Boeing CIM-10 Bomarc Semi-scale Scratch-build

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BigMacDaddy

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I learned about the Bomarc a few days ago reading a thread here where people shared their favorite rockets / missiles.

What do you guys think of my scratch-build?

BT60 Body + BT55 Ramjets + BT20 Top pod + 2mm Basswood fins + 3D printed parts (designed in last few nights - consider it semi-scale since I used standard tube sizes). Comes in at a little more than 25" long (I forgot to weigh it when it was together and I already took it apart). I know there are a bunch of bigger versions of this missile out there but I wanted one that would launch on Estes D or E engines.

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Bruiser

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Looks sweet! I see the ramjet intakes and exhaust are printed. Are the nose cone and ramjet pylons printed also?

-Bob
 

BigMacDaddy

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Looks sweet! I see the ramjet intakes and exhaust are printed. Are the nose cone and ramjet pylons printed also?

-Bob
Thanks, very much!

Yep, basically anything gray in the picture is 3D printed -- ramjet intake & exhaust as well as pylons (go around a 2mm piece of basswood to give structure and slot into tubes on either end), nose cone, top pod nose and tail tapers (as well as some structure to shape it in middle - hope this will work), and boat-tail as well as engine retainer cap and front engine mount -- ah also templates used to mark / cut the fins.

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cvanc

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Really nice work! I've always had a soft spot for the Bomarc. Let us know how it flies 👍
 

BigMacDaddy

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Really nice work! I've always had a soft spot for the Bomarc. Let us know how it flies 👍
Thanks very much and that is, of course, the pudding that the proof is in...
 

RocketTree

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Wow, that looks great! 3D printer seems to be a excellent method of forming custom parts. Do you know what the final mass will be?

I’m also currently scratch building the Bt60 bomarc, with bt55 ramjets, although I’m using bt50 nose cones for simplicity. 24mm motor and estimated 300g on the pad. Build to fly E and F motors.

Best of luck on the painting! Hope to see it when it’s all done.

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BABAR

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I learned about the Bomarc a few days ago reading a thread here where people shared their favorite rockets / missiles.

What do you guys think of my scratch-build?

BT60 Body + BT55 Ramjets + BT20 Top pod + 2mm Basswood fins + 3D printed parts (designed in last few nights - consider it semi-scale since I used standard tube sizes). Comes in at a little more than 25" long (I forgot to weigh it when it was together and I already took it apart). I know there are a bunch of bigger versions of this missile out there but I wanted one that would launch on Estes D or E engines.

View attachment 475790 View attachment 475791
I built the mini Bomarc i Canadian livery 45 years ago, I always like this bird, not exactly the sleekest rocket from an altitude standpoint, but a real looker.
 

BigMacDaddy

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Wow, that looks great! 3D printer seems to be a excellent method of forming custom parts. Do you know what the final mass will be?

I’m also currently scratch building the Bt60 bomarc, with bt55 ramjets, although I’m using bt50 nose cones for simplicity. 24mm motor and estimated 300g on the pad. Build to fly E and F motors.

Best of luck on the painting! Hope to see it when it’s all done.
Looking great -- I could not scratch build these type of rockets without the 3D printed parts...

Right now best I can tell from balancing all my parts on the scale is that I am at 122 grams (without glue, engine, shock cord + chute, etc.. - ah also no nose weight yet, no idea where CG will wind up). 3D printed parts can be pretty light if they are printed thin. All depends on the design (including reasonable print orientation) and how much stress the part needs to handle. I mostly try to print 1.2mm thick walls which works out to 3x .4mm layers.
 
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burkefj

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I like that you have the horizontal surfaces down below the top of the tube, it's very tempting to mount them on the top as a swag to make things simple and robust, and I've done that myself, but I applaud you doing it the "right" way...

There are two main versions if you didn't know, the early one with a double tapered ramjet tube with intake cone and nozzle and the later one with tapered front but no real tuck at the rear and less obtrusive nozzle. The wing is also mounted more forward on the later super version. You could print a shell to go around the ramjet tube to give you the double taper if you desired.

it's interesting you made the ramjet struts with an angled end on one end, I've never seen one in person or in photos that had this, they always were straight ends on the ones I've seen or seen photographs of, was there one you found that showed this? I'm just interested.


Frank

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Rob Campbell

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Very nice. Those ramjet inlets are probably the best I've ever seen on a flying BOMARC model.
 

BigMacDaddy

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There are two main versions if you didn't know, the early one with a double tapered ramjet tube with intake cone and nozzle and the later one with tapered front but no real tuck at the rear and less obtrusive nozzle. The wing is also mounted more forward on the later super version. You could print a shell to go around the ramjet tube to give you the double taper if you desired.
Thanks, this is good to know - I did not realize the different versions. I was patterning mine roughly off the version in the 2nd picture you shared but compromised on the ramjets to simplify so they could just be tubes with intakes and exhausts.
 

BigMacDaddy

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Very nice. Those ramjet inlets are probably the best I've ever seen on a flying BOMARC model.
Thanks so much -- I really appreciate that!

A while back I actually made a set of various ramjet/scramjet nozzles and exhausts that were sized to use the yellow motor spacers (figured this could be a good use of them as details). These were adapted from some of those.

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boomtube-mk2

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The ramjet intakes look good but I can't help but wonder if they won't create a lot of off center drag and cause instability as a result.
 

burkefj

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Typically they don't, the models with a center mounted engine in the main body tube typicall arc toward the spine with the upper wing and tail offsetting the ramjet drag. In my R/C rocket glider version that is BT-80 based, I actually offset the motor to the top of the inside of the body tube since the wing/tail drag is usually more than the ramjets and it boosts very straight like this. The offset motor would tend to pitch the model toward the ramjets but the wing/tail counter it.

The ramjet intakes look good but I can't help but wonder if they won't create a lot of off center drag and cause instability as a result.
 

BigMacDaddy

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The ramjet intakes look good but I can't help but wonder if they won't create a lot of off center drag and cause instability as a result.
I won't really know till I try flying it (OpenRocket does not model pods or drag particularly well in my experience). The ramjets do let air go through -- about 3/5 to 2/3 of total surface area is open based on diameter of internal ramjet details and hole / pass-through.
 
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