Ron Gray Posted February 2, 2021 Share Posted February 2, 2021 I've created this new thread as it's more about the trials and tribulations of retro fitting this beast of a motor into an existing airframe and the problems that I encounter on the way. @Jon - you may want to keep this in with the Laser development thread, if so please feel free to get a mod to move it. The donor airframe is my trusty Great Planes Giant Super Sportster which is currently the host to another Laser, a petrol GA30 (which is a great match by the way!) The GA30 installation The measurement from the bulkhead to prop driver on the GA is - But the 200 inline is - I subsequently remeasured and it is 230mm, so a difference of 45mm. Now the choices are, fit it to the bulkhead as is and extend the cowl, or chop the bulkhead out and mount it further back. The 200 is quite a hefty lump so pushing some of that mass further forward was not something I wanted to do so my decision was made, chop back the front of the airframe! So GA was removed Together with fuel tank (replacing with a new one) And all electrics and fuel lines running forward to the engine bay The line is the rough position of the new bulkhead I carefully cut around the bulkhead and through the stringers so that I could lever (hit with hammer) it away as I may need it. No turning back now. And yes, that is a panel saw you see in the background, no half measures here! My plan is to keep the fuselage sides in place and to recess the new bulkhead in its position within the fuselage. My reasoning is that if I cut the sides back then the cowl will need extending but by leaving them in place I'll 'only' have to form a new top to the fuselage. Well that's the plan, we'll just have to see how it goes. Edited By Ron Gray on 02/02/2021 18:51:36 Quote Link to comment Share on other sites More sharing options...
Rich too Posted February 3, 2021 Share Posted February 3, 2021 You are a brave man Ron! Watching with interest 👍 Quote Link to comment Share on other sites More sharing options...
Jon H Posted February 3, 2021 Share Posted February 3, 2021 Its good to give this its own thread. Keeps the other thread tidy and all that. I like your idea of recessing the firewall but leaving the cowl alone. Looking at that bottom photo i would probably cut it back to that next former and beef that up. As long as that leaves room for a tank on the fuselage floor ahead of the wing it would be fine. As for your choice of saw, i like. I bought a 2nd hand galaxy mustang once and the dihedral was wrong. About 20 seconds with 24'' stanley wood saw soon had it in half and ready to be reset. Quote Link to comment Share on other sites More sharing options...
Graham Davies 3 Posted February 3, 2021 Share Posted February 3, 2021 Posted by Jon - Laser Engines on 03/02/2021 08:10:49: As for your choice of saw, i like. I bought a 2nd hand galaxy mustang once and the dihedral was wrong. About 20 seconds with 24'' stanley wood saw soon had it in half and ready to be reset. Without wishing to derail the thread... Not enough is made of the use of 'serious' tools! My introduction to Warbirds came with Richard Wills' instruction for creating the polyhedral on my Tempest; "be brave, get the saw out and chop each wing in half'! Yep, wood saw, deep breath and the job's a good'un! Quote Link to comment Share on other sites More sharing options...
Nigel R Posted February 3, 2021 Share Posted February 3, 2021 That is some serious battlefield style surgery Ron! Edited By Nigel R on 03/02/2021 08:35:30 Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted February 3, 2021 Author Share Posted February 3, 2021 @Jon - yes, the plan is to attach the new bulkhead to that semi former but first I’ll be adding some thin (ish) ply reinforcing cheeks to the back of the semi former, glued to the fuselage sides. I’ve also carefully cut out the ‘chin box’ which you can see in the top of photo 7 above (which is with the fuse inverted) so that, together with the old bulkhead, I could rebuild the fuselage to its original lines should this all go ‘tits up’. I don’t think for one moment it will but the problem I may well have is that my plan after testing in the Giant Sportster, is to move the 200 in-line to another airframe I have waiting, an ESM Typhoon! Picking myself up on a detail in my post above, it’s not a panel saw it is in fact a floor board saw! Edited By Ron Gray on 03/02/2021 09:48:48 Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted February 3, 2021 Author Share Posted February 3, 2021 Forgot to add these photos of the new bulkhead. Original is 10mm thick, new one 12mm (based on Jon’s recommendations) Quote Link to comment Share on other sites More sharing options...
Jon H Posted February 3, 2021 Share Posted February 3, 2021 Posted by Graham Davies 3 on 03/02/2021 08:20:16: Posted by Jon - Laser Engines on 03/02/2021 08:10:49: Not enough is made of the use of 'serious' tools! Totally agree. Hammer, chisel, big ol' saw. Just get stuck in, its only wood Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted February 3, 2021 Author Share Posted February 3, 2021 Merrily soldering on, bulkhead slots cut for the fuse stringers and checking for fit. All looks good so adding some infills to the fuse sides to level them up before fitting the strehgtheners Then, once they were dry I fitted the strengtheners using epoxy. Now back with the bulkhead and time to measure for ant fit the engine, but I came across a problem, the engine mount is too tall to fit and to keep the thrust line, and whilst I'm not too worried if it's slightly out, this was 20mm. (Sorry picture isn't in focus). Anyway an advantage of having an engine from a friendly UK manufacturer is that he's only a 'phone call away and I was able to chew the fat with Jon and in the end came up with a compromise solution. the engine has been dropped by 10mm below the designed thrust line (I'm happy with that) but it meant that the slots cut for the stringers were exactly where the T nuts were going! To overcome this I've glued a couple of blocks on the back of the bulkhead behind the T nuts and these will support the stringers. With that little problem solved I was then able to epoxy the bulkhead in place complete with some triangle strengtheners. Things do seem to be progressing quite well and on track for a start up this weekend! Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted February 4, 2021 Author Share Posted February 4, 2021 Just a test to make sure I got the measurements correct! I was still a little bit unhappy about the amount of restraint the top of the bulkhead has as it relied on the stringers in the top of the fuselage for strength, so I set about rectifying that with some dowel cross bracing epoxied to the bulkhead and the fuselage sides. (I'll do some dusting when the glue has set!) Quote Link to comment Share on other sites More sharing options...
Manish Chandrayan Posted February 17, 2021 Share Posted February 17, 2021 Subscribed Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted February 17, 2021 Author Share Posted February 17, 2021 (edited) More to come, very soon but it maybe a bit baffling ? but aiming for a first start tomorrow. Believe me when I say that what I have done so far in hacking the airframe about was easy in comparison with trying to sort out the cooling! Edited February 17, 2021 by Ron Gray Added text Quote Link to comment Share on other sites More sharing options...
Jon H Posted February 17, 2021 Share Posted February 17, 2021 Ron and i have been discussing the cooling aspect at length as it is one of the challenges with this configuration of engine. The problem is you cannot cool the engine from the front, only the side, and this means the front cylinder is almost totally blanked off by a baffle. naturally, this looks rather sub optimal for cooling but it is the way to go. Attached is one of my 'high quality' airflow drawings with pink baffle to try and make sense of it all. Just remember that the cold side of the engine is sealed on the back, top, bottom and side. The only opening for the air is between the cylinders and the air rushing in the front will pressurise it nicely. The exit from the cowl will also be vented to give a nice suction so you should end up with a high pressure cold side and low pressure hot side giving plenty of flow. It is unusual, but it will work. Quote Link to comment Share on other sites More sharing options...
Phil McCavity Posted February 17, 2021 Share Posted February 17, 2021 The 'Venturi' effect. Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted February 17, 2021 Share Posted February 17, 2021 Might also be worth putting some baffling between the cylinders and between the rear cylinder and the firewall to ensure the air flows through the fins in some installations, a bit like the baffles you can buy for the Moki radials. Quote Link to comment Share on other sites More sharing options...
Tim Flyer Posted February 17, 2021 Share Posted February 17, 2021 Very interesting project and great work Ron . Good idea re leaving sides in and moving firewall rearwards . Only thing I may have done is fibre glassed and epoxied firewall in rather than cross bracing. Quote Link to comment Share on other sites More sharing options...
Jon H Posted February 17, 2021 Share Posted February 17, 2021 13 minutes ago, Frank Skilbeck said: Might also be worth putting some baffling between the cylinders and between the rear cylinder and the firewall to ensure the air flows through the fins in some installations, a bit like the baffles you can buy for the Moki radials. Some air needs to get around the back of the rear cylinder to make sure the carb gets nice cool air to breathe and provide cooling for the rear exhaust. You are right though and its something to keep an eye on. Due to lockdown and weather i have not even been able to fly my factory prototype. As a consequence i am giving Ron a hard task as i do not have any info of my own on how much margin we have and he is trying to digest my ramblings and diagrams as best he can remotely. For anyone looking to buy one of these just be aware there is a price to be paid and that price is in the airframe mods. The installation isnt so bad, but the cooling will require some work. In the case of a WWII fighter that will mean all of this stuff and a duct through the firewall, along the fuselage and down through the wing. There is only so much i will be able to do with the instructions. If you dont want that work of sussing it all out, buy a 180 single. If you want the inline twin to keep the engine hidden and have the twin sound, this sort of modification work is the price you pay. It wont be for everyone, but that's fine, i never expected it to be. That said, once we get a few models together and flying we will have more photos etc of cooling arrangements that work so it will take a bunch of the guesswork out. I can also include scale outlines of the engines with the instructions so they can be cut out and used as baffle templates. This is all stuff that would come with a production engine, we just arent there yet. Quote Link to comment Share on other sites More sharing options...
Graham Davies 3 Posted February 17, 2021 Share Posted February 17, 2021 Maybe it's time for a liquid cooled engine? ;-D Some nice scale radiators would be lovely. Cost, complexity, plumbing nightmares? Pffft.. Quote Link to comment Share on other sites More sharing options...
Jon H Posted February 17, 2021 Share Posted February 17, 2021 15 minutes ago, Graham Davies 3 said: Maybe it's time for a liquid cooled engine? ;-D Some nice scale radiators would be lovely. Cost, complexity, plumbing nightmares? Pffft.. It would actually be easier in some respects. But, as you say, it comes with its own share of issues. Weight being the biggest as water is not known for being light. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 17, 2021 Share Posted February 17, 2021 The equivalent on a DH Gipsy would expose the front cylinder but provide a largely sealed chamber on the inlet side with the area blanked between cylinders on the other side to promote flow through the fins. Your design seems to allow rather a lot of wasted flow between the cylinders, Jon (in my totally unqualified opinion) so perhaps it could be worth considering something similar? Seems to have worked OK for DeHavilland with a modest extraction effect from the rear cowling vents (on both sides) and I'm unaware of any cooling problems on the rear cylinders even when being used at high power/low speed work in glider towing...shock cooling after release on the descent being the problem most evident! Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted February 17, 2021 Author Share Posted February 17, 2021 1 hour ago, Tim Flyer said: Very interesting project and great work Ron . Good idea re leaving sides in and moving firewall rearwards . Only thing I may have done is fibre glassed and epoxied firewall in rather than cross bracing. Did think of that Tim but didn't do it for 2 reasons, a)I haven't got your GF skills and b)there's bugger all for it to glass to any the top hence my bracing which should take loads from the top down to the sides. Probably could have achieved the same with some CF bonded to the fuse but see a) above! Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted February 17, 2021 Author Share Posted February 17, 2021 4 minutes ago, Martin Harris - Moderator said: The equivalent on a DH Gipsy would expose the front cylinder but provide a largely sealed chamber on the inlet side with the area blanked between cylinders on the other side to promote flow through the fins. Your design seems to allow rather a lot of wasted flow between the cylinders (in my totally unqualified opinion) so perhaps it could be worth considering something similar? Seems to have worked OK for DeHavilland with a modest extraction affect from the rear cowling vents... This is what Jon is trying to achieve with his cool (get it?) ideas. Most of the air coming into the front is directed into a chamber and because it can't go anywhere else (back, top, 1 side and bottom are sealed) it has to go sideways through the cylinders, back and out. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 17, 2021 Share Posted February 17, 2021 Except that air, being basically lazy, will prefer to flow straight between the cylinders through the gap and around the back rather than being forced to flow through the fins, Only relatively stagnant air will remain in close proximity to the fins and less heat will be removed than if the air had to travel fast through the fins. If you look at the second photo you can see the flat embossed plates between the cylinder gaps which I presume are there to ensure this path is not taken. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted February 17, 2021 Author Share Posted February 17, 2021 The reason this is taking up a lot of my time, is mainly down to two reasons, one is the fact that I'm converting an existing model and its cowl has already been hacked about twice before to accommodate different engines so there is little original structure left of one side and the bottom. If this was a new, uncut cowl I would use Plan A which was to cut it in 2, vertically then it would be so much easier to install the baffles. Once I'm happy that it works then I will use my other cowl (which has only had 1 hack) glass in the bits that I cut out for the previous engine then cut it vertically as Plan A. The other reason is that I've not been in total agreement with Jon over his views on what I had originally done and we've spent the best part of today agreeing to disagree! But the baffling is now done and has had a couple of coats of Clearcoat (the baffles are balsa, really old balsa too, remember the sheets with the red Solar printing?) so if the weather holds off tomorrow should see it fire up! Pictures of the Frankenstein cowl will follow shortly (don't forget this is a test bed certainly not concours!!!!). Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted February 17, 2021 Author Share Posted February 17, 2021 (edited) The Frankenstein cowl, look away those of a nervous disposition! Baffling work, the bit I'm holding is a 'false' bulkhead (part of the old bulkhead) and sits at the back of the engine and has the horizontal baffle attached to it. the horizontal baffle prevents air going over the top of the crankcase. False bulkhead fitted Shot showing front, angled baffle Route that the air is forced to take Doesn't look too bad (from this side) with the cowl in place Bit of a mess from this one though! I will probably remove all of the rather large rivets and replace them with smaller ones when rivet delivery arrives! Edited February 17, 2021 by Ron Gray 2 Quote Link to comment Share on other sites More sharing options...
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