Free flight project

Dizzyman2011 wrote:Oh yes a detuned 049 will be mounted with custom brass tank as yet to build then swinging a 7x4 hopefully around the 8-10k mark but it's gonna be a steep learning curve

Ma main man Bernie sells a rather splendid
1oz Sulivan tank Phill.
A bit easier than making a brassy.

OK so what is the span now that you added the tips?

where are you placing the CG?

chord dimension?

Hey mike span about 34.5 " cg will be around the spars as this is a scratch built there is no actual c of g but will be 25-30% from leading edge will have to go and check the chord

John Goddard wrote:

Dizzyman2011 wrote:Oh yes a detuned 049 will be mounted with custom brass tank as yet to build then swinging a 7x4 hopefully around the 8-10k mark but it's gonna be a steep learning curve

Ma main man Bernie sells a rather splendid
1oz Sulivan tank Phill.
A bit easier than making a brassy.

Hey John yes just had a look at that Sullivan tank does look peachy but think I need a bit smaller than 1oz am thinking 1" x 1/2" section by 1" long very tiny but my train of thought is it's less fuel and weight to be jolted forward in the case of impact !! They do look good though might order some for other projects though

Hey mike the chord is 13cm give or take a
Few mm

the reason i ask is because a lot of people make the mistake of having the CG too far forward on a FF model, sport of competition.
a few guidelines for FF is stab to be 35-40% of wing area with a 40-45% tail moment (that would be 40% of span to be laid out as from CG to 1/3 of chord of stab) with 75-80% CG.
this would put CG 9.75 CM from LE of wing.

if CG is too far forward, it will have a tendancy to loop. remember, we're combing a power pattern along with a glide pattern here so certain coordinates have to get along with each other to be successful.
not trying to tell you what or how to do this, but would like to see your model fly successfully and uneventfully right out of the gate.
your design is real close to the Midwest Sniffer which is a fun model to fly.
here is a link to the plans and article some guys did over on RCG.
on the plans notes, it sets the CG at 1.75" forward of the TE.

http://www.rcgroups.com/forums/showthread.php?t=1265331&highlight=sniffer

Hey thanks for the info tail plane maybe at but in the small side then ? Will try cg at stated point and see how we go why is it that ff cg is so far away from normal point am assuming this is ff power not gliders etc
Cheers

it's a balancing act with FF.
RC or CL you are steering with the tail so no incidence is programmed in for a glide. this means that to avoid the tail from being overly sensitive, the CG is pushed forward to give more control using the thrust of the engine so to speak.
even with engine off on RC or CL models, you still control the flight with the elevator so landing is done without damage.
with forward CG the flight speed is kept up too which is why the model doesn't just fall out of the sky when using up elevator to control the descent.

with FF, the model is flying under power on it's own, then has to make it's own safe descent after the power stops. thus the need for incidence in the wing to control the angle of both climb and glide. if the CG is too far forward then the the satbilizer will need more negative incidence (TE of stab shimmed up) to control the descent in the glide.......this is going to give more up pitch during the power part of the flight right?...........
this is where the balancing act starts......CG too far rearward though and the model now begins to stall and needs less incidence..........this of course will introduce a dive under power.
sounds wierd at first, but one can take a perfectly trimmed out FF model that climbs and then glides as intended, then move the CG forward 1" and the model will then try to loop under power........same goes for moving the CG back 1"......the model will now dive under power because you are pushing on the stabilizer more and causing it to fly more than it was originally set to.

Dizzyman
It' looking good. I want to start free flight myself, but most of the old free flight fields put a stop to gas engines.
Duke

MikeM wrote:it's a balancing act with FF.
RC or CL you are steering with the tail so no incidence is programmed in for a glide. this means that to avoid the tail from being overly sensitive, the CG is pushed forward to give more control using the thrust of the engine so to speak.
even with engine off on RC or CL models, you still control the flight with the elevator so landing is done without damage.
with forward CG the flight speed is kept up too which is why the model doesn't just fall out of the sky when using up elevator to control the descent.

with FF, the model is flying under power on it's own, then has to make it's own safe descent after the power stops. thus the need for incidence in the wing to control the angle of both climb and glide. if the CG is too far forward then the the satbilizer will need more negative incidence (TE of stab shimmed up) to control the descent in the glide.......this is going to give more up pitch during the power part of the flight right?...........
this is where the balancing act starts......CG too far rearward though and the model now begins to stall and needs less incidence..........this of course will introduce a dive under power.
sounds wierd at first, but one can take a perfectly trimmed out FF model that climbs and then glides as intended, then move the CG forward 1" and the model will then try to loop under power........same goes for moving the CG back 1"......the model will now dive under power because you are pushing on the stabilizer more and causing it to fly more than it was originally set to.

Wow this sounds like someone with a few hours of free flight under his belt eh!!!!
Never realised it was this technical to trim a ff model all good though but
My learning curve is getting steeper by the minute so to confirm cg should be 9.ish from the le ok so that should introduce a nice glide should be stable w/o power do I just alter incidence angle at that set cg for nice stable glide introduce say a couple of degrees of rudder to get it circling w/o power but give opposite degrees few more on engine to circle under power opposite way then as andrew said in a previous post then trim for climb under power with up down thrust ? Sounds like I'll be lucky if the first flight under power goes well I'm confident now I think !! With trimming the glide but may be a bit of gues work for flight under power ?? Maybe my first ff should have been off plans !!!! Am not one to give up though and "panic" will be out flying soon hopefully weather permitting oh how different a beast this ff is compared to c-l or Rc I have a lot to learn !!!

Duke
I say start a build while looking I'm sure there must be somewhere to fly gas if you look hard enough we modellers are nothing if not persistent I'm sure you'll find somewhere make sure u put your build up on here though would be very interested to read all about it any ideas yet as to what takes your fancy ??

Yeah. I just have a ton of C/L carrier builds going on. I need to get them done and start practicing, before the contest season starts. I have a friend that is 80 years old and was a huge FF guy. He can't chase anymore, but another friend and my boys will chase. I want to do it for the old timer and my oldest son likes FF also.

nah it's not that technical if guidelines are met with standard settings.

since you are going to use a powerplant that will not be high revving, you might start out with 2 degrees of downthrust.
the old trick of putting the prop on backwards was used for years and is still the way to go on the first flight, so plan on that.............prop on backwards, steady slow rich setting and a 5 second run should get things going. prop on backwards does not mean the model or engine will go backwards as the pitch is still pulling forward, just at a reduced efficiency.....sort like slipping the clutch so even if the model goes earthbound, it's not under the normal force which would destroy the plane.
what it will do though is give you an idea of what tendancies good or bad are present so you can make adjustments gradually......
i certainly did not intend to create confusion or doubt for you as you are on the right track, but there are others who have been FF'ers that may chime in.
i'm only looking at the effort you are putting into this project and feel somewhat obligated to share my experience.
some people will look at someone trying to fly and not say a word to help them, i just can't do that. i'm here to gain more Knowledge of the Cox engines, and share waht i have to share.
i started flying FF competition with my Dad back in 1963 and have flown many designs since......the basics become engrained thru the years.

with that said, your design is looking good and will be a fun model to fly.
i'm sending you a PM with some dimensions i need so i can give you a better answer on the CG.

Hey mike don't worry no confusion had like I said just a steep learning curve I'm gonna write those equations down though for my next ff project and keep them safe am glad we have some ff'ers here to teach this stuff as it would have undoubtedly been a flop if I had just gone with 20-25% cg loop loop bang am very grateful for the knowledge as I am a complete self confessed newbie to ff other branches have been modelling since I was a nipper but never ff but as u say it's good to help people

hey Dizz........on the NFFS site (National Free Flight Society) there is a link that will direct you to more info than you can imagine.
it's a library of tips, tricks and topics about FF.

here you go........enjoy,

http://freeflight.org/DigestOnline/library.htm

Thanks for that mike had a quick look while waiting for takeaway !!! Looks like a really good site loads of info on there thanks for that am looking forward to "panics" maiden

I took a quick look at the site also. Looks to be som good info, thanks for posting it.