Brainlord's LPR SciFi Spacefighter build thread. (no heavy weapons)

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Brainlord Mesomorph

Well-Known Member
Joined
Apr 2, 2018
Messages
266
Reaction score
26
OK in another thread I proposed a bad idea that will be undiscussed here.

That idea was refined to a much more normal design. Some call it an oddroc. Some doubt even this reduced design will fly. I'm building it anyway, and some people have insisted on a build thread. (my first) so here goes:

this is the design:
QaLwBBP.png

EDIT: the OR render sucks. The fins are beveled (but don't appear that way) and ignore the grain, its wrong too.

the whole idea is an excuse to see how far I can push the custom inkjet decals, so here they are:
sAbPSci.png

(that's just WIP)
 
I can't say I don't like it. I'm a designer also. CrAzY about unique fin designs! Which is what I'd like to address. I feel pretty certain OR told you it was over stable? Perhaps. OR can hang it in its techno EAR for all I care. Most of my models are deliberately over stable. Now, the only concern I'd have, is how far forward those main fins are. Darn near to the base of the NC. This creates extra drag at the top of the rocket, which can destabilize a model. I have my proof perched on the "queen shelf". But if you are stubborn like I am, you're going to want to prove this to yourself. This old school dood sees 2 possibilities that you might want to think about. Usually, enough nose weight can balance just about anything. Then there's the longer airframe option. Putting more forward tube and some added nose weight goes a long way.
 
I can't say I don't like it. I'm a designer also. CrAzY about unique fin designs! ... Putting more forward tube and some added nose weight goes a long way.

there'll be 45 g of clay in that nosecone. OR gives it a caliber of .4 (about 3/4 an inch)

plus highly beveled and polished surfaces that I think will help pull the CoP aft.
 
I wouldn't put that much faith in OR. All too many times I've heard someone say, "OR said it checked out fine. I have no idea what happened" My first version of Time Warp never flew right no matter how much weight I put the nose cone. I was told and sorta knew my fins were the culprit. They just started way too forward. 1st pic is the shelf queen that wouldn't fly. 2nd pic is a Corel Draw rendering. I don't have a pick of it yet but it looks like the image on the right. Flies like a champ too. It's also a larger rocket in all aspects.

DSCF3144.JPG

Time Warp pic 9.jpg
 
Any chance you can move the engine mount forward? Keep it less than one motor tube recessed diameter to avoid Krushnic effect, but may buy you potentially significant fraction of a caliber of stability
 
Any chance you can move the engine mount forward? Keep it less than one motor tube recessed diameter to avoid Krushnic effect, but may buy you potentially significant fraction of a caliber of stability

If you're talking about mine, no. There's not enough room to push it forward. It's not worth modifying anyway. Better to just look cool and pretend it's former life was in a Star Trek episode. Redesigning it was a more pleasing option.
 
I want to thank everyone for their design suggestions. But I'm pretty much past that part.

I'm building *this* if she flies, she flies. If not... :D


As I said this is mainly an experiment in decal wrapping. Learning what I'm learning to that, is the point.

That said, I'm obviously farther along in construction than I've posted here (I have to catch up on my picture posting). And I have discovered a new design problem, and I believe its solution.

The question is; where does the shock cord mount go in a rear blow piston design?

and the answer I've gotten (thanks Steve) is in the "combustion chamber" of the piston, and use something fire resistant like kevlar. But I'm certain that with this nose-heavy wing-heavy design it would just zipper. So I think I have a solution:

The Shock Cord Channel! (All shock cord - all the time! ... no):

1. putting the shock cord mount in the aft of the main tube
2. cutting an opening in the forward centering ring of the rear blow section that will clear the mount.
3. putting two 1/16 balsa "walls" down the rear blow section, sealing in that area. (forming a channel)

When the ejection charge goes off, the rear blow section rides around the shock cord mount like a monorail!

The shock cord is folded up in that section, I can put a little piece of wadding in the front of the channel to protect it. The chute goes in the other 3/4 of the tube.

Hmm? Pretty?

I can't imagine it not working.

(I'll get back to my picture posting after dinner)
 
Super Cool. What motor are you planning to use given your final weight?
OR says a C gives it 500 ft.

S Rear eject is awesome but couldn't traditional front ejection have worked?
yeah, but:
1. I was worried about the nosecone getting impaled on those two big points in front.*
2. I liked the idea of a smooth one-piece front end (like a B-52)
3. Never tried read blow before

*but now that I look at it I traded 2 points in front, for 6 points in back!

Keep up the good work.:)

TYVM.



Now... where was I?

It seems I forgot to take more pics of fin beveling, but they all got beveled. Inside corners were a bear. As you work on one side you'r gouging the other side. I muddled through.

While I have precut Estes centering rings, OR gave me the pattern for them and I had what would have been scrap balsa on the fin pattern, so I squeezed them on the pattern and figured I would at least try to cut them.
JT6TwNB.jpg


No that won't do at all. (I should buy a hole-saw... wait I might have one.....)

One came out passably well on the outside, so i decided to use it the bulkhead.
kOqEJiB.jpg


Test fitting the parts:
Yo1cCWs.jpg


Coating tube ends in CA:
EACgfBn.jpg
 
Now it was time to put the 40 g weight in the nosecone.

I have Official Estes clay in the Big Box o' Parts, they gave me 2 lumps. That'll do, I think. Together they weigh 14 g. LOL. But I'm building rockets in what is actually my art studio. So there are no less than six kinds of clay on the self next to me. The tough part was picking one.

Earthen (pottery) clay, looses mass and shrinks when it dries, but when dry it will stick to glue, oil-based (modelling) clay never dries or looses mass, but won't stick to glue. Then I found this artificial German plastic modeling clay called DAS that hardens and the label says you can glue it while wet. That's the very thing we're looking for!

So I weigh out 40g of it:
DzmDHZt.jpg

That's a lot of clay for a rocket

Pack into the nosecone for shape.
gu6PbcA.jpg



Then I took it out, put a bunch of T&Q in the cone, put it back and put more T&Q on top.

e23LFHc.jpg


I used an xacto and put those cuts in it. My hope is that if it cracks, it will crack there, and not pull away from the nosecone. Like putting sawcuts in a freshly poured sidewalk. (it was worth a shot)

And I glued in the bulkhead.
Zstst86.jpg
 
I tried something new with this build,

I usually paint fin edges in CA, (but I hate CA) so this time I tried acrylic nail polish. Goes on smooth, easy to clean up, makes a beautiful edge.

swvpY7W.jpg

Fins drying. Notice the high gloss, smooth finish on the wing on the right side of the pic.

By now the nosecone was dry:
EEJ0l3b.jpg



So I glued it to the main tube:
alhpaId.jpg



This made the rocket very happy:
DxwxJVh.jpg
 
OR gave me the pattern for the boattail. I had to try twice, the first one creased the cardboard was so thick. The second time I rolled it a little at a time up and down the cone until I could get it meet w/o creasing.

nwm3v4M.jpg

More T&Q. ( I think I use more T&Q on a rocket than TB)


And glue it into place:

UUSG4Uz.jpg


OK, I'm an idiot!

Once I glue the boattail to the aft centering ring, it doesn't fit in main tube anymore!! (didn't quite think that through!)

So I have to retrofit the rearblow section w/ a coupler. (good thing I have the Big Box o' Parts)
nqEnF8I.jpg
 
With the rearblow section drying, Its time to start gluing on fins.

The BT60 coupler that I didn't use for the rearblow section was sitting there, it gave me a great idea for a fin jig!
U76qBuE.jpg

There's a piece of 3/16 balsa across the diameter of the coupler as a spacer and to make sure the fins on both sides line up.

And wings:
mFLQxfG.jpg


GdF6KUQ.jpg


Getting there....
 
If this wasn't rear ejection, this design might qualify as a lead contender for a chute snagging award. Here's a pic of my runner up and best in my fleet for eating parachutes at apogee.

19.JPG
 
If this wasn't rear ejection, this design might qualify as a lead contender for a chute snagging award. Here's a pic of my runner up and best in my fleet for eating parachutes at apogee.

I love that. is it scratch?

That is unfortunately close to what I plan to next!
 
As long as you don't exceeded the maximum lift off weight of the C 6 then you are OK. You can always put in more punch with a D15 or 21 if needed. Need to keep up the speed off of the rod. I have always had good luck with the plasticine modeling clay sticking to the Estes cones.
 
Hi guys, I'll get to posting pics this afternoon.

Question: I just spent way too much time figuring how to make a decal wrap fit around an ellipsoid nosecone.

You guys want a tutorial about? (should I go into the math?) or should I just skip over that?
 
One of the best stories I heard from a real Rocket Scientist was that they had to make a large corporate logo look good over a cororgated surface. They told the top management it would be a real pain to do the math and expensive to install. The top man said do it because the most important thing was that it looked good going up for the primary investor's wife present at the launch.
 
One of the best stories I heard from a real Rocket Scientist was that they had to make a large corporate logo look good over a cororgated surface. They told the top management it would be a real pain to do the math and expensive to install. The top man said do it because the most important thing was that it looked good going up for the primary investor's wife present at the launch.

Having dealt with venture capitalists, I totally get that.
 
Back
Top