Mike Chantler

Depends on how 'rough' it is. Main thing is to check that there are no ocaisional rocks, fence posts etc. It's surprising how often the odd one jumps up and hits the nose of a belly landing 🙂

Used tapped hardwood + 4mm bolt 4mm CF tube stopped the drill from wandering. Epoxy in base of fin was laziness - should of used CF sheet or ply which would of been just as quick and lighter!

So as a first step in 'streamlining' I decided to add airfoil NACA 9% fin. I'd dithered about this because I could not think of a simple, strong way of attaching the airfoil section to the 4mm slot for the old tail. It then occurred to me that I could simply alter the 3D model to accept the new shape, duh! So cut foam and laminated in 0.5 mm veneer. Could not be bothered with bagging so used 20kg weights - much less than equivalent of bagging and mostly successful (a little bit of lifting on LE). Added unidirectional carbon across veneer grain for TE - seems to work really well 🙂 White glue for top and LE balsa (gripped enough to sand a couple of hrs later - so may use this rather than contact in future 🙂 ) Used 6.5g epoxy mix and weight ended up same as correx fin 🙂

Interesting article @https://www.mh-aerotools.de/airfoils/linkage.htm on wind tunnel tests of linkages. suggests that it's always best to shroud them

Flew well today 😊 but the correx tail nearly came off each time I landed, and then I noticed on one launch that only the front of the fin was secured 🤫 Hence bit of yellow tape. Flying slightly nose heavy as intended for peace of mind on maiden. Seems very smooth 🙂 Will try and add a bit of stream lining over the next few weeks and see if I notice any difference 🙂

Thanks Konrad, think I'll experiment with a tape style cover for the gap and moulding some small linkage covers - I seem to remember seeing an analysis somewhere that even larger exit shrouds provide less drag than exposed linkages. I'll have a look at Martin Hepperle's pages again and do a bit more research to see if I can understand them more (!) Your point about stiffness is not one I had considered: caused me to look at the correx fin - it has already warped a bit and will likely cause increased drag from both fin and a skidding fuselage. A friend also thought that flat plate tails can accentuate the tail jitter that you sometimes get on planks. This thread also made me think what I wanted out of this model: which is I'd like better energy retention, so that in towards marginal conditions, it will still perform aerobatic manoeuvres. I'm not so bothered about weight per se. Of course someone might rightly point out that if I wanted energy retention I should fly mouldies, I have a number hiding in my garage, but I'm an indifferent pilot and their speed and relative fragility tend to make me a nervous!

Really interesting series of posts - very enlightening, especially stuff on non-linear relationships - much appreciated 👍as I have been pondering adding more streamlining and realised I don't have a clue as to what may be beneficial in the weight/streamlining trade-off 🤔 So being very selfish I'd like to know what folk think about four options on a recently completed build. Options are: 1. exit linkage shrouds or covering up as much of the exit holes as possible: 2. Putting some sort of wiper over the 4mm top elevon gap (they are bottom hinged and just about full length) 3. Covering the veneered wings completely vinyl or similar (currently have 3 coats of water-based acrylic). 4. changing the fin to an aerofoil (say 10% symmetric section) For context it's a 60" 8.9% PW51 airfoil plank. Weight is currently a little over 1000g, ballast can add up to 750g, and i'm expecting to fly it in 15-40mpm winds up the hill, normally on a little over half ballast. The airfoil section is pretty accurate except the TE does not go below 1mm thickness at the end for ding protection. @Konrad I hope you don't feel i have hijacked your thread with such specific requests, but any pointers, suggestions would be very much appreciated. Mike

Balanced and empty, it came out at 1045g. That's 75g lighter than the glass wing and circa 175g heavier than the lam wing. However, it feels much stiffer than both and much more ding resistant. It still needs vinyl decoration so I can see which way up it is! But the main differences are that the ailerons are 25% larger than the previous version and are much closer to the PW51 section. So, needs decoration and rates sorted but then should be ready for an outing on Sunday.

I use plasterboard on top of a heavy steel framed table, even so I have noticed that the table has bowed ever so slightly when I stick a meter rule on top. I slide sheets of a5 or a4 paper under the gap one at a time then transfer to under the middle of the plasterboard. This may seem a bit extreme, but ccaisonally I use it to bag foam veneered wings with live hinges (even slight bowing gives ailerons that behave very oddly). The plasterboard never lasts more than one build but it's cheap 😀 I like the sound of the Sundeala though, never tried that. 👍

Drilled and tapped bolt holes - epoxy/hardwood worked well - very easy compared to Mk4 mess. No idea why I used different sized bolts, from a crash I know that a 4mm bolt at the front would be fine! Hot-melted aileron sub edges Servo mounts and cables in 🙂 And added 25gsm glass over tips to help their ding resistance 🙂 Getting near finished 🙂 🙂 🙂

Just started on under/over linkages Servo frames were too good a fit(!!) and would not release servos once they were in the wing so had to dremel a bit of clearance. Carbon tops and bottoms add 2 x 0.3 mm so had to adjust height. And put lead exit hole in wrong place initially! But mega-chuffed with the way they have worked out 🙂😁

Added 1oz aramid wing bandage as there is very little room for anything thicker, we'll see if this is strong enough when it flies! Started scary part: cutting/hinging the ailerons, followed Speedsterden vid on RCgroups ArtHobby thread this time. Liked the clearance the hacksaw gave at the ends but they needed tidying up a bit (tape does help stop the tear-out). Cutting from the non-hinge side first definitely made aligning hinge and top-cuts easier 🙂 And I really liked the idea of using a blade with the tip ground off to stop it damaging the thin aramid hinge. 🙂

Used 3 coats Hycote spray lacquer on aileron areas, predicably this stuff destroyed test foam when sprayed really close, but did not get though veneer when sprayed 2 passes x3 @ 8". However, it did not prevent brush-on water-based acrylic curling test piece(maybe didn't leave spray to dry long enough). Used the brush-on stuff for the rest of the wing as I got really bored/frustrated using the spray.🙄 For the first time I used gradually increasing grits as all the videos tell you too - made the process real quick - duh, should of been doing this years ago 🤔🙂

I agree, por is a contact adhesive, works well if used as thin film on foam and allow to dry. If it's thick it takes longer to dry and is 'elastic' making it difficult to sand.

Slow progress as have been faffing around a bit. Getting near to varnishing stage, so as the ailerons are pretty thin I've been looking at the effect of varnishes on veneer: Water-based varnish definitely makes it curl! 😮I may well use a solvent based varnish on the wings - but will need to watch I don't melt the foam! I also experimented with shaping hardwood to fit the void above and below the front biscuit, decided this was a bad idea as no matter how careful I tended to distort the unsupported skins a wee bit, so filled them with 20 min epoxy instead (potentially very messy even if you use using syringes etc.) The thing I really didn't like was that even the epoxy tended to distort the skins a little (1/2 mm or so) - not a big deal until you come to join the wings and you are using the edges of root sections as the datum 😞 I did have the beds but like to use the root sections to double check by running a finger across the seam. Nearly forgot the dihedral brace as I was putting it all together! We'll see if the wings each now have the same AOA on its maiden!

Yes - thinking that solvent-based might be better, so tried an experiment, used acrylic varnish on .5mm on flat veneer with no backing just to see what happens: quite dramatic no matter how lightly applied! I guess it's because it's water-based rather than because it's acrylic. Also tried some Hycote clear gloss spray acrylic - as this was the only solvent-based stuff I had to hand - veneer remained flat 🙂 It does say it's meant as a top coat however. Tested on bit of foam and foam seems ok 🙂 Looked at cans (not sprays) of solvent based varnish - but all seem to be aimed at floors etc. and will be too thick I think. Now testing on an old duff foam veneered wing

Thanks, I have noticed it occaisonly on ArtHobby and similar gliders with foam veneered wings. I'll experiment. It's maybe more likely to happen with thin wing gliders I guess. I'll experiment 😀

A bugbear of mine is finishing the model - it's all straight and lovely - then varnishing it or covering it - and the ailerons develop little warps! Most of my planes have balsa ones or cut out from foam veneered wings. I generally finish them with 3 coats of WBP. I did think about spraying with hair spray first to try and stop the WBP soaking into the veneer too much! I do each side at the same time and try to make the first coat light - but any other ideas? Is the hair spray crazy? !!

Aye, good point, got lazy so in places they fit into the foam at the moment. I'll clear a bit out more foam round the bolts and inject in some micro-ballon/epoxy mix in-between the biscuits and the lower skins where needed. The rear mount is pretty tight round the bolt location so won't need much if any epoxy. The front mount will definitely need some below the biscuit on one side (as I only plan to use one bolt at the front). We'll see if this is easier than making the biscuits the 'proper' shape 🙂 The wing is mid-mounted which means that the bolts are really only needed to stop the rear fus section moving away from front fus section, or sliding off to either side; the fus does not need to be squeezed against the wing as tends to happen in a high-wing (or low wing) glider. Also, the large carbon tube down the length of the underside of the fus, keeps all the components in line and the large overlap between front and rear wing sections means that they only need held together (hence the bolts at both ends). The other function of the front biscuit is to reinforce the LE and so it will be well epoxied to it. We'll see how it goes with the biscuits glued into one wing - then I'll think more about which bits need to be reinforced 😮 yup - being a bit lazy in my design thinking, but it'll be all right on the night 🤞 😮 🙂 And thanks for looking out for me and posting your comment 👍

Previously I've cut chunks out of the wing and then replaced with solid balsa, this time I'm trying biscuits 🙂

Balsa tips on, resisted temptation to shape and make them dingable. Used fus to mark out positions of wing bolts: Seemed easy 🙂 hmmm...

lol, that did make me laugh, and I see what you mean 😂

Just started to print a couple of fuselage sections when I found i had already printed them : senior moment or what 🤒 Cut out recesses in rear of wings for fuselage and shaped LEs enough to test fit: Phew - looks fine 🙂 (setting the right kerf on the hotwire program can be a bit hit and miss) Added 3mm liteply sub-tips (with the contact adhesive again as this worked well on the LE strips). Hoping this will stop LE being staved in at the tips on fast landings, and protect the ends of the elevons a bit. Cut and laminated some balsa for the tips - first bit of balsa on the plane 😮 Last time I remember I should of added tip gussets - hmmm...

TE cut with side dremel + 1" L section alu guide -- worked really well 🙂 LE and tips sanded square -- 1m 180 grit sanding bar worked well 🙂 (thought it might be too rough) 3mm cedar (or similar?) LEs glued with foam sort-of contact adhesive (could not remember what I usually use for this! - think I have tried white glue (does it stick?), 5min epoxy (pain to sand), gorilla glue (messy as expands everywhere 😞 and this contact stuff which being a contact adhesive will not fill voids) - so fingers crossed! Noticed that right wing veneer lifting slightly at LE, but taking the chance that the 3mm LE will keep it all together 🤞🤞 Well taped!! Now the hard part - resisting temptation of removing the tape to see if the glue has stuck yet 😳 We'll see if my run of luck continues 🤞🤞🤞 Sunday weather looks good for a fly of existing versions with the Pentlands club 😊

Busy at work - so only had one day building. Bagging had worked ok but for some curl on the TE, and top skin slipping back a little at LE. Forgot carbon reinforcement over wing brace - grrr! Should be strong enough without 🙄 Started under/over servo housings. Miss-placed template for servo linkage channel slightly, as lined up on veneer rather than core - sand root square first next time to provide correct datum! Promised myself last time that I would 3D print servo boxes (making them both took a good afternoon+ I think). Designing took 1/2 day 🙂 Starting to square sand tips, LE and trimming extra 5mm off TE. Next time I should look at extending the TE as one veneer shifted and others did not glue as well at LEs as I would like. Getting there though 🙂