Steve biplane

You can see a Comper Swift  for real at Shuttleworths aka Old Warden but I don't think it is a flyer at the moment.

Tony, during the design process the weight and CofG of the aircraft is calculated by the Weights department, these are fundamental inputs to the overall design and stressing of the airframe. Part of the certification requirements is to state the max allowable weight of the a/c and also the CofG fore and aft positions. Part of the flight testing is to fly the aircraft at these limits and show it has acceptable characteristics.  You can check the calcs by supporting each wheel on a set of scales (actually  load cells) which gives you the distribution of the reaction loads to the weight of the a/c. From these measurements the total weight of the a/c, and its CofG position, can be calculated.  Modern airliners have computers which calc the CofG as a function of fuel, passengers, cargo and luggage weight - it's up to the pilot to check that weight and CofG are within limits before take-off.

Ernie's post got me asking myself  "when did the change over from frayed  to serrated edge rib tapes occur"?    This got me looking in some books with the following result.  AP1107,  the RAF's manual for the rigging of aircraft (1931) shows only frayed edge rib tapes.  The rigging, maintenance and inspection of aircraft. by W Speller. 1935,  says use serrated or frayed edge wing tapes.It surprised me that the change over was so late, I thought  that frayed edges were  WW1 only.Steve

Thanks all for your replies, especially Eric for taking the time to write down a general way of working out a safe C of G position as a starting point.  I will try Ripmax and see if they still have the info on this old model.  Regards,  Steve

The title says it all, can anyone help me out? Thanks, Steve

I've been given an old Gambler 40 airframe which I'm currently putting engine and servos into as well as doing  some, mainly cosmetic, repairs.  Can  anyone  tell me the C of G position I should be aiming for?  Thanks in advance, Steve

If you are looking for something a bit different, a couple of the RAF DH53's were fitted with a 'trapeze' and used launching from and hooking back onto the underside of airship R33. In the Putnam de Havilland book theres a photo of  J - 7325 with the trapeze fitted (and also wearing the fin from J - 7326 so the aeroplane is wearing two different serial numbers - another talking point). I suspect the de Havilland museum or Hendon can supply details. Steve

Thanks Edwards Flyboy.  Just what I wanted.

Hi Mark,  words of wisdom. I can see now that the job would have been a lot easier if I'd done like you said and machined the inner cavities while the outside was a simple rectangular block. After all, a lot of the outside just needs to be something about the right size - not too critical at all.  And it would help prevent the outside machined surfaces getting  marked by being held during later machining.   I will know better next time.   The other thing i'm finding takes a lot of time is making the tooling so I can do the job I want to do.  A simple indexing tool,  boring bars etc.  But they will make future jobs quicker now I have them in the toolkit.   Steve

Hi Mark, Another (very slow) builder here. At the moment I'm trying to figure out how to machine the cylinder cavity, in the crankcase, at right angles to the crankshaft bearing using my tiny, table-top lathe.  I think I will have to make a small angle bracket for the face-plate (but it will be a bit of a squeeze! - not much space)  Good fun figuring out these problems though.   I liked the look of your rear induction version on the modelenginenews site.  Presumably that lets you put in some extra transfer ports to get a bit more power.  But before I set off down that path, I'll make one to the drawings - just getting something to run will be a milestone.  Regards, Steve

Edwards Flyboy wrote :- "or make your own built up version"   A couple of questions about this option :- (a) What would the right size spars, LE and TE sections  be? (b) rib spacing and balsa thickness? (c) I'm assuming it would be sheeted front 'D' section with full depth inter-spar webbing and that would be 1/16th sheet balsa   Suggestions welcome on what would produce a design of  adequate strength.   Regards,   Steve

Michael, I can recommend the Tutor 40 with an OS46LA motor up front. I used that combination to learn to fly and do some basic aerobatics.  Good luck, Steve

Spanner, my choice would be a Chipmunk, take a look at stand-off scale version on the Galaxy Models (Ipswich) site.  Steve  (I've got no connection with Galaxy)

Geoff,  there's a big club in Long Eaton (half-way between Derby and Nottingham). Flying is 7 days a week (the weather is a different problem!).   www.lemac.org   

It was the rigidity the APC props and their very sharp edges that persuaded me to use a chicken stick when starting the LA46. It can be started easily by flicking the prop by hand (in fact the engine is a real pussycat) but I convinced myself that the prop was very unforgiving of a mistake - hence the high tech 9 inches of broom handle. Steve

Eric, everytime I've seen someone start a rotary (at Old Warden) the engine prime is done by the mechanic by squirting petrol into the exhaust ports as they open up when the engine is being turned over by hand. I think you will find the air pressure pump is a common feature on most aeroplanes of WW1 vintage. Ernie The Cross and Cockade I mentioned has a few photos of the Science Museum example but it looks like it's been gutted of instruments at some point in the past. Steve 

I got on a lot better with my LA46 when I stopped having the 'help of the club expert' to start it!  I had a few diesel engines as a kid (c/l and FF), then a 40 year gap, before taking up RC.  The LA46 always starts within a couple of flicks of a chicken stick provided I get the priming right and the glow-stick is fully charged.  The most common fault I see at the field is people turning over a completely flooded engine with an electric starter hoping it will start - it usually ends with the engine locking up because of too much fuel in the cylinder (which can't be doing the con-rod any good at all) And because it didn't start the solution is even more priming before applying the starter again..... Steve

Gary, Thanks for your quick reply and interesting comments re full-size and model Tigers. I've only managed to have one Tiger flight - that came as a complete surprise and was due to winning a raffle at Shuttleworth's several years ago. Best memory from the flight was turning at Cardington and seeing the airship sheds below. I'll be making a DB Tiger Moth over the winter (1/6th size) so it will be interesting to see how it goes together and flies. Steve 

The Tiger Moth introduced the staggered wing and change of rigging geometry as a result of the RAF's requirement that the front seat occupant can bail out as easily as the rear. The staggered wing allowed the centre-section wing struts to be moved ahead of the front cockpit. Both the lift and landing wires run to the forward spar position (at the fuselage) so as not to be in the way of the bale-out.   I'd be interested to hear Gary's thoughts of the difference/similarities of flying full size and large, quarter scale model Tigers.  Steve 

Ernie, Good pics of Eindecker cockpits are rare. The best I've seen are in Windsock Datafile 15. Fuel gauge is halfway recessed into the top decking behind the engine with an streamline aluminium shield over the front. The compass is usually recessed into  the top starboard wing, between first and second rib, just in front of the cockpit opening. What looks to be the dashboard is the rear of the aluminium box for collecting spent cartridges - it has a large, hinged, pull-down flap in it. To the left of this box there is, bolted to a fuselage upright, top : the ignition switch  middle : rev counter, probably the most important instrument in a WW1 fighter because if you over-revved the engine the interrupter gear lost synchronisation and you shot your own propellor off - not recommended! lower :  the carburetter control On the right-hand-side of the cartridge box was the distribution panel, fixed to an upright, with one lever for selecting fuel tank and another for selecting the source of fuel tank air pressure (hand pump for starting and switch to engine driven pump once the engine is going?).  Above these on this panel is an oil pulseometer indicating oil flow.  A couple of instruments are also seen either on or beside this panel (air and oil pressure?) Below the panel is a brass syringe plunger type air pump (used to pressurise the fuel tank at engine start). Hope this helps, Steve. See also :- Flying Scale Models - Sept 2003 and   Cross & Cockade  Vol 12, No 1  (1981) 

Thanks for the replies. I fly mode 2 (aileron and elevator on the RH stick) but without a neck-strap or tray so my thumbs are on top of the stick (fingers around both sides of the tranny).   I'm  aiming for about 4 seconds per roll ie the whole manoeuvre lasts for 8 seconds.  My set-up is about 35% expo on elevator and aileron and I don't use dual rates.  Reading Garry's post makes me reaslise that I could set up the aileron rate switch so that full deflection of the stick gives me the required roll rate leaving me just the elevator movement to concentrate on. That might work because it is  moving  the elevator while trying to hold the aileron input fixed (with the stick in some indeterminate position) that I find so difficult.  I will give it a go when I'm next down the field - that might be a while off because it's more like a pond at the mo! Thanks, Steve 

Can I re-open this thread and ask "how fast should the model be rolling for the B test rolls? or, to put it another way, how long should it take for the model to do the 2 rolls?"   I'm also having problems with the consequetive rolls, I'm ok doing a single roll but lose the coordination on the second.  Either the roll rate speeds up or the model (SpeedAir) starts to corkscrew.   To standardise things I've decided to roll to the left when flying right to left, and to roll to the right when flying left to right (ie. I always see the top of the model first).  Any help or tips on how to better control my thumbs on the sticks gratefully received.  Or do I need a different  model that wants to roll more axially in the first place! Steve 

Hi, the instructions for the Tutor  40 says :- Ailerons 6mm up and down Elevator 10 mm up and down Rudder 15 mm left and right (all measured at the rear of the control surface). Centre of Gravity = 85 mm behind the leading edge of the wing. Have fun, it's a great model to learn on. Steve 

Eric, I don't know what a NO MORE is,  but David must be keen on it if he's given it three votes already. However I'd like to see a .......

Thanks for your help everyone.  A new servo went in tonight and the set-up seems much better. The new servo was another  S148 that  I had spare and I will monitor how it lasts.  I will be investing in some HS-325's when I attend one of the big shows in the near future.  Thanks again for your advice, Steve (who is hoping the weather forecasters have got it completely wrong for the bank holiday!).