Bicycle Mechanics - Wheel building questions

So I'm planning on building up a Mavic Open Pro to a Powertap front hub to match a wheel I bought recently, and I'm wondering about lacing patterns for a 32h wheel, the rear wheel is 2x but how should I build the front? 2x? radial? what are advantages and disadvantages of each? How do I know the spoke length and how do I make sure the hub is centered and the wheel is dished correctly? also how do I choose a good tension for the spokes? Is a tensiometer a good idea?

Sorry it's a lot of questions, but it's my first time building a wheel, I want to learn, and I figure it's a good time to do it.

3x on a 32 spoke is almost like a 4x 0n a 36 spoke wheel.
2x is what the Rohloff company suggests for their hub
for 26 and 29er rims
1x for smaller, 20" rims.
front hub , no disc brake? no dish..
more answers ? hire a professional..

Since it's a PowerTap, you must use 3-cross lacing on both sides. Consult the hub manual.

edit: oh wait, it's a front wheel. I'd still use 3x.

Wheel building is frequently discussed here, and there are several online tutorials available. Sheldon Brown's article on wheel building is a great place to start.
Do some reading first, then post specific questions. Don't think anyone here is willing to restate what's been so well written, and easily accessible already.

3x on a 32 spoke is almost like a 4x 0n a 36 spoke wheel.
2x is what the Rohloff company suggests for their hub
for 26 and 29er rims
1x for smaller, 20" rims.
front hub , no disc brake? no dish..
more answers ? hire a professional..

1. All dual flange hubbed wheels HAVE dish.
2. All wheels properly built must BE dished.

No such thing as a zero dish or no-dish wheel...

=8-)

Is a tensiometer a good idea?

....Sorry it's a lot of questions, but it's my first time building a wheel, I want to learn, and I figure it's a good time to do it.

You have to learn to crawl before learning to walk.

It's your first wheel, so don't try to overthink it or get too creative. Stick to plain vanilla until you have enough experience to experiment intelligently. Build a two cross wheel following the steps available on so many tutorials.

I'm not a fan of tension meters used the way so many folks use them today. If you work carefully by degrees, keeping the wheel aligned before it gets tight, especially radially (hop) you'll end up with even tension automatically. Front wheel tension isn't super critical, so you can compare it by hand to the existing rear. It should be tighter than the left side, close to but less tight than the right.

^ I disagree somewhat there. You can make a wheel true but end up having 2 neighbor spokes (of the same side) off because one is overtensioned while the other is undertensioned to compensate. That being said, standard builds on sturdy rims have a lot of room for error. The tension meter becomes more important when you start getting into super light components and low spoke counts.

^ I disagree somewhat there. You can make a wheel true but end up having 2 neighbor spokes (of the same side) off because one is overtensioned while the other is undertensioned to compensate.

You missed the qualifier "if you work carefully by degrees...". With good practice, bringing all the nipples to the same length then loading tension by multiple passes of less than one turn, all the spokes will come to roughly the same tension, and in theory the wheel will be aligned.

The theory doesn't hold in practice because of variations in spoke length, rim eyelet thickness and how precisely you can turn all the nipples to the same length, but with good habits it comes pretty close. The key to even tension isn't to resolve it late in the process with a tension meter, but not to introduce (or minimize) uneven tension throughout the process. This technique has long served (almost a century) wheel builders before tensionmeters became a must have tool.

BTW- Today's rims are forgiving of uneven tension because they're stiff enough to stay true past a slacker spoke. Older light ring were much squirrellier and the least variation in tension would show up as a local rim deflection. With a very light rim it's very difficult, if not impossible, to build a tight, aligned wheel with uneven tension.

Eh, I didn't miss that qualifier. That's how I have always built wheels. Like you said, it doesn't work in practice. However, you're right that you shouldn't fix tension late in the build. After I finish hiding all the spoke threads (in 1/2 turn increments until they are hidden by about 1 to 2 turns), I check tension and bring any slack spokes closer to the rest (note, no truing yet). Then I tighten by a half turn and check again. This process is repeated until the uniform spoke tension is close to the desired tension for the build. The result is usually a reasonably true wheel to start with. Then I finely true the wheels and check the tension again, backing one spoke off while tightening the other if they vary by more than I want.

Spoke length calculator:

http://sheldonbrown.com/rinard/spocalc.htm

And there are others