Good Afternoon All;

Looking to scratch build (clone) an Estes Gyroc. Already downloaded the pattern template from the Jim'z site, but experienced difficulties in the past with sizing of Astron Sprint documents from that resource.

Hoping that someone who has a set of Gyroc fin templates can measure the length of either the root edge of the fin/'wing' or the hinge line length of either the fin or flap; something that I can then compare my printed file to, to verify that these are printed full-size.

Thanks in advance,
Dave

I can't help you with your specific question, but I do have a recommendation:

Add a bit of nose weight during construction. I did a Gyroc clone several years go - it went unstable the first time I flew it (fortunately without any damage). I never did determine exactly why although my guess is that the modern parts I used change the CG slightly compared to the original (I did use a balsa nose cone from BMS).
That being said, I added some nose ballast and after that it flew fine.

Root edge on my vintage one is 2.5".

__________________
Bill Eichelberger
NAR 79563

http://wallyum.blogspot.com/

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Build floor: Centuri Mini Dactyl Estes - Low Boom SST Semroc - Marauder, Shrike, SST Shuttle

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Good Morning Bill;

Thank you for the data point.

Laying a ruler on the drawing/plan sheet I printed out yesterday after downloading from Jim'z (and printed out at 100% scaling on my HP Office Jet), the root edge on this document is 2 3/8", so clearly I need to enlarge a few percentage points...

r/
Dave

If it's a pdf make sure fit to paper is unchecked.

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WOOSH NAR Section #558

I just checked my old Astron Gyroc K-24 and found the root edge of the fin / wing to be 2.25" and the hinge line length to be 3". I would also say a hearty "Amen" to the suggestion to add a little nose weight, because IIRC on the maiden flight of my Gyroc (likely on an A8-3) it went vertical for about 50', then canted over 90 degrees and shot off horizontally like a cruise missile towards the area where our parents had parked the cars for the launch. Fun times!

__________________
John

Was CAR-ACF# S 337
Was NAR# 91049
Was SAM# 0323

Life begins when the countdown reaches zero!

I uploaded everything I have on the Gyroc.

Dave F.

Attached Thumbnails

     

Attached Files

	gyroc.pdf (141.5 KB, 11 views)
	k-24.pdf (299.4 KB, 6 views)

Good Afternoon and thank you all for the feedback

Question for those who've built and flown Gyrocs... At least one of you commented on the need for additional nose weight. I've looked at the kit documentation and nowhere did I see reference to a c/g location. Looks like Rocket Reviews is offline at the moment, but even a Google search failed to turn up either a Rocksim or Open Rocket file for the Gyroc.

Does anyone have a good starting c/g location (preferably measured from either the nose cone / body tube intersection, or from the aft end of the body tube)? Even better of course would be a .rkt or .ork file.

Thanks again,
Dave

[QUOTE=David_Stack]...Does anyone have a good starting c/g location (preferably measured from either the nose cone / body tube intersection, or from the aft end of the body tube)? Even better of course would be a .rkt or .ork file.../QUOTE]

I don't have an appropriate design file, but I can provide some measurements taken directly from my vintage Gyroc. Measured from the aft end of the body tube and going forward, on my Gyroc the CG is:
- As built, with no motor installed - 2 1/2"
- With typical new A8-3 motor installed - 1 7/8" (i.e. at moment of ignition)
- With typical expended A8-3 still within body tube - 2 1/4" (i.e. at moment of ejection)

Hope those figures are helpful to you. I think even a rough approximation of the CP using the old "cardboard cutout" method will show that a stock vintage or cloned Gyroc (I can't comment on the Semroc version) has the CP and CG a little too close together for comfort; hence the recommendation for a little nose weight to pull the CG forward a bit to provide more positive stability. Good luck!

__________________
John

Was CAR-ACF# S 337
Was NAR# 91049
Was SAM# 0323

Life begins when the countdown reaches zero!

Good Morning John;

Truly appreciate the detailed response/information.

It gives me a good c/g to shoot for.

r/
Dave