Nihjuis Spitfire 62"

[Tim Mackey]

Forgive me for posting so late on this, but a couple of comments caught my eye

Firstly, its quite feasible to use the Tx mixing to arrange the flaps to operate with the undercarriage - although I am not sure you would want to....depending on conditions at the time, you may not want to deploy full flaps, - better IMO to keep them separately switched....even better perhaps to have them o slider or 3 pos switch to vary the amount of deflection.

Second. As to retro fitting them, mention was made of simply using strip of wood or whatever stuck to the cut away wing skin - dont underestimate the forces involved when deploying flaps - ensure that the structural integrity of any foitting and hinges etc is man enough for the job.

Thirdly. I tried "flapperons" on my aileron equiped Spit ( not the TN ) and it was not good.

Problem I suspect is that with the aileron being relatively short span, and at the tip of the wing also, they were inneficient and caused some rather wobbly aileron response, and little in the way of stable increased drag /lift. I think there is a good reason why such wings and aerpoplanes have proper separate inboard flaps.

[Paul Jarvis 1]

Jim,

 

I notice your comment ... " It seems the general opinion is that flaps are all but essential on this model " and to put my mention of retro fitting flaps to my Spit in to perspective, I should add that this is my first plan build and I am a relative "novice",  

 

If TN designed the model with no flaps I am certainly not saying it needs flaps, simply that I personally had issues with fast landings and bending the retracts before, and I ve found it much more "friendly" to land with flaps fitted.

 

And I did not find it to be major surgery, one night or so's work to fit - easy. Fitting the push rods internally would certainly work IMHO.

 

I have simply epoxied 4 small hinges embedded into the existing balsa skin at each flap, yet to see how long these hold up, but they seem strong enuf. 

 

Regards

 

Paul

[Jim Newberry - Nuviation Ltd.]

Well I think I'll definitely fit some flaps to mine. I may even fit them without servos, pushrods etc but fixed in the up position so that I can try the model out without flaps and make them operable later if required. That way if I decide not to use them I won't have added much weight unnecessarily, but if I do decide to use them I won't have to retrofit them. Jim

[John Laverick]

Hi Guys,

 

anyone got any idea's about attaching the undercarriage fairing to the oleo legs? I know Tony suggested using pipe clips but I can't seem to source any.

 

 

regards

 

John

 

[Bruce Richards]

John, what diameter are you  legs? if its not to much of a personal question

[John Laverick]

Hi Bruce,

 

15mm is the size of my legs! and I'm not too steady on my feet I can tell you

 

Regards

 

John

[Bruce Richards]

John,

 

you should be able to by 15mm pipe clips from any plumbers merchant and all DIY shops. Wickes, B&Q, Homebase, Screwfix etc. There are lots of different styles . Here is a selection from Screwfix.

[John Laverick]

Bruce,

looking at the Screwfix website they have the ones I need, I went to B & Q yesterday and couldn't see any. Perhaps I was looking in the wrong place? Thanks for that.

 

However, on to another question aimed at the Spit Builders amongst you. How on earth do you do the wing fairing? Tony  suggests that you roll!!! a piece of 1.5mm balsa to form the wing fairing. I've been trying all afternoon and I haven't got a clue!

 

It's really starting to wind me up a bit. Help.

 

Regards

 

John

[Snaba]

John,

this is indeed a bit delicate job as 1.5 balsa breaks easily if it is not wet enough. Well, this is how I did it.

First, I took the shape of the top part of the fairing from the drawings and cut the balsa to the shape. Then I made the inside of the fairing wet with spray while protecting the first few mm with tape. I then removed the tape and glued the top part of the fairing to the fuse with CA and activator pen (I had marked the position beforehand), by this time te balsa should already have started to bend out to make the glueing really easy. Then, I took the cardboard roll from inside of a used toilet paper roll aund used this to make the curvature. Using the roll you see when the pressure is getting too much before the balsa breaks. Pay attention to have left the balsa sheet so that you have a surplus of it. When I was happy with the curvature I marked the position to the underside of the sheet with pen. Then I applied plenty of CA to the gap between the ply and balsa, used the roll again to set the fairing to the premarked position and sprayed the whole join with activator. I started the gluing from the back part of the of the ply.You then make the other side and mark the curvature so that it is similar to the first side. Then you just cut off the rest and you're done!

Edited By Snaba on 15/05/2010 18:15:44

[John Laverick]

Snaba,

 

you make it sound so simple!!! I'll give it a go, it will have to wait unitl tomorrow as I've used up all my 1.5mm balsa trying it yesterday.

 

regards

 

John

[Myron Beaumont]

And your toilet paper !

[John Laverick]

Well,

I've managed to do it but not the way suggested on the plans. I tried and tried with balsa and I just couldn't manage it. so I changed tact and I've use card instead. it's the same thickness as the balsa and when glued in place it is quite rigid.

More than happy with the result,  just need to add the front bit out of shaped balsa.

Regards

 

John

[John Laverick]

Hi Guy's,

 

just done a run up and this is the stats I've come up with for my set up.

 

Weight 7lb 10 oz

motor E power BL4020 520kv

prop 13x10 electric

battery 5s, 3000ah, 20c

ESC 100 amp OPTO

 

Result of test: 550w at 28amps on full chat which I think gives me about 72 watts per pound. question is, does anyone agree that the watts per pound is enough for the Spit?

I could add a larger prop which would give me more watts, but to be truthfull I'm struggling to get a larger prop to run anything as smooth as the 13x10.

 

I'm using an ali spinner and I'm struggling to get it to run balanced due to the way the spinner is attached to the motor shaft. A larger prop is much thicker and there's not enough room on the shaft to get a normal nut to tighten the prop to the back plate, plus the nut attachment for the spinner. I'm not happy just using the spinner nut to hold the prop in place, plus the spinner. Can't anyway cos it's trying it's hardest to rip the motor mount out!.

 

Of course I could just add a larger battery because the motor can handle up to 7s but at £50 a pop for a 6s I was sorter hoping 72 watts would fly it.

 

regards

 

John

 

motor

[Snaba]

John,

according to AMA Insider 2006 your wattage should be enough for mild aerobatics:

 

http://www.modelaircraft.org/insider/06_03/05.html

 

TN designed the plane to fly with a .61 engine, an OS .61 has 1.8 HP=1342 w. In this respect you may be under powered. Well, how about trying a 4-blade prop for more pull?

[Snaba]

John,

check this out, they have new props that might help to solve your problem:

 

http://www.ramoser.de/home_e/varioprop_e/varioprop_e.html

 

I have one 3-blade setup for my Turbo-raven and its really great to be able to fine tune your system with pitch!

[Trex700e]

well just for a bit if info at 50W/lb it will give you a slow but scale fight. For example, perfect for a sopwith cammel.

 

at around 100W/lb it will give you a slightly fast but still the feel and look of a scale flight. Perfect for a spitfire

 

at around 150W/lb it starts to become faster and more of a "point and it will go!" flight. however it is still perfect for a spitfire as it come in handy doing such scale moves as a very wide loop.

 

anything over 200-250w/lb and its starting to become a 3D and sport model but this power can still be used on a scale plane due to throttle control. However all of the above depends on many things and the biggest factor being DRAG!!!!

 

The more drag the more watts you will have to find. for example a DR1 with all three wings and rigging will have to have quite a few more watts then a sleek design such as an F-16. and another decisive factor is the size of the model and the wing load.

 

Hope this helps!

Will

[Tim Mackey]

I have to say that 70 WPlb for a decent size and weight  Spitfire is marginal. Sure it will "fly" once it gets going, but dont expect nice big loops etc, and the take off could be tricky.

I really advise you aim for at least 100 WPlb.  My electric Spit is fine on approx 150, and frankly I wouldnt want less - you know how it is...sometimes you just know you needed that extra oomph to get out of trouble

Sorry to say it....but I reckon 6s is the way to go on that model and motor if you simply cant get a bigger prop on. I doubt a 3 blader will give the boost you seek, sure it may well lpoad the motor more and the meter will rise....but the thrust may be no better at all.

Edited By Timbo - Administrator on 27/05/2010 21:19:24

[John Laverick]

Thanks guys.

 

looks like I'm having to stick my hands in my pocket again!

 

John

[Hugh Coleman]

My immediate thought is that a 13 x 10 is maybe too high a pitch.

 

Maybe go for a 13 x 6 (that's what I will be running on my ASP 61 FS)?

 

That'll help with the thickness of the prop too.

 

Cheers,

 

Hugh

 

 

[Tim Mackey]

But that will reduce thrust and power further......unless the volts are upped.

[Hugh Coleman]

So, up the volts.  It's a relatively low Kv Motor, so surely there is room to up it to 4 or 5 cells?

 

Hugh

[Tim Mackey]

If you read the rest of the earlier postings you will see that he is already on 5s - and this issue has been discussed.

[John Laverick]

Hi Guys,

 

Thanks for the input.

 

As it happens Hugh, I've had an afternoon of testing different props and I used a 13x6 and the results are pretty poor. I also tested a 14x8 without the spinner and I only got a slight increase of 29 amps and 600watts. Have to say though, when I was testing the plane it was quite literally trying to rip itself out of my hands and took considerable strength to keep it steady! (not a very technical way of finding out if a plane can fly but I felt it could)

 

I think it was a poor decision to buy such a low kv motor, I bought it thinking I could put a large prop on and get loads of thrust, but not really thinking about what size battery I would need. I wonder how many modelers have miscalculated their set up and have ended up with Spare Lipos that won't do that particular job? I certainly have, you never stop learning with electric. Hate to think that I was a beginnner, so many computations, so many motors, so many props, so many ESC's so many Batteries!! bloody minefield.

 

As it happens I only need to buy a 3s as I already have one that was not up to the job from a previous project!!!!! and bobs your uncle, parallel them up and off we go. Thanks Timbo for your input on this thread and the battery thread. Good to know that we have an electric expert to call on.

 

Good job guys

 

Thanks

 

John

 

 

 

[Tim Mackey]

Errr, think you mean series 'em up John

[John Laverick]

Yep, thats's it Timbo

 

only spent 22 years in the Royal Signals, worked with batteries all my life but still can't suss out parallel and series! or even series/parallel Still don't  know how I got the radios to work? I can remember lot's of sparks, but hey, I thought I was good!!!!

 

memo to me, Less red wine is good. Or is it?

Regards

 

John