Hobby King Piper L4 Grasshopper 1.4 metre, plug and fly.

[Colin Leighfield]

 

 

Once again a chaotic year has undermined my attempts to complete projects and fly. I took a week away on the Honda in the Isle of Man in July, a welcome break from other pressures, then back to two weeks jury service that was a complete waste of time as it turned out. Back home then to try and catch up on the accumulation of things undone, to be followed by instructions to keep a week clear for secret family events related to my 70th birthday. That turned out to be a very pleasant week in North Devon with family turning up to celebrate, including my daughter from Australia. Back home to catch up on other things undone and work issues, but while away and in pursuit of something reliable and routine as a basis for getting my flying up to speed, I ordered this from Hobbyking, along with two 4S 2200 Lipos. It had arrived by the time I got back and I have fitted in assembling it in the last few days. Apparently it is actually a Starmax creation and in my opinion the general quality is excellent and the EPO foam is strong and nicely finished. The instructions are useless and I had some real head-scratching, particularly with the undercarriage. However I got there eventually and it looks very nice. If it flies successfully I will create a pilot out of blue foam for it. At last I have the chance to go flying tomorrow so I will be at Fradley starting the process of getting my hand back in. I will take my old faithful Top Gun Edge 540 91, a Durafly Spitfire, the Seafang and this. Between these I want to work myself back in and finally get back to the long delayed objective of a decent photo session for the Seafang.

Lying in wait remain the Chipmunk and Suoermarine 317 project. Also during my last flying session a few weeks ago a clumsy and I'll-judged cross-wind hand launch with the XB42 Mixmaster piled it into the runway and severely damaged it. I've taken this as an opportunity to improve it and make it more presentable and that is now at the stage for finishing, I may accept a little extra weight this time and add some light glass cloth to achieve a more attractive finish.

It looks as if I finally have a bit more time on my hands now so hope to move on. For those who bother to read my ramblings I apologise for taking so long to make progress, but now there's some light at the end of the tunnel.

(I'm sure that some of you will notice that although labelled as a military Grasshopper, it is actually a standard Cub with the military paint scheme, lacking the extended cabin glazing of a true Grasshopper. However, I think it looks the part).

 

Edited By Colin Leighfield on 25/08/2016 21:47:05

[John F]

That sure looks lovely Colin. Good Job.

[Colin Leighfield]

All I did was to screw it together John, anyone can do it! It looks promising though, I'll find out tomorrow hopefully if it does the business.

[zz]

I had one of these. I marked mine as a US Navy NE-1 Cub. It carried the 3 tone Pacific scheme. The Navy Cubs were standard J3C-65 aircraft and as produced by HK, it was correct for this version. Based on an illustration in a Squadron in action book. I found it flew scale at half throttle. The uc need considerable reinforcing. After a while I found it a little mundane and passed it on.

Edited By kooka on 26/08/2016 00:07:49

[Colin Leighfield]

Thanks Cooka, I didn't know about the Navy J3C-65s. Before I bought this I looked on-line and read about undercarriage problems. It was acknowledged and is said to have been altered. It certainly looks robust enough now and the linkages are all sprung, although I can't see that they'll be doing much because it looks tough enough without them. When I decided to get this it is because "mundane" is exactly what I am looking for. I've got too many models in the exciting category and I need something more basic as a back-up practice flyer.

It was encouraging to hear that yours lasted long enough for you to pass it on! Fingers crossed this one will too.

[zz]

No sweat Colin.

I found the 4S 2200 was a very tight fit so I used a strap around the battery, length wise, so as to give me something to pull to extract the battery rather than the battery charge leads.

Hope it all goes well.

[Terry Walters]

Colin- good decision - sometimes you just need something like a foamie Cub to relax with - belated happy birthday too!

Kooka - some say these Cubs didn't exist but I found this pic: Can you spot it! LOL! Nice scheme I've got a 1/4 scale Sig Cub to build and it will be the same scheme.

[Colin Leighfield]

Kooka, thank you. I've found the 4S 2200 a bit tight as well. Also the position of the ESC prevents me pushing it right forward to line up with the step on the hatch that is clearly designed to set the battery position. I could mess with it and re-position it in the engine cowl but that's quite a fiddle, so I cut the step off the hatch and accepted that the battery would be an inch or so further back. Checking the c of g showed that it was a bit rearwards, but corrected that with 50 gms of tyre balancing weight in the cowl, just over 1 1/2 ozs and I think that's acceptable to get the c of g spot on. We'll find out later!

Terry, thank you mate! That's a brilliant photo with 5 Goodyear blimps in the huge hangar! I spotted the Cub, looks like a Grumman Duck and Douglas SBD Dauntless in there as well. Looks like late WW2 or perhaps a bit later, but not much.

[Josip Vrandecic -Mes]

Dear Colin , I wish you, from the heart, to get everything you planed but the most joyous to celebrate your birthday

[Colin Leighfield]

Josep, thank you, you're very kind. This week I had a visit from an old school mate who has lived in Denmark for many years. His birthday is a few days after mine. We agreed that we will meet up on our second seventyth birthdays in 2086. With modern medicine and the will to live it's a worthwhile target. Put it in your diary, you are invited.

[McG 6969]

Hi Colin,

Could you please share the contact data of your 'medicine' man? ...

Happy birthday, young man.

This certainly an occasion for a well deserved Cub of Port...

Hakuna matata

Chris

BRU - BE / CTR Medicine Control

[Colin Leighfield]

Hi Chris. Thank you. No medicine man yet, maybe later. We just decided that we don't want to die, so we'll do something else instead. The Cub of Port is definitely on the menu for tonight. Cheers!

[Josip Vrandecic -Mes]

GA Colin , thank you very much..... count on me, I'm coming.....

All the best

Jos

Edited By Josip Vrandecic -Mes on 26/08/2016 11:41:13

[Biggles' Elder Brother - Moderator]

Best wishes for the maiden Colin - though if its like most cubs it will be a menace on the ground and an angel in the air!

BEB

Edited By Biggles' Elder Brother - Moderator on 26/08/2016 15:19:14

[Bob Cotsford]

A belated Happy Birthday Colin, have fun with the Cub. My only experience is with the big E-Flite Carbon Cub but there are a couple of smaller ones that are regulars at the field, in fact there was a foam one there today. They all seem to fly well, but I have noticed the smaller ones do seem to like finishing the landing on their noses for some reason, often after a ground loop. The big one doesn't have this problem, you may be lucky with the HK one too.

[Colin Leighfield]

Hi Jos, great news, there'll be a beer waiting for you! 2086 isn't so far away.

BEB. Just got back from flying it, it's been a very interesting experience. In a few minutes I'll put some photos up and say what happened.

Bob, cheers mate. This one didn't tip on it's nose in four landings this afternoon, although to be fair, it's a hard runway. Did some other interesting things though! I've got a Black Horse Cub, I think it's 78", I haven't flown it for a while, the TT45 four stroke is worn out and needs replacing. That flies well but has a mind of its' own on the ground, as BEB suggests!

[Colin Leighfield]

 

Here it is. With the c g spot on, even with full up trim it needed continuous up elevator to fly straight and level. Landed safely and removed 30 of the 40 gms nose weight and tried again. It didn't seem to make any difference. Another landing, removed the remaining 10 gms of weight, pulled the battery back a little and screwed in some up on the elevator clevis. It then flew well on half power, it's fundamentally stable and easy to control while still being manoeuvrable. However, as you increase power beyond half-throttle it enters into a progressively increasing nose-down trim and needs constant back pressure on the elevator stick. It's perfectly flyable and looks good in the air, but acts as if it has too much down-thrust, even though it seems to have not much in the first place. I think there is a connection with the highly positive angle of incidence on the tailplane, as you can see in one of the photos. I'm inclined to think that I might experiment with a reduction in the tailplane incidence and then re-trim to suit, that should be a better option than messing with the thrust-line, although it might require some moving forward of the c g again, perhaps no bad thing. The odd thing is that none of the reports on the HK thread mention anything like this, they generally say that it flies well, the main beef being with the undercarriage on early examples. Odd this, does Kooka have any further thoughts based on his experiences?

 

, removed

Edited By Colin Leighfield on 26/08/2016 17:53:17

[Colin Leighfield]

I can only exercise my judgement on this and use trial and error. I made two simple wedges from 6mm balsa and used them to raise the trailing edge by 3mm. Let's see what this does.

[zz]

Colin.

Not much to add. In mine, the motor seemed to have excessive up thrust, so I put small washers in to reduce. I thought it may have been poets day in Chine when they assembled it. Keep an eye on the main wheels. The method of attachment is'nt great. I lost one on take off, but managed a fine balancing act to get on the ground without further damage.

Other than that I kept the power down and it seemed to fly fine.

And, Terry, I saw the Cub. The photo may have been Moffett Field where the subject of my model was based C 1944.

[Colin Leighfield]

Kooka, thank you again.

There's no up-thrust on mine, trying to work out the true datum by eye says there's a couple of degrees of down. this tendency for the nose-down pitch to increase as power increases has the hall-marks of too much down-thrust but it doesn't look like it! The relationship between thrust-line and tailplane incidence looks as if it might be the key here so we'll see what the alteration in the previous post does. Yesterday it was pretty windy and I was using a lot of power up-wind. There's no question on half-throttle it was fine, but if I can get some kind of compromise I will. the point really is that the difference was too great to trim out, so it needs sorting. Interested to see your opinion that Terry's photo was probably taken at Moffet Field. You know your stuff mate. You're probably right about 1944, the markings on the Dauntless certainly point to that. The photo here is another one taken yesterday. It generally flies really well and has the makings of a sound model, but it's not quite the simple easy flier I hoped it would be. Maybe it will later. In the meantime I'll keep an eye on the wheels, but looking ok so far.

[Biggles' Elder Brother - Moderator]

Hi Colin,

Glad the miaden went well-enough anyway! No major incident.

I would agree with your analysis - positive tailplane incidence (relative the main wing) whilst not unknown is not at all common. The most usual set ups are 0-0, or even more common the tailplane at about minus 2 degrees realtive to the main wing.

Altering this positive incidence is ceratinly a sensible thing to try with this model if its pitching nose down at higher throttle settings. Be interesting to see how it reacts.

(yeap - cubs definitely have a mind of their own on the ground - it's the narrow track of the U/C that does it. They need a firm and positive hand on the rudder. Which is why despite their appearance they are not always great trainers. But in the air they do usually fly really well - stable but reasonably aerobatic. I'm sure you'll get this one sorted soon.)

BEB

[Colin Leighfield]

Thanks BEB, I think we're agreed on the analysis! I always found with the Black Horse 78" Cub that it took off differently every time, but always in a variation of sideways! We'll see how this one turns out.

[Colin Leighfield]

Well, I've got this sorted and now it's a great flying scale model. However, to do this I had to raise the tailplane trailing edge by 6mm using balsa wedges, 3mm didn't do it. Significantly, there was previously a triangular gap between the base of the fin and top of the tailplane. Now they are in exact contact along the length. I haven't measured the relative angles of incidence, but now it looks scale and there is probably 1 or 2 degrees positive on the wing, whereas before there must have been 3 degrees positive on the tailplane relative to the wing. It's simply that the tailplane seat is moulded at the wrong angle and makes no sense, because the overall quality and design detail is excellent. It flies in a very scale fashion at 40/50% throttle and is way over-powered on full chat. If you open the throttle wide on take-off it goes up like an EE Lightning. Ridiculous! In truth, although a 4S 2200 Lipo is recommended and I am using, a 3S is probably all that it needs, as long as you checked the c of g with the lighter battery,

Recommended and excellent value, all it needs is a pilot figure, but you need to spend five minutes on assembly correcting the tailplane incidence.

[Biggles' Elder Brother - Moderator]

Great news Colin. Always good to have a nice steady "hack" in the fleet that you know can go down to the field with you on any occassion. And now you have sorted the tailplane this falls squarely into that bracket! Nice work. The amount of incidence change you have had to inject is a surprise though - just shows how far out these things can be.

BEB

[Colin Leighfield]

Thank you BEB. Here is the photo showing how it was as out of the box, you can see the problem! The baffling thing is that there is an extensive thread running about this plane on HK, yet not a single mention of a problem like this! I wonder if there's been a change in the moulding kit or something like that and this has got through without being noticed. Beyond this it's a very nice robust scale model, you might need to keep an eye on the undercarriage but that is well sprung and probably better than a lot of the ARTFs, plug and fly models etc. you can buy.