Andy J Posted February 20, 2022 Share Posted February 20, 2022 Have a DLE35RA which I have now installed in a large Seagull Sparrowhawk obtaining a totally enclosed installation of the engine. The query I now have is should I include a baffle within the cowl to direct air through the cylinder fins? Currently the cowl does have an open front intake below the prop shaft but this is the only cooling aperture so concerned that the engine will run hot. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 20, 2022 Share Posted February 20, 2022 It's most important that the air can get out - I hope the only aperture referred to refers to the inlet side! How is the inlet orientated with the cylinder finning? Unless the natural flow is through them then baffling is a necessity! Quote Link to comment Share on other sites More sharing options...
Don Fry Posted February 20, 2022 Share Posted February 20, 2022 Photo? Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted February 20, 2022 Share Posted February 20, 2022 I admit to never having baffled a model, never cooked an engine and deadsticks have been very rare, not got an arguement against doing it though. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 20, 2022 Share Posted February 20, 2022 A few models have baffled me! 1 2 Quote Link to comment Share on other sites More sharing options...
Don Fry Posted February 20, 2022 Share Posted February 20, 2022 I’ve had aircraft, no baffle, engine ready to fry eggs. In the early non trimmed flights it’s not a great combination. My take, you look for the exit hole to dump heat, as in flow of air.. You look for the entry hole to acquire heat, as in, air goes through the fins. Each needs design features. Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted February 20, 2022 Share Posted February 20, 2022 1 hour ago, john stones 1 - Moderator said: I admit to never having baffled a model, never cooked an engine and deadsticks have been very rare, not got an arguement against doing it though. Might all depend on the plane, friend had a DB Sopwith Pup with an upright OS120FS, with the open cowl it would overheat on every flight, put a baffle so the only air inlet was in front of the engine fins and it was fine. Also he had a Zero with a DLE 35cc with no baffling and that engine almost died on the 2nd flight due to overheating. 1 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 20, 2022 Share Posted February 20, 2022 Took me weeks to convince the owner of a Flair Harvard with the engine basking in the wide open spaces of an unvented cowl to fit a simple baffle and provide an exit but when he did, he completed his first ever flight with it without a deadstick landing. 1 Quote Link to comment Share on other sites More sharing options...
Brian Cooper Posted February 20, 2022 Share Posted February 20, 2022 (edited) I had a DLE35RA installed inverted in one of my Spitfires. It's a nice engine but it does need some decent venting to keep it cool. This is a rear induction and rear exhaust engine. When mounted inverted, the carburettor is above the hot silencer and, crucially, these two items are too close together. The heat rises and it upsets the running of the engine. Ultimately, the engine can become unreliable in flight. The heat also makes the engine troublesome to restart if hot. . Usually it wouldn't restart until everything had cooled down. The solution was to install a sturdy, heat-deflecting baffle between the silencer and the carburettor. Extra provision was also made to vent the heat away from the engine, and definitely deflect the heat away from the carb. . Try to isolate the carb from the exhaust as much as possible. The engine also benefitted from forced ramming of cold air into the area where the carburettor lived. Result: One happy, reliable engine. Edited February 20, 2022 by Brian Cooper 1 Quote Link to comment Share on other sites More sharing options...
GrumpyGnome Posted February 21, 2022 Share Posted February 21, 2022 Must admit I have never installed baffles but this largely because of the models: Wot4 - no cowl; Ultimate Fun Fly - profile model; Ultrastick - no cowl. I have a Yak54 with a 15cc petrol engine that seems fine - no deadsticks once tuned properly; but it does have a very large hot air outlet where a glow engine silencer used to live. I have a Valiant with a Saito 82 - because of the cowl design, air naturally flows over the cylinder so no issues. My next plane is a P47 with a 20cc petrol. Reading all the comments, I think I'll be adding baffles! As you can see, despite being in the hobby for longer than I care to count, I don't have huge ic experience - for a few years I flew exclusively slope soarers, followed by a number of years with just electric models. Now have a growing collection of nice noisy smelly ic planes. Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted February 21, 2022 Share Posted February 21, 2022 I have a P 47 ( seagull ) 20cc DLE RA and no baffles and no heat / carburation problem's, also even with my two stainless steel boat silencers to quiet down it's screaming ear splitting noise even at 30°+where I live. Quote Link to comment Share on other sites More sharing options...
Jon H Posted February 21, 2022 Share Posted February 21, 2022 always baffle. Its hardly any work most of the time and makes a big difference to cooling 3 Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted February 21, 2022 Share Posted February 21, 2022 (edited) 12 minutes ago, Jon - Laser Engines said: always baffle. Its hardly any work most of the time and makes a big difference to cooling ? Air is a bit like electricity and will take the shortest route often missing the parts that need cooling . Fit baffle and direct it to target then give a decent exit . Edited February 21, 2022 by Engine Doctor 3 Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted February 21, 2022 Share Posted February 21, 2022 2 hours ago, Engine Doctor said: ? Air is a bit like electricity and will take the shortest route often missing the parts that need cooling . Fit baffle and direct it to target then give a decent exit . So will an earth wire on the carb do the job ?.? 1 Quote Link to comment Share on other sites More sharing options...
Andy J Posted February 21, 2022 Author Share Posted February 21, 2022 Made a start on a Depron template for the baffle but unsure how much clearance to give particularly around the crankcase. Exit area is very large as much of the cowl has been removed by the previous owner of the airframe. Possible that I may fill this in using wire mesh. Air intake also pictured below is very small so tempted to enlarge this. Propose to extend the exhaust outlets using silicon tube Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 21, 2022 Share Posted February 21, 2022 Getting air in is rarely a problem - I used a very small inlet area on a Hellcat used in 1/12 scale combat i.e. WOT most of the time of around 3/4” x 1/4” (20mm x 6mm) so your inlet should be fine in front of the cylinder (it’s probably taller than it needs to be!) The tighter the baffling fits around the crankcase the better - the cylinder and head finning should do the work. Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted February 21, 2022 Share Posted February 21, 2022 Same here my Hellcat with a Rcgf 15cc, no overheating. Quote Link to comment Share on other sites More sharing options...
Andy J Posted February 21, 2022 Author Share Posted February 21, 2022 Do you think Martin that I also need to extend the baffle backwards so that hot air is directed towards the exit also preventing hot air circulating around the carb mounted at the rear of the engine? Quote Link to comment Share on other sites More sharing options...
Jon H Posted February 21, 2022 Share Posted February 21, 2022 I would add a lip round the opening in the bottom of the cowl as you risk it becoming an inlet otherwise. As a rule of thumb, if you look at your model from the front any hole you can see is an inlet. Just because the hole is in the bottom of the cowl and you think of it as an exit, it might not actually be an exit. If you can look into the hole, so can the air and it will flow in there with no worries at all. 2 Quote Link to comment Share on other sites More sharing options...
Andy J Posted February 21, 2022 Author Share Posted February 21, 2022 When viewed from the front the underside aperture is visible so assume air will flow in as you say. So what shape should the lip be to prevent this? Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted February 21, 2022 Share Posted February 21, 2022 (edited) You don't need an all around baffle like in pic. Baffles fixed either side of the opening of the cowling and going back to either side of fins will do the trick directing most of the incoming air through the fins. Leave the top of the baffles open a bit so that some air can pass over crankcase and keep a cool air flow over carb. I've used light ply in the past with no problems. As John says a lip around the bottom opening will cause a lower pressure in the cowling drawing more air through. Edited February 22, 2022 by Engine Doctor Quote Link to comment Share on other sites More sharing options...
Andy J Posted February 22, 2022 Author Share Posted February 22, 2022 Well confused as to the best approach regarding the aperture around the crankcase. Currently the litho plate baffle is a reasonably tight fit around the crankcase. Rather than attaching the baffle to the cowl was going to attach it using standoffs to the firewall. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 22, 2022 Share Posted February 22, 2022 Ideally, split the airflow so that some cold air is fed to the carb but bear in mind how any flow will take the easiest route. I feel that the cylinder finning is where you need to concentrate on the flow as this is where the heat is generated and the cooling area is most concentrated. Getting the hot air out easily from the cowling is the key to promoting flow - good advice about forming a lip - I’ve used the back of a covering iron on the front edges of holes in ABS cowls quite successfully in the past but pre-formed louvres can be effective and look the part. Petrol engines can be a little fussy if drawing air from the cowling due to changes in pressure and suction pulse pump issues. It might be better to extend the inlet ducting to the inside of the fuselage with an extended vent from the pump diaphragm atmospheric side. Quote Link to comment Share on other sites More sharing options...
Andy J Posted February 22, 2022 Author Share Posted February 22, 2022 Martin, will open up the top of the baffle around the crankcase given the carb is on the centre line of the shaft. As suggested will also construct a litho plate with angled louvres to close up the bottom of the cowl as was never really happy anyway of having such a large aperture on the underside of the cowl. Quote Link to comment Share on other sites More sharing options...
Christopher Wolfe Posted February 23, 2022 Share Posted February 23, 2022 Just a linky to very cluey bloke and what he wrote about cooling of model engines Joe Supercool and principles of cooling large model engines chris 1 Quote Link to comment Share on other sites More sharing options...
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