Ye Olde Rocket Forum

Go Back   Ye Olde Rocket Forum > Work Bench > Projects
User Name
Password
Auctions Register FAQ Members List Calendar Today's Posts Search Mark Forums Read


Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 06-02-2008, 04:51 PM
tbzep's Avatar
tbzep tbzep is offline
Dazed and Confused
 
Join Date: Mar 2005
Location: TN
Posts: 10,267
Default More Nosecone Oddities

I'm working on a Mini Bertha (not the Baby B.) and the downloaded instructions call for a BNC-20L. The BNC-20L is fairly blunt, but it does come to a point, similar to a Civil War mini-ball. It's actually more pointy looking in person than the shadowed Semroc line art. The Estes catalog model is more rounded, almost like the BNC-20B in the old 70's catalogs. I think the nosecone looks more round when actually looking at my 1979 catalog than it does when looking at the 1979 scan from Ninfinger....I guess I'm nuts cause it should be the same image. Does anybody remember getting a Mini Bertha with a more pointy nosecone than rounded?


Semroc BNC-20L


1973 Catalog Model (first appearance), which does seem a bit more pointy than later catalog images, possibly due to lighting.


1979 Catalog Model
Reply With Quote
  #2  
Old 06-02-2008, 05:14 PM
space_bus space_bus is offline
Craftsman
 
Join Date: Sep 2007
Location: Maryland
Posts: 199
Default

FWIW, here's a pic that includes a clone I made of the Mini Bertha with a BMS-made BNC-20L (as per the scanned instructions).



I agree that the catalog pics look more like a BNC-20B. (And my decades old memories of my brother's original are to fuzzy to comment on which it was more like.)
Reply With Quote
  #3  
Old 06-02-2008, 05:25 PM
tbzep's Avatar
tbzep tbzep is offline
Dazed and Confused
 
Join Date: Mar 2005
Location: TN
Posts: 10,267
Default

Woops....I placed a Semroc and a BMS order at the same time and got mixed up on what came from where. The BNC-20L is from BMS, just like yours.

I get my long tubes and long coupler stock from BMS, and I usually grab a few other things while I'm at it, including his most recent clone-of-the-month on the last order.

It's hard to tell looking down from above on yours, but I think a bit of sanding will soften the point and give it a bit more rounded look. I'm going to use the nosecone regardless....I was just wondering how much I should alter it to get the old kit's look. It will look good either way, so it's more of a historical thing for me.

Funny you should use that photo. I've been sanding on my Shuttle's mothership off and on all weekend. The little shuttle has its base coat of white and I'm waiting for a less humid day for the yellow. With all the sanding on the mothership, I have no idea when I'll get around to priming it, much less get some color on it.
Reply With Quote
  #4  
Old 06-02-2008, 05:55 PM
space_bus space_bus is offline
Craftsman
 
Join Date: Sep 2007
Location: Maryland
Posts: 199
Default

Good luck with your Shuttle. Mine is still awaiting rebuild from its disastrous first flight last fall.

I just noticed that the '79 catalog page has a picture in the lower right of some people launching their own Mini Bertha. It looks little more pointy there than the featured catalog pic, but it's pretty hard to tell. You say you have an original catalog -- you may want to take a closer look at the little pic.

I'm wondering if Estes might have built their original with a BNC-20B (which may have been the same rocket for all the catalog pics), but switched to the BNC-20L for production kits.
Reply With Quote
  #5  
Old 06-02-2008, 07:56 PM
tonypv's Avatar
tonypv tonypv is offline
And so it begins...
 
Join Date: Apr 2007
Location: Haverhill, MA
Posts: 106
Default

Here's my original Mini Bertha that I flew yesterday and lost.

I plan to build a clone to replace it.

I don't know if you can tell from the picture but I think the nose is more rounded.
Attached Thumbnails
Click image for larger version

Name:  Mini Bertha 1 otp.jpg
Views: 111
Size:  39.3 KB  
__________________
Tony Vincent
NAR # 45082 L1
CMASS, MMMSC Member
Reply With Quote
  #6  
Old 06-03-2008, 04:23 AM
Mark II's Avatar
Mark II Mark II is offline
Forest Sprite
 
Join Date: Dec 2006
Location: Back Up in the Woods
Posts: 3,657
Default

FWIW, I noticed the discrepancy in the shapes, too. (I built a Mini Bertha clone a few months ago.) The BNC 20L almost looks like a smaller version of the Sprite nose cone (but it's not). Attached is a group shot of four BT-20 balsa nose cones from Semroc, along with a BNC-30D (Astron Sprite) nose cone on the exreme right. A PNC-80BB Super Big Bertha nose cone and a PNC-60L Big Bertha nose cone are across the top for comparison. When it is grouped together with these other cones, the BNC-20L looks even more odd.

Mark \\.
Attached Thumbnails
Click image for larger version

Name:  DSCF0540-1.JPG
Views: 108
Size:  137.9 KB  
__________________
Mark S. Kulka NAR #86134 L1,_ASTRE #471_Adirondack Mountains, NY
Opinions Unfettered by Logic • Advice Unsullied by Erudition • Rocketry Without Pity
+09281962-TAK-08272007+
SAM # 0011
Reply With Quote
  #7  
Old 06-03-2008, 09:58 AM
tbzep's Avatar
tbzep tbzep is offline
Dazed and Confused
 
Join Date: Mar 2005
Location: TN
Posts: 10,267
Default

Quote:
Originally Posted by Mark II
FWIW, I noticed the discrepancy in the shapes, too. (I built a Mini Bertha clone a few months ago.) The BNC 20L almost looks like a smaller version of the Sprite nose cone (but it's not). Attached is a group shot of four BT-20 balsa nose cones from Semroc, along with a BNC-30D (Astron Sprite) nose cone on the exreme right. A PNC-80BB Super Big Bertha nose cone and a PNC-60L Big Bertha nose cone are across the top for comparison. When it is grouped together with these other cones, the BNC-20L looks even more odd.

Mark \\.


Thanks for the photo. That lets me see things much better than drawings and catalog photos. The Mini Bertha nosecone in the catalog doesn't seem as narrow as the BNC-20B to me. It's profile is more like the BNC-30D with the point rounded off, though it's diameter would be a hair too large. The BNC-20L with its point rounded off would probably be closer than the BNC-20B, now that I see a real photo of it. The 20B tapers too early to look right, IMHO.
Reply With Quote
  #8  
Old 06-03-2008, 10:55 AM
Carl@Semroc's Avatar
Carl@Semroc Carl@Semroc is offline
Junior ??? Rocketeer
 
Join Date: Mar 2005
Location: Knightdale, NC
Posts: 1,470
Default Nose cones differences

The BNC-20L has always been an oddity. My original Mini Bertha and a BNC-20L I got off eBay years later looked very similar and nothing like a downscaled BNC-60L that would be expected. I assumed that it was made from a "recycled" stone that had previously cut some other BT-20-based nose cone and had been dressed a few times too many. The lower section is almost parallel to the tube for over half of the length.

The shape of the BNC-20L on Mini Berthas in photos in the catalogs evolved over the years as well. Like many of the Estes nose cones, we had to settle on one shape for a range of shapes to choose from. In most cases, we chose the shape to match an actual nose cone we could scan, measure, etc.

Another example is the BNC-30D that was probably the first balsa nose cone that Vern made, since it was used on the K-1 Scout. Measurements show the exposed length to be 1.38". The earliest catalogs showed a length of 1.5" long. An early one I had was 1.5" long and matched the catalog dimensions. In this case, we released the BNC-30DE (Early version) as well as the BNC-30D (later version). I almost released a BNC-20L version that was a downscale of the BNC-60L. I did release the BC-818L, which is a downscale of the BNC-60L.

But... the BNC-60L is also a moving target. Comparing photos, catalog & MRN pictures, and actual nose cones, there are probably at least four unique shapes over the years. We have changed OUR BNC-60L twice to match what most people perceive to be the “correct” shape.

I have not seen as many differences in Centuri nose cones as I have in the Estes nose cones over the years. I am not sure if this is the manufacturing processes or some other reason. Maybe the sheer volume that Estes produced was much greater. I know that Estes did have to redress the stones many times and that is an art, rather than a science. The new nose cones after a resurfacing will not be identical. Even nose cones cut over a period of time from a stone change shape as the stone wears. In the early days of Semroc, we resurfaced our stones several times as they wore. Since all our stones were ogive or conical, we used a diamond bit on a circular arc (ogive) or straight line (conical) to ensure the stone stayed the same after redressing. If we had done elliptical or parabolic nose cones, it would have been much more difficult to keep the stones the same.

Using computer controlled grinders, rather than fixed stones, allows for manufacturing large quantities of identical nose cones now. Picking which shape to make large quantities of is the much bigger problem. We now produce over 600 unique balsa parts (not all online) and should be able to produce the exact shaped parts years from now.
__________________
Carl McLawhorn
NAR#4717 L2
semroc.com
Reply With Quote
  #9  
Old 06-03-2008, 12:34 PM
scigs30 scigs30 is offline
Master Modeler
 
Join Date: Jul 2006
Posts: 2,075
Default

Carl, thanks for your answer. I have 3 orig. Mini Bertha kits so I will take a picture of the nose cones. I think I may have a Semroc cone to compare it to. Carl, do you make your nose cones from the orig on hand Estes cones or do you do it by other means? David
Reply With Quote
  #10  
Old 06-03-2008, 12:39 PM
Carl@Semroc's Avatar
Carl@Semroc Carl@Semroc is offline
Junior ??? Rocketeer
 
Join Date: Mar 2005
Location: Knightdale, NC
Posts: 1,470
Default

Quote:
Originally Posted by scigs30
Carl, thanks for your answer. I have 3 orig. Mini Bertha kits so I will take a picture of the nose cones. I think I may have a Semroc cone to compare it to. Carl, do you make your nose cones from the orig on hand Estes cones or do you do it by other means? David
Preferable is nose cones on hand. Second is good photos.
__________________
Carl McLawhorn
NAR#4717 L2
semroc.com
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump



All times are GMT -5. The time now is 01:56 PM.


Powered by: vBulletin Version 3.0.7
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
Ye Olde Rocket Shoppe © 1998-2021