Sinbad powered glider build - RC Groups
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Aug 03, 2017, 02:25 PM
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builderdude's Avatar
Build Log

Sinbad powered glider build


Hi folks.

I admit I haven't been very active building this summer. Summers are definitely not good building season, as there is so many other projects going on at the same time. I have an unfinished build I also need to finish up because I'm close. However, I am feeling the need to do a kit where I don't have to do a bunch of designing first. A nice, relaxing kit to build a nice, relaxing park flyer.

My choice was the Sinbad glider. It's a really old design, but Retro RC has recreated it for a very reasonable price. It's a kit.
I'm including a couple of pictures of the Retro RC version. I don't remember the wingspan as I write this, but it's in the neighborhood of 3 ft. So it's a nice park flyer size.

I like to alter kits to make them my own...add my own touch.
Although Retro RC sells a power pod for this glider, I think it would look much cooler with twin motors on the wing. Because the plane is in the 6 ounce range, once built, it probably could get away with pretty small motors in the power pods. And this gives it sort of a Grumman Goose feel to it (although this one won't be aquatic).

I don't think I will mess with ailerons this time, in the interest of keeping this light. Just elevator, rudder, and throttle. It's unusual for me not to do ailerons, but sometimes it makes for an easier, more relaxing airplane to fly. However, if I change my mind later, after flying it, I might cut some ailerons into it. It's not that difficult to do, and I might install some plastic drinking straws as a conduit for wires, should I decide to do that later.
I really don't think I need to worry about installing a wheel. This can belly land, so a skid should be fine. But it needs a skid because we don't have much grass in New Mexico (except for some parks).

I like the retro paint scheme, but I'm going to change that up a little. Mine will have the same stripes, but I think I'll go with darker blue.
And my covering material will be orange Coverlite.

Going to get started this weekend!
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Aug 04, 2017, 12:58 AM
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Hey, my first RC plane in 1976 was Sinbad with a removable .049 power pod, and a Hobby Shack radio. It was over weight with the radio, but it flew. I would take the power pod off for slope gliding.

Keep us posted with picts.
Scott
Aug 04, 2017, 11:54 AM
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builderdude's Avatar
Yeah I know my drag coefficient is going to be higher with two motor mounts on the leading edge of the wing and non-folding props. But with the wing span, it'll still do well.
I'm not going for a pure sailplane this time. Just a fun park flyer with a good glide ratio.

By the way, I'm going to modify this for bolt-on wings. I don't want to mess with rubber bands.

My first build (on that subject) was a rubber free flight Curtiss Robin. It was a gift I got, from Christmas probably. I covered it with tissue provided in the kit and doped it red.
When I flew it, I was so thrilled at the amazing glide ratio and how stable it was, that I was hooked. That was probably around 1970-ish.
Aug 04, 2017, 11:31 PM
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A twin will be interesting. I see no need for ailerons on this. The adverse yaw on that long wing at low speeds will work against you, and the rudder works great at low speed.

Have fun.
Aug 05, 2017, 10:14 AM
AndyKunz's Avatar
Good to see you active again, Tony.

Andy
Aug 05, 2017, 12:05 PM
B for Bruce
BMatthews's Avatar
Down through the years there's been a number of sizes of this classic design depending on the companies that made the kits. At 36" Retro's kit just added another size to the list. You can check out the others over at Outerzone if you have not done so already. There was also a smaller Sinbad which was just 30 inch span

You certainly don't NEED the wheel. But consider that light models like this "skid" about 3 whole inches when they land even on slippery dusty ground. On grass they basically just touch and stop. A wheel would give you a rolling finish to the flight. And since this is a model for fun and relaxing it might be nice to have the roll at the touchdown. Just food for thought......

I'm really liking that second picture. The deep wind screen allows for a short pod if the motor is chosen such that it can use a fairly small prop.

A motor in the nose would not be out of the question either. The Sinbad is DEEP and a motor mounted up high with the prop shaft at the joint line of the to nose block could be fairly large without hitting the ground by too much. You'd still hand launch it and belly land with the prop stopped. And it would aid with keeping the mounting of the wing a lot more simple.

If you go with the twin format then I'd say that the model will be so light that you could likely get away easily with two of the micro motors of around 9 to 12 grams with very simple mounts secured to a 1/8 sheet wing rib. That'll both keep the weight low and avoid a lot of complicated motor mount building.

One thing with a twin that I'd suggest. There will be a lot of wires that connect the wing to the fuselage. Perhaps you could make a carrier rack or box so to pack the model up for transport and storage you remove the wing and leave the wires just a little long and run in such a way that you just turn the wing so it runs alongside the fuselage and fits into the rack or box. That would avoid the need for a lot of connections to be done each time.
Aug 05, 2017, 02:40 PM
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builderdude's Avatar
Good suggestion on the wires. It would help if I could just peg the wing at the leading edge and bolt the trailing edge down with 4-40 screws into blind nuts, so that I could undo it for transport and lay the wing beside the fuselage. Yes. But then again, at only 36", that plane could fit into any vehicle I have with ease, and without the need to remove the wing; which is probably what I would do.

I also thought about stringing bungie cords across the roof of my car and using it to hold a plane by the wings. For long trips, that would work pretty good. It'll just look like an airplane is flying right behind me when I look in the mirror. Ha ha...

Actually you know what? I would LOVE to tackle an actual full scale kit plane.
An actual full size Sinbad would be WONDERFUL! Wouldn't it?

Good point on the wheel. And they're easy to add. So maybe I will, since some of the best runways around here are concrete. Not a whole lot of grass here.

Yes, adverse yaw might be an issue. I built another plane with a similar planform. It was Robert Dance's Firefly. It's a WONDERFUL and stable flyer, but oh man...the adverse yaw on it is sooooo bad that I'm really glad I put ailerons in that. It helps make turns without skidding so bad and being weird. I don't think the Sinbad will be quite as bad, but if it's an issue, I can always add ailerons later. It's not that hard.
...In fact, I should probably go ahead and add the provisions for ailerons but leave them fixed.
Then I can cut them free if I ever decide to add them, without having to remove covering off the wings. That's a thought.

I also am thinking of adding LED lights to the wingtips and perhaps the tail too, so that I could do some dusk flying. The winds die down so beautifully right before the sun goes down.

...And Andy, I am never really gone. I love this hobby too much.
But I do tend to take a hiatus from building during the summer. There's just too much else going on. The Skyray project is still alive. I'm just fighting the nagging feeling that I'm tired of it. But I do intend on finishing it. Just a little break is needed to build something fun like this.
Aug 05, 2017, 02:48 PM
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Here is my old Firefly build log, so you can see what I'm talking about.

https://www.rcgroups.com/forums/show...y#post28333212
Aug 05, 2017, 05:02 PM
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P. Tritle's Avatar
Tony, I love the Sinbad! Built a couple back in the my high school days from the Sig kit. Will be keeping a close eye on the progress.

PAT
Aug 05, 2017, 06:09 PM
B for Bruce
BMatthews's Avatar
I've done the strap thing across the roof of the car thing before. I did this by putting knots in some webbing tie down strap and "trapping" the knots by closing the back doors with the knots outside the joint. The resulting cross strapping worked great for transporting some 6 foot span old timer wings. I even managed to leave a spot clear for the rear view mirror. Not a big spot but I could still see directly behind.
Aug 05, 2017, 10:44 PM
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builderdude's Avatar
I got most of the fuselage done in just the first day.
I've got to say, this is a very accurate and a very good kit. It's a small airplane though, and the fuselage is really built.

Pat, if you had designed this plane it would have weighed half as much.

Anyway, I've modified the bottom of the fuselage for a belly wheel. Don't worry, it all gets sanded.

The nose is very clever. You can drop BB's or bird shot into the holes you see in the nose pic. And then drizzle glue inside the holes to seal it.

Here's the pics.
Aug 06, 2017, 11:24 AM
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I'll finish up the fuselage today. The canopy is also the battery/servo access. I have a receiver, but I don't have the motors, ESC's, or servos yet. The canopy needs to get built.
The kit has Olive Oil as the pilot. I don't really care for that. So I'm trying to think of who or what the pilot should be. I have Snoopy, Woodstock, and a Minion as pilots in three of my other planes.

I think this will be a good little flyer. And although I'll install provisions for ailerons, I won't cut them free unless I need to in the future.

The one plane this reminds me of is Pat Tritle's amazing AJ 404 Interceptor. That was one of my favorite flyers until it crashed. I've rebuilt a new one but the wing warped really badly, and I might have to completely rebuild the wings.

We do have some really nice parks for the smaller planes, with plenty of beautiful grass. The problem are the trees. I've had to climb trees in the past to release my plane from their clutches. But they're also really fun to try to fly around and dodge.

I think I'll probably get the wings done today. We'll see how that goes.
I'll post pics.
Aug 06, 2017, 09:33 PM
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Interesting thing that makes this kit different and unique is the fact that it doesn't use plans!
Every piece you need is laser cut and fits exactly. Thought is given to grain direction and gussets. And every balsa stick has its place. There is literally no need for cutting.
I've never seen another kit like this.

A tip for anyone wanting to build one of these...label the parts before construction. It'll save a lot of brain cells trying to locate the parts you need.

Okay so I didn't get the wing started. Going in order of the directions, the fuselage gets finished first, then the canopy hatch. Then the fin and tailplane.
The wing is actually last.

I really am impressed with this kit from Retro RC, and after this, I will be taking a second look at the other kits they offer.

The Sinbad design would make an excellent flying boat, if in a larger scale. You could either do the center motor pod, or use a twin like me to give it a strong Grumman flying boat style.
It occurred to me that a Sinbad would also make a fabulous full scale motor glider...If one had such aspirations.

Anyway, here are my pics for my progress this weekend.
I guess I'll start on the wings this week.

...I really think I'll be covering this bird by next weekend. It's such a quick build. I'd better get my electronics on order soon!
Aug 07, 2017, 10:14 AM
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builderdude's Avatar
Know what?
Movies are great for sanding. You just sit there and work the piece for 2 hours while watching a movie, and you don't even realize the time going by.
I got the fuselage and canopy hatch all sanded last night and it's looking pretty good.
I need to work on the custom belly wheel support a little more, because that is light ply.
But here is the fuselage and tail assembly, mocked up in bones.

Question:
The kit says to use the covering material for the hinge.
Is that durable enough???
I'm thinking hinge tape is the better option.

I set the plane in front of my little Beta fish tank to give it some scale, but the fish didn't cooperate...
Aug 07, 2017, 07:52 PM
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builderdude's Avatar
I went ahead and ordered all the electronics except for the receiver from Altitude Hobbies. I normally like to use DymondUSA's stuff, but their excellent quality comes at a high price. I still like to use them, but Suppo's products seem to be pretty good for the money too.

Suppo 1504 motors (Park 180 equivalent) will be used, with two 10A ESC's.
I'm also going to use Suppo's 2.5 gram servos.
The receiver is an extra Dymond 2.4GHz unit that I have. I'm pulling it out of the Raven so that I can replace the Raven sailplane's receiver with a 72MHz receiver, which has better range.


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