This isn't a terribly exciting project, but I've been putting it off for 4 years. After some flights at Bong during the Apollo 11 50th anniversary year, the rough landings of this 10 year old build snapped off enough resin-cast flight fins (slightly larger than scale) that I could no longer fly it. The last run of kits was in 2019, and in the past I've been able to get replacement parts, but email exchanges with David since 2019 have been un-successful. Though I've beem able to repair broken fairings with epoxy & glass, there didn't seem to be a way to repair the fins with sufficient strength to fly.

So, I started with some 1/8" plywood from our defunct LHS, Greenfield News & Hobby. It's really nice 6-ply stuff. First, traced one of the original fins on cardstock, then transferred to the pywood, and cut each fin out with a zona saw. This was laborious (!), and a bit painful for my arthritic hands, but the fine teeth made for nice cuts.

The tab that holds these fins in the fairing has 2 thicknesses, so used my cordless Dremel (a big upgrade over my corded craftsman rotary tool) with a carving bit to remove one ply from each side of the top half of the tab, cleaning up with an Excel #10 blade. Two notches were then carved, which are used to hold the fins in the fairings with rubber bands, so they can be easily swapped out for the scale display fins (or in my case, replaced after landing).

After sanding the edges a bit, I was going to just paint them at this point, as they're good enough to fly, but then my OCD kicked in. Got out my Estes Sanding Bars (another really nice tool, a big improvement from rubber blocks I've used for far too long), and added a leading taper edge. Then glued on 1/32" pieces of balsa, and sanded to get a more scale-like profile (not perfect, I can swap out for the detailed cast scale fins for display). In my quest for a new primer now that Bondo is gone, I tried out some Seymour Filler Primer 20-1674. From a performance standpoing, this is similar to DupliColor FP101. While far better than HW store brands, it doesn't sand quite as easily as the Bondo did. It's available on Amazon, free shipping eligible, $12 for a 16 oz can, about the same price as DupliColor 11 oz cans from the local auto supply stores.

1 coat of sanding sealer and 2 coats of primer didn't fill in the grain enough, but I've gotta go back to work tomorrow, and want to wrap this up, so turned off the OCD and sprayed on some Tamiya silver. The tabs need some masking tape on the lower tab for a snug fit, and they're ready for flight.

Digging through my vast stores of half-used decal pages turned up no letters of the right size, so I'll print out some letters on white decal paper for a finishing touch.

I hope Sirius does another run of these kits some day, and not just so I can get more repair parts (I could really use some new fairings). The last one I saw on eBay sold for $1,131.

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Paul
If we weren't all crazy, we would go insane - Jimmy Buffett
NAR #87246 www.wooshrocketry.org

Mine is beat up as well. I do have a set of fins for it though. I am almost thinking about making a set of G10 fins that are attached to the body tube. I have to rebuild my capsule as well. It will probably be in the spring before I tackle this job. The decals will probably be replaced with the set from Cultman. https://www.culttvmanshop.com/Satur...ems_p_2602.html. Not quite the same scale. they are 1/72 scale vrs 1/64.

I like the G10 fins idea.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, TURMOIL, FIASCOS, and HAVOC !

Mine had a rough landing a few years back and snapped off most of the fins. I 3-D printed
replacements and flew it again. Worked nice!

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Clubs: BARC, MDRA

If you still have the STL file please share. Might just be another option.

Hi! As I recall I found a fin and fairing combo on Thingiverse and scaled it to match the Sirius perfectly. There may be more than one of these on Thingiverse. I don't recall exactly which one it was. I looked for the .stl but I think it was on a flash drive that got erased. I'll keep looking...

-Jeff

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Clubs: BARC, MDRA

The nice thing about the original slide-in fins is that they tend to snap off on landing without damaging the fairing, and are easily replaced. I'm not sure if my plywood fins will do that. G10 definitely wouldn't. We'll find out this summer.

__________________
Paul
If we weren't all crazy, we would go insane - Jimmy Buffett
NAR #87246 www.wooshrocketry.org

G10 wouldn't break at all. Most likely would BOUNCE. ZERO BUSTICATION.

__________________
When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, TURMOIL, FIASCOS, and HAVOC !

The fin wouldn't break, it would rip the (cast resin) fairing apart...

When mine had its hard landing it shattered 3 of the 4 fairings into multiple pieces! So the replacement 3D fin/fairing combos were ideal for me. Good luck with your project!

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Clubs: BARC, MDRA