Adrian Day Posted January 18, 2013 Share Posted January 18, 2013 speechless build following this one for sure .. fantastic build and workmanship Quote Link to comment Share on other sites More sharing options...
Phil Cooke Posted January 20, 2013 Author Share Posted January 20, 2013 Not a lot to show thats new from this weekends work as I'd already posted a 'dry fit' joiner shot, but I have now completed the joining of the inner and outer wing panels for both wings at the required dihedral angle. I still have a bit of sanding to do to get the joiners and excess glue back down to the aerofoil profile, and the second panel is still slowly hardening in the relatively cold conditions of my workshop, so willl post with more once thats all done. Time for a beer... Quote Link to comment Share on other sites More sharing options...
Phil Cooke Posted January 22, 2013 Author Share Posted January 22, 2013 With both wings joined and with all the glue fully cured despite the cold, I've spent the past couple of evenings sanding the ply joiners back flush with the wings, filling a few minor gaps here and there and resanding. The wings have come out with a very solid feel about them, although the weight increase has startled me a little. So for the first time we were able to bench fit the two wings together to get a feel for the span... Each wing has been designed to slide mount onto a 25mm sq steel joiner which will be mounted in a ply box set in the fuselage... ...and here they are, 100" span at the moment, still awaiting the curvy tips which will form the final 110" span. Too big to turn around in the garage - so they wont stay like this for too long indoors, but its always good motivation to see these sub assemblies coming together! Edited By Phil Cooke on 22/01/2013 01:24:34 Quote Link to comment Share on other sites More sharing options...
Foamie Dave Posted January 22, 2013 Share Posted January 22, 2013 ooooh its a biggy Quote Link to comment Share on other sites More sharing options...
Phil Cooke Posted January 26, 2013 Author Share Posted January 26, 2013 A little bit more progress today. In an attempt to improve the look of the outer panel to inner panels fit Ive added some scale surface detail in 1/16" ply along the dihedral joint. These are intended to represent the local stiffening rib and inner/outer flap guide rails as per the full-size. Flying surfaces are dry fitted for the camera. Quote Link to comment Share on other sites More sharing options...
Phil Cooke Posted January 28, 2013 Author Share Posted January 28, 2013 With the main wing panels and flying surfaces essentially complete (bar the curvy tips - which I'm putting off!), I've moved on this weekend to the wheel pods. The A-10 is querky in that it has a semi-recessed main gear which on the model I wanted to have proper rotating wheels, allowing rolling take-offs when we aerotow. The plan shows a built up pod, which I intended to replicate as best as possible, however there were a number of issues in need of change and there was some planning time needed today before we started to make any parts. Firstly, the plan had been drawn for a retracting wheel, whereas mine would be fixed in the 'up' position, so I needed a wheel bearer and support designing. Second, we have significantly changed the wing aerofoil section for PSS, removing all the under camber as per the original, and the wing incidence has been altered significantly too (Ill set the glider wing at ZERO degrees to the fuselage datum) I took a paper profile of my inner wing section (above) and marked up the LE and TE datums, this was positioned on the plan at the required zero degrees incidence and once fixed I ran around the edges of this paper overlay with a red highlighter (below) This produced the visual orientation needed to start some replanning. You can see the gross difference in wing section on both the upper and lower surfaces. Quote Link to comment Share on other sites More sharing options...
Phil Cooke Posted January 28, 2013 Author Share Posted January 28, 2013 The wheel mount and bearer was considered next, and with the wheel effectively mounted ahead of the wing in the retracted position my concerns lay with landing load dissipation into the wing assembly. I sketched up a box type wheel mount which would be formed from 2 sheets of 3mm fibre glass, hardmounted onto a ply load spreader and recessed into the wing at the front and rear of the inner panel. The photo above shows the bearer profile, the 'lugs' at the front and back will be set into the wing and spaced with 1/4" ply. The bearers can be seen in position (below) the profile denoted by the red line with black triangles. Effectively, the balsa and ply pod would be built almost cosmetically around this structural fibreglass box mount. Quote Link to comment Share on other sites More sharing options...
Phil Cooke Posted January 28, 2013 Author Share Posted January 28, 2013 I needed to go out and buy the 3mm fibre glass board for the wheel box so, happy with the design concept I moved on to the pod itself. The formers as shown on the plan needed a little repositioning and sizing to accomodate the changes I'd made, once redrawn these profiles were transferred to 1/8th ply using the pin 'pricking-out' method. ..."To the Jigsaw!!!"... A little later after a good session on the jigsaw we had a matching set of 1/8th ply formers. These still need cutting out centrally for the wheel and mount box, plus further weight reduction, but this will be done once the wheel box is made up. I've just placed an order for the fibre glass board tonight, so hopefully that will be sent out tomorrow and work can continue on this shortly... Quote Link to comment Share on other sites More sharing options...
Phil Cooke Posted February 4, 2013 Author Share Posted February 4, 2013 I spent a disproportionate amount of time this afternoon on the wheel bearers. I'd bought a couple of sheets of 3mm Fibreglass board to make these from, I wanted them to be nice and rigid... what I didn't buy was the diamond tipped cutting equipment needed to work this stuff - so it was slow going! My bench mounted jigsaw couldn't cope with it, the blades cut a few inches then they wore smooth leading to burning as opposed to cutting... hacksaws worked ok but the length of the bearers meant there was significant 'unreachable' material... the Dremel came to the rescue but it meant careful cutting with a little 1" cutting disc and then hand filing the 4 pieces clamped together to make them all true. Then there was the weight reduction holes... these were pilot drilled out around the inner of each circle leaving just a little material to dress up to the line. Another long winded process. To add to the lengthy sessions torture there was the dust. I was equipped with face mask and goggles of course but the glass dust got everywhere...it was so fine it seemed to penetrate all my clothes and would not brush or vacuum off - not a pleasant session!!!! I just hope they do the job! Heres the results... 4-Off wheel bearers, total weight less than 1/2lb for the four... and below, the bearer in postion. Tomorrow I should receive 2 wheel spindles which I've had turned in Stainless by a modelling contact via a friend at work, which will mean I can assemble these wheel 'boxes' and drop them into the wing panels before adding the cosmetic balsa and ply 'cladding' around them. Work continues... Quote Link to comment Share on other sites More sharing options...
John Hickson Posted February 4, 2013 Share Posted February 4, 2013 This is a great build thread! Quote Link to comment Share on other sites More sharing options...
Phil Cooke Posted February 5, 2013 Author Share Posted February 5, 2013 Still kitting parts here before the wheel bearer 'boxes' can be assembled... Yesterday I received in the post a pair of bespoke Stainless Steel spindles, turned beautifully for me from my scruffy sketch by Rob Brown, an ex aero modeller who has now turned his hand to metal work. This is a quick dry fit ahead of the ply spacers being fitted. The spindles are designed to sit the 6" wheels off from the fibre-glass bearers with sufficient spacing and their diameter fitted the wheel hubs perfectly. Many thanks again Rob!! Quote Link to comment Share on other sites More sharing options...
Matt Jones Posted February 5, 2013 Share Posted February 5, 2013 Nice shaft Phil! Quote Link to comment Share on other sites More sharing options...
Phil Cooke Posted February 8, 2013 Author Share Posted February 8, 2013 The wheel pods are fully kitted now with all parts made and dry fit tested... The fibre glass bearers have been fittted with the steel spindles, load spreaders and spacers have been epoxied square, and the wheel hubs have been relieved to clear the bearer doublers. Having ensured we have a left and a right pair we are finally ready for assembly. Quote Link to comment Share on other sites More sharing options...
Phil Cooke Posted February 9, 2013 Author Share Posted February 9, 2013 The wheel bearer 'boxes' have been assembled this evening, a left and right handed pair, with all nuts secured with a blob of epoxy, as once these are built into the wheel pods they will not be accessable again without some surgery. The wheels rotate nicely on the spindles, I've just pinched them up a little against the ply spacer so they wont rotate during flight. Now to position them on the wings and drop them into the inner panels... Edited By Phil Cooke on 09/02/2013 00:47:30 Quote Link to comment Share on other sites More sharing options...
Matt Jones Posted February 9, 2013 Share Posted February 9, 2013 That looks like some nicely engineered building, it's a shame it'll all be hidden. If these support the main weight of the model what does the same job at the back? It's not the fins is it?!?! Quote Link to comment Share on other sites More sharing options...
Phil Cooke Posted February 9, 2013 Author Share Posted February 9, 2013 Thanks Matt - The problem and concern we've identified with this design for PSS with the wheels retracted is that it IS the fin bases that will contact the ground at the rear. The wheels sit slightly forward of the CoG so I think on a good landing on a flat surface the wheels will touch down and then it will roll out and settle onto the fin bases - this is of course why Ive designed and made them to knock off rearward. But in reality we don't land on flat surfaces on the slope, the touchdown will normally be a little nose down meaning the nose and wheels may be in contact as its rolling to rest - but you can see in this view you dont need a huge amount of attitiude change to get the tail to groundout... and if this happens on bumpy tufty slope grass/heather when theres still any significant forward movement then Im relying on the fin base sliding design to stop huge loads being exerted into the tailplane and fuselage. Hopefully this will work and I wont be left with a significant amount of repair after every landing. Quote Link to comment Share on other sites More sharing options...
Phil Cooke Posted February 10, 2013 Author Share Posted February 10, 2013 I've fitted the wheel boxes to the wings tonight... I did think maybe these should be fitted AFTER I've glassed the wings for simplicity during that stage but the need for build progression got the better of me - so they are in as I write now drying with slow set epoxy and micro balloons. First job was to mark up the wheel pod position on each wing then work back to a wheel centreline (the wheel is not designed to sit centrally in the pod to allow for the retract leg and axle.) Once marked up I cut recesses into the foam at the L/E and 3/4 T/E positions where the wheel box ply load spreaders would be counter sunk and eventually potted in epoxy. The photos show a 'dry fitted' wheel box assembly, I put the camera away before I mixed any epoxy! All that remains now is to fit the pre cut formers around this wheel box and build up the scale external shape (to the black lines marked on the wing) around the wheels in balsa sheet and block. Quote Link to comment Share on other sites More sharing options...
Truls Loever-Arnesen Posted February 10, 2013 Share Posted February 10, 2013 Impressive build! I planning an A-10 in 1:10 scale for next winter now and I'm in the engineering fase using Solidworks for the stuctural elements. I want to build a model as scale as possible. Do you have any reliable source for the aerodynamics and geometry/settings of the airfoils for the full scale A-10? I have sone reports stating -1% incidence of the NACA 6716 and 6713 profiles, though others state a positive incidence, and a unspecified downward thust of the turbines. Do you have any sources or tips for where to order good blueprints? I'm looking forward to seeing more impressive engineering from your project! Quote Link to comment Share on other sites More sharing options...
Phil Cooke Posted February 11, 2013 Author Share Posted February 11, 2013 Thanks for your comments Truls. I don't have access to details of the full-size design other than a decent 3-view drawing I have here from a Military Aircraft Journal, there is one view of the fuselage sectioned with the wing and tail removed at their root and (assuming this is true to scale) you can see the incidence setting for each. Ill scan this and add it here for reference. I have no reference to the aerofoil section names/numbers, thats all beyond my level of scale modelling!! As for the ducted fan model plans I'm basing my PSS A-10 build on, the wing appears to be set with effectively a zero incidence, the tail is approx 3 degrees negative and there is a significant downthrust component to the thrust line. I have changed this on the PSS variant as explained above, also my wing section is far from true scale as the amount of undercamber was not suited to what we need on the slope. Hope this helps, good luck with your A-10! Quote Link to comment Share on other sites More sharing options...
Phil Cooke Posted February 12, 2013 Author Share Posted February 12, 2013 View of the 2 wheel box assemblies glued into the wing panels before they are shrouded for life by a balsa and light ply pod. Bringing the 2 halves together on the wing joiner like this allows a visual comparison and check of alignment between the two wheels. Quote Link to comment Share on other sites More sharing options...
Martian Posted February 13, 2013 Share Posted February 13, 2013 Phil I've been totally enthralled by your build blog and inovative methods my whole morning has been spent reading all the way through,superb work I look forward to reading more Martin Quote Link to comment Share on other sites More sharing options...
A10FLYR Posted February 14, 2013 Share Posted February 14, 2013 Watching with great interest. Looks good I might add. Quote Link to comment Share on other sites More sharing options...
Phil Cooke Posted February 16, 2013 Author Share Posted February 16, 2013 Thanks for the comments Gents. Honoured to have you on board A10FLYR - Welcome to the RCM&E forum! A little bit more progress on the wheel pods - before the planking can be added the light ply formers were weight reduced a little more then positioned onto the main body of each wheel box assembly. Quote Link to comment Share on other sites More sharing options...
Phil Cooke Posted February 17, 2013 Author Share Posted February 17, 2013 Now to position the former ahead of the wheel, onto which the wheel pods balsa 'nose cone' would be attached. A bit tricky this as I found myself working in open 3-D-space away from the building board. Doing one was easy enough, the trick was to make a matching pair! A cantilevered nose guide piece was formed from a pair of 1/8th light ply formers, and with hardwood stringers accurately fitted in slots to the main body formers, a 3-point location was achieved for the former just ahead of the wheel. Everything was measured and checked for square before I whipped round with the thin cyano to freeze everything in position. Epoxy was later used to reinforce the joints. The wheel pods are finally ready for sheeting using 1/8th balsa - more planking! Quote Link to comment Share on other sites More sharing options...
Phil Cooke Posted February 17, 2013 Author Share Posted February 17, 2013 Weather was nice this afternoon so I took the opportunity to rig the wings and sit them on the wheels properly for the first time, checking alignment of the 2 wheel pods before they are sheeted and any opportunity to make any adjustments is lost. I also made up the 2 nose blocks from laminated sheets of 3/4" soft balsa, glued (and currently setting) with aliphatic resin. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.