UKC

I've rigged a toprope 11m up a big oak tree in my garden.

Next job is to fix climbing holds to it (there are no branches until 8m up). Any advice? 

I'm thinking of drilling into the tree and using M10 treaded screw-in inserts. I'm not sure how deep I'll need to drill. How far behind a climbing hold does a bolt need to protrude? It's a massive tree but obviously I want to minimise damage to it.

Chris 

Depends on the holds and how much thickness. Get 40 to 50mm of screw into the tree. 50mm and it's bomber.

What I would say is, borrow a cordless *impact* driver. Not some £15 from B&Q 7volt screwdriver.

Don't say that! I've been looking for an excuse to buy an impact driver for ages. Excellent idea. I'm off to the screwfix website (other vendors are available).

Think twice about drilling or nailing into a tree, you may harm it and reduce it's ability to withstand disease.

https://blog.davey.com/2019/05/do-nails-screws-or-staples-hurt-trees/#:~:te....

Maybe using a ladder to reach the first branches would be a more tree  friendly method?

It's a similar principle to that of not using a tree to run a top rope or running belay through or around, where fixing a sling and krab around it to run the rope through is a better option.

I saw something like this advertised once.

https://www.amazon.co.uk/4YANG-Climbing-Ratchet-Obstacle-Training/dp/B086VB...

DIY - strap on small plywood boards and screw holds onto boards to avoid damaging tree?

Tree holds or not.... Have a think about which brand for cordless stuff. If you already have a Makita/DeWalt/etc drill then obviously you want the same for impact to share batteries and charger. If you don't have anything already and considering a drill in future, factor that into this choice. Screwfix seems to promote DeWalt (presumably they are getting a good deal on them). Personally I went Makita (18v) but they're comparable. If you can afford the brushless motor option in whichever tools you get, then you get a better battery life and usually better tool, worth paying for IMHO. Impact drivers can over tighten and will destroy delicate stuff but where they are totally brilliant is undoing things. Enjoy..

That's exactly the alternative I've been considering. Using cargo ratchet straps to hold them on. 

Put three rubber feet or door stops on the back of ply - three points of contact so no wobble on knobbly tree.

Genius! Wouldn't have thought of that.

Absolutely. That's why I've discounted using screw-ons as I think that will make too many wounds. I'm trying to decide if a smaller number of bolts will cause too much damage, in which case I'll be going for strapped on marine ply, as suggested by elsewhere.

The tree was here long before I was, and I don't want to do anything that seriously harms it.

I've rigged the toprope with two seperate slings onto a carabiner so there's nothing rubbing over tree limbs as the rope moves.