aussiesteve

Yep
The only minus of doing it that way is that it can be a bit of a pain to get the tristock past the exhaust outlets. A bit of Trial fitting with the bits taped in place then some careful Dremel Work gets around that. For "Round Cowl" planes, I like to either cut holes in the cowl and screw on aftermarket "cheesegrater" vents that actually work or cut the slots open in the molded cheesegrater vents so they actually work.

It can be surprising to the uninitiated just how much difference is made to how an engine runs when it is at the correct temperature by using the outlets to actually draw the air out (instead of just being an opening to let ram air out) and by directing the inlet air properly over the cylinders. I never have issues over cowl pressure buildups (Signs of which are usually engine tune changing with airspeed or a requirement for piping the air pressure reference chamber to remote locations).

Super08

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Like this...

I later added a baffle in the front and opened all the vents up with a dremel. Very time consuming and messy, works good though.

aussiesteve

Exactly like that. (with the baffle added)

I often see people spend a lot of effort on the oputlets but leave the round cowl inlet completely open. They often try to chase engine problems for quite a while after that.

I once had a plastics business that did a fair bit with Polyesters and Fibreglass. Every Time I grind cowls etc, I get reminded of that business. Make sure a good dust mask / respirator is worn when doing the cutting and wash the clothes by themselves afterwards. (Unless you want to play a mean trick on a teenager by washing the clothes with his underwear - I don't think he had much luck with the ladies that weekend - something about scratching a lot - not that I would ever do such a thing of course )

jedijody

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No cowl pressure problems here.

Can't see it in the pictures but the bottom of the canister tunnelis opened up and louvered as well.

Super08

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That must be a nice performing combo, MT70 in a Goldwing 50cc Yak55M?

jedijody

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MT? What's that?

I kind of feel guilty only building a couple dozen of them up for other people. It is a very fun plane to fly.The GW MX2is even better, same engine. That one is baffled of course, I thought I had some pictures but I can't find them. I guess I could take some, it's right over there in the living room, next to the Edge and 100cc Yak 55M.

Tseres

PAU planes come with a louver molded into the cowl. Never felt the need to add any more louvers. I just fly the plane and never adjust anything. I did add Louvers on the Bottom of the plane for the tuned pipes.

Super08

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Well to keep things rolling along until Pat gets his parts, here are a few pics of my AW Edge. I removed the DLE111 today and the 75K canisters. It did weigh a hair over 28 lb before and I am thinking I have lowered the weight by about 1.5 lb. so with the added power of the DA 120 and an airframe under 27 lb dry it should be a real rocket. This is going to be fun.[sm=shades_smile.gif]

Tseres

I got to fly my Extra yesterday with the 120. Ran great on the ground. Couldn't keep heat in the cylinders. Left side 114F right side 130F with a heat gun. Outside Temp 50 F. Kept leaning the engine and got it better. Put Tape across 1/2 The inlets on both sides and got the temps up to 170F. I may have overdone the baffling a bit but I think it's just to rich still. I also had a problem with either my Batteries or Charger or somewhere in between so I only got 4 flights in. Today is going to be investigation day.

Nice Plane Doug.

Tseres

The problem with charging my batteries was one of the extensions in the plane.I removed both external charge plugs and everything is working fine. I can charge them easily with the canopy off. I applied the KISS method here.
I reluctantly have to admit that our outdoor flying season is about over with. I hope to get one or two more days to put some more time on the engine before I have to put my planes into hibernation.

thepamster

How do you know whether or not baffling is needed with a particular plane/engine combo? I thought this was mostly used for twin cylinder engines. My 1/4 scale skybolt plans call for baffling and I was debating on installing it or not but they only seem to plan on an exit for airflow and nothing in the engine box to direct airflow. It was designed for a tartan twin but I am installing a G62 which seems to me I won't be needing any additional cooling as the cylinder sticks out a fair bit out the bottom.
I have searched other threads about info related to baffling but again it seems mostly related to multi cylinder engines, but not always.

The Pamster

aussiesteve

Hi Pam
What matters is that adequate cooling air flows through the cylinder fins at the right velocity to keep the engine at its optimum temperature. It is possible for an engine to run too cool (not particularly damaging to the engine but it robs power) just as it is possible for one to run too hot (can be very damaging and will also rob power).

For your Skybolt, The original design most likely placed the Twin cylinders directly in front of the cowl openings so intake baffling would not be needed. The Tartans tended to stay fairly cool also (partly because they spent a lot of time not running ). With the G62, will the cylinder protrude outside the cowl? If so, it is likely you won't need to add baffling as the hottest parts of the cylinder will be in the airflow. If the cylinder will remain fully within the cowl, and not in line with a "scale" opening, I would say you would need to have baffling, or at least a (non scale) cowl opening directly in front of the cylinder to direct the air over the cylinder. Another option would be to mount the engine with the cylinder horizontal and use an existing cowl opening (whilst blocking off the other side).

In all of my models, as a minimum, I ensure the air opening to the cowl directs air over the cylinder and that the outlets are adequate to remove that air. (The Yak I posted pics of above has all of the vents operable plus another large baffled opening in the base. That particular plane is BME powered and it has a cooling air box over the cylinders also as the BME has a pretty small fin area).

Tired Old Man

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Nice performing combo? Massive understatement. After Jody re-worked the engine the combo has a nasty p/w ratio. Obscene might be a better description.

Sorry I've been out of touch. Out of town on business for a couple of weeks and it has been exhausting. I should be back in a few more days. A couple days rest and things should get started back up again.

Pam,

Some twins do not require a baffle, but that is highly dependant on how the cowl is set up, the shape of the firewall, and a few other odds and ends. I have a Compy Yak with a BME 116 on it that does not need to be baffled because the engine mounting area is shaped similar to a pyramid, forcing the hot air to the back of the engine compartment which is bordered by a good many louvers to let the heat out. Tried it with baffles and found it all worked better without.

As Steve said, if the cylinder of your 62 is mostly protruding out of the cowl you should be fine without any baffling. A Skybolt with a 62? That must be a big Skybolt and one I would not mind seeing. They have very good lines and make nice flyers.

thepamster

Thanks for your replies guys. I hope you don't mind me posting this question within this thread but since baffling came up I thought I would.
The skybolt is a short kit, fiberglass fuse foam wing cores I bought from r/c city back in the '90s. It is sizeable, 77" top wing span. The 62 does protrude out the bottom of the cowl a fair amount, including the plug, so I think I will be ok. I think it sticks out more than it did when installed in my Ace 30% Extra and I did not have any issues then.

The Pamster

Tired Old Man

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You're welcome. Anyone is welcome to pose a question in this thread. It's a big plane thread for big plane people.

jedijody

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I'm a plane big person, does that count?

How high will it go?

apalsson

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Hi Doug,

You sure have done a good job on that AW Edge! Good work on the baffling

Super08

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Thanks, poor mans fiberglassing. Epoxy and fiberglass cloth in layers.

apalsson

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Here are a couple of photos of my Sbach and the baffling.
I used some 3mm balsa and then fibreglassed it with some 0.75oz cloth.
I ended up bolting in one of the original Aussie made YD-A112cc, a 28x10 prop and some 60mm canisters

Also a few shots of my new man cave that is now near ready

Super08

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Here are some more baffles, may help some people out.
There are some baffles attached to the upper cowl to prevent the air from bypassing over the engine that are not shown.

Tired Old Man

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Another reason to love a split cowl.

thepamster

Apalsson,
  Are those vents on the bottom of the fuselage the exits for your airflow? Does this also mean that the inside of the fuselage to the point behind the vents is sealed off from the rest of the fuselage?
  It seems odd to me to have an airflow that flows through a portion of the fuselage and then out the bottom. Does this cause any aerodynamic issues, turbulence of some kind, during flight say when inverted? I am not sure what exactly I am asking here. I would like to see a wind tunnel demo of some sort showing how exactly the baffle passes air through the engine compartment, the fuselage, and then out.
  Baffling is probaby very common to you guys with those VERY large planes but I am finding this very educational.

The Pamster

apalsson

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They are exits at the rear end of the canister tunnel that allow air to flow through the tunnel and escape out the bottom at the back.

Like Super8, I also have a baffle attached to the top half of the cowl that stops air from escaping above the engine and there are more baffles down on the sides of the engine box that direct the air that flows through the fins down towards the tunnel
This is still work in progress because I have visitors here from overseas at the moment so building work has been on the back burner a bit

aussiesteve

So Henry came back to visit you did he?

apalsson

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You're up early and mischievous!
Nah mate, this visitor comes from "the old country"