October 16, 2017, 12:10:15 AM » |
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Scott nice model, you should be very careful with that Cox gray they are known to throw blades anything over 21K.That is why we went to glass props in FAI back in the 70's.If you can't find any I have a few 7x4 cox copies in glass I'll send you. Had a good friend put a blade into his knee testing a motor,would not want to hear of it happening again. Bruce
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Scottl0413
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« Reply #2 on: October 16, 2017, 03:48:20 PM » |
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Bruce, thanks for the heads up on the prop. I'll change it over to an APC! Don't want any objects flying around at 28K rpm.
Scott
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flydean1
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« Reply #3 on: October 16, 2017, 11:03:08 PM » |
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I always wonder how you guys plot out the geodetic or union jack angled ribs. Mystery to me. I have had little success with what I've tried so far. Don't want to learn a whole CAD program to just plot ribs.
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FF Bruce
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« Reply #4 on: October 16, 2017, 11:44:49 PM » |
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What I do is take the airfoil I'm going to use to a copy machine that lets you enlarge in one direction and leave the other direction the same.Then measure the diagonal end to end blow up the length to match that dimension and leave the other or height of the airfoil the same.Most of the new copiers can do this,works real well. And to make sure you can add just a little to the height when you make your template then sand when finishing your wing. Hope this makes sense. Bruce
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billdennis747
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« Reply #5 on: October 17, 2017, 02:28:49 AM » |
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Draw the straight rib on graph paper
Mark off every 1cm along the base line and draw verticals
Draw another baseline for the diagonal rib
Calculate the % increase in length and use this to mark off the baseline divisions
plot dots at each station from the straight to the diagonal rib
join the dots.
Takes about as long as for the computer to warm up
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applehoney
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« Reply #6 on: October 17, 2017, 09:43:28 AM » |
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> plot out the geodetic or union jack angled ribs.
Quit doing that many, many years ago I just cement the straight ribs in place, assemble blanks of same depth as the straight ribs in geodetic fashion - rough carve and then sand them down to match said straight ribs. Works fine, whether parallel chord or tapered.... geodetic, union jack or eggbox structure
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flydean1
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« Reply #7 on: October 17, 2017, 08:11:44 PM » |
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Thanks all for several solutions to this "knotty" problem.
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gossie
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« Reply #8 on: October 17, 2017, 11:14:07 PM » |
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Nice Scott, but personally I would not even trust an APC turning those revs.
Google SUPERCOOL props here in Oz. Stuart is a buddy of mine and does great C/F props that will be safe and I'm sure suit you fine.
I've been using his for a long time and find them very good......28,200 from memory on the ground a while back, Rossi Mk2.
Pic was photo shopped by Mal. Campbell, but gives you the idea I guess.
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Scottl0413
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« Reply #9 on: October 18, 2017, 08:37:21 AM » |
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Thanks Gossie, I'll google him and see what he's got.
Scott
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ddock
Bronze Member
Kudos: 1
 Offline
 United States
Posts: 44
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« Reply #10 on: October 19, 2017, 12:53:09 PM » |
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Hey Scott, NICE looking bird...Color scheme is a little tame for you!!  Denny |
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RobinB
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« Reply #11 on: October 20, 2017, 05:38:13 AM » |
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Same as Applehoney with the straight ribs. Then I use a scribing stick. It's a piece of straight spruce with a piece of pointed thin wire epoxied into a groove at one end flush with the edge. Pin a diagonal blank in place and run the scriber down the straight ribs, keeping the pointer in contact with the diagonal blank. Take out the blank and cut along the scribed line. Replace and check with a straightedge. If it's good, use it as a template for the rest of the diagonals (on constant chord panels). Works on constant chord and straight tapered panels. Ellipticals - you're on your own  Robin |
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For every action, there is an equal and opposite malfunction.
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flydean1
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« Reply #12 on: October 21, 2017, 09:19:09 PM » |
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Thanks Robin. Another innovative and logical solution to the angled rib problem.
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Sandgroper
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« Reply #13 on: November 28, 2017, 11:21:25 PM » |
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Nice one Scott, before I built the Slim Dixie I had a look at the Dixie Gal plan which I think uses a Geodetic Galaxy wing. I also recently discovered the Pearl 450 on another website, just my type of airplane pity it didn't have diagonals.
My little brother uses Supercool props on his F2C control line models so I can highly recommend them. Stuart also makes very nice CNC machined molds if you want to make your own props.
Phil
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Scottl0413
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« Reply #14 on: November 29, 2017, 04:37:57 PM » |
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Phil, I've had the Geodetic Galaxie wing and stab developed into a lazer cut short kit and that's what I've been using for the bases of my A/B class planes, Works really good!
Scott
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flydean1
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« Reply #15 on: March 18, 2018, 10:52:09 PM » |
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Have you flown it and it's 1/2A cousin yet?
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Scottl0413
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« Reply #16 on: March 20, 2018, 09:14:09 AM » |
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Dean, not yet was planning on attending the contest in Palm Bay this month but plans have changed. Waiting on the winds in the area to calm down!! Typical spring conditions.
Scott
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Scottl0413
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« Reply #17 on: June 07, 2018, 08:17:22 AM » |
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Well got a chance last weekend to seriously do some trimming on the "New Hope"! The Conquest .15 is a very healthy engine and pwrs. the 450 sq. in. New Hope with Authority! On to the trimming, after about an hour of trimming this and that it's flying great. Pwr. pattern is a vertical spiral climb and a great roll out at the top, glide is really good also but I think I'll need to open up the right had glide a little bit for the nationals. All and all I am very pleased with the design and results.
Scott
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