Flying Squirrel Posted January 30, 2023 Author Share Posted January 30, 2023 Thanks KC, I'll se if I can get some pictures up tonight as that would be easier than explaining, would also provide a chance for advice on what else I have done... Quote Link to comment Share on other sites More sharing options...
kc Posted January 30, 2023 Share Posted January 30, 2023 Compare any photos Phil Kent put in the article with the plan - do the photos show the side sheeting inset between the sq balsa or on the outside? I expect inset. And is it just the parts shown shaded on the plan or the bit above too? Quote Link to comment Share on other sites More sharing options...
Flying Squirrel Posted January 30, 2023 Author Share Posted January 30, 2023 There's very little in the way of photos, even the ones that are in the article are greatly different from the plan. There's also very little in the way of detail in the articles or on the plan. ( Not a critism, just difficult for a novice but then again the plan does say intermediate/advanced!) Oh well, in for a penny in for a pound and with the forums help I WILL get there and I WILL learn! Quote Link to comment Share on other sites More sharing options...
kc Posted January 30, 2023 Share Posted January 30, 2023 Judging by last Wednesday's photo it looks as though you are assembling the frame correctly. I note the scarf joint at the U/C area ( diagonal line ) which seems important. My view now is that the dotted line on F4 is just to denote that F4 is only 1/8 while the balsa frame is 3/16. Therefore the 3/16 balsa sheet sides are inset between the frame 3/16 sq. The infill balsa should be fitted whilst still on the board in my opinion, and it seems to only go where actually shown 'dashed' to save weight. If you have already chopped the longerons off behind F4 it would seem perfectly OK to build the front half first into a three dimensional assembly, then add the rear part afterwards - with just a little brace part at the joint. If you could photograph the fuselage plan it might help the forum members interpret the construction for you. Quote Link to comment Share on other sites More sharing options...
Flying Squirrel Posted January 30, 2023 Author Share Posted January 30, 2023 Thanks KC, yes, I think you are right re the size of F4, It just threw me a bit as the angle on plan view looks 'sharp' as appose to a sweep, I've already bent the upper longerons so will see how they fit tonight and how to 'scarf'? on to the cabin section. I'll try and put a few pictures up and I also have a full scan of the whole plan but don't want to put it up for copyright reasons. Quote Link to comment Share on other sites More sharing options...
Flying Squirrel Posted January 30, 2023 Author Share Posted January 30, 2023 By the way, what a revelation using plaster board is!! Quote Link to comment Share on other sites More sharing options...
Max Z Posted January 30, 2023 Share Posted January 30, 2023 Just to confuse the matter a little more 😁: looking at the full size J3, it seems the lower longeron is not bent or spliced at an angle, but carries on straight up to the strut attachment point. This seems to be common practice for planes with a welded tube frame, where bends and angles are avoided where possible. I believe this is to simplify the stress calculations as much as possible. Wooden stringers are added, sometimes on spacers, to create a smooth and aerodynamic shape. With Phil Kent's reputation as an accurate scale builder I would guess this is replicated in the model. 1 Quote Link to comment Share on other sites More sharing options...
kc Posted January 30, 2023 Share Posted January 30, 2023 (edited) It seems to me that the fuselage sides should be built flat on the board but behind F4 only below the 'waistline' longeron ( waistline longeron being the one below the windows) Then assembled with formers to F4 only but not aft of F4. Then when glue is fully dried the tail parts are pulled in and the upper formers installed. Only at that stage are the top longerons fitted. Therefore no longerons are bent at inital stage. Just my view but fairly common way to build. There are several splices shown for longerons which should avoid any bends being used when building flat on board. I noted the splice by U/C, also one aft of door, and one just behind F4 at wing root TE on top longeron. Edited January 30, 2023 by kc Quote Link to comment Share on other sites More sharing options...
Flying Squirrel Posted January 30, 2023 Author Share Posted January 30, 2023 1 hour ago, Max Z said: Just to confuse the matter a little more 😁: looking at the full size J3, it seems the lower longeron is not bent or spliced at an angle, but carries on straight up to the strut attachment point. This seems to be common practice for planes with a welded tube frame, where bends and angles are avoided where possible. I believe this is to simplify the stress calculations as much as possible. Wooden stringers are added, sometimes on spacers, to create a smooth and aerodynamic shape. With Phil Kent's reputation as an accurate scale builder I would guess this is replicated in the model. Oh no, not more confusion!! I think I'm ok there as the lower longeron is straight (up until the point i cust it!) Only the upper ones are bent.. Quote Link to comment Share on other sites More sharing options...
kc Posted January 30, 2023 Share Posted January 30, 2023 Max is right but Philip Kent's plan allows for this. The splice by the u/c and strut mounting seems right. Quote Link to comment Share on other sites More sharing options...
Flying Squirrel Posted January 30, 2023 Author Share Posted January 30, 2023 (edited) How the hell can you work that out from the disjointed snippets i've put together!! Your clearly spot on. Typically, I've done it arse about face.. So, I built the sides on plan but up to the front of the cabin area that appears to me to have 2 x 3/16th 'spars'? , were the front section joins to. (theres slightly more added to the cabin sides than this pictures shows, I've also made the upper and lower door frames from spruce) I then, I guess wrongly, severed this frame at F4 before proceeding to fit the cross members, again wrongly by the sound of it, from the front backwards...ending in trying to join the tail end straight.. Also, there are no formers in the cabin area, F1, F2 and F3 are all forward of the cabin, this is another area that confuses me..there are beech undercarriage mounts across the base of the cabin area which is fine but there is very little detail on what the make up is to the cabin roof that forms the center section of the wings (wings are removable two part) Anyway I'm waffling on, so this is were I'm at... still a head full of questions so many thanks to all for the help!! Please don't be shy, if I've messed up tell me! Edited January 30, 2023 by Flying Squirrel Superfluous images Quote Link to comment Share on other sites More sharing options...
Flying Squirrel Posted January 30, 2023 Author Share Posted January 30, 2023 22 minutes ago, kc said: Max is right but Philip Kent's plan allows for this. The splice by the u/c and strut mounting seems right. Said splice, hopefully at least one bit that's right! (it looks like a vertical joint in the picture but that's just a mark!) Quote Link to comment Share on other sites More sharing options...
kc Posted January 30, 2023 Share Posted January 30, 2023 Without seeing all the plan it's difficult but I reckon the fuselage front tapers in at the point where the two 3/16 uprights join. The strength of the fus depends on the engine bearers and a dry assembly of this should be done to see how it all fits. Work out the engine installation at an early stage (mounting holes, throttle, fuel pipes etc. ) If you have plans to use a cast or plastic engine mount then this needs a lot more thought as beech engine bearers are probably integral to the design. The wing joiners ( piano wire I guess ) take lots of the loads and transfer into the fuselage sides via the extra 3/16 ribs outside the fuselage ( again a guess) Maybe there is a ply rib there too. Probably also a cross member alongside the wire? Also the 1/8 aluminium tube may be structural as well as scale like feature.( check the plan ) Quote Link to comment Share on other sites More sharing options...
Flying Squirrel Posted January 30, 2023 Author Share Posted January 30, 2023 Yes the front end tapers in, I think I'm OK with that (until I put it together!) . It does have beech bearers and from me 'eyeing it up' it will take the Saito 40 quite well and as they pass through F1 F2 and F3 they are pretty integral, not sure f I should build in side/down thrust but that plan looks straight so maybe not.. re the wing section, I guess there is a vertical 'Beam' of maybe 3/16 that runs behind the balsa blocks that the ally runs in to, there are balsa ribs on the outside edges but not sure yet what to do were the bals sheet makes way for 'glass' on the top of the cabin but with increasing confidence I hope to be able to figure it out. Thanks again! Quote Link to comment Share on other sites More sharing options...
Flying Squirrel Posted February 9, 2023 Author Share Posted February 9, 2023 I've been away from this for bit but back on it again and with another question.. This time it's around F4 and the adjacent window frame, the top section of F4 is angled which is fine but the lower section is straight and recessed more than the depth of the box section frame it mounts too, diffucult to explain but hopefully a few pictures will help! Said former and how I think it should go..you can see the 'overhang'.. I assume it's something to do with keeping the covering nice but how was I/am I meant to fit the window 'frame'.. You can see F5, F6 F7 etc are all set back and to me that makes more sense for covering? Incidently I'm binning this frame to start again so happy to use as a test peice.. Quote Link to comment Share on other sites More sharing options...
kc Posted February 9, 2023 Share Posted February 9, 2023 (edited) I usually start by looking at a plan and comparing all formers with the plan checking that the notches seem right - if they don't then perhaps I have missed something! Or perhaps the plan is wrong....... best to find out before starting building! Compare all the formers, cross sections etc with the rest of the plan. This is Armchair Modelling which probably takes an evening or two and often results in discarding a plan! As we cannot see all the plan it is difficult to advise you. However I reckon the window frame comes out level with the former at bottom, so it's sloped. It could be the longeron is undersize - you seem to have put an infill strip on the top - maybe put one on the side as well and taper to nothing at rear. Unless you want a dead accurate scale plane anything that looks right and is strong enough will do, so decide what stringers need to be added to make the covering fit properly. Nothing matters as long as it looks right ( and is light enough of course) - just don't tell anybody it's not exact! Edited February 9, 2023 by kc 1 Quote Link to comment Share on other sites More sharing options...
kc Posted February 9, 2023 Share Posted February 9, 2023 It doesn't look bad enough to start again! Two points if you do start again 1. check the size of strips for metric or exact inch size. 3/16 is neither 4mm or 5mm ( 4.76mm I think ) adjust notches for actual size of your material. 2. sides should be ' handed' if you put the window frame in sloping. Quote Link to comment Share on other sites More sharing options...
Flying Squirrel Posted February 9, 2023 Author Share Posted February 9, 2023 It's not really that bad, just a few things I now know will help give me more satisfaction and there isn't a ton of time or money tied up in it, maybe I will, maybe not. Ithink as the plan is in imperial it's making it much harder for me, I'm only young! (ish) I'm trying to figure were the covering will attach, in my mind from F4 rearward it would be the top longeron, then the1/8th stringer (so not the formers or the 'mid' longeron) and then the bottom longeron, maybe I've got that wrong so making it difficult to figure out what happens forward of this. Really appreciate your time and expertise! I'll put the plan up but mods, please remove if not allowed! Clipped cub plan.pdf Quote Link to comment Share on other sites More sharing options...
kc Posted February 9, 2023 Share Posted February 9, 2023 I have got the plan onto my computer now and can see it's not really detailed in the cross sections. Use your framework and do a trial covering to see how it will fit. Then consider adding some tapered stringers if needed. Compare to photos of full size and decide if it looks right. All you need is something easy to build that looks right. Putting a flat sheet of ply against the fuselage and looking from the other side should help see if the covering will attach nicely. I like a Permagrit block for sanding or levelling. Expensive but all I need is the wedge block for almost everything. ( comes out of the household budget as its used for preparing windows for painting My wife found it very handy when she painted the windows last year! The lady at Permagrit told me she invented the wedge block ) I will happily work in metric or imperial, often using both. Metric for small measurements, inches for wingspan. An electronic vernier caliper that switches straight from imp to metric is handy although mine does not seem to turn off and wastes battery. The simple plastic verniers work better than expected and one in imp and metric is worthwhile. Some steel rules are clearer than others and it's worth buying one with only a few markings - 1/16 rather than 1/32. Trouble is the balsa suppliers dont always use exact conversion. Maybe you have undersize balsa? Also its easy to mistake 4mm for 5mm. Studying plans is armchair modelling and never a chore. Quote Link to comment Share on other sites More sharing options...
Flying Squirrel Posted February 9, 2023 Author Share Posted February 9, 2023 I think a few simple cross sections would help a fantastic amount but I guess it's not a model for a new builder and some poetic license is expected. A particular area is the center wing section, there are no formers and almost zero detail so I don't even know were to start. I've got some half decent measuing equipment but will add a permagrit wedge to the shopping list, I've been getting by with sandpaper glued to various shaped timper and plastic pipes that's served me well. Quote Link to comment Share on other sites More sharing options...
kc Posted February 9, 2023 Share Posted February 9, 2023 The Permagrit sanders remove balsa or ply very easily and better by far than sandpaper ( glasspaper ) Actually the old Sandvik sanders were good but now unobtainable. You don't need the full set of shaped Permagrit but they would be nice to have! The 'dust' produced seems larger and therefore less of a problem in confined spaces, but I prefer to sand outdoors when possible. Just a few strokes will remove enough to fit parts so can be done indoors with care. I will study the wing on the plan and report back. Quote Link to comment Share on other sites More sharing options...
Flying Squirrel Posted February 9, 2023 Author Share Posted February 9, 2023 I'll take my pocket money to the shows this year, they normally have a stand I believe!. Quote Link to comment Share on other sites More sharing options...
kc Posted February 9, 2023 Share Posted February 9, 2023 (edited) You are right there is very little info about wing centre section! It appears that each wing half has front and rear 16 SWG piano wire joiners which are turned up at the inner end so they are captive. These joiners would go into close fitting brass tubes which are fitted onto fuselage top, so wings could be slid on and off but retained by bolts. . Maybe just a slight amount of dihedral is arranged by putting the piano wire into wing at a slight angle and the tubes are straight across ( MUST be lined up properly in my opinion) Maybe create a simple drilling jig so that both sides are drilled exactly the same. It is possible the wing retaining bolts ( horizontal it seems not vertical ) could be accessed through some (glazed? ) hatch in the top of wing centre section. I suggest a trial with your ( scrap? ) fuselage would be best to get this worked out quite soon. Maybe make up a couple of ribs into a test piece of wing would help. I guess one should put the tubes into fuselage accurately then only glue the piano wire into the wings at a late stage when the wing struts would be used to get the right amount of dihedral. Studying other plans on Outerzone with wing joiners might help - Cubs or other designs. A one piece wing would be easier of course but might be inconvenient. A decision to make soon though. Edited February 9, 2023 by kc Quote Link to comment Share on other sites More sharing options...
Flying Squirrel Posted February 9, 2023 Author Share Posted February 9, 2023 I think the plan was adapted from the sig plan and I belive that had a one piece wing so maybe lost in translation along the lines, who knows. Also, I notice on the plan the right hand info panel says ' designd by Peter Miller for .15 size engines but then there is a further panel that says designed and drawn by Phill Kent for .40 size? ....interesting.. Not sure if I'll scrap what I've done, I'm feeling a little more confident that I don't need to be 100% as per the plan so maybe I'll use it as a test bed and see how it comes out. Quote Link to comment Share on other sites More sharing options...
RottenRow Posted February 10, 2023 Share Posted February 10, 2023 I would completely ignore the 'Peter Miller / .15 engine' reference in the info panel on the plan, that looks like it was cut and pasted from another plan at the time of publication and never completely changed for this plan. A lot of plans contain errors such as this unfortunately. I think the fuselage sides, from the front at F2 to a fraction behind F4, should have 1/16 balsa sheet on the outside of the 3/16 square frame. This is clearly shown on the cross-section at the F2 position, but there is no mention of it on the fuselage side view. This 1/16 sheet, added to the 3/16" frame, makes the sides 1/4" thick, which is why the lower part of F5 has a 1/4" 'recess'. The 1/8" rear window frame (the one with the curve) will then be aligned with that sloping part of F5 and have its outer face sit flush with this side sheeting. The references 'fill with 3/16" sheet" are for additional pieces of 3/16" balsa filling in the frames in the areas shown around the front and lower half of the fuselage, to provide extra strength in the areas where the engine and undercarriage are mounted. They will make the fuselage sides 1/4" thick in these places. Perhaps the written instructions make mention of this. The plan is rather ambiguous in a few places and some information seems to be missing. Not one for a first-time-builder I think... Brian. 1 Quote Link to comment Share on other sites More sharing options...
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