Here is a list of all the postings John Laird has made in our forums. Click on a thread name to jump to the thread.
|Thread: Slicker 50|
how did your model actually fly - did you have the stalling problem??
dont throw model out just yet - at least not the wings.
Assuming you have had the same wind as us down in the south - too bl.... much....
have you tried flying model early morning or evening when wind is less and with just enough power to climb slowly.. that might let you get a feel for the model and how sensitive the elevator is with the rear cg.
my mallard flew very nicely in low wind conditions once trimmed out and left to fly freeflight in a circle to minimize getting into the unstable stall.
its all a challenge
john ( just back from tenerife where the sun shone but the north easterly brought a very cold wind down from the mountain)
I didn't want to put anyone off - just to warn them. See how your slicker goes and if it behaves like my mallard, try building a small lighter t'plane that will shift the cg forward
dihedral is usually taken as across the wings ( I forget the proper name ) whereas longitudinal dihedral involves wing incidence vs tailplane incidencewith +ve usually the case for stability- ie reduced stalling habits with self correcting built in
from your question, I take it that, in your first post you meant longitudinal dihedral - if so then I believe it should be increased if you shift the CG forward by much.
The competition boys can probably give better advice from their experience but my reading of the pylon,rearward CG and large tailplane design was to obtain maximum lift from all surfaces to extend the glide ( to win competitions ) by rear cg and large lifting t/plane while balancing the glide characteristics with the screaming 10 sec vertical climb for height. The need to keep the t/plane lifting would result in reduced longitudinal dihedral between the wing and the t/plane but this would give reduced stability and if model starts stalling , the stall would get worse. This was resolved by fairly large polyhedral ( across the wing ) and trimming for a fairly tight turn as the model peeled off the climb into glider mode, which also has the effect of keeping the model in thermals ( or downdrafts -which ever they hit - which is why you see comp boys watching their thermal indicators getting ready to launch into lift )
The above is what I learned from flying my RC mallard - any attempt to fly straight needed kid gloves on the elevator to keep speed just right - difficult as not only is the model moving but the air is as well. One of my best flights was during a very calm day ( a rare event ) when i just let the model fly in circles with just the slightest of touch on rudder to keep overhead.
Of course my mallard experience may just be down to my flying ability plus my accuracy of build vs the model design
Edited By John Laird on 10/02/2012 20:19:40
I built a Mercury Mallard - ie a competition model similar to the slicker .
It had a rearward CG to give reduced wingloading with the tailplane adding to the lift and improve glider performance.
The design is based on a short highpowered straight up flight for height and then turns into a glider with a fairly tight turn to keep the model in thermals if it hits one.
My mallard did all that OK but of course it drifted downwind, whereupon I applied RC to straighten flight and bring it back upwind. Now the rear CG comes in to play and the model goes into very bad stalling only cured by application of massive down and loss of height.
From this I learned that for reasonably stable RC, I needed to bring CG forward from the 85% rear position and this was only achievable by extending the nose substantially and also reducing tailplane size,
Re dihedral - i think the model will need it all if you stick with the current design.
Of course - it may just have been me and not the model ???
|Thread: Hand launching heavy models|
Martin is dead on on this - I have seen most people run to launch their model and actually stop before they throw
|Thread: RCM&E index|
Allan's concept is definitely a must in this age of communication and internet.
it then becomes an ongoing database which should easily be kept bang up to date each month - or is this too much to ask for ?
it will save me time scanning and computer filing the odd items I might need in the future but never seems to cover the actual items I end up needing
so save the money from compiling a yearly index and go for an online database instead, please
thanks for the comments on the eaglet - it can be seen flying here http://www.youtube.com/watch?v=vP9-A6T6p8E&feature=mfu_in_order&list=UL
You can also see me having a break sitting in the tailend of my car with the Eaglet,Southerner and Majestic Major in front. On Miks videos listed at the utube's website, there are also videos of the southerner and majestic major with mood music to match.
I have a small stock of modelspan (?) light and heavy weight tissue accumulated a long time ago and used sparingly to eke it out.
John Hook at http://www.flitehook.net stocks tissue which I would think is OK as he supplies to the vintage/freeflight fraternity. There is also another supplier for the same group but I dont recall the name as I get most of my "old" model supplies from John who flies at the same field as I do. Try a google on freeflight and see what comes up.
The purple tissue trim on the mamselle was wrapping tissue - it was the right colour but absolutely horrible to put on as the dope did not soak in to the tissue - I had to dope the main surface first and lay the tissue on then dope over to seal and even then it still peels off.
The Mercury Mallard goes back a long way - not too successful for RC as it is designed for contest and at end of power climb would transfer into fairly tight circle ( to keep in thermals ) and that was OK but any attempt to fly straight into wind to keep it overhead immediately translated into severe stalling. CG was about 85% back from L/edge as designed. Plans can be got from Colin Smith ( Phil's son ) who will scale up/down as req'd ( mines was 150% of original.) Out of date list of plans here with Colin's email address http://www.rcgroups.com/forums/showthread.php?t=229423&page=3.
The original 48" span Mallard was designed for 1.8 to 2.9 ccs with the 2.49 elfin quoted - so you can see it was contest powered for its size.
The rudderbug was ( note past tense really nice to fly. Its on my todo list as well as i still have the flying surfaces - just need a fus -
Edited By John Laird on 28/01/2012 21:31:18
I forgor to insert the motor mount picture of the Eaglet - so here it is now
|Thread: Covering prices|
I agree with Alan. While solartex is probably the best material to work with for the larger model, it is heavy and very expensive. I have gone to doped polyester dress lining which at about £2 per running metre and 40 or 60" wide as both inexpensive, strong and a shade ighter than solartex. Moreover, there are plenty of colours and patterns to choose from - altho you might get some funny looks being the only bloke amongst females in the dress shop - on the orther hand you never know your luck
Dope and thinners from the likes of flitehook are not too expensive.
The dress lining is put on as tight as possible as there is only a little heat shrink left in it. Stuck on with balsaloc,you can pull it tight with heat on the balsaloc allowing you to pull tight. 2 to 3 coats of 40/60 shrinking dope/thinners gets the material drum tight. Any slackness will pull to one corner, so dope towards a corner which will not be too visible. Use the solarfilm iron to shrink any wrinkles that might develope if material not tight enough to start with. Beware too much heat will take the colour out of the material.
See my albums for examples. The wing pics in the Mamselle album is lilac colored with purple tissue trim - as befits a lady. No wrinkles and gives a nice drumming for those wanting to practise their drum rolls.
The 72" southerner has been covered in dress lining which had a sheen on it , the yellow staying quite strong with just enough translucency (?) to show up the framework as befits vintage models.
The round fuselage was covered with just 2 pieces of material applied from 1/4" top spine to bottom spine. The orange tissue trim hides the material join nicely. Limited longeron area to balsaloc the material to reduced the ability to pull material really tight. 3 coats of 60/40 dope/thinners applied lengthways from top to bottom left one wrinkle on one side at the bottom, most of which came out with heat.
I almost forgot, doped finish is fine with electric models, for glow engines, fuelproofing is needed
Steve is bang on in adding " lightness" - I saved 2 ozs in 20 ozs by changing motor and ESC to lighter less powerful ones after I maidened the scaled up Eaglet (48") and decided it was a bit heavy and didnt need all the power. Fortunately I had anticipated this and made provision for changing out the motor - see pic which actually shows the initial motor and esc, both of which have been changed to less powerful/weighty versions. You can also see slot to slide in the motor mount.
|Thread: Vintage Roll Call for Greenacres|
Thanks for info Andy,
John Hook flies at our local field at Beaulieu
you must have a ben buckle kit speccing 3" wheels - I have an original Mercury Matador plan and it specifies 2" wheels.
have you tried white polyspan with thin dope and tissue trim - strong and light. see pics of my Eaglet in my photo album for an example
|Thread: Vintage aero-tow combo.|
Colin Smith is carrying on Phil's plan service and Mercury plans were listed among them. They also included formers and rib patterns where these were not on original plan.
He will also scale up and down if req'd.
Colin has an email address but I cannot pin it down so here is his mobile - evenings only - 07747722724.
Edited By John Laird on 07/01/2012 11:11:27
|Thread: Carbon rod problems?|
. I use slightly epoxied bent threaded control rods pushed inside small dia tube rather than rod - just as stiff and strong , and then when epoxy cured I use thin CA on end of rods to avoid splitting. the ca soaks into the fibres and glues them together
not sure how BB got 3" wheels,but my original Mercury matador plan definitely states 2" and as you observed , 3" looks too big.
How BB can recommend solartex for a 47" span model beats me. No wonder thier weight is 2.4lbs which on the matador wing area is about 16oz/sq ft - a wing loading more suited to a larger bulk standard trainer rather than a vintage model.
I try for about 10/12 oz /ft loading max to keep flight speed down - light wt X low speed equates to low inertia and as we all know its the inertia that does the damage when the model stops on a sudden arrival
3" wheels are too big unless you are using whats in your spares box.
The Mercury plan specified 2" wheels and I would suggest the very light foam wheels - save weight and just as effective.
I am flying an 18oz Keil kraft eaglet scaled up to 48" on a 100 watt low kva motor with 2s 1000 lipo and have never flown it long enough to run out of power. The Eaglet is covered in doped polyspan which is a trifle heavier than litespan which is the way to go with yours
If your motor is low kva - less than 1500 - then you can go for a 2 cell battery with a bigger prop and squeeze the battery in behind the motor to get cg right and the weight down
photos of the Eaglet are in my album and it can be seen flying here http://www.youtube.com/watch?v=vP9-A6T6p8E&feature=mfu_in_order&list=UL
the matador was one of my earlier builds as a teenager and I had no problems with it - just do everything you can to keep weight down and it will then fly slow and graceful as vintage should
Edited By John Laird on 02/01/2012 21:18:40
Edited By John Laird on 02/01/2012 21:19:12
nice piece of stitching. I find that I needed to go straight across at the top before starting down diagonally and then again at the bottom. This stops any up and down slop movement of the control surface, even if the stitching is tight with no sideways slop. I just use dope or tiny amts of cyano to seal and weather/fuelproof the thread and points of entry into the balsa. waggle the surface as the dope/cyano dries.
Steve is right with the "placing" - I launch my free flight mamselle with just a gentle throw at head height - lovely to see it pull away then under its own steam. Too fierce a throw can also momentarily starve the engine of fuel and cause it to stop.
butyrate dope does not shrink much. Nitrate dope both shrinks and fuel proofs against diesel duel - not glo fuel.
Edited By John Laird on 01/12/2011 09:05:21
|Thread: Vintage Roll Call for Greenacres|
present and correct - but waiting till next year to start
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