mike skingle Posted February 27, 2022 Author Share Posted February 27, 2022 The firewall is made from 18mm ply, the fuselage surface was abraded and fibreglass cloth was laid down to increase the glue surface area before the firewall went in, as for ease of access I had removed the top half of the fuselage back to the firewall. The glass cloth was then folded over the front of the firewall. It seams to have worked so far. Ron my original idea was to use a set of keleo exhaust but by building the baffling on the cowl it became very difficult to route the exhuast and to then get the cowl on with out compromising the baffling. It was also quicker to put the exhuast out the bottom of the cowl and get flying it. You could pass the air across the cylinders in the lower half of the cowl and then up into the upper half and out both sets of exhausts to increase exit area and draw. My system has only been tested and works at ambient temperature of 16°C when we get some warmer days it'll be interesting to see how well it works. The ground run will be the most challenging part, I found even slowing the idle got things warming up. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted February 27, 2022 Share Posted February 27, 2022 My experience over the last year with my Sportster and the 200 inline is that the baffling that I've got does work but you just cannot let the engine idle for too long especially in hot weather. It happened to me last year when I had started the engine and then was delayed in the pits, when I eventually went to rev it up prior to wheeling out, the engine died on me. I left it for about 20 minutes and it fired up and flew without any issues but back at home, when I took the cowl off I could see some (slight) discolouration of parts the rear cylinder head, proof that it had overheated. In total I've flown it about a couple of dozen times and that is the only time I've had a problem with the cooling. The baffles on the Sportster are in two parts one attached to the cowl and the other to the motor and I'm planning on doing something similar with the P51. An easier answer could be to split the cowl vertically but I'm not going down that route with it! The exhausting hot air will only be allowed to come out from the 'hot' side of the engine so will utilise only one exhaust port, not both. Quote Link to comment Share on other sites More sharing options...
Jon H Posted February 27, 2022 Share Posted February 27, 2022 On my Ugly mustang i plan to use the whole fuselage as a duct with an outlet in the scale position. This has worked on my P39 with its 300v so i was intending to try it again here. I will have my dummy exhausts open but there is not enough area to keep the engine cool so i will be a little extra rather than the only exit. As we talked about the other day the 3 options are the wooden/plastic tunnel as Mike did, Some sort of flexible hose nicked form an old vacuum cleaner or similar, or the whole fuselage as a duct. With composite fuselages the whole fuz duct is great as its very simple and oil ingress into the fuselage is not a concern. For wooden fuselages i suspect some sort of plastic duct or hose will be a better option. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted February 27, 2022 Share Posted February 27, 2022 The exhaust port area is quite large on the YT P51, the following photos show it. Not withstanding that, it's not too late to cut a hole through the bulkhead, in fact I could do that and plug it up if I want to! Anyway, to ensure that the bulkhead was being glued in at the correct distance I used a bit of 10mm threaded rod secured to it and a 3D printed plate. The bulkhead was glued up, the cowl taped in place and the front plate taped to the cowl with the 10mm rod dead centre. I'v checked it out with the engine in place and everything is looking good so next I can glass the joint between the bulkhead and the fuse sides, front first then try and get in to the back. Just as a precaution, the T nuts and engine bolt holes have been filled with Vaseline to help prevent and stray epoxy getting in. 4 Quote Link to comment Share on other sites More sharing options...
Alan Hilton Posted February 27, 2022 Share Posted February 27, 2022 Nice one Ron 1 Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted February 28, 2022 Share Posted February 28, 2022 Nice Ron and there was I thinking that my threaded rod system through the fuselage was my idea for the last 30 years,,,? 1 Quote Link to comment Share on other sites More sharing options...
GrumpyGnome Posted February 28, 2022 Share Posted February 28, 2022 On 27/02/2022 at 07:35, Ron Gray said: @GrumpyGnome I will abrade the composite fuse then glass the new bulkhead from both the front and rear (difficult to get behind it but can be done). I’ve experimented with the ply fixing blocks, firstly with no abrasion and then with, there is a big difference between the resultant adhesive (expoxy) strengths. Cheers Ron! Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted February 28, 2022 Share Posted February 28, 2022 1 hour ago, Paul De Tourtoulon said: was my idea for the last 30 years Sorry Paul, I didn't realise that you were using the system long before I have! Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted February 28, 2022 Share Posted February 28, 2022 3 hours ago, Ron Gray said: Sorry Paul, I didn't realise that you were using the system long before I have! Nothing to be sorry about "Spread the word",,,,? Quote Link to comment Share on other sites More sharing options...
MattyB Posted February 28, 2022 Share Posted February 28, 2022 On 27/02/2022 at 16:55, Ron Gray said: The exhaust port area is quite large on the YT P51, the following photos show it. Not withstanding that, it's not too late to cut a hole through the bulkhead, in fact I could do that and plug it up if I want to! Anyway, to ensure that the bulkhead was being glued in at the correct distance I used a bit of 10mm threaded rod secured to it and a 3D printed plate. The bulkhead was glued up, the cowl taped in place and the front plate taped to the cowl with the 10mm rod dead centre. I'v checked it out with the engine in place and everything is looking good so next I can glass the joint between the bulkhead and the fuse sides, front first then try and get in to the back. Just as a precaution, the T nuts and engine bolt holes have been filled with Vaseline to help prevent and stray epoxy getting in. Random question from an IC ignoramus... Presumably with such a long engine your ability to set side and down thrust is limited, and you just have to accept mixing it out in the linkages and TX? Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted February 28, 2022 Share Posted February 28, 2022 Good question Matty. With the Sportster I didn’t bother about side and downthrust and tbh it appears to have made little difference. But as you have said, any adjustments can be made through the TX. Quote Link to comment Share on other sites More sharing options...
Don Fry Posted February 28, 2022 Share Posted February 28, 2022 I would say, if the engine is twice as long, the thrust washer is half as thick. Quote Link to comment Share on other sites More sharing options...
Jon H Posted February 28, 2022 Share Posted February 28, 2022 The limiting factor is the fuselage width as the long engine means there is more lateral displacement of the enine mount for the same side thrust angle. The other issue with warbirds like this is they have very large spinners and even small amounts of side thrust can make it look like you were half cut when squaring off the nose. My solution to the problem, like Ron, is to not bother with side thrust at all. All of my large warbirds are mounted dead straight and they all fly fine. I hold right rudder in through loops, but as i fly with a very active rudder anyway it is no hardship at all. As with many things in model flying i suspect side thrust is linked way back in history and its importance has reduced over the years with our more capable radio systems. In a freeflight or single channel escapement controlled model i would say its vitally important, but not so much with our full house gear. Clearly some models will see an advantage like patternship's, but for sport/scale i dont bother any more. 2 Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted February 28, 2022 Share Posted February 28, 2022 The way I looked at the YT P51 was that any side / down thrust would have been allowed for when they made the front of the removable engine cowl so by having the threaded rod securely fastened to both the aligning front plate (the one taped to the front of the cowl) and the engine bulkhead then any angling of the bulkhead would be conditioned by the front plate (as they are parallel). Now as it happens, my bulkhead was made to the same size as the front of the cowl, otherwise I couldn't get it in as I didn't cut the top of the fuse back as Mike did which meant that there was a bit of 'wiggle room' when it was positioned in its new location - as the fuse tapers out as you go back. This meant that even with the locating threaded rod positioned in the dead centre of the bulkhead the bulkhead had a bit of room to move sideways thus offsetting the engine but in reality if it did move it was only by about 3 or 4mm. I used 30min epoxy which gave me plenty of time to apply it to the plywood locating blocks and fully coat them before I pushed the bulkhead back, attached the cowl to the fuse with tape then wiggled the front plate (and because they were connected, the bulkhead) into place on the front of the cowl and taped that into position. Once the bulkhead epoxy had set I then set about filling some of the gap between the bulkhead and fuse sides with blocks of plywood epoxied in place. when that lot had dried I then mixed up a batch of laminating epoxy with chopped fibreglass to make a nice thick gloopy mixture which I could press into the remaining smaller gaps and also to form a rough fillet between the bulkhead and fuse sides. That was all done yesterday so tonight I have glassed the joint between the fuse and bulkhead, oh yes, I also cut a hot air exit in the bulkhead (see Jon, I do listen to you). Quote Link to comment Share on other sites More sharing options...
Jon H Posted February 28, 2022 Share Posted February 28, 2022 I think yt models are zero zero on thrust lines. All of mine are i am sure of it and i just slap the engine on the front. seems to work out fine ? Certainly the ugly mustang will have a straight engine. I even have to add a wedge to the cowl to straighten it out! Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted March 1, 2022 Share Posted March 1, 2022 Looks a bit of a mess but it's strong! 1 Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted March 1, 2022 Share Posted March 1, 2022 You certainly won't be needing any lead,,,,or maybe even your engine,,? Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted March 1, 2022 Share Posted March 1, 2022 TBH the photo makes it look worse than it actually is. Having said that I need to make sure that the bulkhead is secure enough to hold the 160 in-line twin. As Mike has suggested above, moving the servos to the tail will help balance things out. Quote Link to comment Share on other sites More sharing options...
mike skingle Posted March 1, 2022 Author Share Posted March 1, 2022 Ron the firewall looks good. It's not so much will the firewall coming out of the fuselage. It's will the fuselage keep up with the firewall and engine. The Spitfire had a bit of an accident while I was removing the bulkhead and a repair made by the previous owner gave way. I checked the CG with the engine in and it's 140mm from the leading edge the manual says 120mm, so a bit of weight can go up the front unlike the P51D. My previous Spitfire needed some lead infront so not unexpected. The baffling is making progress. i just need to sort out the radiators and get the bulkhead and firewall glued in. The firewall has to be about 5mm bigger than the fuselage to allow for the engine mount and to keep the engine in the right place. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted March 3, 2022 Share Posted March 3, 2022 So on with the ‘Laser’ adjustments, ensuring that the tank is lowered. 3D printed tank support not only supports the back of the tank (the front is support by the tank bung moulding through the hole in the bulkhead) but it also prevents it moving back. This amount of the (12oz) tank needs to be recessed into the wing Recess formed in wing, it will be lined with light ply (or 3D printed?) Quote Link to comment Share on other sites More sharing options...
mike skingle Posted March 3, 2022 Author Share Posted March 3, 2022 Ron the firewall looks good. It's not so much will the firewall coming out of the fuselage. It's will the fuselage keep up with the firewall and engine. The Spitfire had a bit of an accident while I was removing the bulkhead and a repair made by the previous owner gave way. I checked the CG with the engine in and it's 140mm from the leading edge the manual says 120mm, so a bit of weight can go up the front unlike the P51D. My previous Spitfire needed some lead infront so not unexpected. The baffling is making progress. i just need to sort out the radiators and get the bulkhead and firewall glued in. The firewall has to be about 5mm bigger than the fuselage to allow for the engine mount and to keep the engine in the right place. Quote Link to comment Share on other sites More sharing options...
mike skingle Posted March 3, 2022 Author Share Posted March 3, 2022 Repairs have made some progress. The firewall is almost ready to be glued in place along with another new former, after removing the old broken bits. Best of all the cowl still fits. Ron Sorry I can't use your 10mm threaded rod method had to resort to bolting the engine on the firewall and lining it up with the spinner on the cowl. as you can see the engine mount is outside the original fuselage, but just fits inside the cowl so all good. Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted March 4, 2022 Share Posted March 4, 2022 A bit messy, but I will forgive you if you can tell me where you got that loverly engine mounting,,,? Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted March 4, 2022 Share Posted March 4, 2022 It comes with the motors! Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted March 4, 2022 Share Posted March 4, 2022 That's quality for you,,,,? Quote Link to comment Share on other sites More sharing options...
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