The Sprat - A new year's build

[speedbirdted]

One of these might work, and they ship from the US:
https://www.backcountryrc.com/product-page/5ch-micro-servo-esc-brick

Oh dang well that's nice to have a US source for those things. It looks real similar to the RX62 board that crapped out on me though (it even says it on there) though that's the V3 version and mine is the V1 which means it's probably both just old and well-used and there might be some improvements between the V1 and V3. I did some looking and apparently the V1 and 2 have the same problems I had but no mention of the V3.

 

[GrizWiz]

This seems exciting. I have a couple of broken toy helis, I'm guessing their motors would work in this too? Seems like a nice idea for a frankenstein build.

I believe a little rc heli should work like a ez pack with 2 motors and differential thrust!

 

[speedbirdted]

So I did some more snooping around about the Oversky bricks and apparently I didn't look hard enough earlier as people have been suffering failures with all models of it. It seems they just get sticky on one or both servos after a while. So not touching them again. What a hunk of crap...

I found this though. About the same price, but this is a copy of the Spektrum 6410L which I know to be good (I have one, but it's already in something) but the problem with the genuine Spektrum is it's 65 bucks. Has anyone used the clone? Is it worth it? Generally I've had decent luck with the fake Spektrum stuff peddled on ebay but this isn't just a PCB which either works or it doesn't, this has actual mechanical components...

 

[The Hangar]

So I did some more snooping around about the Oversky bricks and apparently I didn't look hard enough earlier as people have been suffering failures with all models of it. It seems they just get sticky on one or both servos after a while. So not touching them again. What a hunk of crap...

I found this though. About the same price, but this is a copy of the Spektrum 6410L which I know to be good (I have one, but it's already in something) but the problem with the genuine Spektrum is it's 65 bucks. Has anyone used the clone? Is it worth it? Generally I've had decent luck with the fake Spektrum stuff peddled on ebay but this isn't just a PCB which either works or it doesn't, this has actual mechanical components...

I’ve only tried one aftermarket board and that was a random one on AliExpress. What a waste of $30 the stabilizer had elevator and rudder reversed so it corrected all weird. I’ve probably got an extra board I’d sell you off you want.

 

[speedbirdted]

Thanks @The Hangar!

Time to get back to this build. I got the board installed and all the pushrods routed and stuff. Works fine, amount of binding is low. Initially I thought the previous board's problems might have been caused by a bunch of binding in the control system but that seems to be a non-issue. Only thing I don't like about it is the control horn is a little short for the elevator, so I had to turn down the rates a bit. Though I'm probably not going to be using the elevator much anyway. If it proves to be a real issue I can just cut off the horn there and make a longer one.

I got the idea for the removable pushrod connector things with the heat shrink tube from someone on here. They do their job real well. Don't remember who it was though; If it was you feel free to stand and claim credit...

The CG seems pretty good with the battery here. It leans nose down when the spar is resting on my fingers. Moving it forward or adding a tad of weight wouldn't be too hard if I have to though. I might not even need to do that - I can scoot the wing about 3/16 either way because the mounting pegs are kind of far apart so if the CG is wrong I might as well just move the wing instead to fix it.

I hesitate to use the D-word as most of the time when I say it I'm wrong but with the exception of the windshield and windows, I think I'm done with at least the building process Unfortunately for now said windshield and windows can't go on as canopy glue sucks when used in tiny quantities I thought I had a bottle of BSI Super Gold somewhere but upon finding it I hadn't used it in so long that it had degraded to uselessness like opened CA tends to do over a few years. Time to buy more. I wish Willy Nillies would stock this stuff...

I think it's ready to maiden. I've maidened airplanes that had much more significant parts of them missing so I don't think a lack of a windshield will cause anything bad. If anything it'll cause better battery and ESC cooling. I taxied it a little bit around the shop and it seems to get the tail off the ground easily and tracks straight... and only straight. It doesn't turn well when it gets moving. Hopefully the throw will be enough once it gets in the air. We'll see soon enough...

 

[TooJung2Die]

She looks awesome! Very Old-Timer with a classic livery. Good luck with the maiden flight. I hope you have an indoor venue because it's nasty outside. I use the wire and heat shrink push rod connectors on lots of my builds. I can never get the z-bend length exactly right so this idea lets you fine tune the length. It's been used since the beginning of RC.

 

[speedbirdted]

She'll have windows on the maiden after all. Went back to the store to see bottles of Super Gold on the shelf and was quick to snap it up!

These little clothespins are a godsend. Good thing at the dollar store you can buy them in packs of 100. Masking tape is also helpful. To keep it from pulling the tissue up you can stick it and unstick it to your finger a few times which will dull the adhesive to the point that it won't hurt the tissue. There is low-stick masking tape available, but I see no need to spend the extra money on it.

Another nice thing about this glue is that if it touches tissue, it dries invisibly. No splotch is left; in some of the photos I've sent here you can see a couple from normal CA on the left side of the fuselage where I had to glue the crossmember back on after breaking it like an idiot The Super Gold stuff doesn't do that. I would build everything using it but a 1 ounce bottle is 19 dollars...

Now that everything that's supposed to be on this airplane is there I guess I can check the AUW. Considering my target originally was 50 grams I'm pretty happy with how this came out. It should float along just fine.

I'm pretty surprised I came in underweight too. I measured the density of the 3/32 sheet I used to make most of the fuselage and it's almost 14lb balsa! I'm sure if I used lighter stuff I could have gotten it to weigh at least a few grams less. It's the lightest sheet the store had. I wish they could get better stuff...

Glamour shots will have to wait until the weather improves enough to take it outside. Right now it's been alternating between rain, snow and hail for about a straight week. What's most annoying about that is the wind has been light to nonexistent the whole time. If it doesn't get any better an indoors maiden is really all I guess I can do. But that'd be a last resort. I've always been terrible at flying inside buildings and wouldn't want to stuff it into a wall...

Overall I'm happy with how this came out. Considering a lot of the things here I'm doing for the first time...

 

[The Hangar]

She'll have windows on the maiden after all. Went back to the store to see bottles of Super Gold on the shelf and was quick to snap it up!

These little clothespins are a godsend. Good thing at the dollar store you can buy them in packs of 100. Masking tape is also helpful. To keep it from pulling the tissue up you can stick it and unstick it to your finger a few times which will dull the adhesive to the point that it won't hurt the tissue. There is low-stick masking tape available, but I see no need to spend the extra money on it.

Another nice thing about this glue is that if it touches tissue, it dries invisibly. No splotch is left; in some of the photos I've sent here you can see a couple from normal CA on the left side of the fuselage where I had to glue the crossmember back on after breaking it like an idiot The Super Gold stuff doesn't do that. I would build everything using it but a 1 ounce bottle is 19 dollars...

View attachment 191371

Now that everything that's supposed to be on this airplane is there I guess I can check the AUW. Considering my target originally was 50 grams I'm pretty happy with how this came out. It should float along just fine.

I'm pretty surprised I came in underweight too. I measured the density of the 3/32 sheet I used to make most of the fuselage and it's almost 14lb balsa! I'm sure if I used lighter stuff I could have gotten it to weigh at least a few grams less. It's the lightest sheet the store had. I wish they could get better stuff...

View attachment 191372

Glamour shots will have to wait until the weather improves enough to take it outside. Right now it's been alternating between rain, snow and hail for about a straight week. What's most annoying about that is the wind has been light to nonexistent the whole time. If it doesn't get any better an indoors maiden is really all I guess I can do. But that'd be a last resort. I've always been terrible at flying inside buildings and wouldn't want to stuff it into a wall...

View attachment 191373

Overall I'm happy with how this came out. Considering a lot of the things here I'm doing for the first time...

Beautiful work!

 

[rockyboy]

Beautiful indeed! Love the mini-clothespins too - I need to keep an eye out for a bag of those...

 

[Willy Nillies]

Great job Ted! That looks really good! Nice job keeping it so light!

 

[speedbirdted]

It flew!

Tail heaviness turned out to not be a problem. If anything it's nose heavy. This is the second flight; on the first flight I was holding a lot of up elevator as it didn't want to climb otherwise. The black on the tail is a single screw taped there; that made the CG perfect. Honestly most of the time I didn't even touch the elevator. If you want it to go higher you can just increase the power. Unfortunately it's still a little too fast for the indoor venue we get access to, though with just a little more room it would be a lot happier. I pretty much trimmed it to fly in a circle because that's all you could really do with it. As soon as the weather is good enough I'll try it outside.

I also crashed it into the walls a few times. However, no damage resulted; it doesn't really weigh enough to hurt itself. The motor fell off once, but some CA was all I needed to fix that.

 

[Willy Nillies]

Congrats Ted! Looks like it flies quite nicely!

 

[TooJung2Die]

That's fabulous! Power up to climb, glide to descend, that's perfect. Congratulations!

Tail heaviness turned out to not be a problem. If anything it's nose heavy.

I'm often surprised at how far back the CG on rubber power designs has to be to fly right. It's not uncommon for the CG to be mid-chord on the wing or even farther back. Where did you find the sweet spot for the CG on this wing?

 

[The Hangar]

It flew!

Tail heaviness turned out to not be a problem. If anything it's nose heavy. This is the second flight; on the first flight I was holding a lot of up elevator as it didn't want to climb otherwise. The black on the tail is a single screw taped there; that made the CG perfect. Honestly most of the time I didn't even touch the elevator. If you want it to go higher you can just increase the power. Unfortunately it's still a little too fast for the indoor venue we get access to, though with just a little more room it would be a lot happier. I pretty much trimmed it to fly in a circle because that's all you could really do with it. As soon as the weather is good enough I'll try it outside.

I also crashed it into the walls a few times. However, no damage resulted; it doesn't really weigh enough to hurt itself. The motor fell off once, but some CA was all I needed to fix that.

That looks like it flies really nice!

 

[speedbirdted]

I'm often surprised at how far back the CG on rubber power designs has to be to fly right. It's not uncommon for the CG to be mid-chord on the wing or even farther back. Where did you find the sweet spot for the CG on this wing?

I found it was a little bit behind the spar, but here the spar is at almost 40% wing chord. Usually I find this phenomena occurs on airplanes with lifting tails, very large tails, or large amounts of positive incidence on the tail. This has none of those, so I've honestly got no idea why it flies best with the CG that far aft. I think I will remove the tissue from the tail to add a few BBs or fishing weights inside the fuselage, to avoid having them taped to the outside like so.