How to fly Sharkface??

[Major]

Hi.

Could anybody give me some instructions? Cause right now I just don't understand this plane. Let me describe what happened.

Yesterday I had two 10 mins flights with it. First one took me four launches to get in the air, but everything was ok, no damages etc. Second flight was just straight single launch. I've used a bit more than half throttle in both cases.

Today I had two attempts. At first it looked like there was lack of power, but anyway Sharky flipped to the right side and beautifully kissed Mother Earth. No damages, quick check, all right, another try. I applied some more throttle, just a bit less than 3/4, threw plane and it looked like before - right wing, steep dive and proper kiss again. This time I saw pieces of wood emerging from aircraft... Nose was heavily damaged, front top and bottom of fus, followed by sides and first former, motor has pulled wires of ESC, motor shaft was pushed backwards to the fus...

By now, Sharky is almost repaired, just soldering and nose former left to be done, luckily my last prop survived and shaft is not bent. Can anybody tell me, what do I do wrong? Overcontroll? I wouldn't say I used too much of rudder, there wasn't a lot of elevator as well. How should I launch her to spend more time flying rather than in workshop on repairs? I didn't pay too much attention to the angles of launch, but it was just slightly upwards, of course towards the wind.

The setup installed in her bases on

18A ESC no name

Motor CF2812 1650KV Brushless Outrunner Motor

http://www.giantshark.co.uk/cf2812-1650kv-brushless-outrunner-motor-p-52.html

Prop 6x4 TGS Sport

**LINK**

Radio gear Futaba 6Ch 35 MHz.

It is worth to mention, that there was no any problems with radio link.

Please somebody help me with this problem.

Cheers

Tom

[Martin Harris - Moderator]

Usually a hand launched model will try to turn left due to propeller and airflow effects. You could check for significant lateral imbalance (starboard wing heavy) - there's always the danger of a stall from a handlaunch before the model attains proper flight conditions and a heavy wing can drop at this point.

A level to slightly nose down launch will reduce the possibility of a stall.

Edited By Martin Harris on 20/05/2012 22:01:27

[Major]

Thank You Martin!

What I have noticed, I've never had left turn - just and only right ones. Plane was ballanced to the CoG shown on the plan, also I couldn't say that one side is heavier than another - all equipment is put right in the middle of fus...

AUW was 330g, as far as I can remember - wing's weight was far less than 30g, about 21-23g.

Maybe bigger prop would help a bit? I mean instead of 6x4, put 7x5 and see what is gonna happen??

Regards

Tom

[Biggles' Elder Brother - Moderator]

Hi,

well this all sounds a bit frustrating doesn't it!

Two possibilities come to mind: either its badly out of talignment/trim or your launching technique needs serious improvement!

We don't know which one, so here's a couple of points on each.

Trim & Alignment:

First take a really good look at the model. Are the wings straight and warp free? Is the tail plane level. Is the tailplane aligned with the wing? Is the fuselage straight. Is the motor thrustline where is should be with the right amount of right/down thrust. Are all the control surfaces secure and do they move smoothly through the recommended amounts? Is the CoG in the right place - with the battery in? Is one wing heavier than the other - so does it balance side-to-side? Is the wing really secure - no chance of it lifting or moving? Is there no slop in the control links?

Launching Technique:

Unless the model is very powerful I always launch at full throttle. Do not launch upwards - not even a bit. Launch level - with a good firm, level, throw. You need to put a bit of effort into this - unless the model is very light, with a lot of power, it really need flying speed as quickly as possible. Unless you know the model well its a good idea to get someone to launch it for you at first. Are you right handed? I am and launch right handed, which means there isn't much time to get back on the right-hand stick!

Somewhere in there I think your problem lies! If you check over the alignment and trim etc. get back to us and we can advise some more.

BEB

Edited By Biggles' Elder Brother - Moderator on 20/05/2012 22:12:56

[Major]

I had really big hope to see Your post here Beb!

So let's move on:

Are the wings straight and warp free?

Yes

Is the tail plane level?

Yes

Is the tailplane aligned with the wing?

If You mean fin - yes, I check it every time.

Is the fuselage straight. Is the motor thrustline where is should be with the right amount of right/down thrust. Are all the control surfaces secure and do they move smoothly through the recommended amounts? Is the CoG in the right place - with the battery in? Is the wing really secure - no chance of it lifting or moving?

Yes. But please note, that Sharky does not need side thrust, and down thrust is set just by first former, so I just screwed motor onto it. I also always check wing position. To hold them in place I use 5 inch bands, which are strong enough to peel of paper covering when I'm not careful.

Is there no slop in the control links? Is one wing heavier than the other - so does it balance side-to-side?

No, everything remains as build and works correctly.

I remember the guy from Blackburn who maidened it and he didn't use full power. I've heard that motor is far too powerfull and I shouldn't do that, so I don't, like yesterday. Just to remind - AUW is 330g, motor can pull more than 900 as far as I know. So maybe there was my problem - launch wasn't level - it was with nose upwards. Could You tell me why is this wrong? Before Sharky reaches flying speed, goes down slightly and most of the time just grounds.

I am right handed and use mode 2.

So maybe bigger prop would help? Like I said, 7x5?

Thank You for this Beb, already helped a lot!

Regards

Tom

[Major]

I've met with uncle Google and asked about this. I've found some older posts, which say that it's just Sharky's nature - 50/50 chance to get it flying. Is that true?

And You're right here. It is very frustrating. Maybe even not crashes themselves, but my lack of knowhedge about reasons and that stupid feeling, when I can't do anything...

[Biggles' Elder Brother - Moderator]

If you launch nose up you run the risk that it will stall. There is also more drag in this postion - so its harder for the model to reach flying speed. Its always better to launch level - or as Martin says even a little down. Dipping down immediately after the hand lauch is not uncommon. That's why mode 2 and right handed you need to get that hand on the stick very quickly!

By the tailplane aligning with the wings I mean if you look from a above are they square to each other, and if you look from the front and and back are they parallel to each other. (The wings and tailplane that is!)

A couple more points: run the motor up, then pause a second or so, then lauch. That way you avoid a big torque reaction on release.

Second - you mention rudder. Is it 3 channel? If not and has ailerons you shouldn't really need rudder straight from the hand launch. Rudder again adds a lot of drag and slows the model's acceleration to flying speed.

BEB

Edited By Biggles' Elder Brother - Moderator on 20/05/2012 22:44:04

[Martin Harris - Moderator]

Having looked at the plans for the model it seems like an awful lot of downthrust for the configuration. I wonder if its behaviour would be improved by reducing it a little as it's likely to be trimmed with a higher AoA than if there were less?

Edited By Martin Harris on 20/05/2012 22:56:35

[Major]

By the tailplane aligning with the wings I mean if you look from a above are they square to each other, and if you look from the front and and back are they parallel to each other. (The wings and tailplane that is!)

If so, yes, everything is aligned.

A couple more points: run the motor up, then pause a second or so, then lauch. That way you avoid a big torque reaction on release.

I always do it this way - just not to rush and take time.

If you launch nose up you run the risk that it will stall. There is also more drag in this postion - so its harder for the model to reach flying speed. Its always better to launch level - or as Martin says even a little down. Dipping down immediately after the hand lauch is not uncommon. That's why mode 2 and right handed you need to get that hand on the stick very quickly!

Now I understand... It looks like plane climbs a bit, and very quickly gets too weak to fly further, than falls on the right wing and downwards. When I try to rescue it anyhow, it is controllable, but altitude is just next to nothing, so I don't have a time to do much. So by now I could say - everything is just my fault, as I launch it like stall is planned. Ehhh, hate to be newbie in any kind of hobby or job...

However will give it a go on 7x5 - maybe it will be easier...

Thank You very much Beb!!

[Major]

Martin

I was very confused if I should make it with that much downthrust. But as many people say, and even I have noticed - it works.

I forgot, Beb

My Sharky is 3 channel - elevator, rudder, throttle. No ailerons on the wing unfortunately...

[Martin Harris - Moderator]

Many people also seem to say that launching is a lottery!

[Major]

Well, You're right here.

So would You advice me to make it with, say 2* of sidethrust and 3* of downthrust?? It would improve flying abilities, but from other side... it will not be Sharkface anymore if You know what I mean...

[Martin Harris - Moderator]

You could shim the motor mounting which would maintain the angle/character of the firewall or build in a recessed firewall.

Perhaps someone like Peter Miller, Tim Hooper, Lyndsay Todd, Tony Nijhuis etc. could give the benefit of their design experience to advise a starting point for experimentation but a couple of degrees may be sufficient? The wing isn't mounted very high and you'll soon know if there isn't enough as there will be excessive pitch changes with power changes.

(Copy of plan here)

Edited By Martin Harris on 20/05/2012 23:56:56

[Eck]

My Sharky is fitted with a 2212/6 motor(2200Kv) and 3-cell 1600mA/H battery through a 30A ESC, turning a 6x4 prop. Contrary to the advice on here, I give it 3/4 throttle and launch it upwards at around 45 degrees. Not a little push, but a "chuck it like it's burning your hand off" - the idea is to put as much distance between the twitchy little beast and the ground as possible as quickly as possible, to give as much time as possible to get the thumbs settled on the sticks and working!

Not recommended but it works for me.

Until you have the model trimmed out to your satisfaction, so that you can predict which way it will twitch when it leaves the hand - get a helper to launch it for you, while you concentrate on the sticks!

[Major]

Hi Alex and thanks for posting!!

It might be a solution on the closer look - will give it a try tomorrow. If something goes wrong - I got very familiar with repairs in this particular aircraft.

The problem with helper is that I usually go to the local park with it, together with my family - my lady doesn't want to touch it - not to be blamed if something goes wrong, and my daughter wouldn't be able to throw it as she is jus 3 years old. Don't want to bother others, as basically I never know when can get out, as my partner has flexible working hours and I have to stay with kids then...

[Major]

Good morning after sleepless night gents.

Last few hours I was well busy. After I've left forum, started to work on Sharky. I have repaired and doped fuselage, soldered motor to ESC, checked ballances... in one word did everything I could to restore her to previous condition. Thanks to Beb's advice, also measured angles on the tail and supprisingly, discovered that stabiliser was not fitted at 90* to the fuselage. Luckily the rest was all right, so just cut a bit stab from one side, stuck some wood into the gap and glued again using medium CA. Looks better.

After I finished, was about 5 o'clock, so instead of sleep I've chosen test flight, having in mind words of my friend, who told me, that morning is the best time to fly in local parks due to lack of people and weather conditions. After hearing from my lady, just took shirt and gone, there was very light wind, but coldness was terrible.

Before launch, which could be the last for Sharky, did pre-flight checks and finished fag. With little aid of local grass pointed towards the wind and launched it with nose very, very little downwards and half throttle. I couldn't believe it, but my Sharkface gently climbed with small help of rudder to keep it level. After few meters upper applied full power and had very nice 8 minutes in the air. Could have more, but it was too cold for me...

So thanks Beb for perfect advice and good directions. I don't know if I ever get the chance to meet You, but if I will - You've got very big and ice cold bottle of vodka from me!!

After got back home, had a cigarette of victory and some thoughts...

* Sharky will need quite long approach to land. Even with minimum power it was still climbing. In flight it looked like jumping fly. Trim to elevator helped a bit as well as lower throttle, but it doesn't solve problem due to hand launch and my, call it, "experience".

*There is no force in this world, under which I'll put Cox into Sharky. Maybe Surestart with throttle, but for sure not now and not in close future.

*Little thing is very sensitive to any attempt of control. At aproach, it flew a bit further than I expected and in intrest of rescue I pulled to the right. Luckily it was about 4-5m above ground, but had another stall, plane flipped onto the right wing and again kissed Mother Earth. Again battery jumped out, crushing yet fresh front of fus, but repair will take me about 5 minutes now (I'm getting used to it), my last prop of course has gone, but nothing more happened.

Weather forecast was very promissing for this week, so from tomorrow on I'm gonna be busy again unless GS fails to deliver props on time. I ordered a few 6x4TGS and one 7x5 - just to give it a try.

Thank You once more Beb and everybody else.

Regards

Tom

[Martin Harris - Moderator]

If it's very sensitive in pitch, it would be worth re-checking the C of G and if it's anywhere behind the recommended point adding some noseweight or preferably removing some tailweight/moving something forward. When you check it, the nose should hang slightly down from level.

You might like to try it with a slightly forward C of G anyway, which may improve the handling for you.

 

Edited By Martin Harris on 21/05/2012 08:43:51

[Major]

When I checked everything today, CoG was exactly in point shown on the plan and Sharky was level. However moving battery forwards costs me nothing and might be worth checking, cause I am still very fresh as a pilot. In the air in total I've spent about one hour, excluding the time with eRC Micro Spitfire, so You know - I can't say I can fly.

Cheers

Tom

[Olly P]

Major,

I see from your profile you are in Lancs, depending on where a forumite may live/work nearby and be able to help. We might even enjoy the same Metal....

Olly

[Major]

I live just right in the middle of nowhere, but people use to call it Preston (Ribbleton). Would be nice if we could meet someday of course.

Cheers

Tom

[Olly P]

SWMBO has family up that way, next time we are heading up I'll let you know. I used to live near Blackburn, but am a bit further south now, so won't be able to help as easilly.

Olly

[Myron Beaumont]

Major

Glad to hear the radio works OK ! With a design like Sharkface you have to understand that the downthrust is meant to come into its own once a fairly high flying speed is achieved with a "lifting" wing section .Hence the hairy performance with no throttle control on the original Cox .I had one many years ago and flew it on the Avon MC site near Bristol .I was told off for seemingly being out of control .On the contrary ,they didn't have a clue what it was all about .It had a 15 Chinese engine up front as well would you believe .Never forget it .Good mind to build another.It's amazing what id did without ailerons . A very special design that shouldn't be "improved" IMHO

Cheers Myron

[Major]

No problem at all mate and thanks for offer anyway! Just PM me about two hours before and I'll be ready and batteries charged.

[Major]

You're right Myron!

Its flying capabilities are terrifying. Rolls, loops etc... Didn't try to fly inverted, but I've found out ability of figure of eight... vertically. Just need to use D/R and it's completely different aircraft.

Radio is perfect for it! And I see You understand why don't want to put Cox in it. By now, E-Max is on D/R far too much to me.

Design is very good. Mr Eric C. had a brilliant idea, however could design it a bit bigger. I'd like to achieve this at 44 inch wingspan, but for now there is too many ifs and buts about this project...

All the best

Tom

[Martin Harris - Moderator]

Posted by Myron Beaumont on 21/05/2012 13:03:29:

Major

Glad to hear the radio works OK ! With a design like Sharkface you have to understand that the downthrust is meant to come into its own once a fairly high flying speed is achieved with a "lifting" wing section .Hence the hairy performance with no throttle control on the original Cox .I had one many years ago and flew it on the Avon MC site near Bristol .I was told off for seemingly being out of control .On the contrary ,they didn't have a clue what it was all about .It had a 15 Chinese engine up front as well would you believe .Never forget it .Good mind to build another.It's amazing what id did without ailerons . A very special design that shouldn't be "improved" IMHO

Cheers Myron

I see where you're coming from Myron but I understand that Major isn't all that experienced and could do with taming it down a bit for the time being - which ought to be a possibility given that he's got a throttle and what looks like a relatively Clark Y ish aerofoil - despite its hooligan heritage! Hence my suggestion to "normalise" the downthrust to make it easier to launch successfully - perhaps coupled with a slight reduction in wing incidence?

I think (although I could be wrong) that he's built it with an elevator?