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mbeels

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(this is mostly for my own note keeping)

The nose cone currently weighs 1.3 oz. With the wings glued to the fuselage (and the bottom of the wings fiberglassed), it weighs 4.2 oz. All together so far it is at 5.5 oz.
 

mbeels

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After fiberglassing the nose cone with 1 layer of 0.75 oz cloth the nose cone is up to a whopping 1.4 oz. A single triangle shaped piece worked out well to wrap the whole thing at once.

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At first I attempted to make some cardboard jigs to help align the 18mm tubes for the side pods, but that did not work well. I just plain didn't have the right shapes and didn't cut the cardboard well enough. So I started with gluing the top piece in place, I felt reasonably confident I could get that lined up and straight. Then I resorted to a combination of measuring and a sort of feeler gauge I cut out of the jig to situate the 18mm tubes. At least I could get things L-R symmetric that way.

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I also brushed the first two coats of primer on the nose cone. The next steps will be to frame out the side engines, work on the surrounding trim pieces, and the horizontal stabilizer.
 

mbeels

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Tonight I framed up the area around the engines with 1/16" sheet balsa. Again I added 1/16" square in the corners to allow for sanding a bigger radius. I cut out 4 identical side pieces with the inlet scoop shape, and then tweaked their shape a bit so they would fit on the curved bottom side of the wing. Then I started the sheeting process. Probably ought to do the horizontal stabilizers next.

P7070684.JPG

Weight at this point so far is 6.2 oz. I'm guessing that I'll end up closer to the 9-10 oz range.
 

neil_w

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Looks really good. I foresee D24s in your future... :)
 

mbeels

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Looks really good. I foresee D24s in your future... :)
Yes, I was just thinking that as well. I ran some quick sims on thrustcurve.org. (I've got a Rocksim model going as well.) This is getting rail buttons, so maybe with a 6' rail lower thrust motors will be an option, we'll see. But it looks like with a 3' rod, it'll be D24s!
 

BABAR

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Looks great. If weight becomes an issue (looks like d24 maxes at 424 grams if this source is good


There are some outside the box methods to retrofit a 24mm Mount to an 18 mm mount, although they are a bit unorthodox, and you are going to have a tight fit for a chute already.


Post 9
 

mbeels

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Looks great. If weight becomes an issue (looks like d24 maxes at 424 grams if this source is good
Yeah, the weight seems to be stacking up quickly. I should be well under 454 g (16 oz) though, I hope. Had I increased the size by a factor of 1.5, a 24 mm motor mount would open up many more options, including 3 gr and 6 gr CTI cases.

There are some outside the box methods to retrofit a 24mm Mount to an 18 mm mount, although they are a bit unorthodox, and you are going to have a tight fit for a chute already.
That is an an interesting 24 mm mount retro fit, reminds me a lot of CHAD staging. Everything about 6" forward of the motor is BT-55, so there ought to be comfortable space for up to a 24" parachute.

I'm also using 18mm tubes for the side engines, so I'm leaving the possibility open for a 3x18mm cluster.
 

mbeels

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I've hemming and hawing about the horizontal stabilizer, I'm not quite sure how to best go about it. So I'll just plow forward. I cut out a template to scale using the top view, but I decided to slightly increase the size, and tilt the stabilizer downwards. Hopefully this somewhat improves the stability.

The balsa box is getting notched out, and the horizontal stabilizers will attach to the bottom of the BT-20 tubes. Getting them straight depends on how well I got the balsa box straight, which is supposed to be straight with the tubes, which are supposed to be aligned with the airframe. In principle it should be ok, but there are a lot of places for errors to stack up.

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I still plan on giving the horizontal stabilizer parts a symmetrical airfoil shape. The tail end of this will take some time.
 

mbeels

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I glued a second 1/16" horizontal stabilizer piece on the top of each one for thickness, but cut it short with an angled cut so it sits up against the balsa box. So the top piece sits against the balsa box, and the bottom piece goes through the slots to the tube. I sanded an airfoil shape and gave them a layer of 5 oz fiberglass. They're very thin on the edges, the 'glass gives it some strength. The pair together weigh 0.1 oz.

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The fuselage with nose cone is now up to 6.3 oz. It's kind of a strange spot back here behind the wings, but once that is all closed up the building phase of the build will be over, which means the filling/sanding/painting will begin.
 

BABAR

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Maybe I missed it.
Are you going with lugs or buttons?
 

mbeels

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Maybe I missed it.
Are you going with lugs or buttons?
Both. I'm going to tuck a lug between one engine nacelle and the fuselage, and I'm going to add rail buttons to the bottom of the fuselage. I think flying off a longer rail may open up more motor possibilities.
 

mbeels

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I peeled off enough layers of a BT20 - BT50 centering ring to get the right OD, and added a paper shroud for the engine nozzles. Then it was a matter of filling in the remaining openings and gaps with balsa. There will be a fair bit of filling, sanding, and finishing work yet to do.

Weight so far is up to 6.5 oz without parachute, shock cord, launch lug, rail buttons or filler/paint.

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P7110727.JPG
 

kuririn

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Looks like you're on track to launch your B-1 before Boom does in October.
 

mbeels

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Looks like you're on track to launch your B-1 before Boom does in October.
I think so, and I wouldn't be surprised if their test flight got pushed back farther.
 

mbeels

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After filler, the weight is up to 6.5 oz, so I didn't use enough to register on my scale. It is still a work in progress, but I like the way this is going.

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Because of the wood grain and uneven surface texture from the peeled centering ring, I decided to fiberglass the tops of the wings. It isn't necessary for strength, but it will add some ding protection and make finishing faster and easier.

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After trimming the excess fiberglass, weight is up to 6.7 oz. Not too bad. I'm undecided about fiberglassing the engine air scoops, I may just fill that wood grain with thinned CWF.
 

mbeels

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I did a layer of thinned CWF, and after sanding the weight is up to 7.0 oz. I've got a bit more sanding with 400 grit and clean up to do in a few spots, but it is nearly ready for primer.

I started thinking about paint, I might try mixing gloss, satin, and flat. I think that has potential, but I'm not exactly sure how yet. Something like gloss yellow, with satin white, and maybe both gloss and flat black.

P7140783.JPG

P7140784.JPG
 

neil_w

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Looks beautiful. Are you going to go with the prototype paint scheme?
 

mbeels

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Looks beautiful. Are you going to go with the prototype paint scheme?
Thanks. I'm not sure, probably not exactly if I do.

The 3D model has a fade between white and black which would be difficult to pull off, and I'm not sure it would look right with a masked hard edge. I like the blue/white/grey of the 1/3 scale mockup, it's quite simple and would probably be easier to do. But it isn't terrible exciting. I'm curious what the paint scheme on the full scale will look like.

I'm inclined to at least include some black, as a nod to the composite construction of the real thing. Maybe even some faux carbon if I found the right decals or patterns. I'm also curious how a gloss and matte black combination might look. So those are some of the rambly thoughts I'm mulling over.
 

BABAR

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May want to put some Mylar on the central side of that tailfeather, it may get a bit singed.

Build looks great, I didn’t think that could be done with wood.
 

mbeels

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May want to put some Mylar on the central side of that tailfeather, it may get a bit singed.
Yes, I was considering a strip of aluminum foil glued to the bottom of that "thing".

Build looks great, I didn’t think that could be done with wood.
Thanks, based on what I've seen others do with wood, I'm pretty sure it can do darn near anything. Some of the most surprising stuff was from the C/L stunt folks, they bend solid balsa sheet in ways I never thought possible. I think @Mugs914 does stuff like that. One of these days I want to learn their secrets.
 

BABAR

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Yes, I was considering a strip of aluminum foil glued to the bottom of that "thing".



Thanks, based on what I've seen others do with wood, I'm pretty sure it can do darn near anything. Some of the most surprising stuff was from the C/L stunt folks, they bend solid balsa sheet in ways I never thought possible. I think @Mugs914 does stuff like that. One of these days I want to learn their secrets.
This guy can literally build balsa circles around most of us
@Rktman

 

mbeels

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Primer is nearly done. Yes, that is regular old exterior latex primer, applied with a regular ol' brush. Rail button holes are drilled. Just a few touch up spots, final sanding, and it is ready for paint.

P7160786.JPG
 

jqavins

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One of these days I want to learn their secrets.
Ammonia. I'm not talking Windex here, but high concentration ammonia solution, or ammonia gas in a steam box. I've seen video of a brook stick made into a pretzel. For that matter, steam in a steam box lets you do quite a lot, and if you use "household ammonia" (about 5% to 10% by weight) instead of water to generate it then you could surely do more. (Windex contains several other ingredients, and if my nose is even a little reliable, its ammonia content is rather low.)
 

mbeels

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Ammonia. I'm not talking Windex here, but high concentration ammonia solution, or ammonia gas in a steam box. I've seen video of a brook stick made into a pretzel. For that matter, steam in a steam box lets you do quite a lot, and if you use "household ammonia" (about 5% to 10% by weight) instead of water to generate it then you could surely do more. (Windex contains several other ingredients, and if my nose is even a little reliable, its ammonia content is rather low.)
Yeah, I checked the MSDS for Windex, but the concentration of NH3 is below the reportable level. According to the 1969 patent, it would contain 0.05% of a 28% NH3 solution, so about 1.4% NH3.

Whelp, I wouldn't be too thrilled working with high concentrations of ammonia, it is pretty stinky stuff. We occasionally use pure NH3 gas at work, and take extra measures to make sure everything gets vented properly. The nose threshold is about 50 ppm. We design and build sensitive gas analyzers, one of which detects NH3 down into the ppt range. We once did a "stinky shoe" demo that turned into a marketing video, but that is another story.
 

jqavins

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Yeah, the five to ten percent stuff is mighty stinky, but not terribly dangerous. One day I might try putting some into a trigger sprayer and wetting some basswood with it. Outside.
 

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