Martyn K Posted October 4, 2012 Author Share Posted October 4, 2012 Posted by Chris Poulton on 04/10/2012 12:49:21: Try this Martyn. I believe this is the set I have. Thanks Chris.. I presume that they are shown in the retracted state, in which case, the depth of the main actuators looks to be about 20mm deep. I think they could be accomodated in the wing without too much difficulty. I haven't plotted the intermediate ribs yet, but the wing root thickness behind the main spar is about 45mm so should be possible to fit these quite easily. However, I am struggling to visualise how the nosewheel retracts and how much space is required. The space under the fuel tank floor is just over 25mm. The floor could be made of thicker ply (currently planning to use 3mm ply) but that would reduce the space further. The 6mm ply front bulkead/firewall/engine mount has a balsa triangle cross brace to link the floor and sides with the bulkhead. There isn't much space for stregthening the front end - I would be reluctant to leave this out... There isn't much space available in front of the front bulkhead either.. Regards Martyn Quote Link to comment Share on other sites More sharing options...
Chris Poulton Posted October 5, 2012 Share Posted October 5, 2012 If I find the time I will dig them out this evening and send you the dimensions Martyn. Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted October 5, 2012 Share Posted October 5, 2012 The heavier duty DSR2 retracts are exactly 1"/25mm deep. The usual way of fitting them is behind the engine bulkhead undr the tank, either screwed to the bulkhead or to the tank bay floor depending on the configuration. The HK ones all look to be designed for fitting to a horizontal surface eg the bay floor. I don't think it would matter that half of the wheel would be exposed when retracted, it's getting the bulk of it and the leg out of the way. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted October 5, 2012 Author Share Posted October 5, 2012 Thanks Bob There should be enough space for those. I presume that there are no undercarriage doors to be fitted. Do you know the distance from the pivot to the wheel spindle and the diameter of the wheel. I think there will be space to mount them with the wheel diappearing into a slot behind the tank. As I am about to start work on the wing detail, I could also do with having any salient measurements for the wing units. From the photo, it looks like there is a mounting plate that is fastened into the wing (how?) and then the U/C units are screwed to the plate. Is that correct? Appreciate the help. Martyn Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted October 5, 2012 Share Posted October 5, 2012 The usual trick with wings is to use ply doublers on the two adjacent ribs to support parallel hardwood beams under the wing skin level, ie flush with the rib surface. The retract is screwed to the beams so it's mounting is flush with the wing surface. The bulk of the retract mechanism sits between the ribs with U shaped cutouts in the next few ribs to clear the U/C leg. Noseleg/wheel height is limited by the distance between the engine bulkhead and the front of the wing For instance on my Tornado this limits me to 12" props, even then I can leave a channel in the grass if it's not really short. I can't remeber what size props would go on a 25, but my Evo 37 uses 10" so the thrustline for that would need to be 5 1/2 - 6" above ground level. If the bottom of the fuselage at the retract mount is, say, 2" below the thrustline then the total leg length would need to be 3 1/2-4". Add on say 3/4" for the offset of the pivot in the retract body means we need 4 1/4 - 4 3/4" between bulkheads 1 and 2. So much depends on the exact retract unit and engine/prop being fitted that it may be best to leave retract mods to the builder in the end Martyn. Usually plans will show retract fitting for a particular brand. Cetainly my Top FLite kits contain lots of 'adjust to suit your installation' clauses. Edited By Bob Cotsford on 05/10/2012 11:25:56 Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted October 5, 2012 Share Posted October 5, 2012 The critical part with built up wings is usually the spar location - does it clear the proposed wheel wells? Quote Link to comment Share on other sites More sharing options...
Martyn K Posted October 5, 2012 Author Share Posted October 5, 2012 Thanks Bob The original did so I would imagine that the reduced size model can also get the retracts made to fit. I dont think there will be any problems with retracts in the wings. Martyn Quote Link to comment Share on other sites More sharing options...
Martyn K Posted October 5, 2012 Author Share Posted October 5, 2012 Sorry, I forgot to mention. I use a 9x6 prop on my SC25.Ground clearance should be if the nose wheel leg plus wheel is c4.5" long. Martyn Quote Link to comment Share on other sites More sharing options...
Chris Poulton Posted October 5, 2012 Share Posted October 5, 2012 OK, I've dug mine out and measured. The set I have is the DSR-A set. Dimensions: Noseleg. Mount is 35mm wide x 33mm long and approx 3mm thick. This mounts above the retract unit. Overall thickness of unit plus mounting plate is 26mm. The unit needs to be mounted on rails, the top edge being 26mm above the fuselage bottom if the mounting screws are accessed from the tank area. If the mounting plate is to be screwed in from the bottom, the bottom edge of the rails needs to be 26mm above the fuselage bottom. The overall length of the unit with leg retracted is 132mm, and the length of the leg extended (including wheel) is 115mm from the fuselage bottom. Important to note when retracted, part of the wheel protrudes 13mm above the mounting plate level. The wheel is 35mm diameter and the noseleg is sprung (nice!). Mains. Mount again is 35mm long (measured fore-and-aft onthe wing) and 33mm wide (between ribs). This is slotted for the leg as it extends. For the mains, the mount in flush to the wing bottom. Total depth including mounting plate is again 26mm. Overall length retracted is 138mm, and extended is 120mm from wing bottom. The main wheels are 46mm diameter and the units are also sprung (very nice!) In both cases, the units are 18mm wide. Phew. Hope this is helpful. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted October 5, 2012 Author Share Posted October 5, 2012 Very helpful... thanks. The only tricky bit will be the front wheel and retract assembly. You will need to increase the depth of the fuselage by abt 5mm below the tank floor. I think though that I will do as you have suggested and let you sort out the exact mechanics.Martyn Quote Link to comment Share on other sites More sharing options...
Martyn K Posted October 8, 2012 Author Share Posted October 8, 2012 This is the latest update.. Here is the latest version of the plan (as a jpg). Very nearly completed,I just need to sort out the dihederal braces, the front u/c leg mounting and the woodwork around the engine.. Click for a bigger image. The wing ribs are here: The wing uses a NACA 0014 tapering to a NACA 0012. The tail is a NACA 0011. Sheet 1 Sheet 2 Tailplane All should(!) print full size on A3 paper... Biggest structural change on the model is a solid fin rather than built up. The wing span is 48". My Astrohog 25 is 50" span and is not underpowered, but you will need to build it light.. I would welcome comments.. Regards Martyn Quote Link to comment Share on other sites More sharing options...
Chris Poulton Posted October 9, 2012 Share Posted October 9, 2012 I have a special request. can the Hon Mr. Ashby run this through their cnc cutters, pretty please looking great Martyn! will download the rib drawings tonight and see if i can get them printed on A3. what thickness sheet balsa are you recommending for these? Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted October 9, 2012 Share Posted October 9, 2012 Nice one Martyn, especially including jigging tabs on the ribs. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted October 9, 2012 Author Share Posted October 9, 2012 Posted by Chris Poulton on 09/10/2012 07:01:12: I have a special request. can the Hon Mr. Ashby run this through their cnc cutters, pretty please looking great Martyn! will download the rib drawings tonight and see if i can get them printed on A3. what thickness sheet balsa are you recommending for these? The inner 5 ribs on each panel will be 1.5mm lite ply, the rest 1/16" sheet balsa quarter grain balsa. The tail ribs are all 1/16" sheet balsa quartergrain. All will become clear. Hang on cutting until I have printed and checked my set though... I am never really confident with pdf printing. Martyn Edited By Martyn K on 09/10/2012 11:49:12 Quote Link to comment Share on other sites More sharing options...
Martyn K Posted October 9, 2012 Author Share Posted October 9, 2012 Posted by Bob Cotsford on 09/10/2012 09:28:51: Nice one Martyn, especially including jigging tabs on the ribs. Thanks - but you can thank Profili for the tabs.. martyn Quote Link to comment Share on other sites More sharing options...
Martyn K Posted October 9, 2012 Author Share Posted October 9, 2012 One area that I am struggling with is the front end and getting enough strength around the engine mount firewall. The fuselage is very slim, I normally add thick cheeks front and aft of the Firewall but there isn't enough space. I am planning to make the cockpit floor and fuel tank base integral with the firewall to lock the whole lot up. However, this means that there will be no access to the tank once built - in effect, it will be built in and sealed in. Will you lose and sleep with that approach? Martyn Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted October 9, 2012 Share Posted October 9, 2012 Could you use tabs on the firewall bulkhead sides locking into vertical slots in the fuselage side doublers? The usual way of accessing the tank on these style models is to pull it back through a hole in F2 at the wing LE. You just need to select your tank with care! Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted October 9, 2012 Share Posted October 9, 2012 Posted by Martyn K on 09/10/2012 11:34:54: Posted by Bob Cotsford on 09/10/2012 09:28:51: Nice one Martyn, especially including jigging tabs on the ribs. Thanks - but you can thank Profili for the tabs.. martyn I'm sure you can! Can it generate cutting files to get ribsets lasered? I'm getting lazy in my old age. Edited By Bob Cotsford on 09/10/2012 15:00:57 Quote Link to comment Share on other sites More sharing options...
Martyn K Posted October 9, 2012 Author Share Posted October 9, 2012 Hi Bob the problem is that the internal Fus width is 52mm (enlarged from about 47mm), the tank width is 49mm so there really isnt space to do that. However, I may be able to split (laterally) the canopy base and allow access to the tank that way. Adding slot would help, but the fus is only 3mm thick sheet (inc; 1/32" ply doubler) Needs a meatier solution, Martyn Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted October 9, 2012 Share Posted October 9, 2012 What size and make of tank? If all else fails, it just means a bit of surgery in the unlikely event of a burst tank. Quite often on larger models the tank bung can be extracted through the centre of the radial mount for plumbing maintainance, would that be viable at this scale? Quote Link to comment Share on other sites More sharing options...
Martyn K Posted October 9, 2012 Author Share Posted October 9, 2012 I am looking at using a square SLEC fuel tank 6oz 180cc) Maxi Fuel Tank Red Ref: SL088A-R Max volume in minum space. however no bung... Martyn Edited By Martyn K on 09/10/2012 15:08:26 Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted October 9, 2012 Share Posted October 9, 2012 What size and make of tank? If all else fails, it just means a bit of surgery in the unlikely event of a burst tank. Quite often on larger models the tank bung can be extracted through the centre of the radial mount for plumbing maintainance, would that be viable at this scale? eg Sullivan slant oval: No. Size Height Width Length S445 6 Ounce 2-1/2" (64 mm) 1-1/2" (38 mm) 4-5/8" (117 mm) What is the largest cutout that can be made in F2? We can find something I'm sure. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted October 9, 2012 Author Share Posted October 9, 2012 Posted by Bob Cotsford on 09/10/2012 14:59:20: I'm sure you can! Can it generate cutting files to get ribsets lasered? I'm getting lazy in my old age. Edited By Bob Cotsford on 09/10/2012 15:00:57 Yes - what format do you want? Martyn Quote Link to comment Share on other sites More sharing options...
Martyn K Posted October 9, 2012 Author Share Posted October 9, 2012 What is the largest cutout that can be made in F2? We can find something I'm sure. I'll take a clser look later, at the moment I am supposed to be working (tea break) Martyn Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted October 9, 2012 Share Posted October 9, 2012 Posted by Martyn K on 09/10/2012 15:10:07: Yes - what format do you want? Martyn ermmm, - SLEC, LiteWorks or Belaire format? I guess they use whatever Autocad generates, that seems to be industry standard - .dfx? Plenty of time for that once you have the details worked out. I'll see if I can find out for certain. Quote Link to comment Share on other sites More sharing options...
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