Gourds should have ventilation features added to them, if they do not already come that way (as in the case of BO-11Ps with cooling caps). On this page, I will show you how to add 1/2" and 3/4" elbows to a Supergourd, but this same method could be used with any plastic gourd.
Supergourds are great gourds, and as far as plastic gourds go, are quite well-made. However, when the outside temperature gets into the mid and upper 90's and above, this gourd can get quite hot inside when hung as-is, and oftentimes, baby martins will show heat stress by panting and spreading out in the gourd. In addition, the humidity inside a gourd can rise to the point where condensation appears inside the gourd, runs down the sides, and causes the nest to become wet. This is especially an issue in Troyer Horizontal gourds. Proper ventilation can help keep the nest dry.
I like to use two ventilation elbows in these gourds when using either 1/2" or 3/4" screw-in 90 degree PVC elbows. Do NOT use unthreaded elbows! You may think that you can drill the hole wide enough to accommodate a regular elbow, and you may think you can glue it into place, but the moment it is dropped and lands on that elbow, it will pop right off. Save yourself the trouble and use threaded, screw-in elbows from the start!
First of all, you need to decide which size elbow you are going to work with. 1/2" elbows are the cheapest, and generally run 70-85 cents a piece, depending on where you buy them. If you are using 1/2" elbows, you will need a 3/4" drill bit or hole saw. Why is that? The reason is that the outside diameter of the screw-in elbow will fit inside a 3/4" drilled hole. The 1/2" measurement on the elbow refers to the INNER diameter of the elbow, not the OUTER.
This picture shows the 3/4" drill bit, ready to drill a hole into the Supergourd. Click to enlarge.
Here we have the hole, just drilled out. We are ready to screw in the elbow.
In this photo, you can see the 1/2" threaded elbow, getting ready to put it in the hole.
I do not screw the elbow all the way in. I like to leave the elbow pointed slightly up to allow for less wind resistance and better ventilation. It just seems easier to me for hot stuffy air to escape an elbow that's not pointed directly down. This position is still quite rain-resistant.
I screw the elbows in at an angle, so they are pointed slightly up, instead of at a 90 degree angle flat with the gourd. I believe it helps with the chimney effect of the elbows. Here are both screwed in and ready for caulking.
If you want to use 3/4" elbows, you will need to drill a 1 inch hole. In this picture, I am using a 1" hole saw to drill the needed holes.
Important - after you have put in your elbows, caulk around the elbow to seal out rain and prevent leaks. I use a product called Lexel. It is the best caulk I have found for this job. It does not shrink or harden (totally), it sticks really well, and is paintable after a few days' curing time. It also makes a great glue. It is a little more expensive than standard silicone but it is well worth it!