Wildman V2 2.6" Cp and Faux Fins

Can any one validate my estimated Cp for a Wildman V-2 2.6" model.

Ok, I don't own a version of RockSim needed to model Boat Tail rockets. I do have it drawn up in OpenRocket, but I'm sure that is simple a waste of time.

So I went old fashion... I cut out an outline on some luan plywood.


Found the CG for the outline to be 13.8" from the tip.


Can someone confirm that the Cp for this rocket is very near my estimate of 13.8"?

THANKS!!!!

If someone knows the CP for the V2. Does anyone know CP for the 4" SAAB?

Has anyone used faux fins as a means to force the Cp in OR to be correct? And if so, does the simulations then work?

If my means to determine the Cp is correct for the V-2 2.6" rocket, I still needed a way to have the Cp modeled correctly. I decided to make some fins with 0 thickness, and move them in a position that forced the Cp to 13.8. Weight and Cg remained correct, and Cp moved to my estimated position.



i've added 2.8 oz of nose weight to move the Cg to 12.34" from nose tip without the motor. But I still needed a way to simulate the Cg and the stability factor with various motors. Using the Faux Fins seems to work.

Anyone else attempt this with success?

I've got the Wildman 2.6" V2 and Rocksim so I can give it a shot based on actual part weights, hopefully in the next day or so. I just got my order with this rocket and the Punisher and the small SAAB and I haven't started any construction yet. I assume you want the CG measurement with a motor loaded, any particular one you had in mind?

Thanks!

Here is my version in OR. It has nose weight added, and a mass for epoxy and foam used in the fin can. Maybe it will help in creating the RockSim file.

It also has the faux fins which is simply my experiment to determine if OR can be used for simulation this rocket.

View attachment TRF_WM_2.6_V2.ork

External fin fillets still required to complete the build. And then if it flys, it can earn some paint.

Hopefully I can finalize if more nose weight is required before its maiden flight.

Okay, I think my Rocksim file is pretty accurate and it is telling me I need 4 ounces of nose weight to get 1 caliber of stability with a G80 loaded. CG is 11.7" from nose tip, and CP is 14.1" from nose tip. I'm using a Sky Angle Classic 32 parachute in the nose cone as well. Using the Rocksim Stability method, not Barrowman. I did not use any Faux Fins that are sometimes needed for short and stubby rockets to sim properly, because I don't consider the V2 to be extremely short. I'm just guessing at epoxy weight, so I could be a little off. Total weight with motor is 36.5 ounces.

MisterMan said:

Okay, I think my Rocksim file is pretty accurate and it is telling me I need 4 ounces of nose weight to get 1 caliber of stability with a G80 loaded. CG is 11.7" from nose tip, and CP is 14.1" from nose tip. I'm using a Sky Angle Classic 32 parachute in the nose cone as well. Using the Rocksim Stability method, not Barrowman. I did not use any Faux Fins that are sometimes needed for short and stubby rockets to sim properly, because I don't consider the V2 to be extremely short. I'm just guessing at epoxy weight, so I could be a little off. Total weight with motor is 36.5 ounces.

Click to expand...

Thank You!

The more accurate Cp will help...

My build must be really light, although it is currently missing the external fin fillets. Even with 2.8 oz of nose weight, my total weight with 18" thin-mil topflight parachute is currently only 23.4 oz empty, and 27.1 with a G80.

Looks like a lot more nose weight is necessary.... Too Bad...

MisterMan said:

Okay, I think my Rocksim file is pretty accurate and it is telling me I need 4 ounces of nose weight to get 1 caliber of stability with a G80 loaded. CG is 11.7" from nose tip, and CP is 14.1" from nose tip. I'm using a Sky Angle Classic 32 parachute in the nose cone as well. Using the Rocksim Stability method, not Barrowman. I did not use any Faux Fins that are sometimes needed for short and stubby rockets to sim properly, because I don't consider the V2 to be extremely short. I'm just guessing at epoxy weight, so I could be a little off. Total weight with motor is 36.5 ounces.

Click to expand...

Just received mine yesterday, though fin slots are out of alignment. So will have to get a new boat tail. But 4 oz seems like a lot. This is my first V2 model, so not really sure what is typical for these types, but is that pretty standard for a shorter rocket like the V2?

I only have OR, not RS, so haven't tried messing around with simming it.

blueapplepaste said:

Just received mine yesterday, though fin slots are out of alignment. So will have to get a new boat tail. But 4 oz seems like a lot. This is my first V2 model, so not really sure what is typical for these types, but is that pretty standard for a shorter rocket like the V2?

I only have OR, not RS, so haven't tried messing around with simming it.

Click to expand...

V2's typically need a lot of nose weight, often in the range of about a pound for 4 inch rockets.

Willie - I have built three V2's. I have only added NC weight to one kit and only because it came with the kit. Both of my Wildman kits require no NC weight. I have talked to several people including the kit manufacturers and they have all told me that Open Rocket sims aren't reliable for boat tail rockets. Just keep your velocity off the pad high enough and the thrust to weight ratio above 5:1 and you'll be ok.

Willie said:

My build must be really light, although it is currently missing the external fin fillets. Even with 2.8 oz of nose weight, my total weight with 18" thin-mil topflight parachute is currently only 23.4 oz empty, and 27.1 with a G80.

Click to expand...

That does sound light, but I think most of the difference is your parachute only weighs 1/2 an ounce and mine weighs about 4 ounces. Here is the breakdown of component weights in my Rocksim file:

All the fiberglass components: 17.6 ounces
Sky Angle 28 Chute: 4 ounces
Kevlar 1/4" harness, 10' Kevlar 1/4" cord, 10" Nomex: 2.8 ounces
Epoxy (8 internal fin filets, 8 external fin filets and a centering ring filet): 3 ounces
Nose Weight: 4 ounces
G80 Motor: 4.5 ounces

Total: 35.9 ounces

CG is 12.17" from NC Tip, CP is 14.1 from NC TIP, Margin of stability is .75 caliber.

With my chute Rocksim says the decent velocity will be 21 feet/second and I really don't want it coming down faster than that.
With your 18" nylon chute Rocksim says the decent velocity will be 35 feet/second, and while a fiberglass rocket will probably survive that, I would hate to get bonked on the head by 2 pounds coming down that fast. :^)

The V2 is not a short and stubby rocket. It does not qualify for any of the tail cone/faux fins type of treatment in a sim. The tail cone invalidates all of that, for certain.

V2 rockets are represent a typical problem from a hobby standpoint. A lot of the scale rockets/missiles are designed to deliver a payload of a certain mass using active guidance. In the case of a real V2 it needs to have a ton, yes 2000 pounds, in the nose. So, that means that essentially all V2 models will need additional mass in the nose. They will also benefit from fast hitting, high thrust motors to get them moving so the fins have enough corrective force.

MisterMan said:

Okay, I think my Rocksim file is pretty accurate and it is telling me I need 4 ounces of nose weight to get 1 caliber of stability with a G80 loaded. CG is 11.7" from nose tip, and CP is 14.1" from nose tip. I'm using a Sky Angle Classic 32 parachute in the nose cone as well. Using the Rocksim Stability method, not Barrowman. I did not use any Faux Fins that are sometimes needed for short and stubby rockets to sim properly, because I don't consider the V2 to be extremely short. I'm just guessing at epoxy weight, so I could be a little off. Total weight with motor is 36.5 ounces.

Click to expand...

Launched this Wildman V2 2.6" on a F52 with the delay trimmed to 6 seconds. The nose weight of 2.8 oz worked great!

Old thread resurrection...

FINALLY built my Wildman 2.6" V-2. I've read both threads (I only found two) dedicated to this rocket, and the nose weight answer seems to vary from zero to 5.5 oz, with some consensus at 4oz.

A little extra stability never hurt anything, and this is not a record setting rocket. My Rocksim shows 0.75 caliber stability without noseweight, but I am curious if RS models the boat tail correctly or not. Does anyone else have anything to add to this after a few years of this rocket being on the market?

Also, what brand and size chute did you use? I used to fly from a dry lake bed and always had to oversize chutes to prevent damage. Out east now, and flying from a sod farm, it's a little less of an issue. But, relatively stubby rockets always make this a challenge. I am inclined to get a 24" Top Flite with a chute protector and call it a day, but interested what others have done here.

Viperfixr said:

Old thread resurrection...

FINALLY built my Wildman 2.6" V-2. I've read both threads (I only found two) dedicated to this rocket, and the nose weight answer seems to vary from zero to 5.5 oz, with some consensus at 4oz.

A little extra stability never hurt anything, and this is not a record setting rocket. My Rocksim shows 0.75 caliber stability without noseweight, but I am curious if RS models the boat tail correctly or not. Does anyone else have anything to add to this after a few years of this rocket being on the market?

Also, what brand and size chute did you use? I used to fly from a dry lake bed and always had to oversize chutes to prevent damage. Out east now, and flying from a sod farm, it's a little less of an issue. But, relatively stubby rockets always make this a challenge. I am inclined to get a 24" Top Flite with a chute protector and call it a day, but interested what others have done here.

Click to expand...

Try using the short fat rocket trick for rocksim, a cone ( transition on bottom of rocket) of airframe diameter x 3.14 aiframe dia long. I use this in OR to sim my V2's and it showed significantly less nose weight than I thought it needed, and flight testing confirmed that the indicated nose weight was correct.

Edit: Mark earlier discredited the cone method for this rocket, that being said the models of the V2 I have built and flown using it have proven to be stable with the motors simmed with it so far.

Compare the OpenRocket cone to what the Rocksim method predicts. I'd trust rocksim's CP location over OR's since it has fewer assumptions on its calculation.

Guys,

Assuming that you've built it fairly close to scale, including fin size, every V-2 balances at the same point: where the tailcone meets the body tube. From BT-50 to BT-101 (4"), its the same spot. Put in your largest motor and ballast accordingly. I'd be willing to bet the real deal balanced there, too.