FlisKits Corona! Nice!

[eugenefl]

A lightbulb just went off in my head. Have a look at <a href="https://www.fliskits.com/services/dom/2003/10-october/levison_corkscrew.htm">THIS</a> rocket. If the Corona ring fin was slightly off center, wouldn't it cause the rocket to fly incorrectly? Now I'm anxious to go home and look to see if that ring is centered on the body tube.

 

[jflis]

Originally posted by eugenefl
Just curious, but what motors did you use? This info would be important for testing purposes. My flight was on an Estes C6-5.

EDIT: I just looked at EMRR and it appears others have flown their Corona's on C6-5s with no problem. Hmm...maybe the cellulose went down to the bottom adding more weight?

oh, now that is interesting... what sorts of recovery wadding was used? Perhaps ;with the higher density and greater tendacy to move, this could be a contributing factor.

As others have pointed out, with such a long rocket, with that much fin area, instability *shouldn't* be a concern, but *something* is happening...

jim

 

[jflis]

Originally posted by eugenefl
A lightbulb just went off in my head. Have a look at <a href="https://www.fliskits.com/services/dom/2003/10-october/levison_corkscrew.htm">THIS</a> rocket. If the Corona ring fin was slightly off center, wouldn't it cause the rocket to fly incorrectly? Now I'm anxious to go home and look to see if that ring is centered on the body tube.

In such an extreme case as the rocket you pointed out, it is greatly possible, but NOT because the ring is off center (though that contributes).

Two things are happening with that rocket:

1) The greatly offcenter ring is causing a great deal of drag on one side and none on the other. the closer to center, the less this effect and can be discounted on the Corona as you would have to be WAY off.

2) A ring of the nature on that rocket would have a tendency to flex in flight causing all sorts of possible problems with flight path. This can also be discounted in the Corona as the ring is too small and stiff to flex (heck, you can *barely* make that ring flex if you squeeze it between your fingers! LOL)

jim

 

[eugenefl]

Originally posted by jflis
oh, now that is interesting... what sorts of recovery wadding was used? Perhaps ;with the higher density and greater tendacy to move, this could be a contributing factor.

As others have pointed out, with such a long rocket, with that much fin area, instability *shouldn't* be a concern, but *something* is happening...

jim

I use the common cellulose insulation (aka dogbarf). I typically prep rockets the night before. I had the Corona sitting in a corner all night. Cellulose, when compressed to a certain extent, has a tendency to be dense. Interesting...

Jim, let us know what you find out. In the meantime, I think I'll CyA some washers underneath the cone. (Or should I hold off?)

 

[slim_t]

Jim, if you want to send me one, I'd be happy to test it out for you.

Tim

Just kidding; I'll be ordering one soon.

 

[teflonrocketry1]

Does anyone have a RockSim file for the Flis Kits Corona? Can you send me measurements or plans if the RockSim file is not available? I have an idea why this design might fly unstable when the ring comes loose. I want to see more details of the rocket's design before I comment.

Bruce S. Levison, NAR #69055

 

[Mike]

Hmm, been giving this a bit of thought.

Is it possible the two tube sections weren't put togther completley straight. There was scope for misalignment, the instructions said to roll the completed tube on a flat surface to get it completley straight.

If the tube wasn't straight you would get an increased drag on one side which could cause it to loop.

Both Eugene and Kelltym88 said their Corona's went unstable at 50+ ft. This kinda suggests it's related to flight speed, the fins could keep the model stable with the assymetrical drag whilst it's going at slowly (less drag) but as it gained speed the drag became too much and the model began to loop or go off course.

IMHO a misaligned tube would have move effect than a slightly off-centre ring fin.

Interested to hear the results from the test flights at the TRF gathering.

 

[seo]

I am about to begin building my corona and wondered if Eugenio and Jim F came up with anything at Whitakers......

 

[eugenefl]

Originally posted by seo
I am about to begin building my corona and wondered if Eugenio and Jim F came up with anything at Whitakers......

Unfortunately the weather was not favorable for model rockets most of the day. It wasn't until about 3PM (late) in the afternoon that the winds came to pause. By then I was more focused on getting my MPR composite birds in the air! Since it's been brought up, I think I may bring the Corona with me this weekend and try it out on smaller motors - ie B4 or B6

 

[jflis]

Originally posted by seo
I am about to begin building my corona and wondered if Eugenio and Jim F came up with anything at Whitakers......

Sorry, no we didn't, however I have received yet another note (email) about the Corona not performing well.

don't let this scare you off It is *still* a fine looking and flying model rocket. I have poured over the design the past couple of months and I have come to the conclusion that there are several areas of construction that need to be given attention and that I think are being glossed over.

1) There are two 18 inch body tubes joined by a 1 inch coupler. If you are not careful, it is easy to have these tubes misaligned (crooked). In Step 7 of the instructions it says "Lay the model on a smooth flat surface and gently roll the assembly to assure that it is straight. This isn't a *suggestion* You really need to do this and if the tubes are not straight when dried, you need to cut out the coupler and try again with a new coupler and the shorter tubes...

2) The fins are two-piece. You cut out the rearward fin (Fin #1) and the forward fin (Fin #2), matching the grain direction as shown on the pattern. You then glue these two fins together to form the full fin. I have seen several models (even witnessed one fly unstable) where the builder had a *better* idea and combined the pattern into one large fin and cut it out in one piece. In the case of the failed rocket, the grain was parallel to the body tube as that was the easiest way to cut them. Do it that way and the Corona WILL fail. Follow the instructions and you will be ok.

3) When attaching the tail ring, you want to be sure that all 3 fins are firmly attached to the ring. As a test, I separated one fin from the ring and it caused an erratic flight path.

4) I had a really weird personal experience with the Corona... I had painted one of mine such that it was a light color on half and dark on the other half. I'm not talking top and bottom, i'm talking left and right... Well, I got ready to fly it at CMASS one hot afternoon and when I picked it up I noticed that it had warped into a VERY noticeble curve because of the paint heating up the rocket more on the dark side. I *knew* it wouldn't fly straight so I put it into a cool place till it straightened out and it flew fine

Now, I've had a few people tell me that such stringent restrictions on the construction of a model rocket equates to a poor design. I disagree. It is a Skill Level 3 for a reason. Some of the steps are a little more difficult or different from the steps taken in a skill level 1 or 2 model. A *good* design is one that flies as promised when assembled as instructed.

The Corona has a long history of successful flying, even when built by all age groups and skill levels. It was the anniversary kit of the last NEMROC convention where over 100 were built and flown over the course of one weekend and not one was unstable. If anything, your biggest concern may be weather cocking on windy days with small motors...

All I can add is to follow the instructions and take your time. You will *love* this kit

(edit): If I sound a bit testy in this note it is because I received an email referiing to this kit as "deadly" (and i'm a bit tired anyway ) I've been flying mine for 15 years and have heard of hundreds of successful launches since offering it as a kit. I *still* want to be able to see any that fail. If yours fails to fly straight and true, please contact me as I would like to exchange it for a new kit and do a failure analysis of it.

 

[Mike]

I've flown my Corona on a C6, it was a near perfect flight, straight as an arrow and prompted a few people to say "oooo, that was nice."

Jim, looking over your reply and my copy of the Corona instructions perhaps in a future run it would better to explain more to the builder why the tube needs to rolled, ie. "to ensure a stable flight it is essential that the tube is perfectly straight"

Perhaps you would also consider increasing the length of the coupler, 1" seems a little short.

 

[jflis]

Mike,

I agree on both of your points. I will be including some additional explaination for why certain steps are done certain ways. We will also look into a *slightly* longer coupler. We don't want to go too long as then it becomes useless as a "stage coupler" and it becomes another part we have to inventory. Trying to keep inventory (and hence, kit costs) down while still producing quality

I really beleive that providing some explainations in the instructions will go a *long* way with this (and other) model.

 

[seo]

Originally posted by jflis


All I can add is to follow the instructions and take your time. You will *love* this kit

(edit): If I sound a bit testy in this note it is because I received an email referiing to this kit as "deadly" (and i'm a bit tired anyway ) I've been flying mine for 15 years and have heard of hundreds of successful launches since offering it as a kit. I *still* want to be able to see any that fail. If yours fails to fly straight and true, please contact me as I would like to exchange it for a new kit and do a failure analysis of it.

No, you don't sound testy! You sound passionate, there's a difference. Thanks for the lengthy and detailed explanations of the areas I need to watch out for. Being able to get information like this from the designer is one of the reasons I really like Fliskits. Thanks Jim!

Scott

 

[sramberg]

I have had two perfect flights on my Corona, much to the dismay of the LCO. It is a great rocket. This rocket looks deceivingly simple to build, but as Jim pointed out there are some points of the construction that cannot be skipped.


Steve

 

[jflis]

Originally posted by seo
No, you don't sound testy! You sound passionate, there's a difference. Thanks for the lengthy and detailed explanations of the areas I need to watch out for. Being able to get information like this from the designer is one of the reasons I really like Fliskits. Thanks Jim!

Scott

why, *thank* you

 

[jflis]

SInce this thread already exists, I figured this would be the best place for this discussion.

I was contemplating the Corona and realized that one of the most difficult aspects of the assembly is verifying that the lower ring is on straight.

I pondered that and came up with a fool proof method to assure that it is properly mounted. This method would add about $0.90 to the cost of the kit....

Basically, you are trying to get that ring attached such that it is perfectly straight. It being straight is more critical than that of a conventional fin, so this is important.

Now, this ring is simply a coupler for a BT-70 tube. I was thinking about including a BT-70-175 and a CRF-50-70 centering ring. Then, during construction, you would follow these steps:

1) Apply glue to each fin and slide the ring into place

2) slide the BT-70 over the ring such that the other end of the BT-70 is near the mid point of the rocket

3) slide the centering ring from the front of the rocket and into the BT-70, holding this end perfectly centered.

4) wait for the ring fin to dry then remove the centering ring and BT-70.

5) done, perfectly straight and you have a BT-70 and a centering ring for another project.

thoughts?
jim

 

[illini]

We didn't have any problems with the ring on my boy's Corona. Or, let me re-phrase that...we didn't really *think* about it. That being said, I'd pay an extra 90 cents for that since I'd have a use for the tube anyway. In fact, this could open up a whole new approach to selling kits...include a pile of extra parts and charge a couple of bucks more! Just kidding...I like the idea.

 

[jflis]

Originally posted by illini
Or, let me re-phrase that...we didn't really *think* about it.

I'll be honest with you, I didn't give it much thought either. We've received about 5 reports of stability concerns regarding the Corona. Stability isn't really the issue with this kit. Upon research, I've concluded that it has more to do with how it is constructed and I examined the most common problems that I have see in the past regarding this particular kit.

What I have discovered as common problems include:

1) Body tube not straight. When gluing the two tubes together they need to be as perfectly straight as possible. This is easily accomplished by proper rolling on a flat surface while gluing. I will be highlighting this step

2) The two part fin replaced with a one part fin with the grain parallel with the root edge of the fin. This results in a weak fin that can crack during boost (and also durring storage). This area will also be highlighted and explained

3) Tube ring not glued on securly. I've seen one case (ironically, it was my daughter... at NARAM no less... ) where the ring was only tacked in place. It came loose during boost on its first flight. This also is easily addressed with a proper warning in the instructions

4) tube ring not glued on straight. I've seen this on 3 assemblies of this model. I have never encountered this myself nor with the 100+ that were built at NEMROC in the 90's, but it does happen and is a very serious assembly error that can cause erratic flights. The only way I have come up with (that is both easy and inexpensive) to prevent this is the idea of using a BT-70 and a centering ring. Since I can not assume that the modeler *has* these items, I have considered including them with the kit...

jim

 

[Mike]

Jim, can I ask if you extended the length of the coupler? IIRC correctly when I built one of the earlier kits it was very short which led to a large margin for error when gluing the tubes togethor.

£0.02

 

[jflis]

Yes, extending the coupler can help reduce problems with having a crooked joint and it is something that we are looking into. However, it isn't *necessary* to add that extra weight (and cost) when care and attention to detail will suffice.

Care and attention to detail may *not* suffice concerning the tube ring, however

I will be talking to Brian about offering longer couplers, but first we will have to exhaust our current inventory

Good input however. We have received such suggestions before and it is on our list pending our next coupler order.

We will also be getting in couplers for the BT-20 and BT-5 and we will *start* with longer couplers.

The main thing that defined the coupler length (frankly) is that we matched what Estes used to offer back in their older catalogs.

jim

 

[jflis]

This is an old thread but I wanted to revisit it as it covers a critical issue with a very popular rocket.

It has been several months since I have recevied any bad press about the Corona, but have received much good press with regard to the kit and her performance.

This is all well and good, but that still leaves things that need to be addressed.

First, we are near to having exhausted our inventory of CPL-50-01 stage couplers and are re-ordering. I am having quoted a CPL-50-015 (1.5" long instead of 1" long) to help with keeping the tube straight. This gives us an extra 1/2" to help while still being short enough to be used effectively as a stage coupler.

Second, We are going with laser cut 1/16" plywood fins to replace the 2-piece balsa fins. These fins will include a built in *stop* for the tail ring. If you look at the attached photo, you will see our proto type laser cut fins for the Corona and the Corona 2-Stage. The area circled in red shows the "Ring-Stop" on the Corona Fin (the fin to the right). In the upper right of the photo it shows a blow up of the detail and you can clearly see a little nub at the rear of the fin.

When attached to the rocket, the tail ring **just** fits, OH so nice and comes to a firm stop at the nub, perfectly aligned and perfectly straight making it near impossible to screw up.

I am in the process of doing a complete rewrite of the Corona instructions to make use of these new parts and to provide a pre-introduction of the upcoming 2-stage upgrade for the Corona.

Also, I will begin a new thread on the 2-stage upgrade so that we can discuss that *there*.

Again, you (customers) speak, we listen. We don't always implement your ideas but truely know that we consider, discuss and make decisions based on what *you* say.

We will be making an announcement as soon as Corona's with the new parts are available (we have to deplete current inventory first)

jim

 

[cmmeyers]

Jim, if you need a tester for the new instructions and parts, send one my way! I'll be your guinea pig!

 

[jflis]

Well, actually I have a couple of requests out already, but if they are not interested I will send it your way.

thanx,
jim

 

[cmmeyers]

Originally posted by jflis
Well, actually I have a couple of requests out already, but if they are not interested I will send it your way.

thanx,
jim

Yeah, I already talked with those guys. They said that they're not interested!

 

[JRThro]

Originally posted by jflis
... If you look at the attached photo, you will see our proto type laser cut fins for the Corona and the Corona 2-Stage. The area circled in red shows the "Ring-Stop" on the Corona Fin (the fin to the right). In the upper right of the photo it shows a blow up of the detail and you can clearly see a little nub at the rear of the fin.

When attached to the rocket, the tail ring **just** fits, OH so nice and comes to a firm stop at the nub, perfectly aligned and perfectly straight making it near impossible to screw up...

jim

Um, what attached photo?

 

[jflis]

Originally posted by JRThro
Um, what attached photo?

whoops...

it was late and I was building another Decaffeinator and had to drink those 12 cups of coffee, so...

here it is:

 

[rokitflite]

I have found that replacing the nose cone with a wedge of lime in a Corona can help.

 

[jflis]

LOL

What a visual