Estes Crossbow fin placement

[foose4string]

Since the snow is piling up at a ridiculous rate, I figured this would be as good a time as any to get back in the swing of building. It's been a while. I picked up the Crossbow for half price last week and it looks like a pretty easy build. It's small enough where I can finish it quickly and have an interesting looking rocket when I'm done. I have found a couple glitches in the instructions, however.

The first one involves the forward dorsal fin(K) which is supposed to be glued on the "HL" line. The instructions say to mark the tube at 3" and glue the fin there. 3" puts the mark right at the motor mount seam(the motor mount tube gets coupled to the main BT20). The illustration shows the 3" mark well short of the motor tube seam instead of the end, and a portion of fin(K) resting on both sides of the seam. In reality, one end of fin(K) will be flush with the seam.

The other glitch so far is there is no measurement provided for placement of the forward "wing" fins(J). Has anyone else noticed this or have any idea what that measurement is supposed to be? Am I missing something here?

 

[DM1975]

I put the wings on mine at 1.5" from the base. As for the forward dorsal fin, I mounted it 3" forward, right on the seam. I never even noticed it showed it in the instructions sitting over the seam, but then again I just went by the meaurements rather than the picture on that one.

 

[rokitflite]

Since the snow is piling up at a ridiculous rate, I figured this would be as good a time as any to get back in the swing of building. It's been a while. I picked up the Crossbow for half price last week and it looks like a pretty easy build. It's small enough where I can finish it quickly and have an interesting looking rocket when I'm done. I have found a couple glitches in the instructions, however.

The first one involves the forward dorsal fin(K) which is supposed to be glued on the "HL" line. The instructions say to mark the tube at 3" and glue the fin there. 3" puts the mark right at the motor mount seam(the motor mount tube gets coupled to the main BT20). The illustration shows the 3" mark well short of the motor tube seam instead of the end, and a portion of fin(K) resting on both sides of the seam. In reality, one end of fin(K) will be flush with the seam.

The other glitch so far is there is no measurement provided for placement of the forward "wing" fins(J). Has anyone else noticed this or have any idea what that measurement is supposed to be? Am I missing something here?

Can't you build something AT LEAST as big as your fiddle??? Jeeze !

 

[foose4string]

Can't you build something AT LEAST as big as your fiddle??? Jeeze !

I have once or twice...but I haven't made a habit of it. Yes, this thing is dinky, but for $3.50 what do you expect? The Seawolf, Saturn 1B(yes, I still need to finish it), upscale OT, are all about as big as my fiddle... so there! :neener:

 

[foose4string]

1 and 1/2 inches still looked a little off to me when I compared it to the box photo. I went with 2 and 1/8 inches. This puts the trailing edge of the wing fin about even with the front edge of the rear vertical fin. I guess that's close enough. I'm surprised this hasn't been brought up before. If it has, I'm sure I missed it.

 

[DM1975]

I just got mine back out to primer and you are right, it is even with the front of the rear vertical fin. Mine is a bit farther back, but that shouldn't be a problem, it will only move the CP farther to the rear, which should be ok for stability increasing the relation to the CG like that.