Roc Sim help with a 10" Gooney Mosquito

[PSLimo]

Hey Guy's,

I'm putting together a sim file for a 10" Gooney Mosquito and I'm not the best at odd fins or roc sim in general, lol.

Anybody want to scale these fins to the attached Roc Sim file and help me out?

Phil

 

[jqavins]

I see you've posted an ork file, which is from OpenRocket. I can give it a shot in RockSim if you post a RockSim file. One the advantages of OR is that it can use RS files, but RS can't use OR files.

Also, what size do you want it? The easiest dimension to work with would be the root.

 

[jqavins]

At first glance, the curved part appears to be a portion of a circle. On closer inspection, it's not. If I work out the geometry using a circle, it will be pretty close, but I won't be able to get it perfect.

 

[PSLimo]

Hey Joe,

Attached is what I came up with and I'm assuming I should add a base drag cone to it. I put in the actual mass overrides and I'm thinking I can use less than 3lbs in the nose after adding a base cone.

Starting priming it and it's looking like a Mosquito Gooney.

 

[OzHybrid]

Hey Joe,

Attached is what I came up with and I'm assuming I should add a base drag cone to it. I put in the actual mass overrides and I'm thinking I can use less than 3lbs in the nose after adding a base cone.

Starting priming it and it's looking like a Mosquito Gooney.

View attachment 591554

Ooooh, Ahm buildin me one of them....... Get the 161 pipe out and start wrappin some tape.......

 

[PSLimo]

I see you've posted an ork file, which is from OpenRocket. I can give it a shot in RockSim if you post a RockSim file. One the advantages of OR is that it can use RS files, but RS can't use OR files.

Also, what size do you want it? The easiest dimension to work with would be the root.

I didn't know roc sim can't see open rocket files. Here's what I came up with, the fins are kinda close and hopefully won't matter much in the simulation:

 

[jqavins]

I doubt it will matter much, provided the span and total area are good and close.

The second picture, strangely, shows me the geometry a little bit better, so I should be able to take a crack at it tomorrow.

 

[OzHybrid]

With the base drag hack applied, you don't need any additional nose weight. But stability could be interesting after the motor thrust ended. 1st flight is a heads up.....

 

[ljwilley]

The mosquito is about as gooney as a rocket can get by itself. Never thought you actually make it gooney-er, but it looks like you did the impossible! LOL

 

[PSLimo]

With the base drag hack applied, you don't need any additional noseweight.

Can you post the modified file with the base hack?

It took 3lbs to get the stability close to .50 without it.

 

[OzHybrid]

You should learn to do it yourself. It's super easy. Add a transition to the last body tube. Front dia=0, rear dia=body tube dia, length =Pi(3.14)x body tube dia, mass =0 (easiest way is to make wall thickness of transition 0 rather than override mass)

 

[PSLimo]

You should learn to do it yourself.

I just did and thanks for showing me how.

I might still add a pound in the nose for added stability.

 

[kitchw8436]

It's super easy.

As my high school algebra teacher used to say, "Everything's easy when you know how." Maybe, "You can learn to do this," would be a more helpful reply?

 

[PSLimo]

As my high school algebra teacher used to say, "Everything's easy when you know how." Maybe, "You can learn to do this," would be a more helpful reply?

Yep, and everything is easy once someone shows you how to do it.

 

[OzHybrid]

As my high school algebra teacher used to say, "Everything's easy when you know how." Maybe, "You can learn to do this," would be a more helpful reply?

If you read the whole post. I explained how to do it and provided an updated ork file with it shown.

 

[OzHybrid]

The nosecone is a big thing, you could probably get your chute and harnesses inside and deploy from it. This moves weight forward to reduce the amount of any additional weight you'll need to add. You would have to add a bulkhead to keep it there and not move backward under acceleration. That would be bad.

 

[PSLimo]

Hi Norman,

The rocket was designed to have the electronics in the nosecone. I'll install the electronics on a sled perpendicular to the round plate in the nose and the charge wells on other side making a clean and easy set up to just bolt in. Here's what the inside looks like:

 

[OzHybrid]

I'd think your chute and lines would only take up a fraction of that volume. You could do something like this... to hold your gubbins as far forward as you can and avoid adding dead weight.

 

[PSLimo]

Thanks for the input but I need to put the vent holes on the side of the cone. Here's a pic of the nosecone with dimensions.



I don't like dead weight either because I'll need to use punchier motors and I enjoy the low and loud White Lightning motors. This one should be OK on a 54mm J-415W.

BTW, my home field is Bong where LDRS was just held. Anyone that attended can appreciate the need to fly low and loud as there were some boat recoveries!

 

[OzHybrid]

The top bulkhead doesn't need to seal, just hold the bits further forward. There could be holes through it and a reasonable gap at the sides. This gives you some dead space behind that you'd need to pressurise with your ejection charge. But you were going to do that anyway. The one in the photo is 1200grams ready to launch with G64 and goes to 800ft. (that's the max size motor that can be launched at our other MPR site) I used the process I described at the nose, so there is no additional nose weight in this.

You're already quite well down the build process here, so maybe something to think about for next time.

Good luck with the flight

 

[PSLimo]

I'll post a launch pic and hopefully a water and tree free recovery at Bong!

 

[BABAR]

So I am guessing motor eject and featherweight recovery is out?

 

[jqavins]

By the way, here's what's kept me from getting back to you with planform points for that fin shape, as I said I would try to do. The original Mosquito used tongue depressors for fins, which means straight, parallel sides and semicircular ends. I tried and tried to fit that geometry to the picture, and finally concluded that it's just not the shape you've got. If that's the shape you were after - and I'm not saying that you had to - then you took too much off the bottom. So my approach was useless.


If you're still interested, I can take another approach. I'd overlay a grid on the picture and just read points off of that. Come to think of it, I believe someone here has mentioned a web site that will do that for you with a picture that you upload.

 

[PSLimo]

No worries,

I got it close enough to make sure I build it to fly stable. The whole gooney look was to make the fins more stubby than the original.

I think I'm actually getting the hang of open rocket, lol.

 

[PSLimo]

Here's the finished Mosquito Gooney:

 

[BABAR]

Not exactly da Bomb, but pretty darn close,