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Sirius Interrogator G build

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mtnmanak

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This bird is functionally complete.

Note, in the photo below, the nosecone is masked off and has been hit with a first coat of primer and sanded smooth.

Final steps:
- Masking, priming, painting
- Install recovery
- Decals

Probably will take a few days to prime & paint, so anticipate early next week to achieve a fully painted rocket.
 

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mtnmanak

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Got a couple coats of gray filler primer on today, sanded, and then hit with another two coats of white primer. Looks pretty good right now. Going to wait a few days for the primer to cure thoroughly then wet sand and give it a white gloss color coat, then a few more days before detail painting , decals and clear coat.
 

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Scott231

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Looking fantastic MountainMan! Rocket will look more "Aviation-authentic" with Matte Clear applied after the decals (but your preference is...preferred). If you think it takes a long time to paint, just wait until you start applying those three sheets of decals. o_Oo_Oo_O
 

mtnmanak

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Looking fantastic MountainMan! Rocket will look more "Aviation-authentic" with Matte Clear applied after the decals (but your preference is...preferred). If you think it takes a long time to paint, just wait until you start applying those three sheets of decals. o_Oo_Oo_O
Oh yeah, if you check out my build thread for the Sirius Refit USS Atlantis, you will see how the decal/clear coat process can go south VERY quickly (luckily, David at Sirius will really help you out if things go bad). I am going to go with a gloss white coat to make sure the decals stick, then take your advice on the matte clear coat - should look awesome! The decals are some of the best parts of Sirius kits, no one makes a decal sheet like David!

Key for this go around is not rushing it this time around. If you are following this thread, get ready for some long wait times between coats :)
 

mtnmanak

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Looking fantastic MountainMan! Rocket will look more "Aviation-authentic" with Matte Clear applied after the decals (but your preference is...preferred). If you think it takes a long time to paint, just wait until you start applying those three sheets of decals. o_Oo_Oo_O
Also, the matte coating should help bleed off a bit of altitude. I am not looking for altitude records on this one, especially without dual deploy. I will fly it with a JLCR, but looking forward to trying this one out with a cool sparky motor like the AT H115 Darkmatter. That should be a great compliment for this rocket, but won't mind if the rocket ends up a little heavy with a little extra drag to keep it from going really high.
 

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Got the gloss white coat on - took a couple iterations of primer, wet sanding, white gloss, wet sanding, etc, but now looks pretty smooth.

Next up, working on the detail painting, then the decals.

PXL_20201128_201403806.jpg
 

mtnmanak

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The nosecone is also done. It went through numerous iterations of wood filler, primer, and lots of sanding and patching with wood filler and priming, etc. Finally, it got 3 coats of gloss white. Still some small marks and divots, but I am done. From a couple feet away, it looks like a glossy shell, so good enough!

Moving on to the masking for the detail painting. I should have painted the inside of the ramjets before I installed them. Would have been much easier, now going to have to do some complex masking and hope I don't ruin the white paint job.
 

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mtnmanak

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Now that I am close to getting the recovery system done, I need to consider come nosecone weight. I ran the actual weights through some Rocksim launches and it is fine on F motors (only goes up about 500 feet), but by the time you get up to some of the more powerful G motors, the CG is only 1.3 calibers in front of the CP. On an H128, the CG sims out at 1.1 calibers. I am not comfortable with that level of stability. Adding 2 ounces of weight to the nosecone gets me back to a more comfortable 2 calibers of stability on an H128.

That is a lot of weight to add to a balsa nosecone. The kit method of attaching the screw eye to the nosecone is by gluing a 1/2" dowel into a hole in the bottom of the nosecone and screwing the small screweye into the dowel.

If I replace the screweye with a 1/4" shank eye bolt, and bore the hole out in the nosecone bit, I can fill the hole with epoxy and about an ounce of BBs and glue the shank of the eyebolt directly into the epoxy. Should give me right around 2 ounces and will be a lot beefier than the small screw eye.
 

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AfterBurners

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Now that I am close to getting the recovery system done, I need to consider come nosecone weight. I ran the actual weights through some Rocksim launches and it is fine on F motors (only goes up about 500 feet), but by the time you get up to some of the more powerful G motors, the CG is only 1.3 calibers in front of the CP. On an H128, the CG sims out at 1.1 calibers. I am not comfortable with that level of stability. Adding 2 ounces of weight to the nosecone gets me back to a more comfortable 2 calibers of stability on an H128.

That is a lot of weight to add to a balsa nosecone. The kit method of attaching the screw eye to the nosecone is by gluing a 1/2" dowel into a hole in the bottom of the nosecone and screwing the small screw eye into the dowel.

If I replace the screw eye with a 1/4" shank eye bolt, and bore the hole out in the nosecone bit, I can fill the hole with epoxy and about an ounce of BBs and glue the shank of the eyebolt directly into the epoxy. Should give me right around 2 ounces and will be a lot beefier than the small screw eye.
Great idea!
 

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Now that I am close to getting the recovery system done, I need to consider come nosecone weight. I ran the actual weights through some Rocksim launches and it is fine on F motors (only goes up about 500 feet), but by the time you get up to some of the more powerful G motors, the CG is only 1.3 calibers in front of the CP. On an H128, the CG sims out at 1.1 calibers. I am not comfortable with that level of stability. Adding 2 ounces of weight to the nosecone gets me back to a more comfortable 2 calibers of stability on an H128.
Mine flew 3 different motors with the 29/240 case (including the H250) My only mod that impacted weight was to add the cardboard of an altimeter bay (coupler & band) that was installed but never used as intended. That might have been 0.3 ounces. Even with the original nose cone and stretchy band shock cord, I never had an unstable flight. But with the size of the wings/find, don't fly this on a windy day!!!
 

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Mine flew 3 different motors with the 29/240 case (including the H250) My only mod that impacted weight was to add the cardboard of an altimeter bay (coupler & band) that was installed but never used as intended. That might have been 0.3 ounces. Even with the original nose cone and stretchy band shock cord, I never had an unstable flight. But with the size of the wings/find, don't fly this on a windy day!!!
Great feedback, thanks

For this rocket, I am not sure some added weight to the nosecone would be a real liability. At the lower end of the motor scale, it would definitely increase weathercocking, but, as you noted, you shouldn't fly it on a windy day anyway. And even in a light/moderate wind, the bird is only going up a few hundred feet on an F engine, so wouldn't use any kind of chute release on that flight, so a little weathercocking would actually be welcome. For bigger engines, It would ensure the rocket stays away from neutral stability.

If this were a hollow nose cone, I would install a removeable weight system. That is difficult to do with a solid balsa nosecone. However, this nosecone looks identical to the one used in the Sirius Deimos (which my daughter just started building yesterday). I may go ahead and add the weight to this nosecone and see if Dave will sell me a couple extra ones, which I will build out with a couple different weights. This way I could have a set of nosecones with no extra weight, 0.5oz extra, 1 oz extra, etc. Since both rockets are white, the nosecones would be interchangeable and I can make calls at the field based on weather conditions.
 

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Nosecone measured 17g by itself. Measured with the BBs and eye bolt and that came to 60g. Centered the eye bolt shaft in the BBs and secured with some 10mm Tamiya tape. Mixed up some Aeropoxy 2032 with about 1/2 tsp of milled FG and used a syringe to inject into the NC. End weight was about 76g, so almost exactly 2 oz added.
 

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AfterBurners

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Now that I am close to getting the recovery system done, I need to consider come nosecone weight. I ran the actual weights through some Rocksim launches and it is fine on F motors (only goes up about 500 feet), but by the time you get up to some of the more powerful G motors, the CG is only 1.3 calibers in front of the CP. On an H128, the CG sims out at 1.1 calibers. I am not comfortable with that level of stability. Adding 2 ounces of weight to the nosecone gets me back to a more comfortable 2 calibers of stability on an H128.

That is a lot of weight to add to a balsa nosecone. The kit method of attaching the screw eye to the nosecone is by gluing a 1/2" dowel into a hole in the bottom of the nosecone and screwing the small screweye into the dowel.

If I replace the screweye with a 1/4" shank eye bolt, and bore the hole out in the nosecone bit, I can fill the hole with epoxy and about an ounce of BBs and glue the shank of the eyebolt directly into the epoxy. Should give me right around 2 ounces and will be a lot beefier than the small screw eye.
Just curious was the nose cone already pre drilled for the added weight?
 

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Just curious was the nose cone already pre drilled for the added weight?
It had a 1/2" diameter pre-drilled hole (see photo is post #38 - that is the predrilled hole). I used a 3/4" spade bit to enlarge it about half way down to accommodate the BBs and epoxy (2nd photo in thread #42 has the enlarged hole).
 

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It had a 1/2" diameter pre-drilled hole (see photo is post #38 - that is the predrilled hole). I used a 3/4" spade bit to enlarge it about half way down to accommodate the BBs and epoxy (2nd photo in thread #42 has the enlarged hole).
Thanks. I might get the kit just wanted to see if it was pre drilled
 

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Thanks. I might get the kit just wanted to see if it was pre drilled
YMMV on the nosecone weight. I definitely built mine "heavy". On the Sirius website, it estimates overall rocket weight at 21.5 ounces. I was almost at 22 ounces before I put in the nosecone weight and that was without any of the recovery system. I believe most of that weight add came from the fairly heavy epoxy fillet I applied to top seam along the conduit dowel to smooth it out. Probably added a solid ounce or more to the project and most of that weight is behind the CP. If you use a lighter material like wood filler or wood glue, you may end up not needing any nose weight, but, on a bird like this, 1 or 2 ounces one way or the other is a significant difference in CG position. I don't mind the overall extra weight - I would rather fly this one low and slow on larger engines, but if you stick with wood glue, this rocket would be significantly lighter.
 

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YMMV on the nosecone weight. I definitely built mine "heavy". On the Sirius website, it estimates overall rocket weight at 21.5 ounces. I was almost at 22 ounces before I put in the nosecone weight and that was without any of the recovery system. I believe most of that weight add came from the fairly heavy epoxy fillet I applied to top seam along the conduit dowel to smooth it out. Probably added a solid ounce or more to the project and most of that weight is behind the CP. If you use a lighter material like wood filler or wood glue, you may end up not needing any nose weight, but, on a bird like this, 1 or 2 ounces one way or the other is a significant difference in CG position. I don't mind the overall extra weight - I would rather fly this one low and slow on larger engines, but if you stick with wood glue, this rocket would be significantly lighter.
Is that part of the instructions to fill the top seam. I would have used wood filler if that is the case, but epoxy would work better I think.
 

mtnmanak

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Is that part of the instructions to fill the top seam. I would have used wood filler if that is the case, but epoxy would work better I think.
It is not in the instructions. All the illustrations in the instructions show the gap in place and the dowel visible. And if you look at the picture from the website (below) it is clear they did not fill that seam. I just didn't like the seam and wanted to fill it and make a smooth transition. So, if you build this strictly by the instructions, you will definitely end up with a lighter rocket and a CG that is more forward.

1606783410208.png
 

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In an attempt to correct my piss poor prior planning, I constructed an elaborate mask with tape, saran wrap and a trash bag so I could paint the inside of the ramjets orange. In my entire rocket building life, I have never successfully gotten one of these masks to work so none of the paint drips onto my immaculate white paint job. Today was not the day I break my perfect record. I honestly thought I was good, then, as I peeled the last bit of tape off, there it was - a nice orange drip on the white paint. At least I am consistent.

On the bright side, the orange paint looks pretty good. I will let it cure for a couple days, lightly sand it off the areas that are supposed to be white and paint the white parts again. Could have been worse.

As with every Sirius rocket I have built, it takes me two days to build them and two months to paint them.
 

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neil_w

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I honestly thought I was good, then, as I peeled the last bit of tape off, there it was - a nice orange drip on the white paint. At least I am consistent.
I get this all the time. I double and triple check that all the tape is sealed up and still get unwelcome intruders. So annoying.
On the bright side, the orange paint looks pretty good. I will let it cure for a couple days, lightly sand it off the areas that are supposed to be white and paint the white parts again. Could have been worse.
It could be easier to scrape off the unwanted orange bits before it is fully cured. Even if you can only get some of it off, whatever you remove will be that much less sanding you need to do later. Fine targeted scraping with a knife blade (or the back of a blade) works pretty well for this.
 

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In an attempt to correct my piss poor prior planning, I constructed an elaborate mask with tape, saran wrap and a trash bag so I could paint the inside of the ramjets orange. In my entire rocket building life, I have never successfully gotten one of these masks to work so none of the paint drips onto my immaculate white paint job. Today was not the day I break my perfect record. I honestly thought I was good, then, as I peeled the last bit of tape off, there it was - a nice orange drip on the white paint. At least I am consistent.

On the bright side, the orange paint looks pretty good. I will let it cure for a couple days, lightly sand it off the areas that are supposed to be white and paint the white parts again. Could have been worse.

As with every Sirius rocket I have built, it takes me two days to build them and two months to paint them.
I love the orange ram jet. That was an excellent call on your part. As far as the drip get a dull blade and just lightly scrape it off being really careful not to dig into it. You should be fine. Thumbs up on that orange paint!! It really pops!
 

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On a more positive note, the epoxy cured nicely in the nosecone, so that is done pending decals and recovery system
are you going to use the included chute. I mean it would fine, but I watched video of this kit being launched it seems to not stay under the chute too well and swings and with all the wood hanging off it there's probably a good chance to break something if you are launching on a hard surface. Grass and sod you are probably okay with.
 

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Great suggestions on scraping the drips - they largely came off with a bit of scraping with a razor blade, so that will vastly lessen the sanding/touch up.

are you going to use the included chute. I mean it would fine, but I watched video of this kit being launched it seems to not stay under the chute too well and swings and with all the wood hanging off it there's probably a good chance to break something if you are launching on a hard surface. Grass and sod you are probably okay with.
Wasn't planning to use the included chute. A while ago, I invested in a wide variety of Fruity Chutes, so I use those on any rocket under about 20 pounds. For rockets over 20 lbs, I usually use my SkyAngle Cert 3's. Usually, I make a call on the field depending on weather conditions. I have some LOC parachutes I like as well, but I modified them with nylon strap bridles and swivels, so they are very similar to the Fruity Chutes now.

At just under 2 pounds, this rocket should fly perfectly on a Fruity Chutes Iris Ultra Compact 30". I think that will give some nice sub-12 FPS landings. For hard surface landings, maybe move up to a 36" Iris. Fruity Chutes descent rate calculator shows a 9 FPS landing with that chute. With a JLCR, should be able to get this to land close by and have a soft landing.
 

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Great suggestions on scraping the drips - they largely came off with a bit of scraping with a razor blade, so that will vastly lessen the sanding/touch up.



Wasn't planning to use the included chute. A while ago, I invested in a wide variety of Fruity Chutes, so I use those on any rocket under about 20 pounds. For rockets over 20 lbs, I usually use my SkyAngle Cert 3's. Usually, I make a call on the field depending on weather conditions. I have some LOC parachutes I like as well, but I modified them with nylon strap bridles and swivels, so they are very similar to the Fruity Chutes now.

At just under 2 pounds, this rocket should fly perfectly on a Fruity Chutes Iris Ultra Compact 30". I think that will give some nice sub-12 FPS landings. For hard surface landings, maybe move up to a 36" Iris. Fruity Chutes descent rate calculator shows a 9 FPS landing with that chute. With a JLCR, should be able to get this to land close by and have a soft landing.
I think the 30" would be good.
 

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Not having great luck with the detail painting. I repainted the white paint (masked off the orange areas) and that went well. Then I put on a mask to paint the belly an aluminum color. The mask worked perfectly this time, but the two coats of aluminum did not stick to the white paint. I know, I should have lightly sanded the white area before I painted the aluminum, but I didn't and now I need to scrape a bit more. Luckily, the aluminum color paint is peeling of pretty easily. Shouldn't have to sand it off, just scrape, then mask and sand the white and paint again.

I plan to launch this rocket at MDRA this weekend, so I may wait until next week to finish all the painting and decals. Get a flight or two under it's belt and then detail painting and decals. If I continue painting and decals this week, it will not have time to cure the final clear coat before I fly it this weekend.
 

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mtnmanak

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Prepped the recovery system to fly this weekend.
- Put the rail buttons back on
- Using 20 feet of 1/8 bungie cord for the shock cord instead of the elastic band the kit came with
- Bungie is tied to the nosecone with a bowline and 2 half-hitches
- About a third of the way down the shock cord, placed a swivel for connection to the parachute (at the field)
- Kevlar bridle was cut to length and retied
- Bungie attached to the bridle with another bowline and 2 half-hitches
- This weekend, planning to use the screw retainer that came with the kit. Will install an Aerotach 29mm retainer once all the painting is done
- Not planning to use Nomex, going to go with dog barf this weekend and see how things go

Ready for test flight, crossing fingers on the weather this weekend
 

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Scott231

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The stock motor retainer will work fine. Twenty feet of bungee cord made me lmfo. 10 feet of it will stretch to twenty, which is still much more than needed. Yeah yeah, better safe than sorry but you are just adding unnecessary weight.
Good luck with the maiden flights. They are always the most Butt-clenchers 😅
 

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The stock motor retainer will work fine. Twenty feet of bungee cord made me lmfo. 10 feet of it will stretch to twenty, which is still much more than needed. Yeah yeah, better safe than sorry but you are just adding unnecessary weight.
Good luck with the maiden flights. They are always the most Butt-clenchers 😅
Thanks! May not stick with 20 feet long term, I just didn't want to cut up the piece I had since I may use it for something else. Should get me through the weekend. Wind is looking like it may be high, though, so will have to make a call at the field to fly it this weekend or not.
 

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Unfortunately, it was way too windy this weekend at MDRA to fly this rocket (10-15MPH). Great weather otherwise and flew a bunch of heavier rockets (put a Apogee Level 2 up on a K690 to 8000 feet), but this rocket would not have worked in that wind.

Gives me time over the holidays to address the messed up paint on the belly and finish the details and decals. Hopefully will fly in January!
 

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