My Sci Fi space fighter needs heavy weapons (literally- 25g would do nicely)

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Indeed, you are correct. I should like to amend and amplify my previous. It gets fiddly and frustrating when trying to conform a fin to a transition with something different from a conical cross-section. I am really hoping that you will now correct me on this too.

Nope. ;)

Although, using the same technique you can approximate quickly. From a sim standpoint it makes no difference; OR doesn’t know that that edge of the fin is supposed to be flush with the transition anyway. If you’re looking to create accurate fin templates, then you’re gonna probably need to move to a separate drawing program.
 
You could crank the wings back a bit and still keep the look but move up back.

I have, they no longer go 3 inches past the nosecone :)

Version 1c: 40g of clay in the nosecone, and 4 fins

QaLwBBP.png


And starting on decals:
sAbPSci.png


CL1tyID.png
 
OK, those decals are cool.

I'm still doubtful of the flightworthiness with the CP that far forward, but I suppose there's only one way to be sure. ;)

A couple things you could try to fiddle with in OR:
1) reduce or eliminate the tail transition; that is pushing the CP forward. Although it does look good.
2) Another small (maybe cool-looking) change could be to make the forward points on the wings "hollow" (that is, cut out a triangle on the interior so those forward points are just outlines.

If this *does* fly, then... well... I'm thinking upscale. :)
 
With enough power and nose weight you can fly a brick. These were my starter scratch builds and are somewhat in the same vein. The P40 flew OK on a C6 3 but the later Hurricane and Spitfire were upgraded to 24mm D12 power. The Blackburn Triplane needs at least an E composite but likes F power, it's nose cone is packed with modeling clay and copperhead BB's. The amounts of no good, stinking, performance robbing nose weight were appalling to those who value efficiency in rocket science, but they are all stable and fly well in good conditions. The most important thing is that your oddroc's look good. So a little more power and nose weight will solve 90% of the problems associated with making your rocket look the way you want it to.

P40E.jpgP9170001.jpgP9170002.jpgP9140001.jpg005.jpg002.jpg006.jpg003.jpg026.jpg024.jpg
 
Those are very cool :cool:

I thought about shark teeth.

Are you printing decals in white? That's the one thing I can't do, and its a severe limitation

and "oddroc's ??"

EDIT: and might I suggest beveling those fins, according to OR, it adds 100 feet to my Ap.

EDIT2: Oh, OddRocs , "odd rockets" From the context, I thought it was some sort of engineering statistic.
 
You have drawn out a Daddyisabar goonie photo gallery! Thank you on behalf of all of us who appreciate oddroc porn. Now go start another thread and ask about tractor motors. :)

EDIT: and might I suggest beveling those fins, according to OR, it adds 100 feet to my Ap.
I don't think you are looking at rockets designed for altitude. ;)
 
Those are very cool :cool:

I thought about shark teeth.

Are you printing decals in white? That's the one thing I can't do, and its a severe limitation

and "oddroc's ??"

EDIT: and might I suggest beveling those fins, according to OR, it adds 100 feet to my Ap.


The decals are just standard plastic model aircraft decals you can buy off Ebay.

"Oddrocs" is the term used for these sort of rockets. Go down to the Oddroc section of the forum for some weird stuff.

As for square edged fins. Some call them the "Bane" of the hobby. A slap in the face of efficiency and proof positive of laziness and bad design. However, in the land of oddroc reality, it does not make that much difference. Catalog photo models all had square edges because they showed up better on photographs.

OR is a good tool to use, like swing testing, card board cut outs or any thing else you can think of. Fly it as conservative as possible for the first flight, CG as far forward as you can go given your motor choice. Nothing replaces common sense and listening to others with experience.
 
You have drawn out a Daddyisabar goonie photo gallery! Thank you on behalf of all of us who appreciate oddroc porn. Now go start another thread and ask about tractor motors. :)


I don't think you are looking at rockets designed for altitude. ;)

I only gave him the soft porn. Nice, cute, stubby airplane like oddrocs with asymmetrical fins. All based on Baby Berthas or cute Spaceship One models. The hardcore stuff is in other threads. Even hinting on the subject of tractor motors here is forbidden.:)
 
OK, I've pulled the trigger on this!

I've printed fin patterns and laminated them to balsa. Tonight, I'll cut and sand fins, and start in on the body tube and engine mount.

Should I start a build thread? or post updates here? or just check back when I'm done?
 
I only gave him the soft porn. Nice, cute, stubby airplane like oddrocs with asymmetrical fins. All based on Baby Berthas or cute Spaceship One models. The hardcore stuff is in other threads. Even hinting on the subject of tractor motors here is forbidden.:)

Once you get the double-secret password, you can see the hard stuff. Merely seeing them will kill the weak and drive the strong mad. Crazy stuff like a Lancaster with 10 (?) LPR motors. Be warned. :)
 
Once you get the double-secret password, you can see the hard stuff. Merely seeing them will kill the weak and drive the strong mad. Crazy stuff like a Lancaster with 10 (?) LPR motors. Be warned. :)

Yep, the Lancaster had 8 motors. But we have to keep it very soft here. Say some nice late 60's Swedish girls in a sauna with a "Yakety Sax" soundtrack. Again, even mentioning the possibility of mounting canted motors on the forward wing tips would move us up into the vintage Boogie Nights stuff and this is a family forum.

Just look at the nose art on this one! How awesome is that! BUILD THREAD IS A MUST!

YAKETY SAX RULES!

[video=youtube;ZnHmskwqCCQ]https://www.youtube.com/watch?v=ZnHmskwqCCQ[/video]
 
Question on rear blow:
(haven't done it before)

The engine tube is 6" long and goes all the way to a bulkhead at the nosecone. There are 2 centering rings (fore and aft) and the chute and shock cord will be wrapped around the engine tube (loosely). The whole thing is a piston and blows the whole 6" tube out the back. Got that.

No wadding right? The hot gasses are isolated in the "combustion chamber" of the piston.

Does the bulkhead need any protection? I'm thinking of gluing a piece of aluminum foil to it a blast shield.
 
I don't know if anyone touched on this, I didn't take time to read every post.
But I think you want to section those wings or cross grain ply them.
With the wood grain showing the way it is, if it scoops the wind at all it would take a lot of pressure on the point and could snap off.
But I think it looks really, really cool! I too would love to see a video of this fly.
Maybe lengthening the air frame and moving the nose cone forward a bit.
 
Question on rear blow:
(haven't done it before)

The engine tube is 6" long and goes all the way to a bulkhead at the nosecone. There are 2 centering rings (fore and aft) and the chute and shock cord will be wrapped around the engine tube (loosely). The whole thing is a piston and blows the whole 6" tube out the back. Got that.

No wadding right? The hot gasses are isolated in the "combustion chamber" of the piston.

Does the bulkhead need any protection? I'm thinking of gluing a piece of aluminum foil to it a blast shield.

The inner surface of cardboard body tubes are typically exposed directly to the ejection charge exhaust with little damage -- so if your bulkhead is at least as fire-resistant as cardboard it should last for a few launches.

Foiling the bulkhead might actually make it hotter in the ejection cylinder forward of the engine. Some fraction of the heat transfer will be by radiation, rather than conduction by contact with the hot gas. Putting a reflector on the bulkhead will increase the radiant energy incident at some other surface. If you are worried about it, a high heat black paint or a piece of some fire-resistant cloth, might be a better choice than aluminum foil.
 
The inner surface of cardboard body tubes are typically exposed directly to the ejection charge exhaust with little damage -- so if your bulkhead is at least as fire-resistant as cardboard it should last for a few launches.

Foiling the bulkhead might actually make it hotter in the ejection cylinder forward of the engine. Some fraction of the heat transfer will be by radiation, rather than conduction by contact with the hot gas. Putting a reflector on the bulkhead will increase the radiant energy incident at some other surface. If you are worried about it, a high heat black paint or a piece of some fire-resistant cloth, might be a better choice than aluminum foil.

bulkhead is (currently) paper-covered balsa.
My 1st thought was high-temp paint. I don't seem to have any around the house. And I'm not buying a can for 1 square inch.

I could give the foil a spritz of regular Rustoluim enamel. that would address your reflected heat issue, and still give me my metal barrier.
 
bulkhead is (currently) paper-covered balsa.
My 1st thought was high-temp paint. I don't seem to have any around the house. And I'm not buying a can for 1 square inch.

I could give the foil a spritz of regular Rustoluim enamel. that would address your reflected heat issue, and still give me my metal barrier.

What about a layer of glue, like a decent epoxy, or JB-weld, or even a good layer of TB?
 
bulkhead is (currently) paper-covered balsa.
My 1st thought was high-temp paint. I don't seem to have any around the house. And I'm not buying a can for 1 square inch.

I could give the foil a spritz of regular Rustoluim enamel. that would address your reflected heat issue, and still give me my metal barrier.

Seriously, I'd guess it will be fine with or without the foil. Depending on the thickens of the balsa, the greater worry might be mechanical failure. But really, there are plenty of rocket designs that expose untreated paper, balsa, even polystyrene directly to the ejection charge exhaust.
 
What about a layer of glue, like a decent epoxy, or JB-weld, or even a good layer of TB?

That'll do.

The bulkhead is ridiculously heavy. I printed it in margin of the fin pattern so its the same paper-laminated 3/16" balsa they are.

I just didn't like the idea of the EC blasting directly against paper.
 
I don't know if anyone touched on this, I didn't take time to read every post.
But I think you want to section those wings or cross grain ply them.
With the wood grain showing the way it is, if it scoops the wind at all it would take a lot of pressure on the point and could snap off.
But I think it looks really, really cool! I too would love to see a video of this fly.
Maybe lengthening the air frame and moving the nose cone forward a bit.

The grain on the OR rendering is moot.

Grain is parallel the leading edge of the wing. paper-covered 3/16 balsa. Edges coated in acrylic nail polish. I'm going w/ that.

(I am worried about it breaking in the middle where it is narrowest)
 
Getting to the thread late. Sorry, I've been in the hospital for a while and TRF was not on the list of priorities.

1) You've designed the fins as "slabs". You need to get better CG/CP positioning. Making the fins as wedges would be one way to do this. Could also be used to strengthen the fins; strong chance of breaking one/breaking one off.

2) Your design has a tail cone. A "flair" or bell at the base of the rocket will increase the base drag, improving GC/CP.

3) Weight. Go by your nearest shop that turns brakes and ask for the turnings from the brake lathe. You'll get fairly fine powdered cast iron. If they ask, tell them you're putting it on your lawn. You can mix this with epoxy to make "heavy putty", or just pour it into a nosecone and cap it off (a layer of epoxy or Gorilla Glue).

Just some thoughts...
 
Question on rear blow:
(haven't done it before)

The engine tube is 6" long and goes all the way to a bulkhead at the nosecone. There are 2 centering rings (fore and aft) and the chute and shock cord will be wrapped around the engine tube (loosely). The whole thing is a piston and blows the whole 6" tube out the back. Got that.

No wadding right? The hot gasses are isolated in the "combustion chamber" of the piston.

Does the bulkhead need any protection? I'm thinking of gluing a piece of aluminum foil to it a blast shield.

Right, no wadding and although you can glue aluminum foil on the bulkhead, simply coating it with epoxy is all the protection you’ll ever need. For that matter you probably don’t even need to do that. The ejection charge is very short duration and unlikely to burn the bulkhead.
 
Right, no wadding and although you can glue aluminum foil on the bulkhead, simply coating it with epoxy is all the protection you’ll ever need. For that matter you probably don’t even need to do that. The ejection charge is very short duration and unlikely to burn the bulkhead.

Thanks
New question:
Where does the forward shock cord mount go?

I can't put it in the "combustion chamber" of the piston, it'll burn the shock cord (and might zipper the tube), and if I put it in the aft of the main tube, the forward centering ring of the rear blow section will "trip over it" on the way out.

I guess I could put it in the aft of the main tube, between two fins so when it does trip over it, it pivots the rear tube safely between the fins.

Where else can it go? Am I missing something here?
 
Thanks
New question:
Where does the forward shock cord mount go?

I can't put it in the "combustion chamber" of the piston, it'll burn the shock cord (and might zipper the tube), and if I put it in the aft of the main tube, the forward centering ring of the rear blow section will "trip over it" on the way out.

I guess I could put it in the aft of the main tube, between two fins so when it does trip over it, it pivots the rear tube safely between the fins.

Where else can it go? Am I missing something here?

Piston shock cords get placed where the ejection charge gases briefly flow all. You just have to make the cord from a material which is less affected by heat, such as Kevlar, or wrap them in such a material such as Nomex and check the cord frequently to see how it’s holding up.
 
Wonderful project! It has amazing design and you're such a genius!I hope to see it in actual!
 
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