How do you estimate the safety of what I would call "spreading" trees, where rather than a central trunk you have only branches heading up at various angles? For example if a telephone pole sized branch is at a 45 degree angle -- how strong is that? How much can you tell from the "bounce test?" Thanks.

So much to learn and so little time!

The type of tree, age, species, soft wood or hard woods, diameter of the branch, distance from the attachment point, included bark, visual inspection by binoculars etc, etc, etc.
Here is a _link_ to an article that may help some in answering the question.
http://www.treebuzz.com/pdf/tie-in.pdf

I suggest getting a good reading at the Tree Climbers Companion and some of the other literature posted on line here and at the Articles section of Treebuzz. Experience of the climber and knowledge of the local trees is very important. Do not take risks and stay as close to the center of the tree as possible on the largest diameter branch es possible. Nothing less than 6 inches was the rule in Colorado pines during last year climbs.

Whether the branch union has a sstrong U shape on top versus a weak V is high on the list.

Learn brittle trees from flexible trees.

mdvaden wrote:
Whether the branch union has a sstrong U shape on top versus a weak V is high on the list.

Yep, learn about co-dominant unions, they are weak (V).

It really comes down to learning per species what is strong and what isn't. It takes experience in climbing, there's no predetermined formula. Be conservative in your TIP selection. On your first climb on any tree you select the strongest possible TIP in that tree and then stay tied in twice as you explore new TIPs higher up. I'm going on 4 years into climbing and I'm still very conservative (there's no reason not to be for a rec climber) in TIP choice. I want to get to know a particular tree very well (multiple climbs) before I'll start exploring TIPs away from more vertical trunks. You'll see arborist climbers hanging on very narrow diameter branches way out from the trunk. That's _base_d on daily climb experience over many years and is sometimes on the knife edge of safety, again, something that rec climbers have no business playing around with.
-moss

When trees grow they split apart to grow branches. You'll then find either a U shape or V shape union.

The V shape is an included bark union and is very weak. Besides being hard to slide a rope through or retrieve a false crotch they can split quite easily. V shaped unions are codominants. Both sides are trunks.

The U shape is much stronger. YOu'll find that there is a trunk/branch relationship.

Take some time to google 'branch collar' in order to understand the physiology at work here. Another topic to understand is 'codominant branches.'

PUtting the climbing rope around the trunk rather than the branch is always preferred. Trunks are generally larger in diameter and more vertical than branches.

Keep your climbing rope as close to the trunk as possible. Branches loose strength very quickly as they taper away from the union. Besides loosing fiber diameter the fiber structure is different. Trees will shed branch parts in order to save trunk parts. The ends of branches will fail in winds/ice way sooner than the whole branch will fail at the trunk.

A very good way to learn about tree structure and strength is to go look at how trees/branches have failed after a storm. You'll learn a lot about good branch unions and codominant branch unions too.

Well, I think that for some of my trees I'm going to want to buy a 2nd rope and use two TIPs going up.