Tappling 1½" deep this year

[HowardR]

I started tapping 1½" deep holes this year. Here's the way my drill looks with its 5/16 drill bit:

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Dr. Perkins didn't recommend 1½" deep holes. But, in a thread last year about retapping (http://mapletrader.com/community/showthread.php?32354-Retapping&p=351423#post351423) he suggested putting a short piece of 5/16" tubing over the bit as a way to regulate hole depth. I couldn't figure out how to get my tubing over the bit, so I hot-glued (so it wouldn't fall off) a 4-way plastic mainline entrance for ½" lines onto the drill bit.

I decided to go with 1½" depth instead of 2" for three reasons:

1. Dr. Perkins found (http://www.rothmaplesyrup.com/Documents/SpoutStudy.pdf) that holes that were 1½" deep yielded 98% as much sap as holes that were 2½" deep.

2. Copenheaver found (http://pubs.cif-ifc.org/doi/pdf/10.5558/tfc2014-149) that tapping trees can retard tree growth, but only in the two bushes tapped by college students and not the bush tapped by professionals. My guess is that the college students, like most beginners, tapped too deep. (There was no mention of, and thus no attempt to control tapping depth in this study.)

3. Dr. Perkins wrote in the above thread that the heartwood in a maple tree begins at 2" depth and that drilling into the heartwood damages the tree.

I'd be interested in hearing how others regulate tapping depth on their drills.

[Sugarmaker]

Just my 2 cents:
Sorry but I believe your way over thinking it. I guess like a lot of things if you do it a lot you get a good feel for the depth even without a depth guage. Your set up will work but could be a little hazardous? The bit your using will work but its not like most of the newer tapping bits that I have seen? Yours looks like the ones we used in the old brace and bit, when we were drilling 7/16 tap holes by hand.
They also make collars with set screws to clamp to your bit for a depth guage too.
Not sure I helped much? Also makes a difference on how deep your setting your taps.

BTW I probably tap about 2 inches deep on mostly tress that are at least 100 years old. I agree tapping too deep may not be good for the tree.
Regards,
Chris

[DrTimPerkins]

I started tapping 1½" deep holes this year. Here's the way my drill looks with its 5/16 drill bit:

Dr. Perkins found that holes that were 1½" deep yielded 98% as much sap as holes that were 2½" deep.

That was not the actual objective of that particular group of studies, but was an observation. In more detailed work, we've found the following (on high vacuum with excellent spout sanitation practices):

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2. Copenheaver that tapping trees can retard tree growth, but only in the two bushes tapped by college students and not the bush tapped by professionals. My guess is that the college students, like most beginners, tapped too deep. (There was no mention of, and thus no attempt to control tapping depth in this study.)

Whether tapping affects growth in trees is a very valid question. Several studies have shown varying things (much as Copenheaver et al. found in their work). I think the answer is still unclear. The secondary question is...so what if growth is slowed down a little? Is any reduction totally unacceptable, or is a slight slowdown in growth a reasonable trade-off for harvesting sap? To answer the first question with more experimental control (and that is one of the problems with have with prior studies..."nearby" sites are often quite different in their growth histories), we are 5 yrs in to a long-term study comparing the growth of untapped, traditionally tapped (gravity) and high-yield tapped trees. So far, after 5-yrs...there is no significant difference in growth in those three groups.


3. Dr. Perkins wrote in the above thread that the heartwood in a maple tree begins at 2" depth and that drilling into the heartwood damages the tree.

There is considerable variation in the distribution of heartwood in maple trees. In a healthy, rapidly growing specimen, heartwood may be 6" or more deep. In a poor tree growing on wet soil that has been tapped a lot, you could hit tapwood within an inch. The best way to know is to observe the drill shavings periodically to see if you're hitting nice white wood or stained wood.

You've come up with an interesting approach to setting the depth on the tapping bit. Let us know how it goes. As you mentioned, we usually just use a piece of 5/16" tubing slipped over the bit to keep the taphole at the right depth. You could also use a bit-stop. Some people use the Precision Tapper.

We tapped 2" deep this year in the production bush, but we do have one area where we tapped different depths (1.5", 1.75", 2", 2.25") to try to narrow down even better the most appropriate depth of tapping. We're also repeating some of Tim Wilmot's earlier work on 1-tap versus 2-taps. All of this is part of our effort to come up with more scientifically-based tapping guidelines. Hopefully we'll have a guide out within another 2-3 years.

[HowardR]

Sugarmaker,

Thanks for the info about bits. You are correct about the bit. I started tapping with brace and bit and I just kept using the same bits with my electric drills. I've always liked the way those bits grab into the tree and pull the bit in so that you hardly have to push once it engages. That really helps when I'm tapping at an awkward angle.

Howard

[HowardR]

Dr. Perkins,

Thanks for the additional info. That graph you posted shows why 1½" hasn't become the standard. I'm looking forward to reading the study where you compare 1.5", 1.75", 2", and 2.25". Maybe I'll switch to yet another depth when your new results come in.

Also thanks for the tip about the color of the heartwood. I never bothered looking for a difference in color in the shavings, but I'll start looking at my shavings in the future. I've always thought that the faster growing trees could be distinguished by their smoother bark.