Originally Posted by musigenesis
Here are some pics of a seam I laid down today between two roof panels:
I masked off the area, laid down a bead of 550 and then smoothed it as best I could with my finger, then removed the tape. I think the seam is good in the sense that it will be a good waterproof seal, but it looks like straight ass. Any tips on getting a smooth-looking seam over a ridge like this? Would using a putty knife side-to-side give a better result? Is this something that will look a lot better once I sand it and paint over the whole roof?
There are also some pics there of my Dynatron job on two of my windows. Those also seem to be well-sealed but also look pretty amateurish (although I didn't use any masking tape for those). Are there any good tutorials around for this?
I don't know much about buses, But I worked with a lot of caulks over many years.
Never used this brand of caulk, but here is how I have laid down miles of various caulks and it will probably work with this caulk also. It is quick, easy, produces quality, pretty results and any body can do it. Gets better with practice, but is quick/easy to learn. Try it if you can understand my instructions. It sounds complicated, but mostly because I have a problem explaining a skill with words only.
First get an inner tube that you can cut up. I used Firestone rubber roofing back in the day, but any inner tube rubber works fine.
Tools: 1- 5 gal bucket with a handle (can also be hung off of a ladder if necessary), 1- caulk gun, 1- good, sharp pair of scissors. Some small disposable rags or a roll of paper towels, I prefer rags. Some thin nitrile disposable gloves could be handy but I've never used them. A knife to cut the caulk tube if it doesn't have a built in cutter.
The bucket serves as a trash container and keeps all of your gear together so you can move quickly, cleanly, and efficiently around. Also works great off of a ladder. You could also use a second bucket for trash, if you have it, (keeps the sticky caulked up rags and rubber strips from getting everything else messy) - keeps the mess to a minimum
Put 2-3 caulk tubes and all the rest of the stuff in the bucket. Hang the caulk gun on the inside of the top of the bucket (by the handle) so that any caulk drips will fall into the bucket and you always have a place to quickly put your gun. Put your paper towels/rags in a disposable plastic grocery bag (to keep them contained and clean) and hang from the bucket handle inside the bucket. Forget your masking tape. I carry my scissors in my back pocket, handier for me.
Getting Ready: To find out how to cut up your rubber for use (and practice) - get a crisp, new sheet of 8x11 paper, Cut 3 strips lengthwise, 11 inches long. 1 - 1inch wide, 1 - 1.5 inch wide, 1 - 2inch wide. Take 1 of the strips in your hand and lightly cup it so that it curves in the short direction, let a couple of inches stick out between your index and middle finger so that 1 finger rests on each corner. Put your 2 fingers down on a tabletop with the paper down between your fingers and the table top. The paper should be arching up between your fingers. Spreading your fingers apart makes the arch wider and lower, bringing your fingers closer together makes the arch narrower and higher. This arch is going to be the profile of your caulk bead. You control it with your 2 fingers. Make sure that you have a wide enough strip so that there is enough paper/rubber under your fingertips to get a good grip and get the arch profile that you want. Your fingertips can hang over the sides a little, if you like, and it improves your control. You may have to use your thumb (or your other hand) to help form the arch initially.
Try all three pieces of paper to see what you like best then cut a piece that fits you. Bigger fingers like wider strips. When you think you have it figured out, cut a rubber strip to your size and give it a try. They don't have to be perfectly straight edges. You can also experiment with cutting curves/angles on the end of the rubber strip to change the profile, but I always came back to a straight cut. Some plastics/paper may work instead of rubber??? Never tried it. Paper may tear. You can also buy plastic "tools" pre-made. Never tried them either. I have used duct tape instead of rubber, with the tape stuck to my finger tips. It is cheap and gives good control, but my fingers get sore after repeatedly pulling the tape off (the glue tries to pull off your skin, never occured to me to try using gloves).
Caulk gun prep: Make a straight, smooth, 45 +/- degree angled cut on the caulk tube near the tip. Poke a nail or wire into the tube several times to open the seal. Squeeze out a bit of caulk. You want a 1/4 inch - 3/8 inch bead of caulk. Enlarge/re-cut the tube if necessary. If you need to stop and you have a partial tube, use a screw or bolt of the appropriate size to plug the tip (duct tape can be of help)
To use: Lay a bead about a foot long and then work it with your rubber strip. Quickly put the rubber over the bead with 1 finger on each side and hold down firmly while making a continuous smooth stroke. The caulk will form to the shape of the arch. You are in control of the shape by changing the distance between your fingers and the pressure. Sometimes I use my index and 4th finger with my middle finger on top of the rubber center for some situations. Whatever works for comfort and control. The smoothness is controlled by speed and the cleanliness of the rubber tip. When the tip gets nasty, hold it over the bucket and cut it off with the scissors and start over. When the rubber gets too short to handle make a new one. I make several at a time so I don't have to stop (keep them in your pocket or in the bag with the clean rags).
A short length of bead is better to start with. You can have a second person running the caulk gun as long as they don't get too far ahead of the person running the rubber. Work fast, the caulk begins to skin over immediately and quickly gets to a point where you can not work it fast enough to make a pretty, smooth surface. Don't get greedy and try too long of a bead, you won't go any faster and your work will just get crappier. If you don't like it, wipe it off immediately and do it over. Practice makes perfect. In my opinion, lint free rags (cut jeans, t-shirts, sheets) work better than paper for cleanup.
Somethings to keep in mind when using caulk is don't get it too thin, especially over cracks or gaps. It has to have enough thickness to have any strength and really thin tapered edges tend to come undone when it drys. Surfaces have to be really clean for most caulks to adhere properly. Don't be lazy when prepping.
You can also keep a small container of sovent or water (depending on the caulk type) in the bottom of the bucket for quick smoothing and clean ups.