Build #3 - My take on an LPR Saturn

[snrkl]

So, my Estes designer special has turned up, and I am thinking about my next build...

Now for this build, I want to do something I can fly on the playing field with the kids, but also take to launch days and play with the extra altitude available.

The plan is to build it with a 24mm MMT for D/E motors, and I have just ordered an Estes 18-24mm adapter set for just this purpose.

I have been toying with the idea of doing an homage to a SaturnV.. now I know it is difficult to scale a rocket that normally flies with vectored thrust, so I am not trying to do that... I am going the OPPOSITE direction and thinking of putting LOTS of fins on it..

So far, I am modelling it as follows:

4x trapezoidal fins AND 4x18mm tube fins... Why? Because I think it will look cool...

ORK is attached below with a pic of my early attempt at a colour scheme...



Early profiling shows: (I have never flown on E motors, so I am not even sure on local availability.. Consider E flights "aspirational"...)
- B6-4: 100m
- C6-5: 234m
- D12-5: 330m
- E9-6: 494m (not sure yet whether this will work, need to look closer at how the extra 25mm of motor will work...)
- E30-4: 476m

Things I am wondering:
1) The transitions are the ESTES plastic ones, so no long internal motor tube with a paper transition wrap like I have seen in how-to videos. I am wondering if this will be strong enough or will simply buckle when I launch it..
2) Should I be looking at TTW for the trapezoidal fins if I would one day like to launch/lose this on an E motor...

 

[Rex R]

your shock cord and parachute won't be able to ride that far forward, there is a bulkhead in the way (the aft end of the transition). a C11-5 would work, roughly 190m. you should also check your materials...looks like everything is made of cardboard. the transitions should work fine as is, likewise surface mount fins(though I would be inclined to paper them). looks like an interesting design, go for it.
Rex

 

[snrkl]

your shock cord and parachute won't be able to ride that far forward, there is a bulkhead in the way (the aft end of the transition). a C11-5 would work, roughly 190m. you should also check your materials...looks like everything is made of cardboard. the transitions should work fine as is, likewise surface mount fins(though I would be inclined to paper them). looks like an interesting design, go for it.
Rex

Cardboard: Nice catch - changing the fins to balsa just shifted the CG forward nicely and added 20% to the altitude on a B6...

Parachute: leftover from a body tube resize and hadn't corrected the carry on error... fixed now..

 

[Nytrunner]

The plastic transition is pretty stiff, so nothing would prevent you from making one or both of the transition ends disappear if you need to.

Also, it may be a little heavy for B6/C6 flights. May want to stick with C11's just in case

 

[snrkl]

Also, it may be a little heavy for B6/C6 flights. May want to stick with C11's just in case

I have certainly seen first hand what happens with underpowered rockets (I had a few low altitude lawn darts that fired ejection charges with the NC buried in the turf on my first build before I upped from C6 to D12 motors on a rocket that weighed ~250g)

OR profiling for this shows weight at 53.4g with a B6-4 and 59.6g with a C6-4...

MRLOW for Estes B6-4 and C6-4 is 113g, so I figured even with glue and paint I had a healthy margin to work with.

I am interested in more detailed thoughts here..

 

[Nytrunner]

Ah, that sounds better. I must have been reading the heavier weight with an E12 in your screenshots.

 

[snrkl]

Ah - yes, the screenshot doesn't show the configuration being displayed.. I will adjust screenshots in future to capture this important detail!


I have been thinking about paint schemes. The one I originally posted feel boring to me.

Given the fin complexity, I figure if I am to build this right, some thought into how I am going to paint the damn thing is relevant to the construction order. I am thinking that there are some parts that I might just have to paint before attachment (!!!). Mostly I am thinking the tube fins.. I am toying with the idea of red on the inside of the tube fins, <Kraken style!> or maybe doing the inside of the tube fins with the opposite colour, so black exterior, white interior on the even tubes and vice versa on the odd tubes..

Current iteration is as follows.. I think it is much sexier, but I worry about how I am gonna paint the damn thing...

Two screen shots of the same design, just rotated so the roll pattern details are visible.


NC: White
First tube: 50/50 White / Black vertical roll stripe pattern
First Transition: 25/25/25/25 Black / White vertical & horizontal checkered roll pattern
Second Tube: 50/50 White / Black vertical stripe roll pattern 180º rotated axially from the first tube
Second Transition 25/25 White/Black vertical roll stripe
Third Tube: 25/25 White/Black vertical roll stripe rotated axially 45º from the second transition
Trapezoidal Fins: Red
Tube Fins: Alternating Black/White exterior with either red interior or opposing internal colour

 

[snrkl]

So, I'm planning on using a Kevlar SC mounted to the MMT...

I'm pondering if I should use the thin 1mm thick (what look like 1mm laminated ply) CRs I have in the pack or one of the thicker cardboard CRs for the FWD CR/SC mount.



I know the cardboard one will be stronger obviously, and I'm much more certain the cardboard one will cope with a small channel for the Kevlar to pass under it.

Am I overthinking this for a 100g rocket?

 

[snrkl]

Ok. I decided I was over thinking it and opted to use the thicker CRs.

Progress today, built a tube cutting jog out of: LEGO!



Works a treat. I'm always amazed at the manufacturing tolerances of these little magic bricks.

So, BTs cut, filled and edges CAd.
Trapezoidal Fins cut and shaped (rounded LE/TE)
Tube fins cut.
MMT dry fit - decided on a loop of Kevlar around fwd CR and glued into the fillets.



Ive decided to prime and paint the tube fins before attachment, masking the joint - hopefully I don't live to regret it.

I'm out of epoxy and need to get some wood glue, so that's it for today.

Plan for tomorrow:
Fill/Sand transitions and NC.
Fill/sand/prime tube fins.
Glue the MMT


Still to think about: Figure out how the hell im going to paint the roll patterns.

 

[TangoJuliet]

Looks great so far.

When I use the cardboard centering rings for a Kevlar shock cord, I typically cut a small "V" notch in the outside of the ring, just deep enough for the Kevlar to nestle into. My thought is that by putting it on the outside of the ring, it puts the Kevlar that much further away from the hot ejection gasses, even if just a little.

 

[snrkl]

I'd seen that on a few others - wondered how useful it was.

I'll adjust when I glue it all tomorrow.

I'm liking that this is going faster the second time.

I'm just waiting for the "doh, I thought I had this down pat" mistake with this one... &#128540; confidence kills!!

One of my work buddies is hassling me to make a Kraken - maybe I'll have to try a small scale scratch built one while this ones paint is drying on the weekend... I reckon I have the parts I need in this designer kit...

 

[snrkl]

Question: what do people do to prevent nose cone clay from shifting over time?

I have a small Estes NC20 that will be inaccessible once this puppy is constructed. The nose has 5g of the clay from this designer kit in it.

I ended up making sure it was packed into the nose with no air and I ran a fillet of CA around the edge of the clay then CA'd the NC cap on also.

The clay was about 8mm below the rim so wasn't flush with the cap, I'm not sure how it will go over time.

Figured I'd ask for next time.

 

[BABAR]

Painting parts before attachment as you have recognized can be challenging. May consider putting cheater strips (could also call the balsa fillets) in place for your tube fins and even your regular fins. These are cut from 1.588 mm balsa (we use a different measurement in the states!). Basically 1.588x1.588 strip the length of your tube or regular fin (can make it smaller) attached BEFORE PRIMING to provide both an alignment guide on the body tube (really helpful on tube fins, but also for regular fins) as well as more SURFACE AREA for the attachment. Especially with larger diameter tube fins or with a mix of tube and regular fins, the strip can be placed to be inconspicuous or even completely hidden on the final product.
Once attached, you can mask off the "joint" side of the strip and paint the potentially exposed side the body tube color.
This works especially will if body tube color at attachment point is black, as you can easily just use a black marker to color the fillets.

 

[TangoJuliet]

I've never had nose clay shift. Even though it doesn't harden, it won't come out.

 

[snrkl]

I've never had nose clay shift. Even though it doesn't harden, it won't come out.

Thanks. Good to know.

 

[snrkl]

Painting parts before attachment as you have recognized can be challenging. May consider putting cheater strips (could also call the balsa fillets) in place for your tube fins and even your regular fins. These are cut from 1.588 mm balsa (we use a different measurement in the states!). Basically 1.588x1.588 strip the length of your tube or regular fin (can make it smaller) attached BEFORE PRIMING to provide both an alignment guide on the body tube (really helpful on tube fins, but also for regular fins) as well as more SURFACE AREA for the attachment. Especially with larger diameter tube fins or with a mix of tube and regular fins, the strip can be placed to be inconspicuous or even completely hidden on the final product.
Once attached, you can mask off the "joint" side of the strip and paint the potentially exposed side the body tube color.
This works especially will if body tube color at attachment point is black, as you can easily just use a black marker to color the fillets.

I'll have to do some research. I'm a visual thinker - I think this will make more sense once I find a picture. &#128540;

Thanks.

 

[snrkl]

Ok. Busy day.

Papered fins. I think there's wisdom to the "as little wood glue as humanly possible" advice. I wrapped the paper around the LE - I'm happy with the outcome.






MMT glued and trapezoidal fins are on. Used wood glue this time - again, followed Tim Van Milligan's advice of "less glue is more" for the root fillets.



Sanded, filled and sanded NC assembly again (The seams!!) then primed.




Tube fins: I've decided to paint/finish them completely off body and then glue them. Taking my advice from many of the kraken build threads on rocket review.



Still thinking about the best way to get perfect alignment.

I'm thinking of how I can Lego a jig to put them in place perfectly.

Oh, and I WON'T forget the LL this time, as it's gonna be impossible to add after the tube fins go on!

 

[TangoJuliet]

You're moving right along, and it looks good.

 

[snrkl]

#leSigh

White Gloss on tube fins - accidentally pressed down too hard on the last sweep and with one stroke: wrinkles... and because of the way I had both tubes on my fingers painting them at the same time: I hit both tubes...






I've never hit wrinkles before - I wonder if it will sand out.

I guess these will have to wait a few days before I try.

Doh...

 

[snrkl]

On closer inspection, it might have been my decision not to fill the spirals in these tube fins that is the problem.

If you look closely, all the wrinkles start on a spiral line.

#ponders

 

[snrkl]

For the record - roll patterns look awesome.

They are a PITA to mask.

If anyone knows an awesome trick to make it easy - I'm all ears!

I ended up using a whole bunch of 1x1cm, 1x2cm and 0.5x2cm strips for the edges.

I also accidentally cut into the white gloss when trimming an errant edge.

Time will tell if this sucks or not.

 

[snrkl]

Didn't get to painting today - a kids birthday party was a much more deserving of the time.

I'm prepped to prime the body, paint the roll pattern on the NC and re-try the gloss finish on the tube fins after the crackling has been sanded back to the primer.

 

[BABAR]

For the record - roll patterns look awesome.

They are a PITA to mask.

If anyone knows an awesome trick to make it easy - I'm all ears!

View attachment 320909View attachment 320910

Doesn't get easier than this

https://www.hobbylinc.com/cgi-bin/s8.cgi?str_s=trim monokote&p=2

Trim monokote checked patter

 

[snrkl]

Ok, so blue tape worked amazingly well for a total of one of the roll pattern squares, and terribly for every single other edge.

It looked terrible.

Current status: sanding the whole thing back and re-priming, then trying again with the Tamiya tape that everyone raves about.

I also had a mishap with one of the red trapezoidal fins. One fin wrinkled as soon as the paint hit it. I'm convinced I must have broken the CA/Paper seal on the tip edge when fine 600grit sanding the fin. I think as soon as the paint hit it, the unsealed razor thin edge just wicked all the solvent out of the paint.

 

[neil_w]

For what it's worth I use Tamiya, although it's not a magic cure-all. I always try to remember to burnish all the edges just before painting.

Shooting a quick coat of the base color (or even better, clear coat) onto the masked rocket before the top coat can help seal the edges of the tape to reduce bleeding. I haven't personally tried this yet but plan to.

Finally: keep your masking tape in a clean environment. Dust and dirt stuck to the sides of the roll will kill your clean mask edges. When using wide tape like the blue tape, you can clean the edge by laying the tape onto a piece of clean smooth material (glass is good) and cut off the edge with a straight edge and sharp knife. That'll give you a new clean edge.

But for all this, careful use of the Tamiya tape will solve most of your problems.

 

[snrkl]

Ok. Used tamiya tape to mask fin/body lines and to edge the black stripes up the BT.

Sprayed a layer of white base first then a layer of black.

We'll see how it goes.

I've also re-based the NC with white in preparation to have the second go at the roll patterns on the nose. I might simplify them further when I mask it up - all depends on how the tamiya tape goes on the fiddly bits.

Resprayed a new 18mm gloss white tube fin to replace the one I accidentally crushed while trying to sand back the horrible wrinkle.

All up, it's just the wrinkle on the fin whose tip edge seems to have split that is left to resolve.

Once the rest is done I'll ***** whether I fly as is, or try to re-sand/seal/spray the miscreant red fin...

 

[snrkl]

Ok. I'm officially in love with Tamiya masking tape.

This stuff is amazing.

I don't think I could ask for a cleaner edge then this.




I'm going to leave this for the remainder of the 24hrs then remask for the white layer and finish the body.

You can see the red bleed on the fins from the regular masking tape (well, it was the 3M gold painters tape. It's good, but not like the Tamiya tape!)

 

[neil_w]

That looks great!

The shot white before the black also helped, no doubt....

 

[snrkl]

So the roll pattern was better this time, but I still got bleeding under the spots where the Tamiya tape crossed each other, despite how well I burnished it down.

Also, the black wrinkles on two roll pattern squares.

I'm thinking I needed to wait longer between the white base coat and the masking - I think the base layer under the mask needed to wait 48hrs...

So question time:

When using this fine Tamiya tape, what's the process for crossing two masks against each other?

 

[snrkl]

Latest status pic.



I picked the best angle to hide as much of the terrible roll pattern mask leaks as possible... &#128540;