I have a 60 size cub electric and i flow it yesterday .It flew great but when i went to take the batteries out they were real hot the guys at the field said i need to cut some holes in the bottom of the fuselage. the bottom of the plane is one peace plywood should I cut just one large hole or maybe three or four small holes .I don't want to mess up the look of the plane i real like this plane.

Three or four smaller holes

Gee, when i see the subject line "how big a hole" I thought, to myself, I bet I made a bigger hole than you.

I am not sure I would cut any holes at all until I had worked out the cooling flow patterns required. You need to take air from a high pressure area [ usually the front of the cowl ] and exhaust it in a lower pressure area possibly the bottom of the fuz. The exit hole needs to be larger [ 2 or 3 times larger ] than the entrance. Cutting random holes in the fuz bottom may make no difference if the air in the fuz is stagnant

BTW it is normal for the battery pack to be hot after a flight.

For how hot is too hot info you might want to ask that on the lecky forum. Post the EXACT battery type too as heat tolerance varies with types.

Generally holes in the bottom of the fuselage are quite helpful and, if a large enough area, greatly help in keeping the batteries cool. Proper ducting of the airflow inside the fuse is also very beneficial, you want the air to flow over the heat producing items such as the ESC and batteries.

I thought the same way too.

Anyway, you make a number of small holes. Making one big hole will considerably weaken the fuse. Make the holes like j.duncker but make more exit than entry holes. Once you do that, tie up all the cabling inside the fuse so they doesnt fly around in the wind and use safety clips to keep the connectors together (or just use some tape) just as a precaution

Ameyam

well I cut three holes in the bottom of the fuselage about the size of a half dollar . then i went and drilled three moore hole in the fire wall so moore air can pass over the batteries.these holes are 1/2 inch in size .

J.duncker. I thought i would let you know that the batteries are 2 2s 3800ma and they were so hot that they burnt my hands when i took them out I got blisters from them. And i know that this is to hot I was so lucky that they didn't catch the plane on fire.

Just an idea that you can run with. You need air flow, not just holes. In the photos you can see the scoops on the side, those function, there are holes just smaller then the scoops under then. The air flows through those over the battery and ESC then I made a wood directing baffle so the air flow is directed out the bottom of the plane. When I land my battery and ESC aren't even warm so the system works pretty well. The CUB has the engines out the sides so just do a little thinking and you can come up with something that works and you don't notice.

Hot enough to cause blisters??? Is the setup correct? Even with airflow I think it may be masking a configuraiton problem.

You have another problem besides air flow then. Hot warm is about it, blisters is telling you there is a big problem. Like builder said, it's something in your set up. If you go over to Wattflyer you may get a lot more insight into your problem. Go into the beginners forum and post what motor, ESC and battery you have and I know they can help you out.