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Micro Sinbad

Hank, It's all good. I have to say this doesn't look like your work!

I agree with the idea that the best way to gain durability with these micro RC aircraft is to keep the mass out. Hank and I have been building flying and crashing these for decades. It is truly amazing how durable they are.

My concern with the keel has more to do with my ham fist approach to covering. I fear that I'll crack/snap the keel while manipulating the iron on film! I'm looking at the whole life cycle of the model. While I think there is enough support from the lower bulkheads for most of the loads. It is the stresses of building that concerns me. I know, I know just don't pull and push so hard while covering!

CA overflow Sinbad.jpg
 
  • Haha
Reactions: Red
We can replace whatever you need replacing.. Not a problem. We should have parts precut.

You can meet Josh too.
 
Manual
Hank, It's all good. I have to say this doesn't look like your work!

I agree with the idea that the best way to gain durability with these micro RC aircraft is to keep the mass out. Hank and I have been building flying and crashing these for decades. It is truly amazing how durable they are.

My concern with the keel has more to do with my ham fist approach to covering. I fear that I'll crack/snap the keel while manipulating the iron on film! I'm looking at the whole life cycle of the model. While I think there is enough support from the lower bulkheads for most of the loads. It is the stresses of building that concerns me. I know, I know just don't pull and push so hard while covering!

View attachment 13277
Yeah these days I break far more with my 10 thumbs than I do flying lmao.

Red
 
Just got back from Aloft. Lots of good stuff happening there.

On the micro scene there is some good news and some bad news. The good news is that there looks to be a lot of covering options . The bad news is that there Isn't a plug and play micro servo and FrSky RX option. There is one that is close, but as of today I will still need a soldering iron.

I did buy a set of 2 gram rotary output servos if for nothing else, to use when fitting out the glider. I choose the 2 gram servo over the 1.7 gram as I like the higer torque. Also most of my models often need nose weight.
 
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While I was at Aloft "I" mentioned that I didn't like the ultra small control horn in with the kit. I like much larger control horns to get the most out of the servo resolution.
Well without any prompting from me, in 3 minutes Rafael handed me these. Now there's customer support!

I have no feedback that there is any problem with the control horns supplied. But my experience with these small RC models is that they need the longer arms. Note that what Rafael gave me was just an upscaled horn. I'd like to see Aloft offer a control horn more in line with what I show on my P6-E. This allows the horn to overhang the elevator LE (on models that use built up tail surfaces) and aligns the push rod pivot to be over the hinge to eliminate differential control movement. Please remember that control set up will be one of the areas I deviate from the micro Sinbad plans.

P6-e and Sinbad control horns.jpg

P6-E control horn offset.jpg

laser horns.jpg
 
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Found my Sig Sinbad 40 kit. Wow, what a difference 6 inches makes!

This micro Sinbad is looking to be a really well thought out kit. I point to the fact that just an inconsequential change like making the control horns longer has a lot of ramification. The designer had planned for the pushrod passages and exits. With the longer control horns these will change, forcing me to change some parts like the last bulkhead and the stab mounts. This is not a complaint rather an acknowledgement that the designer has given a lot of time to system integration.

Somethings I’d like to see changed with the cut file (blue arrows) is the front lightening hole be redrawn to allow for the use of rotary servos. The canopy top can be moved to some other part of the sheet. Also the push rod pass through in the rear bulk head need not be larger than 0.020” (just a burned mark).

I also noticed that the splines aren’t rendered properly (red arrows). I saw this in my drawing of cut files using Adobe Illustrator. For some reason if I drew the spline (curve) in a right hand pattern the laser would render the spline smoothly. But if I drew the spline coming the other way, left handed, the curve would be rendered with a very faceted curve. I really don’t know why this is.

Sinbad dual plans.jpg

Sinbad cut files.jpg

Sinbad exit.jpg
 
@Red I love the shoutout to Alien Technologies! lol
What are you looking for in that statement?

I have no idea who are all the players involved in the production of this fine kit. What is @Red’s relationship to Alien Technologies? Where is the link to Red Jensen to the Red of our forum being the Red Jensen of Alien tech.

I assume that if the @Red of this forum was the Red Jensen of Alien Tech and he wanted it to be known he would have mentioned it in his earlier posts.

As it is now and to protect the privacy of the individuals I make reference to the great work of the designer.
 
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What are you looking for in that statement?

I have no idea who are all the players involved in the production of this fine kit. What is @Red’s relationship to Alien Technologies? Where is the link to Red Jensen to the Red of our forum being the Red Jensen of Alien tech.

I assume that if the @Red of this forum was the Red Jensen of Alien Tech and he wanted it to be known he would have mentioned it in his earlier posts.

As it is now and to protect the privacy of the individuals I make reference to the great work of the designer.
Just a comment about something I noticed in one of the pictures you posted. Maybe "signature" or company stamp or logo would have been a better term.
 
Ok, let's start getting to the nuts and bolts of this build. First I have to say I've been building this size RC aircraft for decades as such I have my own ideas as to what works best. This is not a review of the product Alien Tech or Aloft Hobbies is selling. This is MY take on how I assemble and change the design to fit my needs and expectation. Sorry I had to make that statement as so many think that what I write is written as gospel. This is how I skin this cat! My apologies to the cat!

It is MY experience that with the very small contact area of the glue joints found in this kind of model that CA glues are not the best or even desired as the basic assembly glue. I much prefer an aliphatic glue like Titebond Original Formula. This glue is much more flexible, sandable and yes even faster drying than CA. And get this it even allows for a longer working time. You say how can this be. Well the trick is to have a large enough radar range to allow the parts to fit inside. I force dry the glue on high in 15 second power intervals followed by about 60 seconds of cool down or adjustment intervals. After about the 3 cycle of this the bond is ready to sand. This works great in that during the cooling down cycles you can make adjustments and alignments as you see fit. Heck if you find an error later in the build a little bit of microwave energy and the joint will soften up a bit and allow another adjustment prior to cooling back down. Oh, don't use pins to hold any of the parts together prior to the glue reaching the tack stage. I use tape and maybe some rubber bands.

The first problem was to heel the cutout under the canopy to allow the rotary servo to mount. I just healed the kerf by forcing some titebond glue into the kerf. I cut the servo outline in the crutch. As I really don't like to glue servos to balsa I added some 1/64 ply reinforcement to aid in servo mounting and to support the damaged cutout.

The first head scratcher I ran across was that there is no parts layout in the manual and the parts aren't etched. It took me a while to figure out which was the F2B and F3B parts. (the one with the larger cross web is the F2B bulkhead. also many of my parts weren't cut all the way through the balsa sheet. This can be a problem for the laser operator as wood can have various densities even in the same sheet. I normally used a longer focal length lens or upped the power about 5%.

As I'm going to change the wing hold down system I added the necessary armor 1/64 plywood to the parts that might need it.I made the necessary relief cuts in F3 and F4.

I added the Titebond glue to the bottom bulkheads and keel. Gave it the first shot of radiation. Let it cool down and adjusted all the bulk heads to make sure they were square to the crutch. Zapped 2 more times and was ready to add the basswood keel cap strip (not part of the kit design). I made a small relief cut in the front and rear of the keel to inlay the cap strip.

Again I used a very light bead of Titebond along the top of the keel. I pressed the basswood cap strip into this bead of glue. I then zapped the keel and cap strip for 10 seconds. I then pressed the basswood cap strip into the hot Titebond glue. I kept rubbing the cap strip down until the glue cooled. This held the cap strip in the serpentine shape of the keel. I reheated the assembly 2 more time making sure the keel cap stayed down. You can see the results.

One thing that concerns me is that I don't see any anti warping inserts in the simple sheet surfaces. It is my experience that this will cause trimming problems for the life of the model. I'm think of changing the tail feathers to a classic built up construction. I also don't see any benefit to lightening holes in a monolithic wood structures. It is my experiance that this just weekens the sheet and causes the sheet to split prematurely.

Sinbad radar range.jpg

Sinbad sheet layout.jpg

Sinbad glue kerf.jpg

Sinbad armor added.jpg

Sinbad check fitting.jpg

Sinbad basswood cap.jpg

Sinbad cap blend.jpg


Sinbad strengthen keel.jpg
 
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I’m also liking the build. So far no gotchas!! I did break the keel once. And it was upfront trying to fit it into the front blocks. The concaved section held up fine to allow me to add that cap.

I see that the idea for the cap wasn’t mine. Rather it was how the Berkeley plans were drawn.
 
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This brings up the subject of tolerance. The balsa sheets that the laser cutter uses are not a perfect thickness. I've seen the thickness vary more than 0.2mm* on 1/16 sheet (Love the cross units(n)). This is a problem for the designer as the slot width is defined by the material thickness. It would be prohibitively expensive to select the sheet stock to fit the defined slot width in the cut files. So it is up to us the builder to make sure the tab is the proper width prior to forcing the part into the slot.

This is what got me in trouble with the front of the keel. The way the wood grain was oriented I couldn't put any force on the keel to drive it into the front bulkhead slot without the keel shearing along the grain. I should have opened up the bulkhead slot so the parts had a slip fit. Note; the designer does allow for this wood grain problem in that he provides keel doublers. This helps a lot after the parts are assembled.

BTW; I like that the slots in this kit are cut for the maximum material condition (MMC). That is you will have to sand the tab a bit for a nice fit. (I do mean just a swipe or two with your 100 grit sandpaper.
Note; with balsa not only is the grit size important but so is the sharpness of the sandpaper. I always start my builds with a fresh sheet of sandpaper as I want to cut not crush or smear the wood fibers. Far too often I see folks using worn out (dull) sandpaper and then they wonder why the results are so poor.

So a sharp #11 blade is needed and so is sharp sandpaper!

* 0.20mm is the same as 0.008" or the same thickness as three human hairs.

(When are we going to kill the king's units! Heck, the foot is now defined in metric units)!
Sinbad slot fit.jpg
 
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I'm seeing some areas of concern. First is that there is very very little wood fiber holding the left and right elevators together. I'd have to make a coupler or redraw the whole stabilizer structure. I'm going to redraw the stab as I like the look and strength of built up tails.

I'm also puzzled as to what is going on with the wing saddle. Looking at the plans and seeing how the cut parts fit it looks like the intent was to have the wings keyed between the bulkheads. Holding the wings captive this way, nullifies much of the benefit to breakaway wings (rubber banded on). (The wing will act as a wedge splitting open the bulkheads during a cartwheel)!

Should I hit the wings on landing I want them to depart the fuselage freely. So I'll be sanding down the proud aft bulkhead (F4) to allow free movement of the wing. This might have actually been the intent of the designer as I see the rear spine is below the top of bulkhead F4.

Sinbad Gotcha.jpg

Sinbad captive plan.jpg
 
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It really is starting to take shape! What I really like about the micro Sinbad is that it does NOT look like the classic Hershey bar wing on a cigar box model. The fuselage has a lot of curves. This makes a pleasing shape. Yes, it is a lot more work both in the design and build, but it is so worth it!

I know I said it was pleasing but while shaping the canopy I kept having this image of the creatures in Jim Henson's Dark Crystal, it sure has a beak.

A nice feature of the bottom bulk heads is that they are cut with a scallops. This will result in the covered model NOT looking like a starved horse. Seeing bulk heads sticking through the covering looks like a distressed animal with its ribs sticking out.

Also of note is that with the laser cut stringers placing the sanded side out will give a nicer appearance.

Sinbad canopy fitting.jpg

Sinbad scalloped.jpg
 
In this thread I go into more detail as to what we are trying to do to define the shape of the covering. But here I'm showing how these processes apply to the micro Sinbad. I test by laying a straight edge on two defining features, the crutch and the keel. As you can see I hit a bump (protrution) where the stringer ends. This will look like broken rib when covered. (Not something I like to see). The fix is to sand down the bump until the straight edge will pass without you being able to feel the transition to the stringer.
(In the last photo notice how the former scallops work).

Sinbad covering test.jpg

Sinbad bump removed.jpg
 
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