SLEC Chipmunk build blog

After a bit of checking I have found what I think is a small error in the kit. The locating hole in the firewall I believe to be drilled in the wrong place . It is actually in the centre but it should be located 3.2mm to the left to allow the prop to centre with the built in side thrust . The right fuselage side is a bit shorter than the left which tilts the firewall to build in side thrust. The instructions say the hole is already offset but it is in the centre according to my measurements.

Edited By Tim Flyer on 29/10/2019 16:01:48

I always ignore measurements like that. I just build it, fit the cowl an then plonk the engine on the front. As i deliberately mount the engine slightly short on its mounts I then make whatever modifications are needed to get the engine where it needs to be.

Hi Jon . Yes I can see why you do that . Certainly if I had blindly followed instructions on this bit it would have been a pain moving the engine sideways later on in order to get the spinner in the right place. 😉

This is my build so far, the Dynaflite seems to have the same design as the SLEC one. I enlarged the Roger Pegg / Radio Moddeler plan and made some changes to the tail surfaces to make it closer to scale. For the wing I went the foam wing route so that I could add the missing ribs. I got further than I thought, airframe is glassed, the wing needs filling and then MS primer so that rivit detail can be added. The idea was not to have a super scale aircraft but rather a nice flyable aircraft.

That looks really nice Chris and an excellent finish . I’m not going for scale either, but rather “stand off” / “sport scale” , so I don’t think I will be putting on rivets panelling etc although I agree that the look really good ,

Im in the 'scale at 10 paces' club myself. I have always wanted to do a fully detailed build with rivets and so on but once you are a few feet away you cant tell anyway and the time investment just dosent seem worth it. Even at 5th scale rivets might be only 1 or 2mm across anyway

Agreed I would love to do a real scale build if I had the time. If I did it would probably be an SE5a or similar. The Chipmunk is such a great everyday flyer I’m concentrating on making it a durable and practical flyer that can handle lots of flying and car journeys,

I have now decided just to mark the adjusted centre line on the firewall. I’m going to drill later like Jon suggested and just as I have done one on a number of other planes and do the drilling once the fuselage is built and I can check the cowl fit . That gives more time to decide optimal position. Possibly a 7 o’clock mounting might work well here and give the possibility for a more elevated fuel tank position , as long as my baffling is ok. 7 O ‘clock also allows easy needle valve access. Anyway all that will be finalised much later . Next the fuselage sides !

Yes but it's worth it for the smug feeling when all around are congratulating you on the finish

My SLEC Chipmunk, one of the first kits they made after they took over the Apache Aviation business. Laser 150 powered - perfect.

Wow that’s superb David ! You have a right to feel very proud of that .

Thanks Tim - hope you have as much fun with your Chipmunk as I have with mine.

Well horrible weather this week! I did manage to do some flying on Thursday though. I have started on the fuselage now. I’m not posting photos of the flat side as that would be dull. I think it is definitely worth doing a dry run on the fuselage assembly. The triangular balsa edging needs to be very carefully placed too. I initially tacked the two sides together via the radio tray with the help of thin cyano and activator. That makes the clamping less critical. Luckily my fuselage does seem to be fairly straight. I also epoxied the firewall in today . The kit provides a triangular firewall square made of liteply to check the firewall is square. What seems a little silly to me is that the triangle is totally square but the firewall is designed to have an offset to provide right thrust! This means that if the firewall is correctly fitted it will not meet the fuselage sides at perfect right angles . Anyway that’s just me being picky . Maybe the square is just used to prove it’s not at right angles and is left offset? Anyway my firewall is stuck down now and it wasn’t particularly difficult.
Today I ordered some more bits , a 16oz Sullivan flexi fuel tank which is 5 3/4 in long and should fit well at the bottom of the tank bay. The flexi tanks by Sullivan are really good and can easily be softened to fit into awkward spaces. I also ordered a metal 3 inch Aluminium Spinner which I will need later on.

Edited By Tim Flyer on 02/11/2019 15:53:12

I’m a little further on now. I have completed the wing bolt to fuselage fixing and the wing dowl fixings. I replaced the soft liteply dowl caps with my own stronger Birch ply caps . The fuselage is coming on a bit . All the lower formers are fitted and the shell for the air and exhaust outlet. I was wondering to keep the fuel bay access hatch which the instructions describe via the air exhaust. I probably will as it might be useful both for building and servicing. I fitted the supplied heavy duty M3 push rods and glued in the sleeves . Final assembly will be after covering.

Here is a picture of my tank bay and engine mounting ( the blind nuts will be put in after the bay is glassed and epoxied inside. In order to lower the 16 oz Sullivan tank to the correct height for the laser 180 I cut down the level of the former F2 . I then internally reinforced the lower half by laminating a birch ply cutout on the lower half and a spruce beam from side to side on the bottom edge of F2. I’m now happy with the yak height , To hold the tank down i epoxied two bolts as an anchor for a zip tie which will be added later . I will add the tank bay floor before epoxying the whole area,

Hi Tim, I'm enjoying your build, great work.

I'm in the latter stages of the RAF trainer version, 2 piece wing (maybe 1 - jury's still out), & laser 150.

Are you levelling the centre line of the carb with the centre or bottom of the tank? Just trying to make sure I've got the right level tank.

Hi Applewood good to hear you are also building one and thank you for your encouragement . I have now fitted the stringers on the fuselage and sheeted the engine bay which I will epoxy tonight . Next main job is fuselage sheeting. I am going to keep the wing as 2 piece as I think it will be strong enough like that . I do have a small gap in the underside edge when the wings are joined. I was thinking of possibly eliminating it via car filler covered with cling film when joining. That will make a flush fit.
Regarding my carb level the carb centre is a tiny bit below the middle of the tank when the plane is horizontal , but once it’s on the ground and angled by the undercarriage the spray bar will be above the top of the tank( so it won’t siphon) . I have never found the 180 , or other Laser engines over sensitive to tank position unless it’s much too high ( e.g bottom of tank in line with carb). If you have middle of carb in line with middle of tank when horizontal that will be fine. By the way I lowered the tank by lowering the bottom of former 2 as described above also moving it back slightly away from the air outlet slope on the firewall which would have lifted the front. My tank is a nice relatively compact Sullivan 16oz tank ( just 5 3/4 inches long) 

Edited By Tim Flyer on 11/11/2019 12:32:12

Edited By Tim Flyer on 11/11/2019 12:37:24

Edited By Tim Flyer on 11/11/2019 12:37:54

I have started sheeting the fuselage now. While the glue was drying I painted the very good latex model pilot bought from Nexus models for about £11 . They delivered fast . It seems to be one of the few decent sport pilots available in 1:5 scale. I hope he has done is “A” Cert 😉 His reg number will be put on his overalls 😉😉😊. I’m starting to think about covering and the dreaded painting. If I film cover I’m still going to end up having to match painted areas on wing fairings and cowl. After speaking to Jon yesterday I think I might consider glassing this fuselage and using Solartex/glass on the tail , but possibly just use the film and Solartex on the wings. I will probably try Halfords car spray paint as it should be fairly easy to match film . Will have to cross my fingers for fuel proofer compatibility too. 

Edited By Tim Flyer on 13/11/2019 09:42:10

Thanks Tim, you build is coming on really well. Are you going for twin flap servos or single?

I’ve measured my setup, the carb centre line tank is 18mm above the bottom of the tank. It’s also a 16oz Sullivan tank. Is the siphoning issue only a problem when static, or in flight too. Do you think the tank is low enough?

cheers

Cheers Applewood sorry I missed your post . I have a number of Laser engines and although ideally the spray bar is supposed to be at tank centre line , I have not had problems at all with centre line of intake at tank centre. The tall tanks (large tanks) can possibly lead to Syphoning on some planes but normally the fact that the undercarriage points the nose up stops ground siphoning . The other important matter is to properly tune the low speed needle setting. Many flyers leave their Laser engine low speed needle alone. It governs mixture up to around half throttle and does need occasional adjustment and should not be just left at factory setting. Jon at Laser is always happy to help with advice. A very rich low speed needle and tank a bit high can lead to cut out due to plug cooling.

I have moved my tank slightly back from the firewall so the middle of tank is level with the carb intake