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I'm in the process of making a bridge for my ABG build and am stressing over the exact placement of the bridge and the saddle slot angle. I've seen questions about the compensation of these guitars but haven't been able to find anything stating what the best guess for a starting position would be. So, here is my logic, could someone take a look and tell me if I'm way off base?

My best guess logic is simply using the gauge of the string, height of action and scale length, since all other variables are too hard for my limited brain cells to deal with. So, I just have take a 34" scale, and action is the same as my martin dreadnought, whatever that is. On the Martin, 5th string is .045 and compensated roughly 1/16 past the theoretical scale length(maybe not but this is just an exercise in logic so please don't focus on any inaccuracy).

Anyway, the strings I have for the ABG start at .045 for the high string, same as the Martin's 5th string. So, I'm thinking a good place to start with saddle/bridge placement would be 34 1/16". Then the low string .105 would just keep an angle the same as the Martins, roughly 1/8' back from the high string. Then adjust once installed. Does that make sense? Is that a good guess?

If you have access to an electric bass with adjustable saddles, you can use it as a test bed to determine compensation requirements for the strings you want to use,
Adjust the saddles up to appropriate height, adjust the intonation, then measure saddle position.
I just completed an ABG using Savarez classical bass guitar strings(nylon core) with very different compensation needs to steel core strings. I checked using this method and ended up with only 1/16" compensation reqd

You can also make a temporary tailpiece of sorts, and test the position in "realtime" with a good electronic tuner, then mark the bridge position with tape. Pieces of string can act as temporary saddles, for a more exact fulcrum point for the string. Then, fine tune things by filing the saddle profile after the bridge is glued on. Here's one I did like that a while back

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Rian Gitar og Mandolin

I don't have access to an electric bass. Great idea though, and thanks for the info about the Savarez strings. What's the tension on those by the way?

As far as I could tell they were about 25% less than bronze/steel core
When I do a string change and cut off the ends, I'll be able to weigh them more accurately for unit mass
I went this way to allow a more mobile soundboard.

This is probably what I'll do, it makes sense and is probably simplest with the materials I have available. Thanks Arnt. Nice bass too!

I just picked these strings because the tension was similar to medium gauge strings for a six string. I used J200 plans for the body and bracing so figured I should be ok. We'll see.

Thanks Jeff!

Ok, I figured I'd post a followup to this because I tried something that didn't work before getting it right. Long story short, the high G plays in tune when adjusted to exactly 34", or as close as I can measure, and likewise the low E is 34 1/8". I got this using the setup Arnt showed in the picture above. Thanks again!