It is also problematic that the Moldin Oldies description says it is a BT-55 nose cone and 55-60 transition. My Saros instructions indicate that the Estes model is BT-20 and 20-50.

Dave, the 3D printer makes it easy to upscale or downscale. I just downloaded the Thingiverse file and imported it into Cura. The original size is on the left. Then I copied it and click on scale. Increased the scale to 120% and the result is on the right. You can see the scale figures in the box on the left. Took me longer to type this than it did to scale up the nose cone.

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My measurements (from my built, painted model):

Base length 0.38"
Taper Section length 0.76"
(Straight) Section diameter begins at 0.55", tapers very gradually throughout, down to 0.53"
(Straight) Section length 1.28"
(Note that the Section/Ogive transition is very indistinct)
Total length Base+Taper+Section+Ogive = 4.11", so Ogive is 1.69"

Hmm . . . I'm not a "3D printer person".

Can you break that down to provide incremental measurements of the nose cone ?

I am looking to do a 2.2715163 : 1 upscale ( BT-70 ).

Dave F.

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Thank you , sir . . . That will really help !

Dave F.

I have been attempting to "channel Mike Dorffler" and take myself back, mentally, to the era in which he designed the SAROS . . .

I am believe that, when Mike was designing the SAROS, he was thinking in terms of using existing Estes "off the shelf" parts, at least for the initial design, before the injection-molded version was created.

This is my "back in the day" thought process . . . To create the "SAROS" Nose Cone.

Tools Needed :

X-Acto Knife - #1 Blade
Razor Saw
Glue
Sanding Sealer
Fine Sandpaper

Parts required :

1 - JT-20 Stage Coupler - Length 3/4" ( .750" )
1 - TA-520 Balsa Adapter - Effective Length 3/4" ( .750" )
1 - BNC-5W Balsa Nose Cone - Effective Length 2 7/8" ( 2.875" )
1 - BT-20 Body Tube - A short section - Length 3/8" ( .375" )

Total "Effective Stack Length" = 4" ( 4.000" )

Construction Procedure :

( 1 ) Cut the BT-5 diameter "shoulders" off of the TA-520 coupler & BNC-5W Nose Cone.

( 2 ) Glue the "butt ends" of the TA-520 & BNC-5W together, to form a single unit.

( 3 ) Cut a 3/8" ( .375" ) long section of BT-20 Body Tube.

( 4 ) Glue the JT-20 into the 3/8" ( .375" ) long section of BT-20, to a depth of 1/8" ( .125" ).

( 5 ) Apply glue to shoulder of the TA-520 ( cut to 1/4" / .250" long ) & inside of the BT-20.

( 6 ) Slide BT-20 onto shoulder of the TA-520 & wipe off any excess glue that oozes out.

( 7 ) Allow to dry . . . Sand all seams smooth & finish with Sanding Sealer & fine Sandpaper.


Thus, the prototype "SAROS" Nose Cone is created . . .

Similarly the "SAROS" plastic Interstage shares the same dimensions as the TA-2050 . . . Effective Length 2" ( 2.000" ).

As for the Fin Can, I believe that the "original prototype" used sections of BT-50, glued between the Fins, to increase the diameter and give the impression of a "Fin Can" structure. A "Paper Adapter" provided the "simulated nozzle" of the "SAROS".

The overall "Effective Length" of the Nose Cone, using this method, is 4" ( 4.000" ).

"Tramper Al", who measured his plastic "SAROS" Nose Cone, came up with an overall "Effective Length" of 4.11".

The 0.11" discrepancy in length could be accounted for in however the dimensions were supplied to the maker of the Injection Mold, used to create the mass-produced "SAROS" kit.

Thoughts ?

Dave F.

Anybody ever have any stability problems flying the Saros?

I built mine in 1970 something as a kid, stock, no mods.

The one and only time I went to an officially sanctioned NAR launch with competition points I flew it twice. First flight with a B4-4 and it did a perfect loop. Second time with a B6-4 and it looped again. That was the last time I ever flew it.

Tiny fins, heavy motor (relative to an A8-3 which I think is what I flew it on originally),??? who knows. I think I did get some inadvertent style points.

That's odd . . . I would never have suspected a CG problem on a long, slender rocket, especially a kit. I know that the SAROS kit did not come with any modeling clay or other "ballast" material.

Was an excessive amount of glue used to assemble and install the Motor Mount ?

Dave F.

I have one built in much more recent years, but have not had a chance to fly it yet. But…I have heard of the stability problems before.

Earl

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Earl L. Cagle, Jr.
NAR# 29523
TRA# 962
SAM# 73
Owner/Producer
Point 39 Productions

Rocket-Brained Since 1970

Gosh, I do not know...I built this one over 43 years ago so maybe.

I think I may have been flying it for B streamer duration (again, first time at a NAR Meet with points (and only 4 other people there)) and that was the smallest rocket I had brought. Maybe without the weight of a parachute it was enough to push it over the edge.