SBR 'The Bomb' Rocket Kit

[TXJeff]

I read everything that people wrote about the fins, did a lot of test fitting, then put it all together quickly with 5 min epoxy and holding it securely with very large rubber bands and my hands until it dried. The tabs were beveled, they match up with the fins but also with the tabs on the other side. And the full length of the fin and the "box" intersect tightly.
This was a bit of trial in my mind until I understood what was intended. It was easier than I thought at first because the design is very good - trust SBR's design.
The end result is "square". Then reinforced the fin/box intersection points and right over the tabs with RocketPoxy, then on the inside of the box with West System G/5 Epoxy, then "painted" the entire assembly and the entire rocket with West System 105/205 epoxy resin.
It all seems very strong and I think the assembly will survive a harder hit given all of this than a single fin would. At our site there is a good chance this will come down on an asphalt runway, so I am using a bit larger chute and wont fly if the wind is sending them over in that direction on launch day. Because of our launch site "feature", I usually prefer rockets with up-swept fins and with a very solid AeroPack engine mount so that the rocket can "land" on the AeroPack which will take the hit. But The Bomb is different so we will see how it does if it has the misfortune of coming down on the runway - but I think it will be ok. We will see.

 

[jFlds]

Here's mine from this weekend at URRF. I223 skid to about 2,100 ft

 

[TXJeff]

Beautiful flight!!!

 

[TXJeff]

I've finished building The Bomb, a really great experience. I learned a lot building this ingeniously designed kit from SBR.
Now to fly it... unfortunately this has been a bizarre year for weather - at first unusually cold and more recently an unprecedented nearly 2 months of >100 degree weather. In an uncooled garage workshop this means building and panting at either midnight or 6 am. I've got a lot backed up waiting to go together, including my SBR Honest John.
Now to find a launch date with low winds and from the right direction for the first flight. I have I140 and an I161 engines waiting...

 

[jFlds]

I've finished building The Bomb, a really great experience. I learned a lot building this ingeniously designed kit from SBR.
Now to fly it... unfortunately this has been a bizarre year for weather - at first unusually cold and more recently an unprecedented nearly 2 months of >100 degree weather. In an uncooled garage workshop this means building and panting at either midnight or 6 am. I've got a lot backed up waiting to go together, including my SBR Honest John.
Now to find a launch date with low winds and from the right direction for the first flight. I have I140 and an I161 engines waiting...

Both great loads for this one. Are you using a JL chute release? The I 140 will put her up there around 2k

 

[TXJeff]

I had a bad jl experience... I know I need to try again. I have build a rocket out of spare parts specifically for testing the jl. That should be my focus first, you are right.

 

[jFlds]

I had a bad jl experience... I know I need to try again. I have build a rocket out of spare parts specifically for testing the jl. That should be my focus first, you are right.

Yeah I've had 2 JL units, went 1 for 4 on flights and decidedly took a break from them. I'm going to get another one for Fall and try it all again.

 

[DMehalko]

I read everything that people wrote about the fins, did a lot of test fitting, then put it all together quickly with 5 min epoxy and holding it securely with very large rubber bands and my hands until it dried. The tabs were beveled, they match up with the fins but also with the tabs on the other side. And the full length of the fin and the "box" intersect tightly.
This was a bit of trial in my mind until I understood what was intended. It was easier than I thought at first because the design is very good - trust SBR's design.
View attachment 523832The end result is "square". Then reinforced the fin/box intersection points and right over the tabs with RocketPoxy, then on the inside of the box with West System G/5 Epoxy, then "painted" the entire assembly and the entire rocket with West System 105/205 epoxy resin.
It all seems very strong and I think the assembly will survive a harder hit given all of this than a single fin would. At our site there is a good chance this will come down on an asphalt runway, so I am using a bit larger chute and wont fly if the wind is sending them over in that direction on launch day. Because of our launch site "feature", I usually prefer rockets with up-swept fins and with a very solid AeroPack engine mount so that the rocket can "land" on the AeroPack which will take the hit. But The Bomb is different so we will see how it does if it has the misfortune of coming down on the runway - but I think it will be ok. We will see.

Good to hear and see, you must of got one of the later kit revisions with needed adjustments.

 

[FlyBy01]

I had a bad jl experience... I know I need to try again. I have build a rocket out of spare parts specifically for testing the jl. That should be my focus first, you are right.

What was your final build weight?

 

[Joshua Smith]

I'm sooo tempted by the SBR Honest John. However, having to assemble the fins seems a little nuts for a kit that expensive. Tho, more importantly, I need to finish several other large rockets first including 2 3" diam Bull Pups and my LOC Ultimate. I'm a sucker for Bull Pups & Honest Johns and most anything that's modeled after a real missile.

Photo compliments of Harry Spears

 

[Joshua Smith]

Photo compliments of Harry Spears

Sorry, didn't mean to post the image twice.
It was on a CTI I223 Skidmark. Flew very nicely. Used motor eject and just popped the main. 1605 ft AGL, 2252 ft ASL

 

[Brent]

Is SBR rockets still in business? All kits out of stock on the website.

 

[Joshua Smith]

All the 4" ones I checked seem to be in stock, I was able to add them to an (insecure) cart

 

[Joshua Smith]

All the 4" ones I checked seem to be in stock, I was able to add them to an (insecure) cart

At binderdesign.com anyway. At fusionrockets.biz they seem to be out, at least of the bomb https://www.fusionrocket.biz/store-2/?model_number=BOMB

 

[cwbullet]

Is SBR rockets still in business? All kits out of stock on the website.

it may be a coincidence. They seem to go out off stock late summer to fall every year that I have watched.

 

[Joshua Smith]

Mine came off too. I drilled a small hole down the center of it and thru the nose cone. I then put a small picture-hanging nail with a largish head on it down thru it and into the cone. I bent the nail after it enters the nose cone (I couldn't really get great leverage on the nail, so it's not bent much. Oh, I also roughed up the sides of the nail using pliers and wire snips. I put a small amount of epoxy in the hole and around the nail etc. I let that setup a bit and taped the nub and nail onto the nose (on the outside of the cone) so it would stay in place and not let the epoxy run out of the nose. I then put epoxy mixed with West System 404 high density adhesive filler in the nose around the nail. I didn't overdo it with the 404 so the epoxy still flowed a bit so I could move it around by tilting the cone. I kept doing that until the epoxy started to stay stuck to the walls and I let the rest settle down with the nail. When that got tacky I did another layer. I will probably do one more cuz the epoxy isn't quite coating all of the interior of the nose.

An update on this: I dropped the bomb on the "detonator" accidentally and a chunk of epoxy and paint came off (exposed about 25% of nail), but the detonator didn't budge. I just put some medium CA on to fill the missing chunk and I'll paint it when I get a chance, tho it isn't terribly noticeable as is.

 

[Joshua Smith]

The Honest John fin assembly is straightforward and it makes for accuracy that you couldn't get otherwise. It's a brilliant design. Take a look at Scott's extensive assembly videos for details on the assembly.
Mine arrived yesterday and looking thru the box is amazing. So typical for SBR - everything is carefully wrapped, even the box is carefully sealed with tape neatly cut and folded all around. The time and the care is obvious. It reminds me of the quality packaging of a high-end RC 'copter kit I bought 20 years ago. This is the exact opposite of a "couple of tubes in a plastic bag". Excellent "out of the box" experience.
View attachment 523768
I can't wait to get this one started... but with my "junior" assembly skills I'll be going slow. I'll have pics on a specific thread.
Joshua, stay tuned and you'll see it fly after the summer, although probably at Hearn. I have to make some decisions about the electronics for this. My RRC3 refuses to connect to any computer and that is holding up everything (it's been suggested that it is faulty but I have no way of checking that).

Me wants! Have you launched it and did you do a build thread? I'm going to attend the 9 Dec launch if the weather improves a lil

 

[TXJeff]

My build thread is above for the last several pages. Lots of pics!
It is a COOL pic!
I was going to launch it this weekend at Hearn... but the weather is ??? And the wind is probably too high... I don't want to loose it over the fence or land it on the runway.

 

[Joshua Smith]

My build thread is above for the last several pages. Lots of pics!
It is a COOL pic!
I was going to launch it this weekend at Hearn... but the weather is ??? And the wind is probably too high... I don't want to loose it over the fence or land it on the runway.

On the upside, if anything would survive landing on the runway, it's that box tail lol

 

[TXJeff]

On the upside, if anything would survive landing on the runway, it's that box tail lol

I often make the "Hearn Modification" to fins for landing on scraping over the runway. That is, I remove the point on the bottom edge of the fins. Both of my Maxi Red Maxs have that mod. It's saved a lot of trouble, although in the Dec Hearn launch the smaller one of the two just went over the fence into a tree in the field beyond. Fortunately found the secret entrance into that field and got it back.
I hope SBR comes back online... I want a second Bomb nose cone to build an electronics bay into.