"1/2 A" & "1/8 A" airplanes These are the small ones...more popular now than ever.

SlipStream 74 (Video and plans added)

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Old 06-12-2012, 11:12 AM
  #26
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Default RE: SlipStream 74 (Video and plans added)


Quote:
ORIGINAL: hllywdb
Mr Cox, I wish I had your patience and buiding skills. That is a gorgeous plane.
The Chipmunk is a mere ARF from Carl Goldberg so I cannot take any credit for that...

I love the way this plane flies, does everything well apart from knife edge, there is a little too much V-shape in the wing for that.
I have put a short video on youtube that's shows the throttle respons of the engine from idle, remember that this is an inverted .074 engine, running the stock glow head and 10% nitro (skip to 1:10 for the idle);

[youtube]http://www.youtube.com/watch?v=trSCx-6zlAo[/youtube]
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Old 06-12-2012, 11:14 AM
  #27
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Default RE: SlipStream 74 (Video and plans added)

Thanks Andrew. I have done the servo covers on planes down to about 20 size. I'm not sure I have the patience at this size Or maybe I'm just lazy, but it would make a much cleaner install. Usually I'm down under 10% on the airfoil for 1/2A so I don't have room. I forgot I made this one a thicker wing.
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Old 06-12-2012, 11:53 AM
  #28
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Default RE: SlipStream 74 (Video and plans added)

Where did you get that cowl? What servo's did you use?
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Old 06-12-2012, 12:01 PM
  #29
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Default RE: SlipStream 74 (Video and plans added)

The cowl is coke bottle, see a few posts back for details. For servos I'm using Futaba 3114's. A little heavier than the 9g tiawan ones, but I have to crash to strip them.
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Old 06-12-2012, 01:34 PM
  #30
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Default RE: SlipStream 74 (Video and plans added)

What's that inside the canopy, batt pack ? if yes id rather use LiFe batt pack they'r small cheap and lite.
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Old 06-12-2012, 04:08 PM
  #31
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Default RE: SlipStream 74 (Video and plans added)

No, that is the pilot LOL. I am using a small pack from Radical RC. About 1oz. It's in the fuse about 3" from the stab.
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Old 06-12-2012, 04:16 PM
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Default RE: SlipStream 74 (Video and plans added)

looks a lot like my old 60 size dick hansan tipporarie , it was a smooth and great flying airplane anyway looks really good you will enjoy it a bunch
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Old 06-13-2012, 01:31 PM
  #33
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Default RE: SlipStream 74 (Video and plans added)

Mr Cox
Is the super chipmonk a kit or scratch?


Never mind.. just noticed the answer in a post.. sorry.
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Old 06-13-2012, 04:04 PM
  #34
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Default RE: SlipStream 74 (Video and plans added)

Well, IT FLYS! Actually flys quite well. Came out lighter than expected, no weight number yet. As I expected, it needed a bit more aileron mixed with the rudder in knife edge with the larger canopy/turtledeck, but I like the looks. Knife edge takes surprisingly little rudder and slow rolls require a very light touch on the elevator to stay true while inverted. A lot less than I am used to in this size. Speed is excellent, just slightly less than the 8% airfoils I hav done in this size. Slow speed is great with no tendancy to drop a wing. Was a bit windy today, around 10mph, but had no problems even on landing. No videos or final pictures yet.

On another note, I just got the latest Tower flyer and I see they have just re-released the small electric Super Chipmonk (they bought out Carl Goldberg awhile back.) $129 isn't cheap, but I do have an extra .074 hmmmmmm

Mr Cox, how much work was it to convert? Firewall, tank install, etc... Did you do a build thread? I can't get over the ground handling on grass. Did you need to remove the wheel pants for grass?
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Old 06-13-2012, 09:36 PM
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Default RE: SlipStream 74 (Video and plans added)

The wheel pants only worked when the grass was newly cut, so I removed them and put slightly larger wheels on it (see picture below).
I have made a little build thread here before; [link=http://www.rcuniverse.com/forum/fb.asp?m=9052204]Chipmunk conversion[/link]
Since that I have swapped the position of the tank and battery, the tank had to be lower in order for the the lower rpms to work well at full tank.

Here are the larger wheels (2");

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Old 06-14-2012, 04:54 AM
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Default RE: SlipStream 74 (Video and plans added)


Quote:
ORIGINAL: hllywdb

As I expected, it needed a bit more aileron mixed with the rudder in knife edge with the larger canopy/turtledeck, but I like the looks.
Great to hear the maiden went well and that it flies well. The lines followed a typical pattern plane, but when downsizing, performance sometimes changes.

I had looked at your pics, then the plans, then the pics, ...., thinking that the fuselage profiles were not the same and that your plane had a taller profile due to the canopy and turtledeck. Apparently you modded it a bit. I like your version better - although it may require some trim adjustments on your part, it looks nicer than the plan version..

andrew
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Old 06-14-2012, 06:16 AM
  #37
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Default RE: SlipStream 74 (Video and plans added)

Hi Andrew,
Thanks, yes I did alter it a bit. I left the front deck the same heigth but rounded the top of the firewall and deck formers all the way down. Then I just traced the back of the canopy to make the first rear former. That way the mini sportster canopy (Tower #GPMA2769) fits right on with no cutting. I also added a 1/8 X 1/8 balsa stringer on each side of the rear. I should have braced them with an 1/8 X 1/8 between them 1/2 way between the formers as one did pull just a bit when shrinking the covering. I like the way it looks, but I did have to add about 25% aileron mixing to hold knife edge. But it adds a bit more of a sport plane look and leaves room for the all-important pilot If you decide to build one, you may want to move the firewall back just a tad to make balancing easier, I had to locate the battery back by the tail. Although you could mount the servos in the tail which would accomplish the same effect and tighten up the linkage as well.
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Old 06-15-2012, 06:32 AM
  #38
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Default RE: SlipStream 74 (Video and plans added)

Here are a few finished pictures. Also one at the field across the street. You can see why I don't spend a lot of time worrying about landing gear

Also, after getting a few more flights on this, I don't think it is the canopy that makes it need so much aileron in knife edge, because the canopy also creates a lifting surface. Looking more at the plane, I think I just need to re-shape the rudder. It looks like I have way to much rudder on the top of the fin, which would tend to roll it a lot more in knife edge. So I am going to trim the rudder to have more angle going from bottom to top. Should be fine as I only need about 1/4 rudder for knife edge now. Any thoughts?
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Old 06-15-2012, 06:59 AM
  #39
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Default RE: SlipStream 74 (Video and plans added)

I think going the extra mile to iron out handling issues will set your plane apart from the multitudes of published designs that might look pretty but are mediocre handling planes.
Like you stated in your first post...keep at it until you have come up with the best.
1/2A planes without lots of side area will tend to be a handfull in slow KE flight. It's really amazing to see how much better a profile fuselage is at that task.
Changing your aileron linkage to slow roll response might also improve the way the plane feels in KE flight.
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Old 06-15-2012, 07:44 AM
  #40
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Default RE: SlipStream 74 (Video and plans added)

Thanks CP, and yes, you are right. Too late to stop now. The extra side area was worth the change as it will knife edge at 1/2 throttle. Most people don't realize how effective reletively small ailerons are on a tapered wing. These are less than 7/8" (and not full span) with only about 1/4" deflection and I fly 90% of the time on low rates which cuts them down to 65%. I am also using 30% expo to smooth them out as well. This is also quite a bit of taper, 8 1/2" at the root down to 4 3/4" at the tip, so it takes on some of the charecteristics of a delta. I still have some wiggle room to move the CG back even more as it is still rock solid at slow speed. Right now it holds knife edge at about 28% aileron mix, I just don't like inducing that much drag if I can design it out. The more I look at the rudder the more I believe I just engineered it wrong and need to put it under the knife. Up on it's side that much rudder at the top of the fin wants to roll the plane. I forgot to take into consideration that I moved the stab on this design lower, which amplifies the effect of the top of the rudder. That's an easy fix. Might as well do it now as the next two days are windy anyway.
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Old 06-15-2012, 08:36 PM
  #41
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Default RE: SlipStream 74 (Video and plans added)

Years ago my EU 1/2A had the rudder
trimmed to 3/8" at the top. that helped
with roll coupling a lot.
Ralph
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Old 06-15-2012, 09:25 PM
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Default RE: SlipStream 74 (Video and plans added)

What you're desribing in knife edge is due to too much dihedral, not too much fin area. You can augement the roll coupling a little with getting the areas of the fuselage similar around the centreline of the plane, but ultimately dihedral has more of an effect than fuselage area differential.

You can experiment a little bit by fitting beveled wing tips to it, these add to the overall dihedral of the wing, or take away. If the plane is rolling with the rudder, you need less dihedral, conversely if it's rolling away from the rudder you need more.
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Old 06-15-2012, 09:39 PM
  #43
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Default RE: SlipStream 74 (Video and plans added)

Looking at Post #1 I don't see any dihedral
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Old 06-15-2012, 11:14 PM
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Default RE: SlipStream 74 (Video and plans added)

Then it's more than likely rolling out of the knife edge, rather than into it.
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Old 06-16-2012, 04:20 AM
  #45
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Default RE: SlipStream 74 (Video and plans added)

You're correct Skaliwgy, there is 0 dihedral, and it is rolling into the knife edge, not out of it, which is why I think I just need to trim the top of the rudder. I'm going to start with that and I'll let you know the results. I can also move the CG back, which would then require less rudder deflection, then less aileron correction. Rudder first.
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Old 06-16-2012, 04:38 AM
  #46
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Default RE: SlipStream 74 (Video and plans added)

The other reason I suspect the rudder is that it also wants to roll away from the rudder deflection in a stall turn. So the same aileron mix works in a stall turn, so I think CG or dihedral plays little part in this.
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Old 06-16-2012, 06:27 AM
  #47
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Default RE: SlipStream 74 (Video and plans added)

Flight report: After cutting the rudder back 7/8" on the top and leaving the bottom (start conservative), I am about halfway there. I also noticed I tend to use more rudder than I need, so I am adding 30% expo to the rudder. I am going to cut it back another 3/4" and should end up where I want to be. Not sure I will get a chance to test again as it is already over 15mph. But I figured "Hey, what a GREAT opportunity to see how it flys in the wind." Turns out wind is pretty much a non-issue, even at slow speed. The more I fly this one the more I like it.

I think next I need to adjust the downthrust as it requires just a bit of down trim for level flight and tends to pull to the canopy slightly in the up lines and knife edge. Any thoughts? It was way too windy to day to get a meaningfull "chop the throttle" test.

PS: I will post new adjusted plans with the higher turtledeck, battery location, thrustline and rudder corrections when I have it flying where it needs to be. I think I am going to cut another one and put it away as a spare anyway as I am getting quite fond of it.
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Old 06-16-2012, 10:46 AM
  #48
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Default RE: SlipStream 74 (Video and plans added)

That's good news, improving the plane performance is something I've always tried somehow.

Will wait till you have the plane setup and post the arrangments you talk about, its always good to have a spare model ready
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Old 06-16-2012, 11:13 AM
  #49
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Default RE: SlipStream 74 (Video and plans added)

Thanks Rafa, I have already changed the plans for the turtledeck, formers, rudder, and battery. I will re-post the plans when I have all the changes and trim worked out. Like CP said, there's lots of planes out there that look nice and fly mediocre, I don't intend to add to that list. I've trimmed another 3/4 off the rudder, but it is way too windy to fly right now. So I am finishing my daughter's 4 channel Jr Falcon for her. It is a flatter wing, ailerons, and I have a big mig .061 for her. I also set the wing at more of a zero incidence (the original plane was rudder only) and dropped the wing down in the fuse just low enough to do a bolt on wing with dowels in the front. Keeps me busy when it's too windy to fly and too hot to ride.
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Old 06-18-2012, 05:05 PM
  #50
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Default RE: SlipStream 74 (Video and plans added)

Ok, all changes made and final plans are posted. Thrust turned out perfect, needed the aileron linkage retrimmed (they were drooped just a bit). I moved the CG back quite a bit more and now she has no bad habits and flys like a dream. I have to get a video up for this one as it has to be seen to really appreciate.

I am also including a quick reference trim chart. I can't take credit for it, it comes from a club in Orlando, but I have been using it for the last 15 or 20 years. It really should be followed like a bible, in order, and it is applicable to all planes from 1/2A to 1/3 scale, to 2 meter pattern planes. The difference it will make in a plane's flying is amazing if you have never done a full trim and balance to a plane.

I do have a few points to add specific to 1/2A trimming.

1. SEAL YOUR GAPS. The reasons are many. Even the tightest gap on a 1/2A plane is proportional to a 1/2" gap on a 40 or 60 size.

These will make your ailerons and elevator 20 to 30% more responsive. They will take less throw, which means less drag, the enemy of 1/2A planes. We also use smaller servos and pushrods on 1/2A, so any kind of flutter is devestating. You would be amazed to find how many non-crash servo failures are due to flutter that you can't even hear on a plane this small.

2, Don't be afraid to move the CG, it makes a bigger difference than you think. When doing a CG test, roll both ways and split the difference. This will eliminate any margin for error caused by incorrect yaw.

3. Make sure to remove any warp from your control surfaces AFTER covering but BEFORE hinging them. Most of us will check the wing for warp, but it is easy to warp ailerons and elevators this small when covering and will give you bad habits that are almost impossible to trim out.
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