Need electronics help for blue foam delta

[DBacon]

Originally Posted by Insomniac

I also added a bit of reinforcment to the rudder, as it looked a little weak on the other plane.

I think I've figured out one of the reasons our planes are so heavy... the only glue we used was 5 minute epoxy. On the plus side it's made the planes pretty darn sturdy.


This brushless and LiPo setup ought to be a lot more powerful than my Stryker's brushed motor and NiMh batterys. It makes me a bit more confident that this thing will actually get off the ground.

Just a string from the top of the vertical fin to the tip of the right horizontal stab, under to the fuse, to the tip of the left horizontal stab and up to where it started does wonders for strength.

Gorilla glue, mixed in very small quantities with water is just as strong, sets in a few hours, and much lighter. Without mixing with water takes 12 hours, and foams up out of control.

The brushless are WAY more powerful, you will be pleased.

[pvtzemerak]

Good Job so far!
Subscribed!
--PvT

[Insomniac]

I've been hearing a lot about Gorilla glue, but I've never actually come across it. I did test somthing called 'tarzan's grip' when deciding what glue to use, but it ate the foam.

A litte research indicates that Selly's sells somthing called durabond which is essentially the same as Gorilla glue. I'll have to try and find some to test.

[pvtzemerak]

I use the good old Hotglue method for bluecore foam.
Works pretty good, it may add a little weight though.
--PvT

[DBacon]

Originally Posted by Insomniac

I've been hearing a lot about Gorilla glue, but I've never actually come across it. I did test somthing called 'tarzan's grip' when deciding what glue to use, but it ate the foam.

A litte research indicates that Selly's sells somthing called durabond which is essentially the same as Gorilla glue. I'll have to try and find some to test.

Actually Sumo glue is a good replacement for Gorilla glue, and it doesn't yellow as much, kicks off at about twice the speed. Then there ia a new white gorilla glue that I have heard about.

And like pvtzemerak says, Hot Glue! That is what I use, because it won't allow water through it. But the Gorilla Glue holds up to being in a hot car, Hot Glue won't. Of course we mean Low-Temp Hot Glue.

[Insomniac]

Hmm.. I tried roughly arranging the components on the plane, and it looks like I might have some trouble getting the CG right. Hopefully the reciever will be heavy enough to balance it, or I'll have to start lightening the tail and weighing down the nose.

[DBacon]

Originally Posted by Insomniac

Hmm.. I tried roughly arranging the components on the plane, and it looks like I might have some trouble getting the CG right. Hopefully the reciever will be heavy enough to balance it, or I'll have to start lightening the tail and weighing down the nose.

Arggh, never add weight, horrors! How about:
1. moving that one servo back forward, glue it right to that one that is was close to before.
2. Moving the battery forward.
3. Extending the nose, they did that with the Turbo Raven!

And the Pilatus Porter
http://www.bush-planes.com/Pilatus-Porter-PC-6.html
Both pretty high performance planes...

[Insomniac]

I'll probably end up lengthening the nose then... What a pain, I've already cut the balsa stick to size, and now I'll need to lengthen it.

The additional reinforcement I'll need will probably weigh enough to mean that I can cut the stick back to it's original size

[DBacon]

Originally Posted by Insomniac

I'll probably end up lengthening the nose then... What a pain, I've already cut the balsa stick to size, and now I'll need to lengthen it.

The additional reinforcement I'll need will probably weigh enough to mean that I can cut the stick back to it's original size

Cut the sticks at an angle, then you get a strong glue joint without additional bracing, because the glue surface is much more than just a cross section.

[Insomniac]

I think I'll just cut them straight, but add a short bit of balsa on each side, and a tiny bit of foam above and below... it should still be quite light but also strong.

If I try to cut the sticks at an angle i just know I'll end up with a crooked join.

[DBacon]

You can lay one on the other and cut both at once.

[Insomniac]

True... I'll decide what to do once I get my radio gear and see how it ends up balancing. I'm going on holiday for about a week, so I won't be able to respond for a while. When I get the radio gear I'll update this thread.

[DBacon]

But, but, building planes IS a holiday, what could you be doing that is better?

[Insomniac]

It's been a while since I've posted into this thread, so here's a bit of an update with a couple of unrelated questions.

Due to a few delays in when my friend can order the rest of the parts, we still don't have the transmitters or receivers, so we haven't done any more work on these planes. We've both got the school certificate exam in 2 days, so study has taken a bit of our time too. On the plus side, after this week is over we've got very little that needs to be done, and then 8 weeks of holidays, so we WILL get these planes up and running in the near future.


Now, onto a couple of questions for anyone still reading this thread. I recently bought a cheap, lightweight camera to strap to my planes, and tried flying it on my electrafun. Sadly, while I did get one flight in, the electrafun's crappy radio gear is on the way out (servos twitching madly, and it's not the servo's fault).

So, I've gone and ordered one of those cheap 6ch 2.4 ghz sets, and I'm gonna throw it into my Stryker B (it's electronics also died after a few flights, and I never got around to fixing it)

For the moment I'm just going to use the old NIMH packs and stock brushed motor with a 30A brushed ESC, but I intend to upgrade it to brushless in the near future.

I've done a bit of looking around, and I think I've found an ESC, motor and prop that will work for me.

I'll buy a couple of 2200mah 3S lipos as well, as the 1300mah ones I have arn't heavy enough to balance it, and I don't want to accidently push them too hard, with their lower Mah rating and hence lower discharge rate.

For the motor I think I'll use one of these, they both seem the same but one has a heatsink while the other doesn't. Not sure what would be easier to fit in the stryker's motor mount, but I guess with a bit of cutting I can make anything fit.

http://www.hobbycity.com/hobbycity/s...idProduct=4201
http://www.hobbycity.com/hobbycity/s...idProduct=5221

I think this prop ought to work. With the included adapters, should it just slide right onto the shaft, or do I need somthing else to correctly attach it?

http://www.hobbycity.com/hobbycity/s...idProduct=7936

From what I've read, a 60A speed controller ought to be more than enough for this setup. Is this one any good?
http://www.hobbycity.com/hobbycity/s...idProduct=2166

I don't yet have a wattmeter, but I'll get one of these with my next order so I can ensure I don't burn anything out.

Thanks

[DBacon]

The camera, was it also transmitting to the ground? Sometimes this can interfere with your plane's reciever. I have used this on a few different frequencies, but always at low power to be legal. If the antennas are separated by as much distance as possible, it shouldn't interfere at all. Do a range check with the camera on, then one with it off, should be the same.

Your upgrade from NiMH and brushed to brushless and LiPo will be dramatic, prepare yourself for a rush...

Sweet looking motors, but I have not used inrunners. My outrunners (some from HC too) provide lots of torque at lower RPM, and seem perfect for direct drive of a prop. The KV number is an important guide for this, it is the RPM per volt of your battery.
I have used a lot of these:
http://www.hobbycity.com/hobbycity/s...3.8_Prop_Combo
produce about 30 Oz thrust on 3 cells.

The 60 A controller looks good, but I have had good luck with their 40-50 amp unit that is much cheaper, but no BEC, which can be bought separately, or you can add some electronics to make your own.
They just came in stock, And I have posted the missing instructions in their review section. They don't stay in stock long!
http://www.hobbyking.com/hobbyking/s...idProduct=6459

35 Amp motor, 60 Amp controller, this is a lot of power, you sure you need all of this?

Nice WattMeter, I have had my eye on that one too, but for now I must multiply E x I, which is pretty good...

[Insomniac]

No, the camera does not transmit. It's just a tiny little DVR that records to microSD. The plane's radio or reciever is definitely the problem, happens with or without camera, and when attached to different servos.

I don't know how I'd go about mounting an outrunner on a Stryker, it seems the majority of people use inrunners.

And no, I'm not sure I need all that power. Essentially what I want is Stryker C performance, or better. So unlimited vertical is the bare minimum, and a bit of speed wouldn't hurt either. I don't want so much power that I'll need to glass the body so it can take it, I just want to turn my F-27B into a slightly improved F-27C. The Stryker is a somewhat heavy plane that can't accomodate a large prop.

I don't think that motor/esc/prop combo would work as it is... The 8-inch prop is too bit to fit within the cutout at the rear of the Stryker.

[DBacon]

Yes, I understand now why you have the inrunner, it may have a higher KV rating (which I misstated as KVA earlier) which means small prop higher RPM. In that case I like the one with the heatsink. Everything is better cooler...

If your thrust exceeds the weight, you have unlimited vertical. If it just equals the weight, then you can't accelerate vertically. My Son's foam Mig 29 has thrust of 2X the weight and it takes off like a rocket! So I would think if your thrust was 1.5 to 2 times the weight you would have all the vertical performance you want.

What is the weight of the plane, complete?

[Insomniac]

Not sure on the exact weight, as I don't have any decent scales. I think I'll get that motor anyway, it'll be an improvement on stock and I can always upgrade and use the motor for somthing else if I want more. I think it should do vertical at least for a little while though, even if it is slowly slowing down as it goes.

[DBacon]

You might make a simple balance scale out of a rod and three strings. You could hang a know qty of water on one string, and your plane on the other.
If the support string is right in the middle, then there is no inaccuracy introduced by the weight of the rod. You can be quite accurate this way...

It is a little more difficult if the rod is hung off-center to multiply or divide the effect of the reference weight, but you don't need to do that.

[Insomniac]

Finally got around to solerering up the ESC and attaching it to the reciever, and tested out the motor.

At first the motor would 'stall' and whine at high throttle, so I had to increase the ESC's timing to medium, which solved the problem.

When running wide open throttle during a static test, amp draw reached 23 amps (from an ESC only rated for 18) Is this accemptable? I assume that the amps will be lower in flight as there is less resistance to the prop's rotation. How big is the differerence generally, between a static test and in-flight amp draw?

Hopfully it won't burn out the speed control...

Thanks

[DBacon]

Originally Posted by Insomniac

Amps reached 23

I wouldn't chance it, I would put on a smaller pitch prop that drew less than the max of the ESC, then you are much safer. You will get better thrust too.

[Insomniac]

Tried it again (after LiPo had sat for a few hours) and now it only draws 20 amps at WOT... motor still gets quite hot. I'll whack a 6x4 (only prop I have handy) on and see what happens... if it still has the thrust to lift it I might stick with that.


EDIT: The 6x4 only draws about 9 amps, but it is only about a 1:1 thrust to weight ratio, quite a bit less than the old one... It also doesn't quite fit my prop adapter as well as the old prop and has a slight vibration because of it.

I think maybe a 6x6 or 7x4 would be better... the one drawing in the 20 amp region was the 7x6. Might go down to the LHS and grab a few different ones. I think rather than a smaller prop, I just need a shallower one... I'm not looking for super high top speed, just decent thrust.

[DBacon]

See if they have 8 x 3.8 I'll bet that will be perfect.

[Insomniac]

I'll take a look. I need some music wire to rig up my pushrods so I'll grab a couple while I'm there... Knowing the LHS though, the'll probably be $5 per prop...

Also, will extending the nose to give me more room to adjust the CG, affect the position where the CG should be? IE, should the CG still be the 1.5-1.75 inches from the leading edge marked on the plans, or will the extended nose move it from the original position? I'm starting to wish I'd just used lighter foam to avoid all this hassle with the CG. BTW the servos arn't glued in in those pics, if you're wondering why they're so crooked.

[Sky Sharkster]

Hello Insomniac,
At this point I'd stick with the original C.G., as it represents a % of the wing chord.
However, I can forsee several problems related to the nose lengthening.
One, that unsupported stick is going to break on the first hard landing.
Two, there are very likely going to be some gyroscopic forces related to the motor and prop that will induce a twisting or wobbling force to the stick and it will snap in flight. It may take a certain (high, probably) RPM, but sooner or later it will crack, my guess is right where it comes out of the fuselage. The furthest forward supported/unsupported joint.
Three, at best, you will change the pitch response (elevator control) since the mass is moved so much farther forward. It will be less responsive to elevator input. A typical adjustment to THAT problem would be to move the C.G. back, but that will present other (instability) problems.
The most efficient solution (to me) would be to build a new fuselage with a fully-supported stick. Although the foam won't add greatly to the length-wise strength, it will absorb a lot of rotational force and side forces. A longer full fuselage should allow you to move the battery forward. Any weight you can remove from the tail will help, also.
I suggest making a mock-up longer fuselage and tape all the components in place until you have a full fuselage that yields the right C.G.
JMO,
Ron