Which Spitfire?

[Erfolg]

If you like flying and do not count rivets, I would gp for a Ripmax Spitfire, if you can find one.

They fly very well, look fine. The downside if you know the Spitfire, well it just looks like one.

[Tony F]

He's already bought the JP Seafire fella...

Tony

[Chris Anthony]

Congratulations on the buy Masher. How are you getting on with the build? Did you order the Seafire off LMS's website? As I can't see it listed there atm, nor on their eBay shop.

Also, could I possibly hi-jack this thread, and encourage people to continue posting Spitfire options, even though Masher the OP now has his model. I have exactly the same requirements as Masher; an ARTF Spitfire that must be wood and IC. Around the 40 size would suit me well. Thanks!

[Masher]

Hi Chris

I can't start it for a week or two because of work but I will post progress updates as I go. It was on the LMS website and they turned out to be the cheapest I could find.

Yes it would be good if people keep adding suggestions. Anyone who's been flying a while has probably been through a few spits but for us newcomers, it can be a bit of a minefield. I am preparing by flying a fibreglass Yak 54 -an ARTF from China. This has been through a few club members who have experienced "interesting" characteristics in the "tends to stall without warning" category. So far it has helped me strengthen certain muscles that I mustn't mention here!

[Codename-John]

Posted by Chris Anthony on 10/05/2014 14:49:21:

Also, could I possibly hi-jack this thread, and encourage people to continue posting Spitfire options, even though Masher the OP now has his model. I have exactly the same requirements as Masher; an ARTF Spitfire that must be wood and IC. Around the 40 size would suit me well. Thanks!

Kyosho spitfire 50, flew great on a 56 4 stroke so 40/46 2 stroke world be fine too

[Tim Tolhurst]

Hi Masher, I have the Seafire with an SC120fs in it (same as the ASP) and would like to congratulate you on your choice, its a great aeroplane to fly, lots of presence in the sky, and sounds great. With the flaps it flys surprisingly slowly, which I like as I have an awkward approach to land mine.

Its built well, though one thing I will criticize are the oleos. Unless they've changed them, they're not very good. Mine lasted about four flights and fractured around the grub screws at the retract end. I put air up/down retracts in mine with decent oleos, and have had no problems since, though there's not a lot of room for the air bottle in the fuse.

Another point (not really a criticism) the radiator scoops are a bit flimsy, and shattered on an unscheduled belly landing, so watch that.

The only other thing I would change, or at least have another look at are the retract mounting points. You will have to glue blocks in (supplied) to get the wheel well clearance and rake angle for the undercarriage, which looks a bit of an afterthought. If I was building mine again, I'd have a longer think about a better solution! However their system does work so if you just want to fly, it doesn't detract from the looks once its in the air.

Cheers

Tim

[Tony F]

Bit pricey even for HK = **LINK**

Tony

[Tony F]

And seafire here = **LINK**

Tony

[stuey]

My kyosho 50 size flies well on a ASP 61fs, needs a few tweeks and the cg at 95mm imo. Still needs some down trim so could do with a bit more downthrust. Check before commiting to the cowl fit first though!

[Masher]

Tim - thanks that gives me some confidence in my choice. I don't intend to rush the assembly so will consider the Oleo's etc.

Tony F - Yes that's the one but about £172 from Leeds Model shop including p+p!

[Tony F]

For Chris Anthony......**LINK**

Tony

[Masher]

That's the one! Who could not buy one at that price?

[Chris Anthony]

Thanks chaps. I've got a spreadsheet with all the pro's and con's weighed up for each Spit model at the moment! Come pay day on the 28th I'm sure one of them will be on it's way to me. Which one it will be, I'll let you know when I know.

In the mean time, how do you all imagine I will cope with a Spit after an Acrowot? Would anyone suggest any intermediate models that would help me transition between the two?

[Colin Leighfield]

I've had very good experience with the VQ Models Macchi 205 Veltro. It's not expensive, the retracts are a few quid extra but not much and although a bit fiddly to set up work well enough. Although not dead scale, it's nicely finished and really looks the part in the air. 63" span, flies beautifully with an ASP70FS. No vices, nicely made, a great warbird intro.

[Jon H]

I know that Seafire quite well as a clubmate has one. A 120 is over the top performance wise and a decent 90 or 100 would do. He flew his on an enya 120 (the up bored 90 not the full fat version) and reported no lack of performance even though he thought it felt slow. Video footage confirms it was not slow at all!

In any event, to help with landing the beast and to prevent 'random' tip stalls I would recommend you fly with low rates and NO EXPO!! the reason for this is that most warbirds only need small elevator movements anyway and if you use expo to prevent them being pitchy you can get into a situation where the elevator movement increases rapidly for only a small stick movement and will induce a stall. Even if a stall is not induced you may suffer the dreaded porpoise on approach.

All of my warbirds are set up in this way and are no bother to land. I would also not recommend any elevator flap mixing as (in general) you should not need it. You will only need flap mixing if you are flying too fast for the flaps to be deployed and they are creating too much lift. try slowing down and seeing if you still have a problem.

My final suggestion (on the first flight) is to take the model up high and deliberately stall it a bunch of times. Do it gear up, gear down, with flaps without, in a turn left and right etc etc. This should give you a little experience of where the limits are and you may find the model more benign that you expect.

[Jon H]

Chris, I missed your message. If you are competent with your acrowot then you should be fine. Warbirds are not hard to fly just different and require slightly different skills. They are also best left to 'run' around the sky and look much better than if they are banked and yanked. If you let them run you can also use less throttle and everything becomes much smoother. You will use the throttle much more than in a sport model.

I would suggest you read my comments above and practice landing your acrowot to the point where you can perfectly put it on the same spot with no bouncing every time. This is very important as retracts tend to be more fragile than fixed gear and many people come to grief as they get a few inches off the ground and abandon the model there! practicing and continuing to use a proper approach will also help no end as most of the landing (lineup, height, speed) are all dealt with before you arrive at the runway so all you have to worry about is the touchdown.

Just remember that while it is still moving it still needs control.

[Chris Anthony]

Thanks for that practical advice Jon - very useful. The fragility of retracts is something that, as you said, I had not even considered. I'll begin landing training on my acrowot with this in mind. If you don't mind, I have a few questions based on what you said:

1. What kind of mixing are you referring to, with regards to elevators and flaps? Do you mean that some people might add in some down-elevator to accompany flap-deployment, to overcome the extra lift seen by them flying too fast?

2. Can you describe "the dreaded porpoise on approach" to me, this is something I am not familiar with.

[Jon H]

Hi Chris

You are quite correct with your first point, It is often reported that models fitted with flaps need down elevator mixed with the flaps to prevent ballooning and unwanted climbs when they are deployed. This is usually due to the model flying too fast and in fact all of my warbirds (between 70 and 80 inches) have almost no trim change at all. My YT La7 has a slight nose down pitch attitude to it which is why I select a slightly higher elevator rate for landing. Also the reduced speed means I loose elevator authority. Now some models will balloon up no matter how slow you fly, in this instance they are basically too light for flaps to work correctly and they can be more or less ignored.

Porpoising is a term used to describe PIO or pilot induced oscillation. There are many factors that can effect/cause it but in essence it is any unchecked oscillating motion which effects full size as well as model aircraft. In this case (landing approach with expo) the effect would show its self with the model rising and falling and (invariably) hitting the ground quite hard at the bottom of one of the arcs of the sine wave the model is drawing. This is caused (often) by the use of high expo as the response of the elevator is not linear to the stick movement. This has the effect of damping the center stick position making the model less sensitive (which is the goal of people who use it). The downside of this is that beyond a certain point the elevator travel increases rapidly leading to an over control situation resulting in an unexpected pitch up. The solution is to use a lower rate in the first place as this will make the model less sensitive and you will not need the expo.

While it is entirely personal and varies depending on the type of model you fly, as a general rule I never use expo. I have only 1 model which I do use it on as aileron effectiveness at low speeds is very poor but they become very sensitive at high speed. I only use 10% to get the desired damping effect. For warbirds I use as little elevator rate as I can get away with but ailerons and rudder can be as much as you like (within reason).

The only downside to using no expo is it will punish you for any inaccuracies in your flying. So if you screw out of a loop then most likely you are not pulling the stick exactly straight. While this may put some people off I suggest they stick with it as it will not take long to get used to and it will improve your flying. I have been resetting a number of models at my club for various people and they all reported a more solid feel to the model, even if it was a little more sensitive when they first got their hands on it.

Sorry if that's a bit long, if you have any further questions let me know

[Chris Anthony]

No apology needed for the length of the post Jon, it was all good stuff that I enjoyed reading and learnt a lot from, thanks for taking the trouble to type it. What you say about flaps and elevator trim makes perfect sense to me. And it turns out I have heard of PIO, just never heard it referred to as porpoising before - interesting! I know on occasion I have caused it myself during a flight or two with my trainers.

What you say about the limitations of replying on expo is also very interesting to read. I have been wondering what the benefits of it are for a few weeks or so. I still haven't been completely persuaded to give it a try yet, and your cautions align greatly with my intentions to not bother trying it, at least for a while, whilst I'm still learning

One more question, could you explain why war-birds, perhaps Spits in particular are more prone to tip-stalls? I think I've experienced it on the Phoenix flight sim so know what to look out for; where the plane seems to drop a wing very easily at the point of stalling, even with no roll rate or aileron input at the time of stall. I've not experienced that with any other model on the simulation program, so am assuming it's common for this type of aircraft but not much else?

Edited By Chris Anthony on 13/05/2014 23:30:33

[The Wright Stuff]

Hi Chris,

First I will apologize for not having the time to write a lengthy email.

War birds are prone to tip stalling because of a combination of factors present in the replication of the dimensions and shapes present in the full size aircraft. This is effectively because the original planes were designed for outright performance rather than to have a forgiving nature: in the particular case of the Spitfire: speed!

The particular factors are: a tapered or elliptical wing (as opposed to a constant chord wing, which all stalls at the same time, at least in principle); a heavy wing loading (meaning it has to fly faster or with an increased AoA to stay airborne); and finally small tail surfaces, and a relatively short distance between the wing and tail: the effect here is that the elevator in particular becomes very sensitive as described above, and can aggravate a tip stall.

That's just a very brief summary, but there's lots of interesting reading out there...

Cheers.

[Jon H]

Hi Chris, i am pleased you find this information helpful. This all makes good sense to me as I did Aero Engineering for my degree.

But, tipstalling. Another dreaded trait of warbirds and any tapered wing model (caps extras etc), that is actually simple to avoid. Just to confirm exactly what happens, when a tip stall occurs the wing tip of the model will stall (as the name implies) and the resulting lift imbalance will flip the plane over. usually tip stalls will occur in a low speed turn as in inside wing is effectively flying slower than the outside wing. When the inside wing stalls the model will flick into the turn and the rest is well known to us all.

While we are here, stalling has nothing to do with airspeed and is related to angle of attack and comes about when the airflow separates from the upper wing surface. This is important when it comes to working out a recovery from the situation as well as spotting the early signs.

If we take a left hand turn to final approach our left wing is low and slow. This may cause a slight tendency for the model to roll into the turn as the outer wing has more lift. In this case right aileron may be applied to correct the model. This should be your first warning! In this instance the left wing (with aileron deflected down) has a greater relative angle of attack than the wing with the aileron up (relative angle of attack is derived from airspeed, actual AOA, control deflection etc etc). If we continue the turn with constant speed and load everything will be perfectly ok. But, what happens when we try and pull a bit of elevator to lineup? well, pulling the elevator increases angle of attack and our inside wing may drop a little more. THIS IS YOUR FINAL WARNING. If you now apply aileron to pick up the wing you will increase its angle of attack and may push it beyond the stalling angle. The airflow will separate and lift will be lost causing the wing to drop. Adding more aileron to correct the situation only makes it worse.

In this video you can see a brilliant example of a tip stall. wings rock a few times (wing rock of death, another warning) as he tries to pick up the wing and then its all over. He made a few other mistakes as well like pulling the nose high with flaps full down (loads of drag) and not putting more power on until very late. The model stalls left in this case due to engine torque yawing the model left which slows the airflow over the left wing and, yep you guessed it, increases relative AOA. **LINK**

Now, if you get into this situation the only chance you have is to use full aileron deflection to pick up the wing BUT it must be combined with rudder in the same direction. This is because the kick of rudder will increase the airspeed on the stalled wing and hopefully unstall it. Some power and reduction of elevator will also help but you need to make sure you don't induce a flick in the opposite direction.

The best plan is to notice the signs of the stall and fly in such a way that you limit their effect and do not get into a stall in the first place. This is why I would recommend a gently curved landing approach (as speed is harder to judge when flying at yourself) which is flown with almost no elevator input. Any changes in pitch should be done with small (2 or 3 clicks) of throttle for a second and then back down. Clearly elevator can be used, but keep an eye on that wing tip. once lined up the flair should be made as low as possible because a stall 1 inch off the floor is not likely to be an issue. At a foot or more you are in trouble!

As an example have a look at the video below. I have the same model as the one flown above and if you watch my landing approach I hope you will see what I mean. You do not have to watch the whole flight if you don't want to, although you may see what I mean about letting the model run. Also be aware that warbirds are not easy to trim as trim changes with speed. I trim for 1/2 power in level flight, this means I hold almost 30% down elevator when doing a pass totally flat out. This is not a fault with the model or its balance, just the way they fly.

enjoy **LINK**

 

 

One final thing I forgot. you will often hear people talking about washout when tipstalling is mentioned. Washout is a twist (warp of you like) in the wing to give a reduced AOA at the tip. If a wing has 3 degrees incidence then you effectively have 3 degrees AOA before you start and washout will reduce the incidence of the tip. Usually about 2 or 3 degrees is used. This encourages the wing to stall at the root first meaning you still have aileron control at the stall. It is by no means a total fix however as the La7 in the two videos has both washout and a sympathetic aerofoil section at the tip.

Edited By Jon Harper on 14/05/2014 09:10:24

[Concorde Speedbird]

That is very useful for all of us Jon, thank you!

CS

[The Wright Stuff]

Posted by Concorde Speedbird on 14/05/2014 10:13:05:

That is very useful for all of us Jon, thank you!

CS

Agreed, thanks Jon. Sorry, my previous post crossed with yours.

One more comment that comes to mind is that scale model aircraft, and warbirds in particular, can have lots of clutter on the wing, that disrupts the airflow and complicates the effect of the elevator. Underwing detailing, like panel lines, radiators, oil cooler scoops and weapons / drop tank mounts can all have an adverse effect. I wonder why there seems to be a trend in the ATRF markets for later marks of Spitfire at the moment: it occurs that the asymmetrical radiator on the Mk I, II, V is less conducive to stable behavior than the twin radiators on later marks...

 

Edited By The Wright Stuff on 14/05/2014 10:54:46

[Jon H]

No worries Wright Stuff. We are all on the same page and you mentioned a few things I missed.

I think the trend towards late mark spits could be down to the fact that they had longer noses (handy for CG on a model) and in general larger tail surfaces which limits the visual impact of making the tail bigger on the model.

You are quite right about scale detailing and other bits disrupting airflow over the wing and making a stall more likely

[Chris Anthony]

Thanks all, Jon especially. Great description, I'll try and remember it all. That video was great too, apart from the wrecked model as an outcome.