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  #1  
Old 12-23-2019, 05:46 PM
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Default Maxi-Brute Honest John

Time to build something - I'm trying to free up some space, and this one stood out. It's been sitting there for around 13 years, and it takes up a lot of space on the shelf, so here goes.

This is the re-issue kit (from around 2001?). One reason I've been putting it off is the vacu-form fins. After looking into some 3D ones, the cost didn't make sense, considering what I probably paid for the kit back then. So, I decided to see what I could do with the stock parts. I'm taking the lead from Jeffy's HoJo build, by making some 1/16" basswood TTW blanks, and will cover them with the vacu-form skins. The basswood profile fins weigh about 0.20 oz each. Since I'll be flying it on RMS 24/40 & 24/60 motors, the little additional weight won't be a problem. I'll need to create some sloping stringers, probably just out of 3/32" balsa, as that'll be easy to sand to profile.

Stock weight is listed as 14oz, if this is accurate, I expect mine to be about 16-18oz when done. I'm not looking for a turbo-charge here, just a little more durable flier.
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Last edited by PaulK : 12-26-2019 at 08:48 AM. Reason: Add photo
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Old 12-23-2019, 06:44 PM
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While pondering the fins, I started the motor mount. While I'm trying to keep the kit largely stock, I didn't like the idea of using AP with standard thin BT-50, so cut a piece of BT-50H. The kit comes with just 2 CRs, and I'll be adding a 3rd aft of the fin tabs to eliminate that long unsupported tube. I'm saving one of the card stock CRs for this, so used a BMS fiber ring for the center. So far just raiding the parts bin for these minor upgrades. I've built up a good stock of spare parts in the 14 years since getting back into the hobby.
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Old 12-23-2019, 06:50 PM
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I need to figure out how to get a CR in the tapered tail cone. Ideally it will be at the aft end of the fin tabs, so I can glue them well to the MMT. The problem here is how to get it in there? I'll need to glue the tail cone in, then the fins - but the aft opening is far too small to get anything in there. Even if I remove all the aft support, the TC is still tapered...
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Old 12-23-2019, 06:55 PM
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When I don't have a ready answer, I set it aside, and move to a different part of the build. Some might call that procrastination, or avoidance, I call it "pondering time".

The NC shoulder is really short, especially for such a huge cone, so I moved onto that. A piece of LOC 2.56 coupler was in the parts bin, now that's handy! First step for this was to cut & split a piece, and epoxy into a well sanded NC base.

It was inserted a little above the narrowest portion of the NC base, and set vertically for curing, so a bit of epoxy could pool in the gap. Once this is dry, I'll glue on a shorter piece of coupler, giving me about a 2" total shoulder. This modification is going to cost an ounce or two, but my calibrated eyeballs say this shouldn't negatively affect the CG.
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Old 12-23-2019, 07:19 PM
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Put a 29mm mount in it.
You can ALWAYS adapt down to 24mm.
It is a BAD JOKE for a rocket this big to have a 24mm mount no matter the weight.
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Old 12-26-2019, 08:52 AM
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The finished NC shoulder fix, after adding another piece of coupler. This should keep the huge NC much more stable in the BT.
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Old 12-26-2019, 09:04 AM
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Now for a bit of work on the tail cone. I used an xacto to cut away most of the end, so I'd have access to the fin tabs, and be able to insert some sort of aft CR. This plastic is really thin, and a sharp #11 blade cuts through it far too easy - it'll require a little filling when done.

A short length of BT-80 will be used as a reinforcing ring, it took a little trial-and-error to get a tight fit, by slicing a progressively larger wedge. After roughing up the inside of the TC, I smeared a thin layer of 30m epoxy, inserted the BT-80 piece, and pulled it back tight against the aft lip. This seems plenty strong, and should provide a good gluing surface for an aft CR. The aft CR will need to be some sort of 2-piece job to get past the taper - I'll figure that out when it's time.
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Old 12-30-2019, 12:07 PM
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I'm running out of things to do other than the fins , so time to tackle those. I cut just one set of skins, to see how it fits to the core. The fit seems nearly perfect - after notching out the fin tab, I think they will glue nicely around the perimeter. The vacu-form is thick enough that I don't really need cross braces, but it will stiffen up the diamond profile, so I think I'll do that next with some 3/32" balsa. No more fins until I get this one completed and fitted to the tail cone, just in case I've missed something.
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Old 12-30-2019, 12:12 PM
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That fit looks great, can you post the dimensions of the fin edges and tab?
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Old 12-30-2019, 12:14 PM
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The NC shock cord attachment is similar to stock, with a loop through the NC base, except I'll use Kevlar. I stiffened up the top with a 1/16" piece of basswood epoxied, and further reinforced with a popsicle stick. The 'ol calibrated eyeball says this should be sufficiently strong.
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