# Alien warship scratchbuild being considered

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#### Bill S

##### Well-Known Member
Here's another design I am fooling around with. 20" long, uses BT-55 and 60 tubes, has unusual center wings with missiles on them. Flies on 24mm motors from D12-3 to E12-4, or an Aerotech E20-4. Stability looks okay even with E12 motors.

Here's the latest version (close to final): Not sure if I like the rear fins or if I should add something to them.

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Looks heavy...

#### Bill S

##### Well-Known Member
Rocksim says 3.9 oz, but I assumed 5oz. Hard to tell without all the parts on hand. Kind of draggy though. D12-3 should go about 475 feet, E12-4 should go about 750 feet, E20-4 about 950.

#### les

TRF Supporter
Rear fins need something or shaped a bit differently. Main part of the rocket is cool, but the simple rectangular fins don't quite make it..... Just my $.02 worth #### Bill S ##### Well-Known Member Rear fins need something or shaped a bit differently. Main part of the rocket is cool, but the simple rectangular fins don't quite make it..... Just my$.02 worth
I tend to agree. The rear fins aren't rectangular, but not far off either. I tried a crosspiece on a fin and I dunno, not sure about that. I'll keep tinkering and hopefully I'll come up with something.

#### boatgeek

##### Well-Known Member
If it was mine, I would make it 4 fins aft. Two smaller ones in line with and echoing the weapons pods and two larger ones that echo the strakes.

#### Bill S

##### Well-Known Member
I did up two versions with fins similar to what I put on the Talon scratchbuild I did. 4 fins gave a stability of 1.31 with an E12 motor, whereas 3 only gave 1.13.

4 fins, offset by 45 degrees:

3 fins:

#### Funkworks

##### Well-Known Member
Since it has 2 main horizontal "wings", it seems to me like it might only need 2 vertical fins, and maybe their shape could somehow align with the small, long vertical "wings". Just my 2 cents.

#### Bill S

##### Well-Known Member
Here is a version being considered that fixes the potential issue I have with Rocksim not recognizing the proper nosecone diameter since I had to cobble together one. Doesn't incorporate Funkworks suggestion - I'll look at that.

#### modeltrains

##### Well-Known Member
If there are 3 boxes on the nose I would use 3 fins on the rear to tie the design together.

#### Bill S

##### Well-Known Member
If there are 3 boxes on the nose I would use 3 fins on the rear to tie the design together.
I just tried that, here is what it looks like. I don't care for it, personally. Thanks for the suggestion though - its how we learn.

#### modeltrains

##### Well-Known Member
I just tried that, here is what it looks like.

View attachment 460842
That's not what I meant; I meant the drawing referenced in quoted material, as it was drawn, not a new and different thing.
Here, maybe expressing my thought like this will work,
[3 boxes on nose]+(body of rocket)+[3 fins aft]
3 and 3 visually "bookend" the design.

#### neil_w

##### Good at some things
TRF Supporter
Here is a version being considered that fixes the potential issue I have with Rocksim not recognizing the proper nosecone diameter since I had to cobble together one. Doesn't incorporate Funkworks suggestion - I'll look at that.

View attachment 460841
I think that one is getting very close. There's a lot of good stuff in there.

I have a couple of further observations on the chute-snaggers rear fins.
1. From here it looks like the left and right fins are really quite close to the missile pods in front of them (and they'll be right in their turbulent wake as well, for what it's worth). It seems like there should be some more separation there, although I'm not sure the best way to achieve it. One way would be to lengthen those fins so they extend further out. Or add another inch to the body between the rear fins and the stuff in front of it. OR, make it three rear fins but offset 60 degrees from the strakes (can you call them strakes if they're 1/2" wide? ) That might look weird.
2. Somehow the shape of the tip extensions just doesn't look quite right to me. Here's one suggestion that has been used on other designs and always (IMHO) looks good. As always you'll need to fiddle to get it just right.

#### Bill S

##### Well-Known Member
Neil, with the 4-rear fin design I favor, the fins are offset 45 degrees, so there should be clearance of the rear of the front wings. When I was fiddling with the design trying modeltrains suggestion, I re-oriented them, forgot to put them back. This is how they should look:

As for the rear fins having more of a rear tip, never tried that, but you know what? I think it works better.

#### Bill S

##### Well-Known Member
Neil, those rear fin tips concern me. I would think they would be prone to breaking off if the rocket doesn't land squarely on the motor mount. Have you any experiences with that?

#### neil_w

##### Good at some things
TRF Supporter
Neil, those rear fin tips concern me. I would think they would be prone to breaking off if the rocket doesn't land squarely on the motor mount. Have you any experiences with that?
I'm not sure, but now that I see them I don't like them anyway. Too much extra complexity on top of an already complex design. I don't have a great idea for it yet. Can you post the Rocksim file?

#### Antares JS

##### Professional Amateur
Perhaps a sharpened dowel at the end of each fin could get a similar effect without being so complex to cut out or easy to break?

#### Bill S

##### Well-Known Member
I'm not sure, but now that I see them I don't like them anyway. Too much extra complexity on top of an already complex design. I don't have a great idea for it yet. Can you post the Rocksim file?
I'll remove the fin tips and post the file for you. I think the dowels will work well enough.

##### Oddrocs Rule!
TRF Supporter
But that rug really tied the whole room together! The Dude abides.

#### neil_w

##### Good at some things
TRF Supporter
The dowels look better.

I'll see if I can get that Rocksim file into OR (should be an adventure) and play around when I have some time.

#### Bill S

##### Well-Known Member
I went back to the older version with the fin tips to the front only, and made the fins a tad longer. I think the fin tips protruding out the back will be too fragile, and when I played around with dowels on the fin tips, stability went down significantly.

I updated the file again, so this is the current version:

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