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CPMcGraw 09-07-2012 07:39 PM

SKY AYE Skyletto
 
3 Attachment(s)
Brain, this was interesting!

Length: 35.10"
Fin Span: 5.34"
Diameter: 1.34" (ST-13)
Weight: 3.26 oz


D12-0 / D12-7......1919'......Dv 14-17 FPS......Avg of 10 runs


All flights require a 48" x 3/16" rod.

Nice design. Should make a great kit!

Brain 09-08-2012 10:03 AM

Quote:
Originally Posted by CPMcGraw
Brain, this was interesting!

Length: 35.10"
Fin Span: 5.34"
Diameter: 1.34" (ST-13)
Weight: 3.26 oz


D12-0 / D12-7......1919'......Dv 14-17 FPS......Avg of 10 runs


All flights require a 48" x 3/16" rod.

Nice design. Should make a great kit!

Excellent! This makes for seven designs that have demonstrated worth, either in the field or on the screen:
*Dead Ringer
*Stanger
*D-Marie
*Bulldog 24-D
*Skyletto
*Nomad
*Big Brew (a re-bash of an Estes Menace [that I had originally bashed into the gloriously failed El Dorado], which I have not posted here before, but what a beautiful flyer!)

Question: Does RockSim generate a list of body tube sizes, NC sizes and such for designs?

Brain 09-08-2012 10:22 AM

1 Attachment(s)
Quote:
Originally Posted by Brain
*Nomad
*Big Brew (a re-bash of an Estes Menace [that I had originally bashed into the gloriously failed El Dorado], which I have not posted here before, but what a beautiful flyer!)

The Nomad is left, the Big Brew to the right (that's the Gryphon SDV in the center... which flew OK its only time - might need weight in the nose or something, I dunno).

CPMcGraw 09-08-2012 10:51 AM

Quote:
Originally Posted by Brain
Question: Does RockSim generate a list of body tube sizes, NC sizes and such for designs?


It uses a database of components that can be added to as needed. Somewhere here on YORF is a set of component files for SEMROC parts. It's been a while since they were updated, though.

Each design file [RKT file] contains a parts list for that design. It works OK for simple designs, but when we start putting together these complex birds, that parts list often gets really crazy to interpret. An example is where you might have a paper transition with a tube on the inside, but that tube also becomes an outside tube on the small-diameter end. It's often easier to break that long tube up in RS and treat each section separately; yet the tube in real-life is still a single tube. The parts list will show it as separate pieces.

When I'm working on a design where I have to break up a piece to work with it, I'll often make a notation in the "part name" field to show what I've done.

Brain 09-08-2012 11:33 PM

1 Attachment(s)
Quote:
Originally Posted by CPMcGraw
It uses a database of components that can be added to as needed. Somewhere here on YORF is a set of component files for SEMROC parts. It's been a while since they were updated, though.

Each design file [RKT file] contains a parts list for that design. It works OK for simple designs, but when we start putting together these complex birds, that parts list often gets really crazy to interpret. An example is where you might have a paper transition with a tube on the inside, but that tube also becomes an outside tube on the small-diameter end. It's often easier to break that long tube up in RS and treat each section separately; yet the tube in real-life is still a single tube. The parts list will show it as separate pieces.

When I'm working on a design where I have to break up a piece to work with it, I'll often make a notation in the "part name" field to show what I've done.

And knowing the length of said transition & front section can just be added together with the small tube length you have, and voila!
Computers are stupid... ;)
But if anyone wanted to take a crack at this Gryphon bird in RS, here's the ortho (I'd like to know what the problem was - it went fairly high, but arced over way more than the other ones we flew that day, same engines - all Estes; and the nose on the actual bird is not rounded as in this pic, but a simple cone; I can provide measurements, if necessary - I can tell you the upper body tube is BT-20, the transition is 20 to 55 [I think] & the lower tube is off-spec [close to 55] - "Best guess, Mr. Sulu."):

CPMcGraw 09-09-2012 09:43 PM

3 Attachment(s)
Quote:
Originally Posted by Brain
...if anyone wanted to take a crack at this Gryphon bird in RS, here's the ortho...


I'm fudging on this first draft, Brain. I like the feel of Centuri (SEMROC) tubes, so the body tubes in question spec out as ST-7 and ST-13. You didn't say if the pods were hollow or top-plugged (I'm presuming hollow, like tube fins). I'm also taking a rough stab at the shapes of the two fins I'm looking edge-on at. If your flight vehicle is close to this, then the dynamics should be close.

You also didn't mention which engines you were using. I'm selecting a D12-5, and so far, the numbers are good.

Length: 32.215"
Diameter: 1.34" (ST-13) and (ST-7)
Fin Span: 7.59"
Weight: 2.4 oz


D12-5......870'......Dv 10 FPS......use a 48" x 3/16" rod......Avg of 10 runs


Let me know how close I got on those fins...

Brain 09-10-2012 04:59 PM

Quote:
Originally Posted by CPMcGraw
I'm fudging on this first draft, Brain. I like the feel of Centuri (SEMROC) tubes, so the body tubes in question spec out as ST-7 and ST-13. You didn't say if the pods were hollow or top-plugged (I'm presuming hollow, like tube fins). I'm also taking a rough stab at the shapes of the two fins I'm looking edge-on at. If your flight vehicle is close to this, then the dynamics should be close.

You also didn't mention which engines you were using. I'm selecting a D12-5, and so far, the numbers are good.

Length: 32.215"
Diameter: 1.34" (ST-13) and (ST-7)
Fin Span: 7.59"
Weight: 2.4 oz


D12-5......870'......Dv 10 FPS......use a 48" x 3/16" rod......Avg of 10 runs


Let me know how close I got on those fins...

As far as I'm concerned, everything is perfect!
I always sway to the notion that things like engines are going to be determined somewhere later in the design process, based on - like you said - preferentials and/or whatever materials you have available to you to use. The design itself screams for a 'D' or better, so we're right there. 32''... yes!!

The fin shapes are always mutable at this point, but you got them right on. I launched the real Gryphon (which may differ slightly from the version I've created [and you've created] for all this) on a C6-3, but I never considered using a 'D' in it, even though the off-spec main tube would have allowed it (I just don't want to spend more money on engines than I need, so I stick with the 'C's... for now! I keep looking at that Estes Ventris... yummy!) The side tubes are made from Nerf darts (closed end up), so whatever gets close will work. Probably don't even need to stick with those squared-off tips...

Once again, my gratitude. This is all very enlightening and what I would have had to do myself anyway, were I to get serious about this... :D

CPMcGraw 09-11-2012 10:26 AM

If that "off-spec" body tube is just slightly larger than the Estes BT-55, it's probably the Centuri ST-13. Estes calls it their BT-56, and they use it a lot in their ARF/RTF designs. I'm partial to the Centuri (SEMROC) version, as their's has a slightly thicker tube wall.

Something I've learned with RS is that fin shape can be more important than fin area or size. Some shapes generate more corrective action than others. There is a lot of "play by ear" with this, and what works on one design doesn't always work on another.

I actually thought you might have used a "C" in this model, from the way you described the flight. A quick run of the simulation with a 24mm C11 didn't give me satisfactory results. The ideal time delay would be 4 seconds, but there ain't no such animal...

What RS lacks in graphic ability, it more than makes up for with the simulations.

CPMcGraw 09-11-2012 12:09 PM

New Design for Sky Aye -- Auriga
 
3 Attachment(s)
Brain, this one was a challenge, but I think the results will be satisfying.

Length: 36.70"
Diameter: 2.64" (Transition Diameter; ST-13 main BT)
Fin Span: 8.14"
Weight: 4.69 oz


D12-5......706'......Dv 4-7 FPS......48" x 3/16" rod required


There may be a need for some additional internal stiffening underneath those cardstock transitions. You could probably use some 0.02" matteboard rings to do that, with plenty of material removed from the rings to reduce mass.

The Dv numbers are what got my attention once the design was tested. I never thought the numbers would be so low (good thing!).

Brain 09-11-2012 04:35 PM

Quote:
Originally Posted by CPMcGraw
If that "off-spec" body tube is just slightly larger than the Estes BT-55, it's probably the Centuri ST-13. Estes calls it their BT-56, and they use it a lot in their ARF/RTF designs. I'm partial to the Centuri (SEMROC) version, as their's has a slightly thicker tube wall.

Something I've learned with RS is that fin shape can be more important than fin area or size. Some shapes generate more corrective action than others. There is a lot of "play by ear" with this, and what works on one design doesn't always work on another.

I actually thought you might have used a "C" in this model, from the way you described the flight. A quick run of the simulation with a 24mm C11 didn't give me satisfactory results. The ideal time delay would be 4 seconds, but there ain't no such animal...

What RS lacks in graphic ability, it more than makes up for with the simulations.

I can tell you that the off-spec tube is just that - my wife handed it to me from a depleted roll of something (plastic wrap?) - and it's got to be only by coincidence that the sizes are close.

in your estimation, the top problem with the Gryphon is using the right engine (size)? I had it in my head that nose weight might have been a possible problem. I recall that one of the fine folks on this forum sent me that main transition as a favor (but I don't remember why...), and that I did have to do a little work on the inside of the tube to make it fit.

I did try to recreate one of my designs (Stanger) in OpenRocket, and I think I was successful in coming up with a working bird (a flight sim gave me all green) that uses a C6-7. Only as an exercise, though... I have already launched that one on a C6-3 and it was great! So, OpenRocket seems to be a good rough draft prog, if nothing else. I don't know what issues are involved with the delay-time differences.


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