HELP! Homemade Incubator vent size? Need help regulating temp, are vents too big?

[Wrightsx4]

Please...advice? - I'm seven days into my first hatch in my homemade incubator. Temps stayed nice and constant for several days prior to setting my eggs, but I wasn't adding humidity. Darn humidity is playing havoc with my thermostat I think. Here's my basics: Thick styrofoam meat cooler approx 20"x15"x15" (guessing, I'm at work so I can't measure), lower unit water heater thermostat - drilled out to make more sensitive as recommended, 25w lightbulb, pc fan in upper corner pulling the heat off the bulb at upward angled . Tried reversing fan, bad idea. I have four vents, two up high on one end and two down low on opposite. My vents are 3/4 - 1" diameter and I tape them partially shut. How much can I safely tape them off? There are other tiny hole where I've inserted tubing and moved the thermometer probe around a little. Seems like when I add water (warm) the temp falls, the thermostat kicks in at lower temp and turns off at a lower temp so the inner-egg temp can't recover without me manually short cycling it. I leave it alone until it falls into the 96 range (inside egg temp) but I step in at that point because it's not recovering. Any advice? sooooo tired of staying up all night and egg sitting. If I don't add water the temp will spike.

since this picture I've replaced the knob on front with a huge dial so I can better control thermostat when needed. Thermostat is put in backwards so metal side faces bulb.

Sorry so dark. this was after setting the eggs.

I've also put in a larger 25w bulb that sticks out a little further. There's a sponge on one wall and a larger one underneath the turners.

 

[Wrightsx4]

Has anyone had this issue with their homemade incubator? Really hoping for help...I need sleep, I need to not be stressed about my eggs while I'm at work...two more weeks to go.

 

[Brookhavens]

What is your humidity level? I keep mine at around 35-40% for Day1 -18 and then raise to a constant 55-65% for lock down. I do not add water until the humidity drops into the high 20's.That's about every 3-4 days. I also made my own bator out of an old Igloo cooler and have had no problems keeping steady temp and humidity. I drilled 2 holes on sides and back and then 3 on the front and top. All holes are 1/4". To keep humidity up you can cover up some of the air holes during lock down all holes are opened. I would be careful with the sponge you have up on top in the wire basket. When you add water it can drip on your eggs and you do not want that to happen (unless they are water fowl eggs.)

 

[Wrightsx4]

Thank you for your input. I am trying dry(er) incubation - keeping humidity at 40 seems to stay pretty well. I do add about a teaspoon of water when I notice the temp going up and humidity going down to low 30's and that seems to settle things again without touching the thermostat, although I'm not sure why. I closed off my large holes at the bottom last night completely and added several pencil sized holes on each end to replace them. I also taped off the large top holes so they are only about 1/4 open. I believe it has helped. Humidity had been dropping into 20's before closing those. I think I had too much airflow between the large holes and my fan. The sponge on the wall is going to be used only during lockdown to add surface area - by then the turner will be removed and I can situate the eggs away from it a bit. quite a few will have been removed by then I'm sure. Candled last night - several hopefuls and one dancing around inside the egg - a definate hopeful I started with 15 but most were damaged in shipping, some crushed, many with bad air sacs. Hoping at least the one little one makes it! I'll have to find it some friends. Thank you for telling me your incubator's air hole size, that helps confirm I'm on the right track.