David Wilson 25 Posted September 11, 2018 Share Posted September 11, 2018 Well, I think it's about time I got this party started! I can't be leaving a free plane on the shelf! Having decided that "to make things easy", I'll go the route of a Turnigy G46 motor to replace the recommended .40 or .46 IC motor. Obviously, it's easier to modify as I build, so the first consideration is a hatch to get at the battery as I really am lazy and don't want to have to remove the wing each time. I want to have 2 batteries; one to fly while one is on the charge, so not going to go the route of "charge in place". Thing is, the space between formers isn't sufficient to ease a battery in. I think that the only option is to cut the top off one former (the one on the right between the jig brackets) to make a "U" former and strengthen the hatch opening with 3mm ply. To that end, I've cut the ply reinforcement first and made two "brackets" to form the front and rear of the hatch out of two layers of 1.6mm balsa laminated together at 90°. They won't be loadbearing, so I think they should be strong enough. I haven't cut any formers yet, just in case anyone advises against the plan! I'll bow to superior knowledge and craftsmanship. I've filled in the predrilled holes in the firewall as I intend to use a Great Planes adjustable motor mount to hold the G46 and the fitment is different... Quote Link to comment Share on other sites More sharing options...
Dwain Dibley. Posted September 11, 2018 Share Posted September 11, 2018 I built this model and also converted it to electric, it flies very well indeed. I will try and put some pics up for you of the build if it will help. D.D. Quote Link to comment Share on other sites More sharing options...
David Wilson 25 Posted September 12, 2018 Author Share Posted September 12, 2018 Dwain, pictures would be gladly received! Quote Link to comment Share on other sites More sharing options...
David Wilson 25 Posted October 3, 2018 Author Share Posted October 3, 2018 Finally getting back to this after several mental weeks. If nothing else, I can't fault the instructions! Perfectly clear and well illustrated; youry have to be an idiot not to be able to follow them. What I've realised tonight is that where I'd intended to place the hatch, in front of the cockpit, actually is partially under the cockpit... I'll have to rectify that. None-the-less, I've pushed on and glued a few more bits together. I think, to try and keep the weight down, I'll have to cut a hole in the firewall to move the battery as far forward as possible. Hand cutting that square will be a test of my abilities. Edited By David Wilson 25 on 03/10/2018 22:41:10 Quote Link to comment Share on other sites More sharing options...
David Wilson 25 Posted October 4, 2018 Author Share Posted October 4, 2018 If there's anything I've learned, it's never work off the originals if they're likely to get damaged... So, photocopies done without scaling, and I can get on with something else while glue is seeing elsewhere. In the interest of saving weight and mindful of an electric motor weighing less up front, saving weight behind the CoG is prudent. The question is, where? From the templates, there seem to be chunks of balsa used where a hole could save a little bit, without sacrificing strength... Quote Link to comment Share on other sites More sharing options...
David Wilson 25 Posted October 4, 2018 Author Share Posted October 4, 2018 My assessment is that some weight could be easily saved from Template 20-3 parts D Template 21-3 parts B At a push, perhaps a few small holes along Parts D in Templates 21-3 and 22-3? Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted October 4, 2018 Share Posted October 4, 2018 Save weight yes David, but not there The saving would barely be noticeable, but the integrity of the parts would be weakened The tailplane experiences huge forces Save weight on internal bulkheads And using glue carefully Quote Link to comment Share on other sites More sharing options...
David Wilson 25 Posted October 4, 2018 Author Share Posted October 4, 2018 Coming from somewhere renowned for not being too flush with cash, I think I can be sparing with glue... (So I don't have to buy more!) Being absolutely ruthless in seeking weight trimming, I weighed the wheels... 88g (3.1oz). Unfortunately, that send to be the weight of similar 3.25" Robart wheels. Only possible alternative is foam wheels which could just look, well, naff? Quote Link to comment Share on other sites More sharing options...
cymaz Posted October 4, 2018 Share Posted October 4, 2018 If you can , build some washout into the wings Quote Link to comment Share on other sites More sharing options...
Dwain Dibley. Posted October 5, 2018 Share Posted October 5, 2018 Cymaz, the wings are built with a jig, which you have to build first, and I think washout is included in the build, I had no probs in flight with my one. A little reflex (up) on the ailerons would be easier to do maybe. D.D. Quote Link to comment Share on other sites More sharing options...
David Wilson 25 Posted October 5, 2018 Author Share Posted October 5, 2018 At the moment, washout is the least of my concerns... You know the adage, "measure twice, cut once" and everything similar, like reading instructions? Here's what I've managed to do... Here's what the instructions say... See the difference? I've used the LHS as the RHS and vice versa. Which means that the thrust angle is in the wrong direction. I remember looking at it after gluing and thinking about the reasons for thrust angle, getting confused as to why it was left angled. Question is... What do I do? Immediate thought was to fit a CCW prop, but that means mounting the motor offset to the left, and then the cowl is shaped wrong. The other consideration is: can I gently cut the joints and reglue? That'll be great fun! Especially since I've all this done... Quote Link to comment Share on other sites More sharing options...
David Wilson 25 Posted October 5, 2018 Author Share Posted October 5, 2018 I just realised... I'm overthinking it.I want to make it electric.I need to build a motor mount box which will also carry the battery through the firewall.So just build a more offset box to restore the correct thrust angle. Quote Link to comment Share on other sites More sharing options...
eflightray Posted October 6, 2018 Share Posted October 6, 2018 If you need to mount the motor ahead of the firewall, how about using long screws or threaded rod. It also allows you to adjust the thrust angles slightly. Ray. (72" span Spitfire). Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted October 6, 2018 Share Posted October 6, 2018 Don't forget when you get to to building the wings to dump the long twisty torque rods for ailerons and fit a servo to each aileron . It improves the models response enormously. Quote Link to comment Share on other sites More sharing options...
David Wilson 25 Posted October 7, 2018 Author Share Posted October 7, 2018 I thought about threaded bolts, which may yet be used, but need to get weight forward to replace the original IC .40 motor; hence the battery box through the firewall.I'll also be putting a servo per aileron; it makes perfect sense given the size and price of them when compared to 10 years ago. Quote Link to comment Share on other sites More sharing options...
David Wilson 25 Posted October 18, 2018 Author Share Posted October 18, 2018 Got a bit more done over the last week and a bit, but didn't have an opportunity to update the thread. I pushed on with finishing off the rear of the fuselage and put off rectifying the firewall error for a bit. I also pushed in the fin for a quick "dry fit" to keep the interest fueled! In the interim, I built up the forward hatch. I'm a bit fussy on maintaining a snug fit of the parts I'm making so there's no opportunity for flex. Generally good; not so much for a hatch that's supposed to be removable! I had to cut out the joints with a razor saw, sand the glue off and reposition about 2mm back to give clearance for removal. I put balsa stringers below the ply surround to add strength I've probably removed by creating a hatch. I hope it's sufficient! I also started to cut the ply to create a motor mounting box. I'm assuming that as the original firewall is just glued in with regular glue and a little of square balsa reinforcement at the edges, similar would be suitable to join the box onto the original? Had a quick read up on creating a mount box; some recommend epoxy and glasscloth reinforcement? I admit to being unsure; with a typical weight for these of around 7lbs, the box will need to hold a motor producing 700-850W, minimum. Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted October 18, 2018 Share Posted October 18, 2018 Yes David, at least epoxy. If the box is well designed, then epoxy and the strength of the timber will surfice Sometimes, when we make an area "impregnable" then during a mishap, the energy shudders down the model causing more damage. Building and glueing well is good enough The model is looking very smart BTW Edited By Denis Watkins on 18/10/2018 20:10:49 Quote Link to comment Share on other sites More sharing options...
David Wilson 25 Posted October 18, 2018 Author Share Posted October 18, 2018 The parts I've cut for the box are actually 3mm liteply... I'm guessing "not strong enough".Not sure what to use instead as I only have 4mm regular household ply offcuts. Too heavy and coarse is my assessment of that. Quote Link to comment Share on other sites More sharing options...
Dwain Dibley. Posted October 19, 2018 Share Posted October 19, 2018 It's coming on well David, Here are some pics of my build, How I did my hatch and my motor mount ,hopefully they will help you. I did not build a battery box, I just put a tray in the fuz. Might be a bit late, as you appear to have made a fine job of the hatch already. I laminated balsa till I got the right length, it could be advanced in 1/32 increments if need be. Quote Link to comment Share on other sites More sharing options...
David Wilson 25 Posted October 19, 2018 Author Share Posted October 19, 2018 Compared to your photos Dwayne, I appear to have over engineered everything! 😁Still, it means that it should all work out ok.I'll have to commit to a motor to ensure I don't build the box too long. Spacers can be added, length can't be taken away too easy. Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted October 19, 2018 Share Posted October 19, 2018 Posted by David Wilson 25 on 18/10/2018 21:35:35: The parts I've cut for the box are actually 3mm liteply... I'm guessing "not strong enough". Not sure what to use instead as I only have 4mm regular household ply offcuts. Too heavy and coarse is my assessment of that. Liteply has its place, but not good for engine mounts Liteply is strong in both directions, where balsa has a single grain direction Your 4mm ply would be ideal for engine mounts and front bulkheads Edited By Denis Watkins on 19/10/2018 07:55:53 Quote Link to comment Share on other sites More sharing options...
David Wilson 25 Posted October 19, 2018 Author Share Posted October 19, 2018 When I checked the ply, it's actually 5mm... 20% extra weight free. Wasn't having a lot of luck in deciding how to proceed as a "butt" joint wouldn't be particularly strong and to allow space for a battery to fit in leaves only 10mm of the original firewall on either side. I gave up thinking about it and sanded the few bits that needed done. Quote Link to comment Share on other sites More sharing options...
Shane Sunday Posted October 19, 2018 Share Posted October 19, 2018 Hey There David. Your spitfire is looking great. Neevr worry about over engineering. that 5mm ply is perfect for the firewall. If you are going electric then stand off spacers are easy enough to make up any difference when it comes to mounting the motor. also don't worry too much about weight up her at the front end of the model. It's a spitfire and it will require additional weight up front. best of luck and keep up the good work. Quote Link to comment Share on other sites More sharing options...
Dwain Dibley. Posted October 20, 2018 Share Posted October 20, 2018 Everyone has there own ideas of how to go about things, at the end of the day if its functional, and you are happy with it, it's OK... Shane is right, i mounted my Rx battery right on top of my motor mount, and my ESC underneath to get the C of G. I did buy my motor and batteries up front and built to accommodate them, again as already mentioned, bolts and tubes to make standoffs are the way to go if you buy your motor last. However, I would defo get the batteries I would be using first. My tray is just a plank of lite ply, glued to the internal structure, with a strip of velcro on it. This allows for cables and wires and Fingers to fit in. D.D. Quote Link to comment Share on other sites More sharing options...
Dwain Dibley. Posted October 20, 2018 Share Posted October 20, 2018 Just to show anything is possible........How about this one, that replaced a chunk of 3/4 inch roofing ply. D.D. Here's the repaired Model. Quote Link to comment Share on other sites More sharing options...
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