Estes Bullpup 12D Clone (with 2 major modifications)

[mh9162013]

Here are some pics of my recently completed Bullpup build. Used parts from the Designer's Special (parts for the modifications did not come from the Designer's Special, though) and purchased the genuine Estes decals separately. Nothing notable about this build except for the modifications to the nose cone and boat tail. I just wish my finishing was as clean as my engineering.

 

[kuririn]

Is that a screw on tail cone motor retainer?

 

[mh9162013]

Is that a screw on tail cone motor retainer?

Yes it is.

 

[kuririn]

Yes it is.

Ingenious.

 

[DocSeuss]

The Bullpup was my most-flown rocket when I was a Boy Scout down at Argonia. I love it, but never loved the motor retention. How... would one build a retainer like this? I'd love to build a new one but this looks like an amazing mod.

 

[mh9162013]

The Bullpup was my most-flown rocket when I was a Boy Scout down at Argonia. I love it, but never loved the motor retention. How... would one build a retainer like this? I'd love to build a new one but this looks like an amazing mod.

You'll need an Estes 18mm screw-on motor retainer and possibly a slightly longer piece of BT-20 to use as the motor mount tube (MMT) (I'm not 100% sure about length, as I built mine to hold a removable baffle. If it needs to be longer than what's provided in the kit, it will only need to be half-an-inch or less longer).

Then you glue (I used epoxy) the screw-on portion of the retainer into the boat tail piece. You may need to do a little sanding of the retainer to get the right fit.

The pictures should explain the rest. The only tricky part is figuring out how far deep into the main body tube to glue the motor mount. What I did was build the boat-tail retainer first. After the epoxy was dry, I screwed it onto the completed motor mount, then carefully glued that into the main body tube. So now you have the boat-tail perfectly flush with the bottom of the main body tube while it's also fully screwed onto the MMT.

 

[DocSeuss]

This is fantastic, thank you! I am gonna try this!

 

[mh9162013]

This is fantastic, thank you! I am gonna try this!

Please do! The world needs more Bull Pups without motor hooks or friction fit motor mounts.

 

[Raythain]

This is brilliant. I found a partially mangled (the word built is far too generous for the state this kit is in) Bullpup on eBay that I’m rehabbing, and I have a pack of 18mm screw on retainers I keep forgetting about in my parts bin. Going to have to this this out.

 

[mh9162013]

This is brilliant. I found a partially mangled (the word built is far too generous for the state this kit is in) Bullpup on eBay that I’m rehabbing, and I have a pack of 18mm screw on retainers I keep forgetting about in my parts bin. Going to have to this this out.

Good luck with the restoration project! And feel free to share how it turns out.

 

[Imaknow]

One question, what is the compartment in the nose cone used for? Adjustable nose weight or something more?
Thanks.

 

[DocSeuss]

I went to pick up my old Bull Pup and the clay has gotten loose since I built it in like 1998. I bet this would make it easier to replace the nose weight.

 

[mh9162013]

One question, what is the compartment in the nose cone used for? Adjustable nose weight or something more?
Thanks.

The nose cone payload bay was designed to house two altimeters. But the weight of the parts needed to create that payload bay (plus the 2 altimeters) won't be enough to fully replace the necessary clay nose weight. Therefore, if launching with a C or D (RMS), I will probably need to add some nose weight. If my calculations are correct, it'll only be a small amount of weight, like 1/3 of an ounce...or something like that.

 

[mh9162013]

I went to pick up my old Bull Pup and the clay has gotten loose since I built it in like 1998. I bet this would make it easier to replace the nose weight.

Absolutely