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