depth of tap hole

[ir3333]

Does the depth of the tap hole have any effect on the volume of sap flow?

[DrTimPerkins]

Yes.

On gravity, tapholes of 2.5" deep are recommended. On vacuum, tapholes of 1.75-2.00" deep are sufficient.

Those values include bark. If you're only tapping large, thick-barked trees, a little deeper is probably OK. Beyond that, any gain in sap is negligible, however you are making a larger wound in the tree that reduces tapping sustainability in the long-term.

There is an article coming out on relationship of tapping depth to sap yield and sugar content in the next issue of Maple Digest. :)

Several videos at https://www.youtube.com/c/UVMProctorMapleResearchCenter/videos have info on this and other variables affecting sap yield. I'd suggest https://www.youtube.com/watch?v=3wXxByeuc48&t=384s as a place to start

[berkshires]

Yes.

On gravity, tapholes of 2.5" deep are recommended. On vacuum, tapholes of 1.75-2.00" deep are sufficient.

Well now that is interesting!!! I had always thought that 1.5 - 2" was the limit (not counting heavier bark). I thought more than that and you don't get much benefit compared to how much more of an injury you do to the tree. Maybe I was following the limit for people on vacuum/tubing? Thanks for the tip!

And I'll look for that article when it comes out.

GO

[berkshires]

There is an article coming out on relationship of tapping depth to sap yield and sugar content in the next issue of Maple Digest. :)

Several videos at https://www.youtube.com/c/UVMProctorMapleResearchCenter/videos have info on this and other variables affecting sap yield. I'd suggest https://www.youtube.com/watch?v=3wXxByeuc48&t=384s as a place to start

I would love to learn more about tapping depth on gravity, but I don't think any of the videos you suggested mention that. Are there other resources you could suggest?

Thanks again,

GO

[DrTimPerkins]

I would love to learn more about tapping depth on gravity, but I don't think any of the videos you suggested mention that. Are there other resources you could suggest?

The North American Maple Syrup Producers Manual 2nd Edition (aka the Sugarmaker's Bible) https://holmes.osu.edu/sites/holmes/files/imce/Program_Pages/Maple/North%20American%20Maple%20Syrup%20Producers%20Man ual%20full%20pdf.pdf
Tapping guidelines around page 85+

New version (3rd edition) coming out in a year or so (working on one of the new chapters today in fact), however most of the material on gravity sap collection (buckets, bags, tubing, not 3/16" gravity-vacuum) is still valid and not going to change much.

[ir3333]

Good video. Outside sapwood caries more and sweeter sap!
I'll be much more careful when i tap now.

[BoerBoel]

On gravity, tapholes of 2.5" deep are recommended. On vacuum, tapholes of 1.75-2.00" deep are sufficient.

Does 3/16" gravity-vacuum fall under the gravity or vacuum depths?

[DrTimPerkins]

Vacuum is vacuum is vacuum....however it is generated.

[edward]

[QUOTE=DrTimPerkins;389972]Yes.

On gravity, tapholes of 2.5" deep are recommended. On vacuum, tapholes of 1.75-2.00" deep are sufficient.

Those values include bark.

I will be using 5/16 taps with half on buckets and half on gravity. Tapping mostly old trees with thick bark. How far INTO THE WOOD should I drill for a gravity or bucket tap?

Thank you,
First-time tapper
Central Mass on NH border.

[DrTimPerkins]

On gravity, tapholes of 2.5" deep are recommended.

Those values include bark.

if the bark is really thick, you can scape a little off, or, if the trees have been tapped/overtapped for a while, go 2.5" deep including bark. If EVERY tree has thick bark, then you can maybe go 3" (INCLUDING BARK) if the trees haven't been tapped much previously.

Not sure what you mean by half on "gravity". When I say gravity, I mean buckets, bags, or gravity tubing, NOT tubing with ANY type of vacuum, whether pumped or natural vacuum.

[edward]

I apologize if I am using the terminology incorrectly. This will be my first year tapping, so basically I know nothing. ;-)

However, I have tried to rectify the situation by reading and attempting to learn from others. I have been very puzzled by the depth guide for drilling almost always includes the bark which would seem to introduce a significant variance.

Although this study is very old, these researchers were sensitive to the variance introduced by the bark thickness and devised a methodology around it:
https://www.nrs.fs.fed.us/pubs/rn/rn_ne61.pdf

I am not sure if this is the latest version, but the Vermont Guidelines for Licensing Requirements for Tapping specifically limit depth into the white wood, which would exclude the bark:
https://fpr.vermont.gov/sites/fpr/files/State_Lands_Administration/Leases_Licenses_and_Permits/Library/SugaringTappingGuidelines.pdf

I am guessing that the reason the recommended depth always includes the bark is because it would be totally impractical for a person tapping 500, 1,000, or 10,000 trees to measure the depth of the bark for each tree and adjust their drilling depth accordingly. However, for a "backyard" sugaring enterprise of ten, twenty, or even a hundred trees, there might be an advantage to taking the extra time to adjust drilling depth to account for the thickness of the bark. Based upon the fpr.vermont.gov requirement that taps not exceed 1.5 inches into white wood, I was planning to measure my bark thickness for each tree and drill 1.25 inches into the white wood. I guess what I would like to know is if that is close to the Goldilocks Zone or should I go a little deeper or back off a little?

I provided a more detailed description of my setup in the "Introduce Yourself" part of the Forum, but I have about twenty maples on the property and none of them have ever been tapped. About half of them are over 18" ABH and several are almost 30" ABH. The thing is, some have very very thick bark and some don't. About three quarters of them will be tapped with a bucket hanging from a stainless steel spile and the rest are at the top of a hill and will be on tubes with some suction created by gravity going to a collection bucket about ten or fifteen feet down the hill. Those are the one's I referred to as being "on gravity".

Any suggestion on the depth of the drilling or my overall set up is appreciated.

Thank you.
First-time tapper
Central Mass on NH border.

[buckeye gold]

I set my depth gauge at 2" and stop soon as I hit outer bark, that usually leaves me a white wood tap hole of 1.5 to 1.75"+. I'm almost all sugar maples and 3/16 natural vaccuum

[DrTimPerkins]

I am guessing that the reason the recommended depth always includes the bark is because it would be totally impractical for a person tapping 500, 1,000, or 10,000 trees to measure the depth of the bark for each tree and adjust their drilling depth accordingly.

You've answered your own question. It is entirely impractical for the majority of producers to measure bark depth and adjust for each tree. Most people with more than 10 trees would stop doing it pretty quickly. Secondly, we don't know the size of tree of bark depth for each producer, so recommendations have to go by averages that ARE practical, so bark depth is included in the recommendation. Lastly, it is not a good idea from taphole sanitation or leakiness perspectives for producers to be poking around in tapholes to measure bark depth....it'll just cause more problems.

Thus the recommendations provided. However you know your trees....if you feel the bark is extra thick on them, adjust a little for your situation.

The VT FPR guidelines are for tapping trees on leased state land. They tend to be on the conversative side, but they are free to make the guidelines as they see fit. Same as other leasees or inspection agencies (NOFA, etc).

[220 maple]

As Doctor Tim learn that at the Southern Maple symposium in the Fall of 2019, that I and many West Virginia tappers drill maybe a inch and a quarter, then after the extended warm spell that we always get, too restart the trees we bump the tap holes! I have been doing this for many seasons now! Bumping is pulling the tap and going another half inch, depending on the weather can get another two weeks, this is not practical in big sugar bushes, plus I only bump the large trees, Doctor Tim came up to me after the panel discussion, and said he learn a new term “ Bumping a taphole” This not a practice that is approved by Proctor Maple! Though I believe they in the future may do some research on the practice, the bottom line it’s all about keeping the trees running, Steve Child’s has discovered adding a second spile to the drop then drilling directly above the first hole as a way to extend a season.
Mark 220 Maple

[DrTimPerkins]

“ Bumping a taphole” This not a practice that is approved by Proctor Maple! Though I believe they in the future may do some research on the practice, the bottom line it’s all about keeping the trees running, Steve Child’s has discovered adding a second spile to the drop then drilling directly above the first hole as a way to extend a season.

Hi Mark...yes, I recognize the practice (drilling the taphole out deeper), but "bumping" was a new term for me.

Actually, we've already finished 3 full seasons of that work (2018, 2019, and 2020). The amount of additional sap you will get is highly variable....sometimes a little more, sometimes not much more. A good deal depends upon when you choose to do the taphole "freshening" practice. What does happen each time however is that the internal wound is WAY larger than the wound would be normally by drilling to that depth.

Steve Childs (Cornell) second taphole study put in a 2nd tap 8" (I think) above the original taphole late in the season with the objective of tapping within the same stain created by the original tap. We had already done the same type of thing, but only tapped on 2" above the original tap to attempt to remain within the same staining column. While you will often get considerably more sap, we found that the practice also generated far more than twice the amount of wounding, even by tapping only 2" above. The grain in maple is not perfectly straight, and the wounding created by tapping seems to create a zone predisposed to further staining. Basically, it's kind of like two pancakes poured on the griddle a bit too close together, when they merge they create one big (oddly shaped) pancake that is larger than each would've been alone.

Steve did not cut up the trees, but rather just assumed they hit the same stain and didn't create additional stain. That assumption was not correct. We've cut up a bunch of trees -- those types of practices create WAY more stain. Based upon our work, it would be very rare to not generate a huge amount more stain. In effect, double-tapping (putting in a second hole above or below the first hole, even as close as 2" from the first) is more like putting 2-4 tapholes in the tree in one season. Reaming or bumping is like tapping 2-3 times in one season. For those reasons, we highly discourage the practices at the current time, however more research is clearly necessary.

Sometimes trees don't do things the way we want them to.

https://www.youtube.com/watch?v=HoMnuFAcWP8&list=PLZP4fDl-nB9806BqBzubk9c86w-H_5IBv&index=6&t=4s

https://www.youtube.com/watch?v=VH4ceyC_VIQ&list=LL2KD4Pw_9JgJT749KgnE-aA

[TheNamelessPoet]

I apologize if I am using the terminology incorrectly. This will be my first year tapping, so basically I know nothing. ;-)

However, I have tried to rectify the situation by reading and attempting to learn from others. I have been very puzzled by the depth guide for drilling almost always includes the bark which would seem to introduce a significant variance.

Although this study is very old, these researchers were sensitive to the variance introduced by the bark thickness and devised a methodology around it:
https://www.nrs.fs.fed.us/pubs/rn/rn_ne61.pdf

I am not sure if this is the latest version, but the Vermont Guidelines for Licensing Requirements for Tapping specifically limit depth into the white wood, which would exclude the bark:
https://fpr.vermont.gov/sites/fpr/files/State_Lands_Administration/Leases_Licenses_and_Permits/Library/SugaringTappingGuidelines.pdf

I am guessing that the reason the recommended depth always includes the bark is because it would be totally impractical for a person tapping 500, 1,000, or 10,000 trees to measure the depth of the bark for each tree and adjust their drilling depth accordingly. However, for a "backyard" sugaring enterprise of ten, twenty, or even a hundred trees, there might be an advantage to taking the extra time to adjust drilling depth to account for the thickness of the bark. Based upon the fpr.vermont.gov requirement that taps not exceed 1.5 inches into white wood, I was planning to measure my bark thickness for each tree and drill 1.25 inches into the white wood. I guess what I would like to know is if that is close to the Goldilocks Zone or should I go a little deeper or back off a little?

I provided a more detailed description of my setup in the "Introduce Yourself" part of the Forum, but I have about twenty maples on the property and none of them have ever been tapped. About half of them are over 18" ABH and several are almost 30" ABH. The thing is, some have very very thick bark and some don't. About three quarters of them will be tapped with a bucket hanging from a stainless steel spile and the rest are at the top of a hill and will be on tubes with some suction created by gravity going to a collection bucket about ten or fifteen feet down the hill. Those are the one's I referred to as being "on gravity".

Any suggestion on the depth of the drilling or my overall set up is appreciated.

Thank you.
First-time tapper
Central Mass on NH border.

WELCOME to the addiction!

[220 maple]

Dr. Tim
I would prefer not to bump the tap holes, I have had seasons where I did not bump them! The problem we have is extended warm days followed by up to two weeks of near perfect sap producing weather. I go another half inch in the same hole which should not create another stain column, just deeper stain column I rarely drill 2 inches in any tree, I also believe I get sweeter sap by not drilling as deep? Though that could be a false thought on my part,I started this practice of bumping when I went away from a insert that I thought came from Beaver River maple supply, I recently found out they came from a company in Canada by the name of Darv-Eau Inc, these inserts fit perfectly into the Blue 7/16 Leader spiles, if I remember correctly they are 19/64, I would start with that size then when the trees would go thru a heat and basically stop I would pull the insert and drill a 7/16 hole, which made then run just like a new tap! Of coarse the big draw back is putting the same inserts and spiles back into the tree year after year plus they did not seal very good under vacuum, with pumps now and 3/16 creating vacuum the last place I need a leak is right at the tap hole. Going from 19/64 to 7/16 created a wider stain, when my father was in charge he would pull the spile and move over two inches an drill a new hole, a real bad practice.
Mark 220 Maple

[DrTimPerkins]

Matt....I understand why it is done. That was one of the reasons for doing the study...to find possible ways to salvage disastrous (sap yield) seasons.

All I can tell you at this point is that by going from 1/4" taphole 1.5" deep to a 5/16" taphole 2.5" deep, 2.75 times MORE stain than a 1/4", 1.5" deep taphole. If we compare that to a standard taphole (5/16", 2" deep), it still generated nearly 50% more stain.

Our research, like that of Steve Child's, showed that putting in a second spout could produce more sap (the amount depends on the timing of when you do it). But we chose not to talk about it until we cut up some trees and looked at the wounding. When you do that, you find that drilling a second taphole ONLY 2" above (both 5/16", 2" deep) the original taphole usually generates the stain equating to a complete second taphole. In essence, you are tapping the tree twice in the same season. I can't imagine that tapping 8" above the first taphole would make the wounding any less. See the photo below.

21965

Unless the trees are growing like crazy, or our findings are way off (and I think Cornell is planning to cut up some trees for this), neither of these practices are sustainable. So at this point, we can't recommend that people do it, but, of course, it is each individual producer's decision based upon their needs.

This is a great example of why we don't like to talk about some of our research until we: 1) have done at least 2-3 yrs of work and 2) we understand how it affects both yield and wounding (sustainability) and economics. If people hear about just the yield stuff they get all excited and want to go right out and do it....better to wait until we have a good grasp of the consequences....such as the impacts on sustainability. At that point, we can provide all the information and our recommendations, and producers can make decisions based upon complete information.

[220 maple]

Dr. Tim,
I do appreciate the effort that you and Dr. Abby and the rest of the team at Proctor put in to verify or debunk practices that producers try! Yes we producers will always do things that are probably not right! I have to weigh the benefit of doing so, that being said my next crazy idea which I believe will work to extend my season, I’ve drilled all 2500 holes with 5/16 bit around inch and quarter deep, i’m planning on bumping with 19/64 bit another half inch, or even considered bumping with 1/4 size bit, the reason for trying this is I want to keep the first 5/16 hole tight to the spile, if I bump with the same size as first hole any wobble causes a potential leaking spile. I’m I wrong in assuming that the bump hole will have a stain column only the width of the the drill bit size I bumped with or will it be a 5/16 width stain the total depth? My theory is it will be twenty years before I can drill that same area of the tree again. Thanks Again to you and the team at Proctor Maple Research Center
Mark 220 Maple

[DrTimPerkins]

Mark....I think the folks at the southern part of the maple production range do have some interesting challenges, and a longer season with intermittent hot temperatures that cause sap flow slowdown is clearly one of them. I don't blame you at all for attempting various things in hopes of finding something that works.
Perhaps some strategy can be made to work, even if there are trade-offs -- but we need to understand all the effects. I can't say for sure what the result will be with what you suggest, but it seems like any of these things we've looked at so far do end up making a stain bigger than the sum of the two parts. This is probably because when two individual stains are close to each other (even if one is old and one is new), they will extend out a bit beyond where they normally would stop, and can merge. The other unfortunate aspect of "bumping"/drilling deeper is that the "wall" (as part of the walling off or stain development process) that forms in response to wounding in this particular direction (inward) is relatively weak (the vertical direction is weakest due to vessels oriented up/down, which is why the stain extends up/down so much) due to ray tissue running in that direction.

Bottom line...more research is needed to understand how these rejuvenation efforts affect yield and wounding.

[troynh]

The North American Maple Syrup Producers Manual 2nd Edition (aka the Sugarmaker's Bible) https://holmes.osu.edu/sites/holmes/...full pdf.pdf
Tapping guidelines around page 85+

Thank you for that link!

-Tim

[DrTimPerkins]

Thank you for that link!

Just understand that the 2nd edition (that link) was written around 2000-2005. Some things have changed quite a bit since then. Hopefully the new version will be out within about a year or so.

[ir3333]

How do the stain sizes compare for 1/4...5/16 and 7/16 taps? I am planning on going from 1/4 to 5/16 this
year with new taps.Is there a benefit? I do not need maximum flow...this is a hobby for me.I am concerned
about tree health.

[Openwater]

Does anyone know of a website where we can go to look at cut-up trees w/tap scars/stains? Cross-sections and tangential/longitudinal? Maybe comparing different tap sizes?
I figured one of the academic or research people would have some pics or know where to look
Thanks.

[DrTimPerkins]

You should start by reading https://www.fs.fed.us/nrs/pubs/jrnl/1985/ne_1985_shigo_001.pdf This provides a good basis for understanding the process.

You'll have to look through papers on MapleResearch.org and on our YouTube channel https://www.youtube.com/c/UVMProctorMapleResearchCenter/playlists to see various staining in maple. Dr. Abby has some good papers on non-conductive wood...less images, but more calculations of various sizes and impacts of various things (dropline length, taphole depth, etc). There are also a bunch of images online, not all specific to maple. Do a Google search and select images.

[DrTimPerkins]

Don't hold me to it, but off the top of my head I think the 1/4" spout produces about 10-11% less sap and produces about a 15% smaller internal wound (stain, non-conductive wood) volume.

[ir3333]

Tx Dr. Tim. I have used 1/4" taps for my first two years and they worked well..But i was having trouble hanging my "re-purposed"
plastic pails on the little 90 degree taps, so i bought new 5/16" taps with a 30 Degree spout.From this forum
i learned i had been installing my taps too deep and if i Install them properly further out my pails will work fine.
With the 1/4" taps i have a very hard time finding the 2 year old holes on my trees the scar is so small.so i think they are the better choice.
tx to everybody!

[ir3333]

yes..i just watched the video again.Was the video on maximizing sap yields exclusive to vacuum line systems?
Would the trees on buckets have similar results but smaller totals?

[DrTimPerkins]

yes..i just watched the video again.Was the video on maximizing sap yields exclusive to vacuum line systems?
Would the trees on buckets have similar results but smaller totals?

Much of the information was pertaining to vacuum. Parts were relevant to gravity flow as well.

[VT_K9]

Here is a picture of some maple we had sawn into lumber. Long story, but we had 2 trees which needed to come down. I used the boards in one of my shops and I often show friends and customers the difference from the 7/16" to 5/16" taps.

I this board shows a lot. I think I would stay away from 7/16" and recommend 5/16".

Mike

22009

[DrTimPerkins]

Two comments:

1. You've gotta wonder how much sap they were getting out of those holes tapped right into stained areas.
2. It's possible that paraformaldehyde (PFA) was used in those old 7/16" tapholes. Made wounds MUCH larger.

[Openwater]

Dr Tim,
Is it possible that both holes in the same column of stained wood were taps placed at the same time/same year? Would 2 taps in the same "column" produce more sap than 1, assuming that in the future, this is all going to be non-conductive wood anyhow? Or would both taps essentially be pulling sap from the same "source wood"? Or what if 1 tap was drilled 1/2 - 1" deeper than the other in the same column? Sorry for all the hypothetical questions.

[DrTimPerkins]

Would 2 taps in the same "column" produce more sap than 1, assuming that in the future, this is all going to be non-conductive wood anyhow? Or would both taps essentially be pulling sap from the same "source wood"? Or what if 1 tap was drilled 1/2 - 1" deeper than the other in the same column?

I chopped off the first question because I was unsure what you were asking. For the rest, it could vary slightly depending upon whether you're on gravity or vacuum. In general, if you drill a second taphole, or drill another taphole slightly deeper, but close to the first, they will draw from the same sap "reservoir" within the tree. On gravity, this will be mostly above the taphole and mostly on the same side of the tree, but spreading slightly as you go up. On vacuum, sap can be pulled much further, so the "reservoir" is larger, and depending upon the point you are in the flow cycle, could be from above (early part of sap run), across (further into the run) or from below the taphole (longer in the run). The total amount of sap you would extract would be about the same from one taphole or two, you're just splitting it across two tapholes. This is true for strong vacuum (25+" Hg) for trees up to about 20" dbh. For very large trees it is somewhat different depending upon the size of the tree, depth of taphole, number of tapholes, etc.

When we tested this (in red maple) over a couple of years, we found that for trees in the 15-18" range, there was no point putting in a second tap if we were using high vacuum. We use 36" droplines and had one going up and the other going down on opposite sides of the stem to get them as far apart as we could. Even then, the average yield was the same from 1 taphole trees as it was from 2 taphole trees. We are repeating that for sugar maple for the next few years to see what we get. After that, we may relocate the chambers and do some really big trees. Doing that is not easy...there is a lot of setup to get the whole thing right.

Putting a second tap exactly within the staining column above (or below) a taphole is really hard. Even drilling 1" above a taphole you will miss stain entirely some of the time. The further you go, the less likely you are to hit the stain perfectly. The side-side extent of staining is limited to just a small amount beyond the width of the taphole, and it is not always perfectly straight. Maple wood frequently has a slight twist to the grain...at least it does up here on the side of a mountain.

[VT_K9]

In follow up to the pictures....the board came from one of two trees on our family property. The 7/16" holes were made with a bit stock and auger bit for buckets (I have one hole which shows the cut of the end of an auger bit). I could not tell you who hung the buckets back then. We used buckets until about 1993/94 when I was off to college and then tubing entered the picture. I returned to the area each season to help set out lines and clean up. I was in college from '91-'95 and remained in the college town until '01 when I moved back to this area and build my house on the family land in '03.

The two trees the boards came from were approximately 24-30" in diameter and I think the would have had 3 buckets on them. They were on a steep bank with poor footing. That would probably explain close proximity of multiple taps. Not that it excuses poor tap placement. I know that area of maples always produced good quantity of sap...had full five gallon buckets every haul when we used buckets. The youth were often send to collect those buckets.

It was a privilege to be able to have the trees sawn into lumber and see what was inside. Some awesome stories...there is an oak on the property which has a tapping story.

Mike