Another ACME Spitfire build thread?

[Blast it Tom!]

I'm doing this timidly. I've never done a build thread before, and this rocket has been built so beautifully by so many... but I'll try.
Like @Mushtang I won't deviate from the instructions ONE IOTA!!! Err.. uhhh. Except I already bought an AeroPack screw-on motor retainer, so there goes the engine hook. And I'm waiting for an answer about the engine block when using non-Estes motors, so carefully watching the instructions I can start at step 4. You have to carefully cut these out as the top of one matches the bottom of the other so your tube segments will meet:

 

[Blast it Tom!]

So when you're using a metal straightedge and a razor knife, you can make the straight cuts all at once.


For the curvy ones, though, I'll just get my wife's best sewing scissors... OW! STOP IT SWEETIE, I WAS JUST KIDDING! OW!! OW!!!

(Tom will be back after he's recovered from his concussion.)

 

[Blast it Tom!]

She forgot that, being Irish, I have a particularly thick skull.

Anyway, when you get the tube wraps cut out, they should nest together very nicely like this:


I actually did have to take a break cutting those curves, as I wanted to be as precise as possible with those lines. What you're doing here is cutting out what will be matching ellipses, i.e an angle cut on a circular tube. But then you'll rotate the matching tube sections 180° to make the famous profile.

It's kind of amazing how precise you have to be to make a crooked rocket!

 

[Blast it Tom!]

I didn't know how tight these wraps might be, but good ol' @jflis has this dialed right in. I had to ease the tube into the wrap carefully and lightly - very lightly - tap it down to the bottom:

The arrow end points and meeting line are as spot-on as I could get. I taped it in the center first and the matched up the ends.

 

[OzHybrid]

I bought one of these with the intention of scaling it larger, then never did. You've inspired me to actually build the original and forget the scaling...

 

[Blast it Tom!]

Next you mark red and black (or dashed and solid, or aquatangemarine and puce) lines up opposite sides of the tube. Again I figure, be as precise as you can, it can only help later. And when I draw a line like this, I don't want to do anything BUT draw a line. So I jigged the tube up like below on my table saw againt my rip fence. Not shown - I bought a BT-70 nose block and coupler to use as backup when doing the tube cuts, not knowing which might work best; both are in there to keep me from squashing the tube. I measured the thickness of the oak piece, it was flat and uniform to .005".

I did remove the wrapper so that the lines could be extended the full length of the tube.

 

[Blast it Tom!]

Switching back to Step 1, the good folks over here helped me to decide to stay with the engine block in position for a 24 x 70 mm motor, which corresponds to the original Estes D12-4, and also allows up to a fin-ripping Aerotech F. Haven't checked the weights yet, but that ought to be enough choices for this beauty. I understand E impulse is kinda pushing the limit for the Spitfire.

So if the max diameter on the forward extension on an Aerotech is .710".. I removed a wrap from inside the engine block and it seemed to measure .740" - .760". Just to be sure, I found a 1/2" socket in my drawer that measured .730". With much more confidence in that measurement, it fit very nicely, plenty of clearance with the engine block ID. The usual procedure is followed here. About the only thing I could add is that I mark my glue spatula with a piece of tape 2-1/4" from the tip to help me get the glue at the correct depth in the tube.

As I will be using a retainer, the engine hook is omitted, so for now, back to the oblique cuts on those outer body tube segments.

EDITED TO ADD: Yours truly, Mr. EXPERT Rocket Builder, didn't get his spent motor casing out fast enough.
Titebond 3 grabbed that thing incredibly fast. So... I have more BT-50 tube, and so it looks like the engine block will be the end of an spent Estes D or E motor.

Ya gotta be quick with Titebond 3!

 

[Wrightme43]

Thank you, I have one of these to build amd it is intimidating.

 

[Art Upton]

I have almost never used engine blocks since 1975 , masking tape has huge uses; in a 1974 NAR newsletter article called "In Defense of Masking Tape"..

Did you know a Dr. Kosden used a masking tape thrust ring on an O motor at Black Rock?

 

[Art Upton]

If you already glued your engine blocks, then just don't sweat it, your still going to use masking tape since the engine hooks are not used. I quite mostly using them in 1975 as well.

They were designed for non-technical people to fly a rocket at a park.

 

[jflis]

Excellent! Another ACME thread

 

[Alan R]

I designed this several years ago for mine. 3D printed nosecone. A bit sturdier than the cardstock. Check it out if you have access to a 3D printer.
https://www.thingiverse.com/thing:3987864

 

[Blast it Tom!]

I designed this several years ago for mine. 3D printed nosecone. A bit sturdier than the cardstock. Check it out if you have access to a 3D printer.
https://www.thingiverse.com/thing:3987864

Bless you! I haven't revealed my "theme" yet, it's still kind of in-progress, but I am thinking of some 3D printed parts. I don't have a 3D printer though (yet!).

 

[Blast it Tom!]

Excellent! Another ACME thread

Jim (if I may be so familiar), that kit in my opinion is your magnum opus. I'd love to see the "Flis-sim" file on it!
And look, at least 20 years on and people are still deriving great enjoyment from it! Good on you, sir!

 

[Blast it Tom!]

If you already glued your engine blocks, then just don't sweat it, your still going to use masking tape since the engine hooks are not used. I quite mostly using them in 1975 as well.

They were designed for non-technical people to fly a rocket at a park.

Thanks, Art. I glued the engine block AND the spent engine I pushed it in with! (D'Oh!). So my plan is to use an Aero-Pack retainer, and after cutting a new piece of BT-50, I'll likely put the engine block in just for ease of using black powder Estes D's. Friction fit is great, but mechanical retention at both ends without it, to my thinking is better. I never did like engine hooks, to be honest; and as you say, back in the old days, friction fit was it! My K-11 WAC Corporal was that way, along with twin slits in the body tube for the shock cord!

 

[Art Upton]

Well the way it explained in 1974 was not to use just a friction fit.

Wrap a piece of masking tape on the end of the motor till it will no longer go further into the cardboard tube; that is your thrust ring.; I sometimes make these half the width of a normal roll of tape.

Make sure you leave enough of the motor tube out past the end of the centering ring to now wrap masking tape around the motor and the motor tube.

That is now your Retainment Ring.

 

[Blast it Tom!]

Well the way it explained in 1974 was not to use just a friction fit.

Wrap a piece of masking tape on the end of the motor till it will no longer go further into the cardboard tube; that is your thrust ring.; I sometimes make these half the width of a normal roll of tape.

Make sure you leave enough of the motor tube out past the end of the centering ring to now wrap masking tape around the motor and the motor tube.

That is now your Retainment Ring.

Ok, yes, then your thrust ring is in the rear vs at the glued-in engine block, and boom, the problem of engine length goes away.

 

[neil_w]

Nice build so far. I feel kind of lame for never having built one of these...

 

[Blast it Tom!]

Nice build so far. I feel kind of lame for never having built one of these...

Thanks you, but also, you're one of the paint-masters here. I could have done a build thread on the Odd'l Breakaway, which is now finished except for paint - and I may PM you for some advice there!

 

[Alan R]

You are aware of the ACME gallery I hope: https://www.rocketryforum.com/threads/fliskits-a-c-m-e-spitfire-sp007-gallery.15502/

 

[Blast it Tom!]

You are aware of the ACME gallery I hope: https://www.rocketryforum.com/threads/fliskits-a-c-m-e-spitfire-sp007-gallery.15502/

Too aware! The builders there have set a VERY high bar!

 

[Alan R]

The only problem I've had flying this is landing a little too hard will pull the fin off of the lower cardstock shroud. I've had to re-glue one back on after most every flight.

 

[Blast it Tom!]

The only problem I've had flying this is landing a little too hard will pull the fin off of the lower cardstock shroud. I've had to re-glue one back on after most every flight.

Yes. I think someone on here did a thru-wall fin that rooted to the BT-70 inside. I have considered doing the same, and adding some more clay or other such stuff up at the other end to make up for it. And I'd be ever so happy if they'd post their pattern!

 

[Blast it Tom!]

Well, I cut the replacement BT-50 for my jeen-yus screw-up yesterday. Don't have tube cutting guides. So I made my marks by using my razor knife in the valley between the two stood carefully side-by-side, then taped, inserted an old E case for backup and they match lengths within tolerance, maybe 1/64" difference at most.
The E casing will also provide the new engine block.

 

[Blast it Tom!]

The new thrust block went in with BSI 5 min. epoxy. Note I marked my glue spatula with tape to show how far up in the to go with the glue. I also ran a long old machine screw through the nozzle of the D12 to give me something to yank on if necessary! It was kinda handy.

Now I'm back to a normal assembly and, except for not mounting the engine hook, will proceed without further deviation from the instructions... well... I hope!

 

[jflis]

Jim (if I may be so familiar), that kit in my opinion is your magnum opus. I'd love to see the "Flis-sim" file on it!
And look, at least 20 years on and people are still deriving great enjoyment from it! Good on you, sir!

I’ll have to dig that pic up again (Flis-Sim)

interesting (for me) factoid about this design…. All of the other kits in our catalog, to this point, were designs I had done and flew LONG before FlisKits was even a dream. Hell, the Deuce design goes all the way back to the 70’s…

the ACME Spitfire was the FIRST model I designed FOR FlisKits and it was nerve racking as I, quite frankly, wasn’t sure if I still had it in me to design a model that would appeal to others they way my earlier designs did. The ACME, more than any other design, convinced me that FlisKits was a good idea and would go far…

good stuff

 

[Wrightme43]

I’ll have to dig that pic up again (Flis-Sim)

interesting (for me) factoid about this design…. All of the other kits in our catalog, to this point, were designs I had done and flew LONG before FlisKits was even a dream. Hell, the Deuce design goes all the way back to the 70’s…

the ACME Spitfire was the FIRST model I designed FOR FlisKits and it was nerve racking as I, quite frankly, wasn’t sure if I still had it in me to design a model that would appeal to others they way my earlier designs did. The ACME, more than any other design, convinced me that FlisKits was a good idea and would go far…

good stuff

I bought your Acme kit, and the Tomahawk it. I want to practice more before I start on them though.

 

[Blast it Tom!]

Well, I'd better get going again before I have to necro the thread! Thank God for ORDERING us to take a day off, enjoy Him, and relax!

Today was steps 4-6, cutting the external tubes. Two things that are quite important:
1. Mark each section with its number and note the top or bottom. I did this before cutting the section.
2. Maybe it's just me, but I found that having a sacrificial BT-70 balsa coupler (or nose block) inside the tube for bracing really made making these cuts easier.

I also tried leaving the template in place as a cutting guide. I still made the pencil line, but having the guide there helped. I taped it to the bottom end so it wouldn't go anywhere

And, as always, put in a new blade!

Here's some pics:


The other three segments were completed in the same manner. I was able to stack them as I went!

 

[Blast it Tom!]

So then it's back to the engine tube. Time to mount some centering rings! Except, uhh, the directions call to align the alignment mark on the #1 centering ring opposite the engine hook, and blimey, I have no engine hook! So I looked ahead in the instructions carefully just in case the angular alignment of these items carried any consequence, and having satisfied myself that was a firm "negative", I set up some 1/2" precision blocks. You see, the instructions are such that you make a mark 1/2" from the bottom of the motor tube, and set the bottom face of the ring aligned with that. So I figure, let gravity continue doing its job... and that will be it for tonight.

 

[Blast it Tom!]

But I do have some engineering decisions ahead. Ok, ok, the instructions! But... I have no engine hook, and the instructions say to align the rear of outer tube section 1 with the bottom of the engine hook. Ok, I can solve that, pull the hook from the bag, place it against the motor block where it should have been and measure the protrusion - 11/32". That'll be an odd-sized block!

And I've never used card stock structurally, as in the skirt that the fins are glued to. So do I slot that, and attempt TTW fins that glue up to the inner BT-70 section 1? I saw another build, forget whose (but thanks), who double-layered the cardstock, but I don't want to mess up the ID of the skirt where it meets the large centering ring at the base of the outer tube section 1. Either way I feel like I'm skirting disaster... And for TTW fins, it would seem you'd have to temporarily tack the large lower centering ring in place until the skirt dried around its top joint, so you can get at the roots and fillet them to the BT-70.

Now I do trust Jim. But I tend to build as strong as I can for something that I'll want to fly a lot.

I also want to allow for a vented section for my Flightsketch Mini, a delightful instrument.

And I haven't revealed my theme yet, but it will require some windows in either the top segment or the nose cone, which makes @Alan R's offer of a 3D printed nosecone more interesting, too.

Now I have to go check my tiger trap.