Martin McIntosh Posted August 16, 2021 Share Posted August 16, 2021 On my Super Aeromaster bipe I use a similar fixing accessed through the front of the cowl. Steel screws into T nuts work fine. Still making the cowl moulds for mine. I would be very interested to see what you are allowing for engine cooling since my plan shows cooling holes in the front former but the air has nowhere to go after that since the dummy exhausts seem to block it off. Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted August 16, 2021 Author Share Posted August 16, 2021 Yes Martin, this has been on my mind too. i haven’t finalised the work around the exhaust outlet yet, but do have some appropriately sized brass tubing ordered to make up the dummy exhaust stacks. Once these have been fabricated to fit the outlet area I will be able to calculate the total area for outflow and compare to the inflow. I have a photo or drawing somewhere that shows some louvre vents on the underside behind the cowl which I guess must be on the forward wing fairing. I will look for it and report as it may point to an additional heat output area. Where the exhaust exits the holes can be made oversize, so that will be another exit point. Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted August 16, 2021 Share Posted August 16, 2021 Nick, I have some alloy tubing for mine but the total csa will be very small compared with the inlet side and generally it needs to be 3x that of course. Been searching for close ups of the full size in this area but no luck. I shall have to pick Jon Harper`s brain because he has one about the same size as yours with a 360. Wish I could get a 300 because it would be about right if the weight turns out a little high and will fit as is in the space for my 180. My cowl parts were going great until now when some of the resin on the front mould failed to set. If I had known beforehand that Black Horse do a cowl for a 77" SF I could have saved myself a lot of trouble. Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted August 17, 2021 Author Share Posted August 17, 2021 (edited) Martin, that’s bad luck re the cowl. Hope you can find a remedy. The spinner backplate has a diameter of 15cms, the front of cowl opening is 18cms and backplate is level with the front of the opening, so total inflow area is around 10cms2 not withstanding the baffle still to be added around the engine. The output area is currently around 48cms2 though the exhaust stacks and other detailing will reduce this by quite a bit. Nevertheless I think it won’t be hard to achieve 3x exit over inflow. Edited August 17, 2021 by Nick Somerville Quote Link to comment Share on other sites More sharing options...
Jon H Posted August 17, 2021 Share Posted August 17, 2021 Dont worry about the 3x area thing, its not true. Many of my models, sea fury included, have either 1:1 area or a smaller exit than inlet. If you have a lip on it as the fury will have you end up with a suction at the air exit and this pressure differential keeps the air flowing. As you say though, the baffle will help considerably and they are easy to build up with the cowl and engine in situ. I have some photos here on my Hurricane thread 1 Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted August 17, 2021 Author Share Posted August 17, 2021 FWIW here is the picture of the louvre vents from my Sea Fury book. Don’t recall seeing any on the example at Yeovilton though. Quote Link to comment Share on other sites More sharing options...
Jon H Posted August 17, 2021 Share Posted August 17, 2021 The exhaust openings work just fine to get the cooling air out. If you want to fit dummy exhausts make sure they are simple tubes so they dont block the airflow Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted August 17, 2021 Author Share Posted August 17, 2021 Brass tube with simulated brackets silver soldered in place ready for making into a pair of exhaust stacks. Here glued in place and painted. Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted August 17, 2021 Share Posted August 17, 2021 Well, I had trouble with the YS 110 in my Chippy and even changed it for a known good one from another model. I then realised that it was an over heating problem so I fitted a baffle and increased the efflux area since the scale inlet was rather large. Problem solved (I think). The underside louvre with a lip on the SF looks to be a good idea so I shall try that. Regarding my cowl, I gave the offending areas another coat of resin which was fine other than the outside of the mould flange. Hopefully corrected and I shall find out tomorrow. I can only think that I did not mix the resin and hardener thoroughly, even though I am quite experienced with it. Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted August 17, 2021 Author Share Posted August 17, 2021 Martin, If you look at this photo there is a good sized additional exit at the rear of the exhaust cutaway. Some good sized holes inside of the exhausts towards the edge of the firewall and some simple internal ducting will route a fair bit of additional air through to the exit. It would be easier than venting through the wing and fitting louvres. It’s my next job shaping this area so will give it a try and post pictures. Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted August 17, 2021 Share Posted August 17, 2021 That looks more like it. My Geoff Lord plan shows throttle servo operated cooling slats as in your pic.; also folding wings. No thanks in each case. The plan is as clear as mud as to how far the sliding slats open. Now very clear. Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted August 19, 2021 Author Share Posted August 19, 2021 It’s raining again so back fiddling in the workshop. Tbf did manage a bit of flying first thing between light showers but it really is pants again in here in Somerset. Hopefully things will improve for the weekend as Popham Airfield are hosting a good sized model show, not so far from here. Sorry Martin, but decided against making additional outflow air routes as satisfied I will get enough cooling around the dummy exhausts and where the Laser exhausts exit. So have pressed on with the outflow area and made a start on the alloy parts. Will try to get these a close fit but won’t adhere them until the fuselage has been glassed and primes to save fiddly masking. 2 Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted August 20, 2021 Author Share Posted August 20, 2021 First time bringing the wings and fuselage together. Looks like I am well on the way, but rather suspect only half there in reality. 2 Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted August 24, 2021 Share Posted August 24, 2021 For the Geoff Lord version I am building please see Sea Fury 77 inch. Thanks for letting me post the above on your site Nick. I shall continue to follow your build with envy. Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted August 25, 2021 Author Share Posted August 25, 2021 Good to work on the engine baffling whilst there are a few others builders discussing solutions to cool their engine installations on here. Mine is pretty straightforward and basically the same as on my P47, except with a v twin cut out. One thing I have learnt is that I hate fiddling about trying to find bolts hidden away with a long tool, hence the three perspex windows with hex drive access holes. At least I should be able to shine a torch through and see what I am doing. The gap to the cylinder head fins is about 3mm and at the rear of the plate are four thin aluminium extenders 25mm deep at the cylinder sides. The gap at the crankcase is a little less, maybe 1.5-2mm. Doesn’t seem like much room for the air to come in, but it will be forced due to the step down in surface area compared to the gap between the cowl and spinner. The four hex drive access holes will hopefully provide some fresh/cooler air for the carbs to breathe. 2 Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted August 25, 2021 Share Posted August 25, 2021 Not much help but the only other radial cowl I have moulded was for my Super Aeromaster bipe, albeit rather smaller. The original idea was to do it as you propose and use hex screws to avoid external ones after the motor was fitted but as it happened, since the 80 protrudes anyway, I could fit the cowl first. Considering the distance from the holes in the perspex to the firewall and the fact that it will get smothered with gunge I have a feeling that you may struggle. How about thin alloy tubing or similar between the perspex (or further in) and the bolt heads (with a suitable support) then use a ball driver to fit them? Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted August 26, 2021 Author Share Posted August 26, 2021 Now here is something to fiddle together when I am not in the mood for making balsa dust. Arrived this morning from USA, somehow thankfully avoiding customs and additional charges. The kit of parts is made for the ESM Sea Fury which is almost identical scale to my Bates model so hopefully a good fit. Made by Tysplanes.com the chap makes cockpit kits for a whole range of ESM warbirds. Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted September 1, 2021 Author Share Posted September 1, 2021 Earlier in the thread I showed how I had added diagonal ribs at the flap area as the structure was quite flimsy due to the large area and light balsa sheeting. O had a good look at this area on the example at Yeovilton and noted that almost all of the area is skinned, so seemed worth doing the same. I needed to add a few extra strips of balsa to support the front edge of the skins but otherwise it was a simple job to draw and cut around the completed flaps to make up the .8mm skins. A small cut out was required to allow for the flap horn and linkage. Certainly made everything nice and rigid. Outer flaps done now the inners. I would have used .5mm to save weight but it is more than twice as expensive. £12.30 for 4’ x 1’ of .8mm and £14.70 for 2’ x 1’ of .5mm!!! Oh well they do say less is more. Pics in reverse order for some reason ? Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted September 1, 2021 Share Posted September 1, 2021 When you say 0.8 or 0.5mm I take it that you mean ply. 0.4mm is currently around £9/sq ft the last time I tried to but some. Just building the outer sections on mine so I know the flap piece you mean. More later on my own blog. Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted September 1, 2021 Author Share Posted September 1, 2021 Yes 0.4mm to be precise. Probably my favourite modelling material as I may have mentioned previously. So easy to cut with a scalpel or scissors accurately. All the sheeted areas of this 1/4 scale Kirby Kite I built from a plan by John Watkins in the 80’s was 0.4mm ply. 1 Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted September 8, 2021 Author Share Posted September 8, 2021 Weather has been brilliant this way for some days, so lots of flying and only a little progress to update. There isn’t really much on the plan to show how the wing fairings all come together with just a few mentions of filling with scrap balsa. Here you can see how I dealt with the lower front area of the wing. Before moving on to the main wing fairings I installed a pair of hatch hinges and inside of it mounted a plate holding the switch (for an Ar9100 DSMX dual battery receiver) and the compressor/air pump fitting). The hatch will be cut out later after glassing, relieved a little around the edges and capped with an overlapping rectangle of litho. With that assembly in place I have commenced sheeting the gap between the main ply crutch formers with 0.4mm ply. This will give lots of area to firmly bolt the wing down onto without any pressure points. Next I can start shaping the rear parts of the fairing, a task I usually enjoy and then it’s a final fettle and sand all round prior to glassing. 1 Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted September 10, 2021 Author Share Posted September 10, 2021 Thought it time to take a deep breath and get the scales out whilst the wings have been attached to work on the root fairings. Accounting for everything assembled so far inc engine but less cockpit detail, pilot, spinner, prop, receiver, batteries, throttle servo, wing and fuselage glassing and paint job she is currently at 18lbs. I estimate no more than 3lbs to complete so that leaves me only 2lbs of lead up front if I want to achieve 23lbs auw. Quote Link to comment Share on other sites More sharing options...
Nigel R Posted September 10, 2021 Share Posted September 10, 2021 (edited) that's looking great Nick that ply, expensive but looks worth it, the wing around that area looks real neat with the ply in place remind me, one servo per elevator? Edited September 10, 2021 by Nigel R Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted September 10, 2021 Author Share Posted September 10, 2021 Just one servo for the elevator. It’s rated at 20kg with 2s lipo power but I shall have a pair of Life packs, so probably more like 15kg. Should be fine imo. It’s not a model to chuck around, so in reality the servo will have little work to do. The other servo with a carbon pushrod is for the tail retract. Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted September 10, 2021 Share Posted September 10, 2021 Great job Nick. I have not posted further on my blog as yet because I am having enormous problems with the wing construction from the plan I have. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.