PDA

View Full Version : Interceptor-E Fin Marking Guide


Intruder
06-04-2008, 10:26 PM
I've been working on my Interceptor-E lately. Like my 1250 Interceptor, I glued on all of the sub fins and vertical stabs before filleting, filling, etc. Then I noticed that I had a problem: my vertical stabs and sub fins didn't line up. At first I thought that I just can't build a rocket and glued the fins on crooked. Then I looked closer and found that the root edges themselves didn't line up.

I slipped on the fin marking guide and saw that the lines on the tube didn't match the guide. I had forgotten to tape down the guide to draw the lines. So I carefully cut off the sub fins at the glue joint so that there was no damage to the tube or the fins. I erase the lines, slip on the guide, tape it down, and make my lines again. After which, I made some rivet holes since I (thankfully) forgot to do so the first time.

I look at my lines before gluing on the sub fins a second time and see that my lines STILL don't line up with the vertical stabilizers. Now I'm a little frustrated. I look at my 1250 Interceptor, my dad's vintage K-50 Interceptor, and his vintage instructions and all of them have the sub fins line up with the vert. stabs. Now I feel like I'm just plain stupid because I can't draw strait lines. I slip on the fin marking guide, again, and the lines on the tube match the ones on the guide perfectly. Now I'm loosing my mind because I have now idea what's wrong.

Then I vaguely remember this post:

As I was building my Interceptor E the other day I noticed that the fin marking guide is off by 1/16 of an inch. If anyone gets this kit then watch your tube markings. If you measure the distance from the launch lug line to the sub fin lines you'll see what I mean. I contacted Estes about it and they took my name and number. 6 minutes later I got a return call from the designer. I told him the problem, he measured it and in the background I heard him say "Da**it he's right!" So they offered to send me a corrected instruction book of all things. I don't know how many are out there with the mismarked fin guide as the rocket was just released a few weeks ago.

I then thought that it was possible, though highly unlikely, that the problem was with the guide and not my immense lack of ability.

I new that sense the fins are supposed to line up, the distance between the two vert. stabs and the two sub fins are equal. So I folded the guide in half (not including the tab) and slipped it onto the body tube, AGAIN! http://www.rocketryforum.com/images/smilies/hmpf.gif

I turn the guide upside down and match the crease with the launch lug line. The lines aren't even close to matching the inverted guide!

Now I'm interring "Hulk Mode" because now, not only are my lines not in the right spot, my guide is wrong, and I have holes in my body tube.

http://www.rocketryforum.com/images/smilies/14.gif http://www.rocketryforum.com/images/smilies/banghead.gif http://www.mysmiley.net/imgs/smile/mad/mad0251.gif http://www.mysmiley.net/imgs/smile/mad/mad0233.gif http://www.mysmiley.net/imgs/smile/characters/character0192.gif

OK. After my rampage of leveling buildings, knocking out helicopters by throwing cars, and crushing tanks with my bare hands, I sat down and thought of a simple fix.

I made two marks on a slip of paper that was wrapped around the body tube 180 degrees from each other. I lined one of the marks up with one on the body tube I previously made between the vert. stabs. I copied the vert. stabs' position onto the paper, twisted it around so the other mark on the paper lined up with the one on the body, and then copied the marks from the vert. stabs onto the underside.

Now I feel kinda stupid for wasting all my time trying to solve my problem when the solution was so easy, and for wasting all of your time by having you read this novel.

TXFergie
06-04-2008, 11:20 PM
I will have to keep this in mind, since I have an Interceptor - E on my "to build" list. Thanks for the heads up.

Question- is there a way to measure the marking guide and see if it is the right one or not? I mean, can you measure the distance between the fin lines and launch lug and see if it is equal?

Rick

tbzep
06-04-2008, 11:50 PM
I will have to keep this in mind, since I have an Interceptor - E on my "to build" list. Thanks for the heads up.

Question- is there a way to measure the marking guide and see if it is the right one or not? I mean, can you measure the distance between the fin lines and launch lug and see if it is equal?

Rick

Yes. When you put the ruler down on the guide, you will see that something isn't right on the marking guide. I'm actually surprised that only one other person posted about it considering how many people have built the E-ceptor, several being very good craftsmen.

When he showed me the glued on fins, he and I both thought that he had just messed up when he marked the tube. After he redrew the lines, he realized it wasn't him. He's reworked his lines, but I haven't been upstairs to take a look at it yet. Hopefully the ventral fins in their new positions will line up good with the angle of the rudders. The rudders have already been glued into their slots and he won't be able to adjust them. If they don't, we'll just have to make sure we never look at it from the end. :rolleyes:

Leo
06-05-2008, 01:35 AM
I just unpacked mine but haven't started so thanks for the note :)

jetlag
06-05-2008, 03:44 AM
Sorry, Guys,
I should have said something sooner. I, too, noticed the discrepancy and used a simple mm guide to line up the line placements. Even after all that, there is still no substitute for 'eyeing' the fins as you go. My guide was off also. I'm kind of used to this, though. I always check the cg of my aircraft and have been surprised that factory recommended cg was off by an amount. So, I've carried the practice over to my building of model rockets. Ashame no one at Estes bothered to check this as part of a simple QA process.
I try to always second guess the stated measurements of things, especially for a scale project. If you really go through the early Saturn 1B detail instructions (1/70 scale). you'll find a few inaccuracies when compared to the actual full scale machine. I think Chan and Gordon would probably second the assessment that one should always try to verify before gluing.
Unfortunately, one would think a company as skilled as Estes is (or used to be!) would get it right the first time. Just goes to prove we are all human ;)
Allen

Mikus
06-05-2008, 06:21 PM
I will have to keep this in mind, since I have an Interceptor - E on my "to build" list. Thanks for the heads up.

Ditto, I missed the original post. :(

ga1ba2
06-05-2008, 06:58 PM
:confused:
Ok, just a little clarification. We are talking about the sub fins aligning up with upper fins -
-right? On my fin marking guide the upper fins are 1 3/16 or 30mm apart. The sub fins are 1 7/16 or 37mm apart. These distances should be the same. If I move the sub fin lines so they are 30mm apart and each 15mm from the LL lug everything should line up -right?

Intruder
06-05-2008, 08:04 PM
:confused:
Ok, just a little clarification. We are talking about the sub fins aligning up with upper fins -
-right? On my fin marking guide the upper fins are 1 3/16 or 30mm apart. The sub fins are 1 7/16 or 37mm apart. These distances should be the same. If I move the sub fin lines so they are 30mm apart and each 15mm from the LL lug everything should line up -right?

No. After making a quick measurement to answer your question, I noticed the launch lug line is not in the center of the guide. If you lay the guide out flat, and measure the distance from the launch lug line to the near side of the upper fin line, you will see that one side is 65mm (just over 2 1/2") and the other is 63mm (just under 2 1/2").

Leo
06-06-2008, 01:26 AM
Could someone post a picture before the Interceptor turns into an Alpha :D