My Madcow 2.6 Bomarc build thread

[Wally Ferrer]

I've been wanting to do a build thread, if for no reason other than to better document my build process. Any feedback for improvements I get will be icing on the cake. I happened to be in Colorado Springs last year on my trip to launch rockets for my niece in Oklahoma who has CP (sorry, not her center of pressure). I decided to drop in on Apogee as I have been helping build Allison's college fund for years. I got to browse the warehouse section, and wound up grabbing a 2.6 Bomarc, among a few other things. It is overdue to be built:

 

[Wally Ferrer]

The nacelle points were protected well.

 

[Wally Ferrer]

The Decals were inside the instruction book.

 

[Wally Ferrer]

Misc. parts, will be replacing lugs with rail buttons, not yet sure on the location.

 

[Wally Ferrer]

Assembling the motor mount, I want to use a Slimline retainer I already had, it was a bit loose so I cut a short piece of adapter tube to fill the void. Since I would be getting epoxy at the end of the motor tube, I decided to use JB Weld and add the retainer now. I sanded the motor mount tube first.

 

[Wally Ferrer]

Added the Kevlar portion of the shock cord so it can stick to the epoxy. Also used a couple of drops of thin CA to clean up the end and stop any more fraying, no need to trim the end attached to the motor mount. I did add a drop of the CA there as well, that frayed end is not going anywhere.

 

[Wally Ferrer]

JB Weld takes a long time to set up, so I'm not inserting into the body tube just yet. After a break, I'll begin building the wings. That looks to be a fairly elaborate process to glue wing sections together and then build up the structure. I think I'll use parchment paper rather than wax as it releases better.

 

[Wally Ferrer]

Since I want the wing joint to really hold before I do further work, I decided to go ahead and glue that together before pausing. Will resume soon...

 

[Mick Kelly]

I will be watching your progress because I have this unopened kit that I got decades ago. I have a red nose cone and with white airframe tubes and my parachute is orange. This might be the rainy day I've been waiting on. Best of luck with your build! Wish there was a date on my kit.

 

[Wally Ferrer]

I will be watching your progress because I have this unopened kit that I got decades ago. I have a red nose cone and with white airframe tubes and my parachute is orange. This might be the rainy day I've been waiting on. Best of luck with your build! Wish there was a date on my kit.

Thanks Mick, there is no better time than the present...

 

[Wally Ferrer]

Checked the wing this morning and it looked great. The next step is to add a layer of balsa to the top of the wing. After cutting the balsa sheets to length I glued them on to the wing. I usually use too much glue and the moisture plus shrinkage can get real bad real fast. I tried to smooth out and remove what I felt was extra, and laid it flat with some weight on it. Paranoid, I checked it after about four hours, and there was a slight warp. To be honest this was the least amount of warping I've had, so I feel okay about it. To remedy I flipped it over, added more weight and gave it more time. After about four hours, I checked it again, and it was nice and flat. Well, except for one corner which had a slight separation between the balsa and the plywood-flat, but not glued on the edge so I added a little bit more glue and put two clamps on that corner, the other clamps are really just keeping it level. Will now give that more time to set. I realize now I didn't get a photo of the warp. Oh well.

 

[Tobor]

Subscribed!

 

[Wally Ferrer]

Now to trim and mark center-line, top and bottom...

 

[Wally Ferrer]

In case it wasn't clear, I used the razor saw to cut most of the way through the balsa, then finished the cut with a fresh blade in the xacto...

 

[Wally Ferrer]

Glued on the balsa spacer on the stabilizer next...

 

[Wally Ferrer]

Now to attach the stabilizer to the main wing starting with boom core, two 1/2" x 1/4" balsa strips 33" long. They wereslightly bowed, so I placed them tip to tip with the center bowed out, with glue in between and clamped together, lightly. Glue on top of the wings, set the strips down on the glue, add the clamps making sure the boom remains in contact with the wing, added support to the clamps to keep them level, and added some weight to ensure good contact with the wing surface. I actually used the lines on the cutting mat to keep the center line straight and square.



This I will leave overnight to dry.

 

[o1d_dude]

Nice work.

 

[Wally Ferrer]

Thanks. All I'm going to say is I am not yet ready to do a build video...

 

[Nytrunner]

My hands are getting clampy just seeing these pictures.

Great job and keep up the good work!

 

[Wally Ferrer]

My hands are getting clampy just seeing these pictures.

Great job and keep up the good work!

LOL I know what you mean- I really need more of the smaller clamps like the rear one at the stabilizer, bu we work with what we have...

 

[Wally Ferrer]

Clampy goodness continues as building the conduit boxing proceeds, I do not have enough clamps to do the pieces over the wings, I'll do those in a little while- I don't think these need to stay overnight, but I will give them a couple of hours at least before I remove any...



The piece at the rear that looks a tad short should be okay once the conduit gets shaped, so I went ahead and used it. The extra piece under the front boom was just for support so I could align the pieces and clamp easily.

 

[o1d_dude]

Thank you for documenting the Bomarc build. Looking forward to getting a flight report, too.

At a minimum I have found a legitimate use for all those Irwin pistol grip clamps I bought during several moments of temporary but apparently recurring insanity.

 

[Wally Ferrer]

Thank you for documenting the Bomarc build. Looking forward to getting a flight report, too.

At a minimum I have found a legitimate use for all those Irwin pistol grip clamps I bought during several moments of temporary but apparently recurring insanity.

I have had those clamps for years and this is the first time I used more than one.

 

[Wally Ferrer]

Added the strips to support shaping the front of the tunnel as well as the triangular strips that will help attach the wing structure to the body tube. No clamps, these strips were light enough that the yellow glue held it in place, I did use the angle aluminum so I could press it tight against the bottom of the boom while keeping it in alignment. Need these to set well, next step is sanding the rounding of the front and rear of the tunnel and shape the underside to fit the tube.



The slot will also require trimming to allow the tail (vertical stabilizer?) to seat fully.

 

[Wally Ferrer]

oops

 

[Wally Ferrer]

Try again, last post got all wonky, trying again...

Shaping the tunnel, will need a touch of CWF where sanding got over-enthusiastic.

 

[Wally Ferrer]

Shaping the tunnel continues...

 

[Wally Ferrer]

Now I need to trim the slot for the tail...

 

[Wally Ferrer]

The instructions say to epoxy the tail to the wing assembly, I'll wait until time to attach it to the body tube as that will make it easier to get it set at 90° - I think. I believe the hard part is over .Tomorrow I get to start working with epoxy and tubes...

 

[KevinM]

Wow, great memories of a fantastic kit! This is a solid flier, so don't be intimidated by it once you get yours done. A "unfortunate spontaneous motor disassembly" has removed my BOMARC from the flight roster, but even the handful of flighs I got made all the build-work worthwhile. One day I will build another.

I was never a fan of the balsa ramjet cones, so I 3D printed a 2-part cone to replace them, I thought it added greatly to the appearance. If you've got access to a 3D printer I can probably still locate the model file, I'd be happy to share.

Thanks for sharing your build! Here's a little inspiration of what you can look forward to when she's complete!