Build Thread - Wildman Piercer 98

[kswing]

Based on some of the suggestions I received, I moved the parachute down the harness so it is closer to the bay lid and also increased the amount of BP I'm using for the nose to 1.5G. In addition, I packed the chute so that it fits better and switched to a smaller protective blanket. I tried it again today and it worked well this time. Here's a video:
View attachment VID_20220123_113103120.mp4

 

[Theory]

That will work well!

 

[kswing]

Since last weekend I've painted the fins dark green and sprayed all of the red fiberglass with a few coats of clear gloss. Yesterday I received and applied my lettering from Stickershock23 (thanks Mark!). I was going to spray more clear on the booster yesterday, but, it was too cold (high of 27F) and windy. This morning the wind had died so I finally got to apply another coat of clear on the top half of the booster including the sticker. Below is a picture.

I may still add another coat of clear, but, for now it is ready to fly. I'm hoping the weather cooperates for an initial launch at BattlePark in two weeks. I've got a J500 ready to test it out.

 

[Theory]

Nice!!!

looking forward to seeing her fly in two weeks.

 

[kswing]

Today I took this rocket out to BattlePark to try it out on an AeroTech J500G. Unfortunately, upon ignition, the motor adapter thrust ring failed and the motor went up through the rocket and then went horizontally for a few hundred yards. It was one of the most dramatic launch failures I've ever seen. Fortunately, no one was injured and the damage to the rocket appears to be minor, so, it should be ready to launch again by next month. I was also lucky that one of my fellow rocketeers found my rogue motor casing. I was using a cardboard/plywood 54/38mm adapter that I had assembled with 30 minute epoxy. I had used it without problems in the past on launches with similar thrust/weight profiles. Apparently, it must have been gotten weaker over time. I had switched to this adapter when I lost my aluminum adapter (along with a rocket) a few months ago. In the future, I'm planning to switch back to an aluminum adapter.

The damage to the rocket includes two rail buttons getting ripped out as well as a minor cut/crack on one of the fins. Also, the avionics appear to have survived, but, the sleds they ride on were both damaged. The swivel I used for the booster survived, but, the 5/8 tubular nylon shock cord for the booster broke. I'm guessing having a hot motor blasting on it may have contributed to its failure.

Hopefully I'll have all of the repairs completed by next month's launch.

 

[Theory]

Was something to be sure!!!

happy it’s fixable. Look forward to seeing it fly next month

 

[kswing]

I'm happy to report that yesterday I successfully launched this rocket at BattlePark. I used an AeroTech J520W (the only J motor that ships non-HAZMAT) and it made it to about 2400 feet. It was a great day to launch at BattlePark with no mud and light winds and all of the recovery events went as planned. It drifted less than 1000 feet and landed without damage.

 

[BOYLE07]

Congrats on your successful flight! I'm in the process of building a Piercer 98 myself. Did you happen to use any Rocksim files? I'm curious about the unloaded CG. It is stock with the 54mm mount, but pretty much every 54mm motor I try to sim with shows that I need 1lb or more weight in the nose to have a 1 cal stability. I'm thinking about adding an upper payload section to lengthen the whole airframe to make this design more stable without adding a ton of ballast.

 

[jd2cylman]

Congrats on your successful flight! I'm in the process of building a Piercer 98 myself. Did you happen to use any Rocksim files? I'm curious about the unloaded CG. It is stock with the 54mm mount, but pretty much every 54mm motor I try to sim with shows that I need 1lb or more weight in the nose to have a 1 cal stability. I'm thinking about adding an upper payload section to lengthen the whole airframe to make this design more stable without adding a ton of ballast.

I can’t see this needing nose weight. This is HED, correct? So you have to account for that in your sims. Batteries, altimeters, chute, sled, and shock cord are towards the nose. Should be fine.

 

[kswing]

Congrats on your successful flight! I'm in the process of building a Piercer 98 myself. Did you happen to use any Rocksim files? I'm curious about the unloaded CG. It is stock with the 54mm mount, but pretty much every 54mm motor I try to sim with shows that I need 1lb or more weight in the nose to have a 1 cal stability. I'm thinking about adding an upper payload section to lengthen the whole airframe to make this design more stable without adding a ton of ballast.

Good luck with your Piercer 98.....I enjoyed building mine.

Attached is the Rocksim I started with which I received from WM (I guess it was also called a Viper). I upgraded to a longer nose cone and added a few ounces to it so in my version I have the NC at about 25 ounces and the total empty weight at about 144 ounces. I may have built it a bit heavy and I also have it setup with dual-dual deploy so that adds a bit more forward weight. On mine the empty CG is at about 39.5 inches. I use OpenRocket and I update my simulation file to match the built rocket and so far the simulations come out fairly close.

 

[BOYLE07]

Good luck with your Piercer 98.....I enjoyed building mine.

Attached is the Rocksim I started with which I received from WM (I guess it was also called a Viper). I upgraded to a longer nose cone and added a few ounces to it so in my version I have the NC at about 25 ounces and the total empty weight at about 144 ounces. I may have built it a bit heavy and I also have it setup with dual-dual deploy so that adds a bit more forward weight. On mine the empty CG is at about 39.5 inches. I use OpenRocket and I update my simulation file to match the built rocket and so far the simulations come out fairly close.

Oh wow I didn't notice that you did have a longer cone on there. That looks really slick and definitely improves the sims I was doing. WM sent me the rks file awhile back but the length was a little off. I noticed today that the file is now on the website and the unloaded weight is different than the original file I was given so I've been reluctant to go off of that. Of course I will be updating everything once I have mine finished and can actually weigh it.

That being said, I think I might go your route and get the longer nose cone.

Thanks again!

 

[Neo]

I just got this rocket and am planning out the build. Running it through OpenRocket I'm seeing a lot of possibilities with 75mm motors. Has anyone tried or considered sizing up the motor mount to 75mm instead of 54mm? Any advice to offer?

If I go up to 75mm MMT I think it would be nice to be able to fly 54mm motors with an adapter.

 

[kswing]

I just got this rocket and am planning out the build. Running it through OpenRocket I'm seeing a lot of possibilities with 75mm motors. Has anyone tried or considered sizing up the motor mount to 75mm instead of 54mm? Any advice to offer?

If I go up to 75mm MMT I think it would be nice to be able to fly 54mm motors with an adapter.

The main thing I'd be concerned with about sizing it up would be the thickness of the fins. The fins are only 3/32" (.093), so, I'm not sure how well they would handle larger motors. I don't have that much experience with fiberglass fins, so, hopefully there are others on here that will chime in who have tried 3/32" fiberglass fins with bigger motors.

 

[Neo]

The main thing I'd be concerned with about sizing it up would be the thickness of the fins. The fins are only 3/32" (.093), so, I'm not sure how well they would handle larger motors. I don't have that much experience with fiberglass fins, so, hopefully there are others on here that will chime in who have tried 3/32" fiberglass fins with bigger motors.

That's a good point you raise. However, even with 54mm motors OpenRocket says the max speed can reach in the neighborhood of 1,100 mph (mach 1.5-1.6) with a variety of different of L motors. You are making me think twice about those speeds with these fins, unless I'm willing to cover them in fiberglass.

 

[Neo]

Oh wow I didn't notice that you did have a longer cone on there. That looks really slick and definitely improves the sims I was doing. WM sent me the rks file awhile back but the length was a little off. I noticed today that the file is now on the website and the unloaded weight is different than the original file I was given so I've been reluctant to go off of that. Of course I will be updating everything once I have mine finished and can actually weigh it.

That being said, I think I might go your route and get the longer nose cone.

Thanks again!

I'm curious how your build went. I have double-checked all the dimensions and weights of the rocket components and am still coming up well short of a fully-loaded stability result that I'm comfortable with. The longer nosecone that @kswing did is not enough to make much of a difference in my OpenRocket simulation. I'm needing to add 500g / 1.1 lbs of nose weight to fly longer L motors and even for most K motors. Sure seems like a taller fin would be a better way to go than carrying so much dead weight. Even if I add an upper body tube section it doesn't help much, the fins just seem too small.

What am I missing here?

 

[crossfire]

Did you get to fly it yet?

 

[Neo]

Did you get to fly it yet?

No, I haven't even built it yet. I'm trying to get the build planned and I'm not satisified with the OpenRocket simulation results as they are with the stock measurements. I'm looking for opinions and experience from others who have built this rocket.

 

[Handeman]

I usually only use OpenRocket to get the CP initially. After the rocket is built, override the weight and CG with actuals from the rocket when it is fully prepped for flight, but without a motor. The weight and CG will probably be much different than the original OpenRocket estimates. Then add motors of your choice and verify stability.
If you need to add nose weight, then would be the time to do so.

 

[crossfire]

With WM HED recovery I bet no additional nose weight will be needed.

 

[thzero]

I usually only use OpenRocket to get the CP initially. After the rocket is built, override the weight and CG with actuals from the rocket when it is fully prepped for flight, but without a motor. The weight and CG will probably be much different than the original OpenRocket estimates. Then add motors of your choice and verify stability.
If you need to add nose weight, then would be the time to do so.

If you weigh as you go along and adjust, it doesn't drift too much. Paint and epoxy are the biggest additional factors. Overriding the CG for sure is good idea for launches, but to not be surprised I prefer the former approach combined with overriding for launches.