Rocket Racer

[JNUK]

I would like to share details of one of my latest projects. The following description provides its very general overview but please let me know if more detailed description is required.

Inspiration for the design came from several photos of the Rocket Racing League rocket plane.

or here

In fact it is a highly modified version of beautifully shaped and proportioned VELOCITY manufactured by Velocity, Inc.


Check out their gallery for more nice shots of the bird.

General view drawings can be found here (LINK).

Design
I had been learning Google SketchUp8 software. Naturally I wanted to utilise it in the design process. ISO view of the final 3D model I managed to construct is attached below.



The actual SketchUp file can be found here (bottom of the page). It was my first attempt to utilise 3D software in my hobby design process. After passing the initial learning curve I found the tool to be extremely useful. It allows quick evaluation of ideas, simplifies recording of different design variants and what is very important allows quick and easy reproduction of a design. After completing the 3D model, I created component plans (two A4 size pages). Again, they can be found at the bottom of the same page.. All dimensions are adjusted for 1.6mm thick material. I used slightly finer, 1.4mm, Daler-Rowney white core mountboard, but it makes no significant difference.

Assembly
Details are cut out with some margin and glued to the board with a glue stick. After cutting out shapes with a hobby knife, paper templates are peeled off the board. Components are trimmed to fit each other and treated with thin CA glue.

The whole process is shown step-by-step here.
The assembly is bone with CA glue. Yellow glue is used only once to attach the triangular leading edges to wings.
After sanding the model was painted yellow.

Without a motor and a recovery system the model weights about 47 grams. This is including 7g of additional nose weight to bring CG to about 107 mm from the nose tip. Using balsa instead of cardboard will reduce weight to about 25...30g. Combination of different materials is possible as well. For example using balsa wood for fins/wings and retaining cardboard for the rest of the model may eliminate the need for the nose weight.

Recovery system
This aspect has not been worked out fully. The plan had been to use a relatively small streamer to stabilise the model horizontally thus reducing its descent rate. However, it did not really work very well at the end. A conventional parachute worked better and it is a preferred option for now. The recovery system compartment and its hatch may require modification to improve deployment.

Flight test
Estes A10T-3 was used for the maiden flight.

(thanks to Rob House for this shot)
It was followed by several flights again on A10T-3, A3T-4 and Delta B2-3 (this is a motor manufactured in Czech Republic for FAI competition).

In windless conditions the model goes vertically. With some wind (about 3 mph during the test) it travels vertically during the active phase and then coasts at about 60...70 degrees to the horizon.

I apologise for such skinny description. Please let me know if any details or aspect of the design require further clarification.

[chadrog]

Nice work!

[cwbullet]

Very nice. How long was the glide time?

[JNUK]

Very nice. How long was the glide time?

I am sorry if it was not clear from the description. It is not a glider as such. It is better to consider the model a small rocket with rather large fins pretending to be a glider.
However, the original idea was to have a kind of "lifting body" type of recovery when the model hands under a small parachute or a streamer not sufficient on their own, but stabilising the model in a horizontal position allowing for some additional drag from the model itself. It didn't work as I had miscalculated attachment points for the recovery system.

[Serpico]

You need to get an onboard camcorder on that - seems like it would be a great visual!

[JNUK]

It must be a really small camcorder.

[Serpico]

Yup. The use of keychain type spy camcorders is common in smaller rockets. Search the forums for the exact ones used and opinions.

[JNUK]

To be honest I do not think it will be very interesting and worth the effort.

[NJRick]

Beautiful job!!!

I would like to share details of one of my latest projects. The following description provides its very general overview but please let me know if more detailed description is required.

Inspiration for the design came from several photos of the Rocket Racing League rocket plane.

or here

In fact it is a highly modified version of beautifully shaped and proportioned VELOCITY manufactured by Velocity, Inc.


Check out their gallery for more nice shots of the bird.

General view drawings can be found here (LINK).

Design
I had been learning Google SketchUp8 software. Naturally I wanted to utilise it in the design process. ISO view of the final 3D model I managed to construct is attached below.



The actual SketchUp file can be found here (bottom of the page). It was my first attempt to utilise 3D software in my hobby design process. After passing the initial learning curve I found the tool to be extremely useful. It allows quick evaluation of ideas, simplifies recording of different design variants and what is very important allows quick and easy reproduction of a design. After completing the 3D model, I created component plans (two A4 size pages). Again, they can be found at the bottom of the same page.. All dimensions are adjusted for 1.6mm thick material. I used slightly finer, 1.4mm, Daler-Rowney white core mountboard, but it makes no significant difference.

Assembly
Details are cut out with some margin and glued to the board with a glue stick. After cutting out shapes with a hobby knife, paper templates are peeled off the board. Components are trimmed to fit each other and treated with thin CA glue.

The whole process is shown step-by-step here.
The assembly is bone with CA glue. Yellow glue is used only once to attach the triangular leading edges to wings.
After sanding the model was painted yellow.

Without a motor and a recovery system the model weights about 47 grams. This is including 7g of additional nose weight to bring CG to about 107 mm from the nose tip. Using balsa instead of cardboard will reduce weight to about 25...30g. Combination of different materials is possible as well. For example using balsa wood for fins/wings and retaining cardboard for the rest of the model may eliminate the need for the nose weight.

Recovery system
This aspect has not been worked out fully. The plan had been to use a relatively small streamer to stabilise the model horizontally thus reducing its descent rate. However, it did not really work very well at the end. A conventional parachute worked better and it is a preferred option for now. The recovery system compartment and its hatch may require modification to improve deployment.

Flight test
Estes A10T-3 was used for the maiden flight.

(thanks to Rob House for this shot)
It was followed by several flights again on A10T-3, A3T-4 and Delta B2-3 (this is a motor manufactured in Czech Republic for FAI competition).

In windless conditions the model goes vertically. With some wind (about 3 mph during the test) it travels vertically during the active phase and then coasts at about 60...70 degrees to the horizon.

I apologise for such skinny description. Please let me know if any details or aspect of the design require further clarification.

[hornet driver]

Very nice job!! I had to do a double take when I saw the motor size. I looked at the file--had no Idea it was so small---great work!! The pics are outstanding too--esp the flight photos---nice work!

[Daddyisabar]

Great Job! Anytime your airplane looking rocket flies somewhat like a rocket it is a good day.

[JNUK]

Following the experiments described above, I made some changes to the design of the RocketRacer:

1. The fuselage is now wider to allow more space for the recovery system. The panel forming the recovery compartment bottom is repositioned for the same reason. All other dimensions are left without significant changes.
   
2. A special pivot arm has been added to improve the operation of the recovery system. This can be seen in the pictures below.

In the previous design (model B) the shock cord was attached inside the recovery compartment. This did not matter in case of parachute recovery. However, streamer recovery did not work properly. Under all conditions the model went into a dive dragging the streamer behind itself.

Now, thanks to the arm, the model is pivoted by the streamer into position perpendicular to the air stream increasing the drag.

As with the previous design, the model is assembled from a “flat pack”.

Again I used Daler-Rowney white core mountboard for formers, side panels and wings. The series of pictures here explains the assembly sequence.

Due to increased size of the fuselage the model now has a mass of about 50g (w/o motor and recovery), which brings it to the limit of A10 motors. I am not sure if they are still available, but Apogee’s B2 or B7 motors would be an ideal option. As I do not have access to such motors I am planning to reproduce the design in balsa in an attempt to bring its mass to about 20…30g.


Link

Link

Link

[Daddyisabar]

Great job! Just hop across the pond, empty your pockets of all Pounds and Euros at Apogee in Colorado Springs, head on up to Hartsel in South Park at 8,000 feet and I guarantee your rocket will perform much better in the dry thin mountain air.

[Serpico]

Now, thanks to the arm, the model is pivoted by the streamer into position perpendicular to the air stream increasing the drag.

Brilliant ... I love this kind of ingenuity. Simple and effective.

[aerostadt]

Nice model! It reminds me a little bit of the old Estes R/C Astroblaster.

[JNUK]

Nice model! It reminds me a little bit of the old Estes R/C Astroblaster.

Thank you. I didn't know about Astroblaster. Looks interesting, although I'm not planning to build something that big.

[dlazarus6660]

I would like to see this for 'B'-'C' motors

[JNUK]

I would like to see this for 'B'-'C' motors

I have been thinking about modifying and building the design for 19mm motors, but as I have some other ideas in the pipe line, it is not a priority at the moment. However, if someone is interested in building it, I can modify all drawings accordingly.

[dlazarus6660]

I have been thinking about modifying and building the design for 19mm motors, but as I have some other ideas in the pipe line, it is not a priority at the moment. However, if someone is interested in building it, I can modify all drawings accordingly.

I can too and did! I blew these up to 150%. I'm using 1/16" hard balsa. Pics later.

BTW, We don't have any 19 mm motors, but 18mm motors work just fine!
As you can see from my avitar, jet rockets are my thing. I have built and flown a half dozen scale jets such as an A-7 Corsair II, F-4, F-14, F-15, F-16, F-18, F-104, F-105 and I'm working on others. The guys in the club know me as, "if it has wings, I fly it"!
Thanks for a neat design!

[JNUK]

It is the first time someone is building my design! Very very interesting. I am looking forward to seeing your pics.

[dlazarus6660]

It is the first time someone is building my design! Very very interesting. I am looking forward to seeing your pics.

I hope I don't let you down.
I have as yet have someone build one of my designs.
But of course, you have to to like rockets that look like jets!

[JNUK]

BTW, We don't have any 19 mm motors, but 18mm motors work just fine!
As you can see from my avitar, jet rockets are my thing. I have built and flown a half dozen scale jets such as an A-7 Corsair II, F-4, F-14, F-15, F-16, F-18, F-104, F-105 and I'm working on others. The guys in the club know me as, "if it has wings, I fly it"!
Thanks for a neat design!

19mm - It was a typo. I think I was thinking about BT-20 tube OD.
I have just finished another variant of the same design. This time I used light balsa papered with office paper and CA glue. Comparing to the variant above it is about 25% lighter - 40g instead of 50g.

When I said about changing design for 18mm motors, I was thinking about more conservative increase of 25...30%. Your extra 50% is quite a step. Naturally I'd love to know details.
I think you discovered it by now, but if not the thing to be careful with is width of slots for tabs.

Enlarging plans will automatically increase slots making them to large for 1/16" tabs. The same goes for tabs, but it will be easy to send extras off.

I also added a couple of cut outs that may help you: LINK1, LINK2.

[JNUK]

I have built a second RocketRacer. Now I can race them against each other.

[dlazarus6660]

I love the launches.
Got any video of a complete flight?

[JNUK]

I love the launches.
Got any video of a complete flight?

Unfortunately not.

[Montaro]

I have built a second RocketRacer. Now I can race them against each other.

Excelent video camara, very fast, which camara is ?

[JNUK]

Excelent video camara, very fast, which camara is ?

Casio Exilim EX-FC100

[dlazarus6660]

This is as far as I got.
Family issues.

[daniel]

Looking good so far

[dlazarus6660]

It's done.
Well, not quite. I'm gluing on the paper wing extensions.