4 in Hawk stability

[DaHabes]

If you really plan on flying this from H's to K's, you ought to invest in LOCs RNWS. If you add weight via lead shot and epoxy, it's permanent. This system gives you the flexibility to fly any engine on any given day depending on field size and wind conditions. I would swap out their eyebolt for a welded one, however. Can't believe they ship with a standard one....

https://locprecision.com/product/rnws/

 

[Scott_650]

If you really plan on flying this from H's to K's, you ought to invest in LOCs RNWS. If you add weight via lead shot and epoxy, it's permanent. This system gives you the flexibility to fly any engine on any given day depending on field size and wind conditions.

https://locprecision.com/product/rnws/

I think the LOC 4” Hawk comes with the adjustable nose weight system - at least the current description on LOC’s website says it does.

 

[DaHabes]

I think the LOC 4” Hawk comes with the adjustable nose weight system - at least the current description on LOC’s website says it does.

I know, but, he must not have one if he is talking about lead shot to liquid (epoxy) weight ratios and adding weight as he goes bigger. That precludes using smaller engines for different conditions. I think he would be asking how to use the RNWS if he had one. Just sayin'....

 

[Dawgbert]

I know, but, he must not have one if he is talking about lead shot to liquid (epoxy) weight ratios and adding weight as he goes bigger. That precludes using smaller engines for different conditions. I think he would be asking how to use the RNWS if he had one. Just sayin'....

It has one, trying to set it up correctly.

 

[Dawgbert]

If you really plan on flying this from H's to K's, you ought to invest in LOCs RNWS. If you add weight via lead shot and epoxy, it's permanent. This system gives you the flexibility to fly any engine on any given day depending on field size and wind conditions. I would swap out their eyebolt for a welded one, however. Can't believe they ship with a standard one....

https://locprecision.com/product/rnws/

It came with one, was going to go ahead and put enough in the tip of nosecone to cal a small motor. This will also put the weight a little further up.
Cross drilled and put two brass pins to help keep it there.

 

[David Schwantz]

RNWS by LOC

 

[Dawgbert]

RNWS by LOC

Thanks!

 

[Back_at_it]

Dogbert,

I have the 1.63 version of the Hawk from LOC. During the build I first added 3oz of weight to the nosecone and flew on an E12-4. While the rocket did go most upward, it did seem a bit unstable on a very low wind day. I came back and added and additional 3oz bringing the total nose weight to 6oz. I have since flown it on an E30-7 and F44-8. Both flights were dead stable and straight as an arrow.

My recommendation would be to contact Jason or Dave at LOC and talk to them. They will need to know the weight of your completed rockets as well as the CG but they can give you all the info you need.

 

[mo2872]

It came with one, was going to go ahead and put enough in the tip of nosecone to cal a small motor. This will also put the weight a little further up.
Cross drilled and put two brass pins to help keep it there.

The RNWS weight slug container with eyebolt attached goes in first, with the spacer tube at the "back" of the nosecone.....so, feed your shock cord and clip through the RNWS bulkhead, then through the spacer, then connect to your weight slug, then slide it all in the nose cone. That puts the weight you've selected for the motor "forward". I have made three slugs for my 4" Phoenix......300 grams, 462 grams, and 800 grams. If I need to go bigger than the 800, I'll have to get a longer slug tube, and lose some of the "spacer" tube.

I'll get some photos of the assembly this evening......

 

[Dawgbert]

Dogbert,

I have the 1.63 version of the Hawk from LOC. During the build I first added 3oz of weight to the nosecone and flew on an E12-4. While the rocket did go most upward, it did seem a bit unstable on a very low wind day. I came back and added and additional 3oz bringing the total nose weight to 6oz. I have since flown it on an E30-7 and F44-8. Both flights were dead stable and straight as an arrow.

My recommendation would be to contact Jason or Dave at LOC and talk to them. They will need to know the weight of your completed rockets as well as the CG but they can give you all the info you need.

View attachment 449388View attachment 449389

Okay, I like the paint scheme, really cool.
Would you mind if I copied it on a 4" version?

 

[Dawgbert]

The RNWS weight slug container with eyebolt attached goes in first, with the spacer tube at the "back" of the nosecone.....so, feed your shock cord and clip through the RNWS bulkhead, then through the spacer, then connect to your weight slug, then slide it all in the nose cone. That puts the weight you've selected for the motor "forward". I have made three slugs for my 4" Phoenix......300 grams, 462 grams, and 800 grams. If I need to go bigger than the 800, I'll have to get a longer slug tube, and lose some of the "spacer" tube.

I'll get some photos of the assembly this evening......

I was looking at all the parts that came with it and had been considering the possibilities, wasn't sure about using the blank tube for a spacer or not.
Then I noticed a lot of air space in the tip, done some measuring, it seems the weight I need will fill the void plus about 1/4 of the tube.
This would be for the H motor and the individual slugs don't have to be as heavy.
I really appreciate everyone chiming in here, it's going to be great!
Dawgbert

 

[Back_at_it]

Okay, I like the paint scheme, really cool.
Would you mind if I copied it on a 4" version?

By all means. Please do.

 

[dr wogz]

Instructions say sim it and put CG in front of CP with nose weight, no reference to adding a body diameter. I'm thinking some of this may be "understood" in the rocket world, and I just don't know!

Do the instructions mention where the CP should be? (Instead of the CG.. There seems to be no mention of this anywhere in the thread..)

Seems like an oversight on LOC's part, for not including this vital piece of info.. Or even mention it on their 'additional information' tab on their page. (And telling you to sim it yourself, even with their sim file provided, seems lame..)

Pity, as well, that they don't allow the instructions to be downloaded.

https://locprecision.com/product/yhawk4/

 

[Dawgbert]

CP is listed in the instructions, about 4 cm different from my sim, but I don't know how to draw the cutout at the back of fins. Most likely error on my part.

 

[Dawgbert]

Wanted to give an update on my build to anyone that may be wondering.
I emailed LOC about the issue and Jason hit me up with some good information and tips.
I had drawn fins without the cut-outs, re-drew using two sets of fins, this allowed me to insert cut-out in openrocket. Now the cal is 1.32 with 0 nose ballest using H550 motor.
If you think something is screwy please advise, I'm as lost as a small ball in high weeds!

 

[teepot]

I'm as lost as a small ball in high weeds!

You must play golf.

 

[PSLimo]

Hi Dawgbert,

I've built several Hawks from 2.6" to 5.5" and they do require a lot of shot in the nose. The problem with big draggy fins and a heavy nosecone is drag separation and you're going to want to use shear pins. The inserted video is a 5.5" Hawk and you can see as the K550W starts loosing thrust it almost drag separated and without the onboard video I would have never known. And yes it had a 1/4" port hole in the tube.



Good luck with your build.

 

[Dawgbert]

Hi Dawgbert,

I've built several Hawks from 2.6" to 5.5" and they do require a lot of shot in the nose. The problem with big draggy fins and a heavy nosecone is drag separation and you're going to want to use shear pins. The inserted video is a 5.5" Hawk and you can see as the K550W starts loosing thrust it almost drag separated and without the onboard video I would have never known. And yes it had a 1/4" port hole in the tube.



Good luck with your build.

PSLimo,
Thanks for the information. This seems to have been more complicated for a first HPR build than I anticipated. This forum has been extremely helpful, with replies as this.
Do you use openrocket for simulation? My simmed CP is 2 to 4 inches off what LOC states. I had to get a constructive to get the holes in the fins.
Dawgbert

 

[PSLimo]

Do you use open rocket for simulation?

Yes, I'm assuming your dilemma is how much weight to put in the nose for stability. IMO a little more weight than it sim's at in the nose doesn't hurt anything while not enough will. The other consideration is to make sure with the extra weight you choose a motor comes off the rail fast enough.

In my Polcat 5.5" I could have gotten away with 3 ish pounds in the nose but opted for 5 pounds knowing I'm going to fly 3 and 4 grain 54mm motors. That rocket flew on every type of motor from White Lightnings to Smoky's and always flew straight as an arrow.

Always nice to see pic's...




Even in my 2.6" I added a little extra in the nose and flew perfect even on small 1 grain sparkies.

 

[Dawgbert]

Do you use open rocket for simulation?

Yes, I'm assuming your dilemma is how much weight to put in the nose for stability. IMO a little more weight than it sim's at in the nose doesn't hurt anything while not enough will. The other consideration is to make sure with the extra weight you choose a motor comes off the rail fast enough.

In my Polcat 5.5" I could have gotten away with 3 ish pounds in the nose but opted for 5 pounds knowing I'm going to fly 3 and 4 grain 54mm motors. That rocket flew on every type of motor from White Lightnings to Smoky's and always flew straight as an arrow.

Always nice to see pic's...

View attachment 449772
View attachment 449773

Even in my 2.6" I added a little extra in the nose and flew perfect even on small 1 grain sparkies.

View attachment 449776

You have me pegged on the weight, depending on the sim, anywhere from 0 to 450 grams will give it a 1.0 cal. Depends on the numbers I use.
Cool pics!
Dawgbert

 

[Dawgbert]

You have me pegged on the weight, depending on the sim, anywhere from 0 to 450 grams will give it a 1.0 cal. Depends on the numbers I use.
Cool pics!
Dawgbert

How did you simulate the holes in the fins. I ignored the holes in one sim and the CP was 3" forward of instruction sheet. Had to draw them as two sets to get them to look correct. This moved the CP to 2" aft.
Just curious how someone else managed this.
Dawgbert

 

[mo2872]

RNWS assembly photos as promised, if a day or so late.....
Bulkhead, spacer tube and weight slug(s)...


Weight going in the cone.....



Spacer following the weight....



And bulkhead screwed in place....

 

[Dawgbert]

RNWS assembly photos as promised, if a day or so late.....
Bulkhead, spacer tube and weight slug(s)...
View attachment 449790

Weight going in the cone.....

View attachment 449791

Spacer following the weight....

View attachment 449792

And bulkhead screwed in place....

View attachment 449793

Thanks for taking time to do this. Got it!
Dawgbert

 

[PSLimo]

Dawgbert,

I wouldn't worry about the slots in your simulation but I can tell you from flying many Hawks they'll whistle on the way up on a punchy motor!

You're going to get a lot of different opinions here on how to get it just right. I say, just fly safe and stable with a voice of reason and have fun with your Level 1. Then put a good 1lb+ in the nose for your Level 2 and hit it with a 3 grain J-450W and it will put on a show like the picture I posted above and you'll get around 4000'.

P.S. Don't forget the shear pins, lol.

 

[Dawgbert]

Dawgbert,

I wouldn't worry about the slots in your simulation but I can tell you from flying many Hawks they'll whistle on the way up on a punchy motor!

You're going to get a lot of different opinions here on how to get it just right. I say, just fly safe and stable with a voice of reason and have fun with your Level 1. Then put a good 1lb+ in the nose for your Level 2 and hit it with a 3 grain J-450W and it will put on a show like the picture I posted above and you'll get around 4000'.

P.S. Don't forget the shear pins, lol.

Alright, now I'm getting a little giddy!

 

[David Schwantz]

Hi mo, are you sure that you have the assemble order correct. The way you have it set up the card board tube, spacer, is taking all the load.

 

[mo2872]

Hi mo, are you sure that you have the assemble order correct. The way you have it set up the card board tube, spacer, is taking all the load.

Yup, that’s the way the instructions I received showed it from LOC. That puts the weight furthest forward, and the spacer is braced between the slug and the RNWS bulkhead. It’s had three launches on the small slug, and one on the midsize, and had no issues.

 

[David Schwantz]

Ok, all of mine show the eye bolt at the bulkhead, in the spacer tube. That way all of the load it transfers directly to the bolted bulkhead. Glad it works both ways.

 

[Dawgbert]

By all means. Please do.

Here is my best shot at the 4" version!

 

[Dawgbert]

Here is my best shot at the 4" version!

I wanted to thank everyone for the tips, went with doing the following:
2-56 shear pins
RNWS , but put enough weight in tip of cone to balance smallest motor (360 grams)
Tested ejection, third time is a charm.
Changed paint scheme, thanks to Back-at-it.
Hoping to get level 1 certification this Saturday on an H550 at HARA.