Scratch build Falcon 9 v1.1

I've started to build a 1:39 scale Falcon 9. I'm building all the components from the ground up (except for motors) so this build will take some time. I'll post updates of progress every week or so. The tube is 90mm (OD 94mm, 3.7in), 4 wraps paper tape and 2 wraps fibreglass around a 90mm mandrel. I've made one length of tube and the second one is under way. (My mandrel is only 1 metre long - I probably should make a longer mandrel but I have this one now and the short length makes release fairly easy).
The rocket will have 9 motors in first stage and 1 motor for second stage. Minimum motor size for 1st stage is 9 x C11-3 (24mm). I haven't worked out max motor yet. 9 x 24mm MMT only just fit in the 90mm tube. The 24mm MMT in the octaweb layout all touch one another and touch the 90mm tube - but it will fit.
The other option is to use 18mm MMT. However, the minimum motor in this case is the Aerotech D13. Bit too expensive to install 9 x RMS 18/20 motor casings. Also, 18mm MMT is a bit limiting for motor upgrades after the first launch.
Recovery system: Main chute at top of 1st stage, Drogue at base of 2nd stage, main chute at top of 2nd stage, chute at top of trunk, chute at top of dragon capsule. The 1st stage will descend tail first - as per the Falcon 9 - albeit without the propulsive landing that spacex is attempting. The interstage and 2nd stage will descend together under the drogue and main. During descent the trunk and dragon capsule will be ejected to descend under their own chutes.
i haven't decided on the avionics yet - perhaps the TeleMega. Any suggestion here would be welcome.
I'll post updates and photos in a few days.

op:

That is one heck of a first post. That is a very ambitious and uber cool build. I look forward to following along.

Also, welcome.

Interesting to be sure !! How are you addressing stability??---H

hornet driver said:

Interesting to be sure !! How are you addressing stability??---H

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Very good question. I plan to use poly carbonate fins at interstage and at the base. The second stage motor will be in the interstage which will remain connected to the second stage after separation from the 1st stage. This little bit of extra length will increase stability of the 2nd stage. I'll also put a little weight in nose cone. The current design in Open Rocket has .6 cal for the 2nd stage. The combined stages is about 2cal - depending on motor selection. The fins at the base will be shaped similar to the landing legs.

I have completed one length of tube (with white undercoat) and one length of 24mm MMT. The second length of tube is under construction. I'm also building a mandrel for the coupler tube. The second length of MMT is also underway. Once all the tubes are complete I'll cut them to size.

Very interesting. Why did you choose a 1:39 scale?

I, too, did a F9v1.1 build, but it was 1:48 scale (standard tubing sizes) and nixed the second stage because it would have been too hard to stabilize. Still had 9 motors in the booster (29+8x18).

jmattingly13 said:

Very interesting. Why did you choose a 1:39 scale?

I, too, did a F9v1.1 build, but it was 1:48 scale (standard tubing sizes) and nixed the second stage because it would have been too hard to stabilize. Still had 9 motors in the booster (29+8x18).

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1:39 for several reasons. I had a 90mm mandrel, which gives a 94mm OD, and that works out to 1:39. I wanted to use 24mm MMT and the 9 engine octaweb with 24mm MMT just fits in a 90mm tube. If I went with 4" tube the weight would be too much for 9 x D12 motors. Since I make my own tubes and nose cones I can use any diameter that suits the application. The only requirement is standard MMT sizes. I have mandrels for all MMT from 18mm to 38mm.
How did your 1:48 Falcon work out. Have you flown it?

The template is from Open Rocket and I made the alignment guide in Inkscape (although any drawing program would do the job.

Next: Buy the polycarbonate and cut out fins.
Slot the tube
Assemble MMT and CR

You could build scale legs and web them with polycarbonate to act as fins.may be kinda draggy though.

Rad said:

How did your 1:48 Falcon work out. Have you flown it?

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Quite well, though I've only used the core 29 so far. I think I'll be attempting a full cluster at NSL this year.

Ravenex said:

You could build scale legs and web them with polycarbonate to act as fins.may be kinda draggy though.

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Ooooh. I like that idea.

Ravenex said:

You could build scale legs and web them with polycarbonate to act as fins.may be kinda draggy though.

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I did give that some thought, although it looks quite challenging. My Falcon 9 is only semi scale. If I made the fins the same size as the scale legs then the rocket would be too stable. Also, there is too much flex in polycarbonate to make fins that large - unless I went with thicker polycarbonate. But that just adds a lot more weight and drag. The concept I decided was to use clear fins so the rocket looks like a Falcon 9 in flight (the non-reusable model). The fins will have a shape similar to the legs so that when standing upright on display it looks like the version with legs.
Maybe I could make detachable legs to use when on display and remove them for flight.

That would be cool, or just have the ejection fold them it like a copper recovery does and sick the landing under chute.

Ravenex said:

That would be cool, or just have the ejection fold them it like a copper recovery does and sick the landing under chute.

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I like the way you think. The engineering would be difficult. I've just thought of some ideas to do this. The lower part of the legs would need to be be split down the middle (to go over the polycarbonate fins) and hinged at the bottom - as per Falcon 9. The foot of the lower leg would be connected to a rod (probably Carbon fibre to keep weight down) that slides into the body tube. As the rod slides up into the BT it will lift the foot up until it makes contact with the outside of the BT. The rod forms the upper/leading edge of the leg assembly when the legs are extended. When retracted, the rod would slide into a tube that is mounted inside the BT. I would have a spring inside the tube with a catch to keep the leg retracted. A servo controlled by an altimeter would release the catch allowing the spring to push the leg down. Would probably need a hydraulic damper to control the extension. Springs and damper would then act as shock absorbers for landing. Would also need an ejection charge to release the chute after landing - to stop the wind blowing the rocket over.
It sounds pretty complicated - does anyone have any other ideas for retractable legs.
PS Retractable legs are not really part of this build but it's an interesting idea and something I may add on later.

Finished the booster engine mount. I can't see how to insert photos on separate lines to provide a description for each photo - May because I'm working off an ipad?

The template was printed out from Open Rocket. Holes scored with hole saw before cutting out CR.
CR sanded to size before cutting holes all the way through. CR for 2nd stage (38mm MMT) and booster thrust ring also cut out. Centre hubs of CR epoxied to centre MMT then the 8 octaweb MMT epoxied (wrapped in blue tape while epoxy set). Completed mount slides into body tube.

Wow, very nice work my friend !!

hornet driver said:

Wow, very nice work my friend !!

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Thanks for the comment.
I'm working on the fins for the 1st stage now. Since polycarbonate does not bond very well, the fins will be bolted to the engine mount and the whole assembly will slide into the tube.

What materials are you using to make your tubes, I got the fiberglass part, but what kind of paper tape, glue etc. The tubes look great.

rharshberger said:

What materials are you using to make your tubes, I got the fiberglass part, but what kind of paper tape, glue etc. The tubes look great.

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Tubes are made with 4 wraps jointing paper tape (50mm wide plasterers tape) and exterior wood glue (PVA) and 2 wraps 195gsm fibreglass with west system epoxy. I could make tubes full fibreglass but the composite design is lightr and nearly as strong. For a high performance rocket I would go with fibreglass, or phenolic/fibreglass.
The fins are cut out and I'm currently making the mounting plates to hold the fins to the engine mount assembly. I'll post some pics when I have it ready to assemble.

Rad said:

Tubes are made with 4 wraps jointing paper tape (50mm wide plasterers tape) and exterior wood glue (PVA) and 2 wraps 195gsm fibreglass with west system epoxy. I could make tubes full fibreglass but the composite design is lightr and nearly as strong. For a high performance rocket I would go with fibreglass, or phenolic/fibreglass.
The fins are cut out and I'm currently making the mounting plates to hold the fins to the engine mount assembly. I'll post some pics when I have it ready to assemble.

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Thanks for the quick reply, looks like you are using a spiral wrap method, for the tape and a convolute wrap for the FG.

rharshberger said:

Thanks for the quick reply, looks like you are using a spiral wrap method, for the tape and a convolute wrap for the FG.

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Spiral wrap for both tape and FG. The paper tape is wrapped edge to edge. The FG cut into 200mm (8") wide lengths and wrapped with half overlap.

This is very cool! Subscribed!

rocketgeek101 said:

This is very cool! Subscribed!

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Thanks for the feedback. The fins are cut out and I've made the ply mounting plates for the fins. I am in the process of making a fin alignment guide and then I can slot the tube. When the tube is slotted I can assemble/epoxy the mounting plates to the engine mount - while fins are bolted to mounting plate and I will slide the assembly into the tube and keep fins aligned with slots in tube and with the fin alignment guide while the epoxy sets. When it's ready to assemble I'll upload photos that may make this explanation a little clearer.
Only the fin mounting plates will be epoxied, so after epoxy has set the eng mount and fins will be able to slide out. I decided on this design so that I can replace fins if they break. I can also have different size fins for different applications. I can also upgrade the rocket with larger engine mounts. I'll discuss motor retention and eng mount retention in a later post.
I'm busy at work this week so may not make much progress until end of week or weekend.

Your craftsmanship is exquisite. I don't think my [lack of] patience could handle that. I just took a laser cutter to the whole thing.

But I must ask--how are you planning to do motor retention?

Great layout and execution.

Finally have some time to get back to rocket building. I have now slotted the 1st stage tube for the fins.
I included photos of my home made fin slotting jig in case anyone is interested. I made 2 boxes from kitchen whiteboard (left over from a job). The top box slides down over the lower box. The weight of the box is sufficient to hold the tube in place. There are 2 strips of rubber glued to the under side of the top box to "grip" the tube on either side of the slot. The V groove in lower box is made from 2 lengths of pine attached at right angles. It can take tubes up to 6" diameter. Addition of aluminium angle allows for slotting of tubes as small as 24mm. A small piece of timber (of appropriate length) placed in V groove before the tube is used to set the starting point of slot. A piece of timber clamped to the top sets the length of the slot. The 2 lengths of pine screwed to the top are the router guides (set at the width of router)
Tomorrow: Epoxy fin mounting plates to motor mount.

The fins are bolted to the fin mounting plates, then the fin mounting plates are epoxied to the engine mount. I made a fin alignment guide, 2 pieces of ply with hole to suit the tube and slots cut at 90 degrees. The easiest way I made to make this is to mark out 2 lines at 90 degrees and then to cut the slots with router, and finally to cut the hole.
After applying epoxy to the fin mounting plates the whole engine mount with fins was placed in the tube and placed in the alignment guide. This kept alignment while the epoxy set.
The concept with this design is that engine mount is removable to allow replacement of the fins - if ever required

An ambitious design if ever there was. I salute your audacity.

I enjoy watching someone who is obviously skilled, pays attention to the details, and most of all patient...very nice everything so far!