New Design: Drakh Raider

[CoachJT]

This is still a work in progress, but it looks promising

[CPMcGraw]

This is still a work in progress, but it looks promising

Is this being done with RockSim? What are your simulation runs showing?

Wild design!

[James Pierson]

Looking forward to this one CoachJT.

James Pierson
NAR# 77907

[CoachJT]

Thanks everyone for the compliments.

I originally did it in Rocksim v8, then updated it in v9. I love the pod feature :D

Here is some of the flight data.

Wind speed model: Slightly breezy (8-14 MPH)
Low wind speed: 8.0000 MPH
High wind speed: 14.9000 MPH

Launch guide length: 36.0000 In.
Velocity at launch guide departure: 46.9705 ft/s
The launch guide was cleared at : 0.233 Seconds
User specified minimum velocity for stable flight: 43.9993 ft/s
Minimum velocity for stable flight reached at: 33.4321 In.

Using a delay time of : 7.000 Seconds
Velocity: 56.6158 ft/s
Altitude: 882.89042 Ft.

P: Parachute Deployed at : 8.651 Seconds
Velocity at deployment: 56.6158 ft/s
Altitude at deployment: 882.89042 Ft.

The deployment speed is obviously way too fast, and I think I need a longer launch rod. I'm going to keep working on this one though.

[CPMcGraw]

What engine did you select?

On your deployment, is the parachute showing an "ascending" or "descending" arrow?

[JRThro]

What motor?

And I find it hard to believe that those looooooooong forward-swept fins won't flutter at least a bit.

[CPMcGraw]

Good point, John. Although being a work-in-progress, that might be correctable with a stiffener or two. Like the spar of a wing, running the long dimension. A CF "I" beam, with the balsa fitted in the channels, might be enough.

[CoachJT]

I was using n Estes d-12. I definately needed a longer rod. Much better performance after I went to a 48 in. rod.

I too thought about those fins flapping back and forth like a card in bicycle spokes. Without some sort of reinforcement, those things would snap like a twig.

Here is the file if anyone wants to play.

JT

[CenturiGuy]

I too thought about those fins flapping back and forth like a card in bicycle spokes. Without some sort of reinforcement, those things would snap like a twig.
Yours is more faithful (and therefore *much* cooler looking!) than the whack I took at this design:

http://www.oldrocketforum.com/showpost.php?p=46143&postcount=180


I theorized that the fins could be made of a couple of criss-crossed 1/16" balsa. That basic idea might work for you (although you're doing 24mm instead of 18mm like I did).


Cheers,

[mycrofte]

I think the 'safe' thing to do is put clear plastic centers in the fins.

[pantherjon]

I did some playing with it..Changed the fin material for the lower fins to 1/16th aircraft plywood..Which meant I needed to up the nose weight to get a good CG-CP margin(5oz!!:eek: )
But, still flies fine on D12-5's! :D Not too bad a DV if I say so myself..lol..Even did one on an E - it will scoot!

[CoachJT]

Thank you very much for the compliments and ideas.

I was trying to use an 18mm, but I was unable to get good sims out of it with 18mm power. However, I really don't think that a finished prototype would weigh as much as Rocksim says it does. I don't think the weights are all that accurate. If this is the case, 18mm would be able to give it good flights.

In any case, I will be revisiting this design as often as I can.