Ask..Peter Miller

[Luther Oswalt]

Thanks ... I have always thought the airfoil shape had more to do with Free Flight than any others. I always considered the angle of incidence and the AOA, the trust line had much more to do with models than air foil. In my youth, tho that was long ago, I flew a lot of free Fight and under cambered wings always seem to glide best ... but ... I must admitt the flat bottom wings were not doing any worse.

Besides, covering a under cambered wing with silkspan had it's moments.

Just my observations of sport flying models!

Again, thanks for the information.

Leo

[Peter Miller]

Many years ago I read about an American who designed an R/C sailplane with which he won several competitions.

The point was that they were all using Seligs and Epplers etc. While our hero used good old Clark Y .

He was not popular!

[kc]

I think you can still download a free version of Profili to print out almost any airfoil at any size from the Profili site In addition you can vary the thickness etc which might be what you want. Look for 'Trainer 60' for a thick section about 18 percent.

[Richard scarborough]

Hi Peter,

Oodalally is coming along just fine, started the cowl today.

This model will be electric powered and may swing a bigger prop than the I/C version. Would you allow for a degree or so of side / down thrust, or leave it as per the plan?

Cheers Richard

[Peter Miller]

I suppose you could add a little side thrust as the torque could be significant wth a bigger prop.

Now lets look at down thrust. Why is it needed. Well, what an aircraft neds is to have the forces balanced out. If the centre of drag is a along way from the centre of thrust it may been needed. i.e, IF the wings are well above the thrust line you may need down thrust.

Sometimes if teh thrust line is well above the centre of drag you can need up thrust. The Lake amphibian wit the engine on a pylong above the wing does.

Also, if the wings and tail are set at different angles you may need down thrust to compensate.

However, The wings are very close to the thrust line on Harlequin and the wing, tail and engine are all set at exactly the same angle. So you should not need an down thrust.

Why don'e people ask about up thrust on low wing models? Funny that!

[bouncebounce crunch]

G'day Peter. my 12 year old son has asked if we could build a control line model together (yes i am a happy man) I have an OS10 and an Enya 09 i would like to use. Flying wings were the thing when i last had a go at CL. any recommendations. both engines are still strong and cared for. maybe an article and plan could be witchcrafted into the editors minds.

cheers bbc.

[Peter Miller]

Well, lets see. First, I do prefer slightly larger models for learing on as .09s and .10s will be flown on shorter lines and one will be turning round quite fast.

15 size models on 50 foot lines are more practical. FLying wings can be very tough if covered in nylon and will normall bounce.

However looking at what you ask for. If you buy on EBay you should look for a Mercury Viper plan. This was a smaller version of the Mercury Cobra which was a good trainer. Profile fuselage and simple wings.

I may also know someone who may be able to send you the plan by email but would ahve to checck on that.

The Cobra is bigger and would need a .19 to 29 size engine is is quite good and would be flown on 60 foot lines.

Another very good model for a .15 would be a Peacemaker. A very good .10 would probably fly it if kept light as it does go like stink on a .15. You could learn the basics of flying and then upgrade to a.15.

Peacemaker plans and aprt kits on Ebay and again, may know someone who might send ti by email.

[bouncebounce crunch]

Thanks for the reply Peter, I am kicking myself for selling off a couple of larger engines years ago (blasted women chasing) although I got said son (whom has asked to build) as part of that deal, so is that Karma?

I do have an RCM&E magazine that i purposely bought for your plan of Mini Mustang control line. so she will be built after my son becomes addicted, if not she will still be built when wife lets me get motive power contraption to bolt to front.

[kc]

The Viper plans and lots of others are on the Outerzone site.

[bouncebounce crunch]

Kc never knew that site existed , Thank you

bbc

[gerard harrington]

Hi Peter hope you don't mind me contacting you this way but I under stand that you may be able to help us out of a jam , first I will introduce myself Gerard Harrington a name from the past I was a control line modeller with your self and Reg Cuthill ,Brian Mamby in mid 1960s at Sudbury, a young lad on a bike then.

The jam we are in is due to no fault of our own we may lose the use of the cornard school playing field (due to dog walkers not clearing up and kids putting broken glass all over field )it is to be fenced in so the only way we would get to use field is through school which we think the school will stop . I understand from Brian that you may know a contact by the same name as your self who owns a farm on the bypass /newmans green any help that you may be able to give would be highly appreciated ,So you know a bit about us we are a number of up to 12 on a good day down to a hard core of about 5 and all in the BMFA we fly mostly electric due to noise ,it would also be good to meet up again and talk about those good old days when we did displays CL and you used to take myself and models in your 3 wheeler all the best for now Gerry

[Peter Miller]

Hi Gerry.

Only just found this, for some reason I don't seem to get notifications on this thread.

Anyway, I have spoken to Brian Manby about thisd some time ago so at least you got an answer one way or another.

[gerard harrington]

Hi Peter a lot of water has gone under bridge from my last mail to you we have lost cornard now and i have had a meeting with Suffolk county council in view of using waldingfield airfield that got stopped by a big boy at top. was looking good when we meet chap at the airfield he was going to clean up a patch for us and all was very positive have now received a letter to say sorry but no back to drawing board ,Brian has got another farmer to ask but don't hold much hope ,we do have use of nayland airfield bit of a drive but its a flying field grass a bit of a problem as full size don't need short grass ,been seeing some of your plans in mags nice to see your work ,must make a point to come and see you all the best Gerry

Edited By gerard harrington on 08/10/2013 21:06:11

[Peter Miller]

Hi Gerry.

Farmers tend to like wads of green stuff waved at them. We also found that if one can find more than one site it helps if a club rotates round them to avoid flying every weekend and also a strict limit on membership numbers. 15 is about maximum. We used to rotate round three sites. This meant well over a 50 miles round trip for some members as two sites were at oposite ends of the area.

I hate to think of the miles that I drove looking for flying sites over the years.

I keep on producing models. Got too many now, never get to fly half my favourites.

Hope you find a field soon.

[Steve Terpstra]

Hi Peter,

I decided to give your Oodalally a try as I liked the looks of it. This is my first build using bellcranks for the ailerons and was something that I wanted to try. The wing is now mostly built and I discovered that I could dial in some differential on the throws. At this time I have it set up with an 1/8th inch more up then down. Is this a good thing to do with this model or am I better off to leave it "normal"? Thanks for your time.

Steve

Edited By Steve Terpstra on 04/01/2014 02:11:34

[Peter Miller]

Hi Steve.

Not really sure how you can dial in differential with the bellcrank set up. You might get that dfferential one way but with a single servo you would get the opposite differential going the other way,

In other words if you get more up on the right aileron with right stick you would get more down aileron on the right aileron with left stick which is snot good.

I suggest you would be better off just haing equal movements each way. Oodalally doesn't really need any differential anyway.

[kevin b]

Hi Pete.

It is possible to introduce differential at the bellcranks in the same way you would do it on the servo arm, only you are working at right angles to the push rod (or not quite, if you understand). The bellcrank acts just the same as the servo arm as it rotates. The use of seperate servos reduces the number of linkages and therefore free play. However modern servos are so light, it can also reduce the overall weight of the aileron system.

kevinb.

[Peter Miller]

The only way that you can do it properly with the bellcranks is to make special ones with about a 45 degree angle, not 90 degrees, otherwise they will just work the same as when set up at right angles.

With the 45 degree version you have the are connected to the servo at right angles to the pushrod and connect the 45 degree arm to the aileron.. Note that this set up is for a bellcrack connected to the horn under the wing and with the 45 degree arm away from the centre of the aircraft.

This is how the full size do it.

[kevin b]

Yup !

See. you were kidding us. You did know. I thought it a strange comment from someone so knowledgable. However I didn't know how they did it on full size aircraft. Thanks.

kevinb.

[Peter Miller]

You should see the Taylor Monoplane.

The specicifaction for throws is." 25 degrees up aileron, Almost no down aileron" and the bellcrank is virtualy about a 10 degree angle.

I admit that I answered the question for someone using the same 90 degree bellcranks shown on the drawing.

[Steve Terpstra]

O.K., looks like I was wrong about using the 90 degree bellcranks, I understand what your are trying to explain to me  and will readjust them as per plans, thanks for the responce.

Steve

Edited By Steve Terpstra on 04/01/2014 21:02:28

[Steve Terpstra]

I need a little help here please. I have my Oodalally mostly built except the covering. At this point I like to do a preliminary balance test to see if I need to modify anything and about where I'll need to place the battery. All of the models that I have built before were constant chord wings and balanced on or near the main wing spar. Rib 3 on the Oodalally measures 3-3/8in from the leading edge to the center of the main spar and the CG on the plan sheet shows it needs to be 2-11/16in. I thought it odd that the balance point would be ahead of the main spar, but this being my first tapered wing build I figured that I better ask first before I continue. So, on a tapered wing, how far out from the fuselage do you need to support the wing to balance a model? Or more importantly, where on the Oodalally wing do I need to support it to give it a proper balance? Thank you.

Steve

[kc]

I am sure Peter will answer this officially in due course. I would expect it CG to be at wing root ( or even central -almost the same) as it is on all models. It's usual to put a mark or a piece of tape along the CG line so you can feel it and balance it on your fingers ( clear of the u/c)

Edited By kc on 27/01/2014 13:47:54

[Peter Miller]

Forget CG inrelationship to the spar. The CH is at 25%or a 1/4 of the chord back from the leading edge of the wing.

So measure the chord at the root divide by four and measure that distance back at the root.

The spar is at 30% back from the leading edge so it will be behind the CG.

I make up about three layers of solartrim and cut narrow arrows and stick them on top fo the wing on the CG location.

You can then turn the model upside down and hold the model on your figer tips. You can feel the arrows.

[Steve Terpstra]

Got it, thank you.

Steve