1/40 Delta III

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Jun 7, 2009
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Over the past week or so I have been working on a approx 1/40 scale of the Delta III. The exact scale factor I used was 1/39.6 - Thanks to Silverleaf who has some nice drawings of the Delta III on his web site. These sure made the job easy!
Upper airframe is 4" bt I got from A2Z hobbies and lower bt is bt-80.

The nose cone was the biggest challenge for me as I have always made them out of balsa. I didn't have any balsa big enough to turn a 4" nc so I decided to try and make it out of cardstock. I used the VCP software to print the nc shroud. I cut a 4" circle out of 1/8" ply for the base and I used a 2" styrofoam ball for the rounded tip. I filled the styrofoam with Elmer's Fill-n-finish and then I gave the whole thing 2 coats of West Systems epoxy. A bt-80 coupler is used as the nc shoulder.
The lower airframe's bt-80 runs the length of the entire rocket and the nose cone mates to that.

At the beginning of this project I thought about making the boosters separate but after beginning I decided that I didn't want to make this that complicated. The 9 boosters are all solidly attached.
This rocket will fly (I hope!) on 4 24mm D's (1 in main and 3 in boosters) and 6 18mm something or other in the remaining boosters. Should be fun getting a 10 motor cluster to light!
here's a pic of the nc - I am very happy with how this turned out for my first attempt at a cardstock nc. I used the same technique on the boosters - cones are all made of cardstock with a 5/16" wooden bead for the tip.

I am going to make some clear fins for this thing - where do you guys get the clear plastic to make fins out of?
VERY NICE! I love it! Beautiful Job! Now, you better post pics of the flight....or else.


thanks guys - I'll get flight pics for sure.

Up here in NW Iowa we are patiently waiting for the crops to get harvested so we can fly rockets again. Out here where I live the corn and soybeans are so big that you'd never find your rocket after it landed. The soybeans are starting to turn yellow now so that means in a couple more weeks the farmers will be taking them out.

man I can't wait - almost every day my son and I talk about the big lauinch day we're going to have as soon as the fields are clear. I have been stockpiling motors since June and we are going to try and fly every rocket in our fleet when the day comes.
Gosh, now I know how Peter Alway feels when someone creates a model based on one of his drawing. 8)

If possible, I'd love to see some more pics, and even a video of the flight.

where do you guys get the clear plastic to make fins out of?

Most people use Lexan - check your local Lowes - they sell it there.

Thank you for the kind words, and for making my day !.

I put some finishing touches on the Delta III last night -
You can see Siverleaf's drawing pinned to the wall behind the model.
thank you Stymye -
ever try to find a can of Teal Blue in a spray paint can? I went to 2 different super Walmart's with no luck. Local hardware stores, Lowe's, nada - Someone had posted that he found a Krylon paint called Real Teal at a Walmart but no sign of it around here.
I stopped by Hobby Lobby and picked up a couple little bottles of Testor's acrylic paint in Teal.
I dug out the old airbrush (haven't used it in years), and sprayed the testors teal with it. It took several coats to get an even color but I am happy with the results. This is one of those models that I really like to look at.
That looks excellent !

Love the colors, and the detail on the upper section really shows through on your model.

Now that I've seen a built model based on my work, I'm truly glad that I oversized the drawing to show all the details. When I first drew it in DeltaCad I was concerned about the larger image format, but seeing this made it all worthwhile. 8)

The DM-F3 Delta 3 (IMHO) remains one of the lovliest of the now extinct designs out there, and I'm really happy to see how well your model turned out.

thanks SIlverleaf - your efforts really helped me out.
I only hope this thing will fly - gonna need a lot of nose weight with 10 motors in the back end! Gotta get a new 12v car battry before I try to light this one.
It weighs right at a pound as it sits empty.

I'm thinking D12-0's and C6-0's in the 9 nine boosters and a d12-3 in the sustainer.
Steve -

That's nice work! I started building a Delta II in the same scale (based on BT-80) once, but it's on my "unfinished" shelf now. I may have to pick it up again after seeing your Delta III.

p.s. You may want to try A10-PT's (13mm plugged motors) in your strap-ons. They're really light and give a real kick off the pad (I use a D12-3 in the core and 4 A10-PT's in the strap-ons on my Vostok).
Originally posted by stevem
Thanks to Silverleaf who has some nice drawings of the Delta III on his web site.

Silverleaf, can you post a link to these drawings?, also what else have you drawn up? Your drawings look as though they are an excellent scale data source. I'm sure there are alot of us who would appreciate seeing them.
vjp - thanks for the idea of using the 13mm motors - I never thought of that - I already have 6 boosters set up for 18mm but I can sure make some adapters. I was worried about having too much power but I won't really know until I start working on CP and CG. I think this thing is gonna need a ton of nose weight.
The 13mm would keep the back end a little lighter too.
Silverleaf does some awesome work both on his drawings and his models. His pictures don't do his projects justice. I found that Rustolium Teal is a close match for "Delta Blue" , however I haven't seen it in stores lately. Below is a link to picture of my Delta II, color seems a little greener in the picture than it actually is. https://rmpitzer.syr.edu/launch/nypower02/pages/4scan23_4.htm

steve - beautiful Delta II! I think that needs to be my next project - do you have a good source for specs? drawings?

Did you have motors in all the boosters? What did you fly it on?
How much did it weigh? How was the flight?

Steve M.
Most of the data came from Sport Rockerty and RotW. I did some CAD drawings but not to the extent that I do now. No motors in the GEMs, just a central I357. The flight was straight, unfortunately it was horizontal. Not exactly sure what happened. I have a picture somewhere of it leaving the rod with a vectored exhaust. Either I had a faulty motor nozzle or the trimmed Fat Boy nosecone I was using for the scale nozzle melted from heat off the blast defector causing the vectored thrust. Anyway, another one on the repair pile. (Actually thought about™ converting it to a 3)

sorry to hear the thing gave you trouble Steve - on my DIII I am not going to fly it with any nozzles but I am planning on making a set of nozzles for display - if the rocket makes it through it's maiden flight.

In any case, I'll bet that Delta of yours looks just as good going sideways as it does going up! Great looking rocket!
I was wrong - it would defintely look better going vertical!

Thanks for the pics Steve - all I can say is OUCH !
Today we finally launched the Delta III!

This one's been waiting for her maiden voyage for a long time.

We launched a few rockets earlier today but the wind came up. About 5pm the wind settled down and we decided to go for it.

We had it all loaded up with 4 D12-3s and 6 C6-3s - this is by far the largest cluster I have attempted.

here's Justin holding the Delta showing the cluster
lift off - I really need to figure out how to get better pictures
for those of you who would like to build one of these I have included a picture of all the parts required to assemble the Delta...
I'm guessing, chute didn't deploy (remained stuffed in tube), came in semi-ballistic, hit grass, went crunch.
came in semi-ballistic

that may be an understatement - but you're right, chute did not come out. I am not sure why.

the central 24mm MMT went all the way to the chute bay.
The chute bay is, er, was BT80.

I gotta say the flight was very exciting. All 10 engines lit and the thing got high enough to almost disappear from sight.

It sounded like firecrackers going off as the 9 booster engines ejected themselves. We could see the nose cone come off but the chute did not come out.

The thing came down so fast when it the ground it sounded like a shotgun going off and pieces went everywhere! The sound it made as it came roaring in was really cool!:D

My son and I just kinda stood there for a moment and then started laughing. What else ya gonna do? :)

I will rebuild this one and try again
I have this happen to me all the time with larger diameter rockets and Estes motors. The ejection charge pressurizes the tube but the nose just blows off, relieving the pressure, and the gasses simply bypass the chute(s). I have improved my luck by making a large "pillow" wad by wrapping lots of ejection wadding around some dog barf (for filler). This creates kind of a piston which cuts down on the gasses bypassing the wadding/chute. Also, by attaching the chute(s) to the nose cone itself, instead of further down the shock cord, the nose will always pull the chute out with it.