Video Today... Possible Natural Vacuum?

[DonMcJr]

Here's my Sap Flow video from today. Near the end my Tube line really picked up....is this natural vacuum or is that just how much it flows 15 taps on Gravity Tube?


http://youtu.be/JS-M2PlcdMg

[unc23win]

Nice video Don. A little windy? Did you get any reading on your vacuum guage? Looks like a pretty good run.

[DonMcJr]

The gauge says " no vacuum" but theres a stop for the needle and it wasnt on the stop but it was still in the no vacuum range.

[DrTimPerkins]

The gauge says " no vacuum" but theres a stop for the needle and it wasnt on the stop but it was still in the no vacuum range.

How much total elevation fall do you have from top to bottom of the line?

[DonMcJr]

I'd say about 6 feet or so... actually probally more like 10 feet cause I forgot about the slope. Highest tree is tapped 6 feet up but the ground slopes probally another 4 feet...

[mapleack]

Don, not to rain on your gravity vacuum parade, but have you read this? http://www.uvm.edu/~pmrc/highvacuum.pdf Very informative article by Tim Wilmot.

[Starting Small]

Good article, why then does everyone use 5/16 tubing instead of 3/16 if it is easier to achieve vac with 3/16?
-Dave

[lastwoodsman]

As the article states it was done in 2012 and is a new method. I am sure it will become more mainstream as we have just learned of it. I just ran a new 5/16 gravity line system last fall, had I been a little more on top of things I would have went with the 3/16. The tubing and fitting are in limited supply right now and only available from a one source for the tubing and one source for the fittings that I am aware of.
Woodsman

[DrTimPerkins]

Good article, why then does everyone use 5/16 tubing instead of 3/16 if it is easier to achieve vac with 3/16?
-Dave

3/16" will work well under certain conditions (you definitely need slope). 5/16" will work well under different conditions. All depends what your situation is. You definitely wouldn't want to pull vacuum (pumped) through a 3/16" line.

[not_for_sale]

Don,

your gauge is at the wrong location. At the bottom of the line where you have it it will always read nearly zero. Vacuum is created through a natural column of sap sitting in the lines. Highest vacuum in that arrangement will be at the top of the hill/slope/tube.

Joe

[DonMcJr]

I knew the gauge was at the wrong end. I had the Gauge and fittings to put it there so I threw it in for the heck of it.

So I just read that article. Seems like you need a lot more slope than 10 feet. So my question now is my tube system is leak free. I read in a leak free system the sap still creates a small vacuum that holds the sap in the tube. SO does this mean that by not having enough slope the sap is kinda stuck in there and not flowing as good as it could?

Should I vent my lines to just get natural flow like if I were using buckets?

I cant believe after reading all the threads on here about natural vacuum it leaves one to believe it's possible like I did it but after reading the article and not having much slope I think I would have been better off with a larger mainline like I wanted to do in a previous thread where I was asking questions and the folks that replied said to go with all 5/16 and hope for natural vacuum...:confused:

[DrTimPerkins]

Should I vent my lines to just get natural flow like if I were using buckets?

NO Do NOT vent.....unless you'd like 33-50% LESS sap. The sap will run slowly in an unvented (tight) system, but that is what creates the vacuum. You will get some natural vacuum, but you need at least 30' of fall in elevation to develop good vacuum.

[FDA]

In you video you mentioned that you didn't touch anything for the last 15 minutes. Are you closing that valve and letting the sap back up in the tubing to create vacuum ? If so than maybe you need a actuator valve on a timer to open and close the valve at a set time to create vacuum ? Just thinking out loud here..

[palmer4th]

I have a 5/16 line with perfect elevation to play with natural vacuum. Is there a gage I could get to put at the top of the line to see if it works?

[DonMcJr]

In you video you mentioned that you didn't touch anything for the last 15 minutes. Are you closing that valve and letting the sap back up in the tubing to create vacuum ? If so than maybe you need a actuator valve on a timer to open and close the valve at a set time to create vacuum ? Just thinking out loud here..

I had to shorten some lines to tighten them. That created air in the system. So I figured alot of that air was out by then.

Funny you say that about an actuator valve... If I close that valve right above the bucket for 10 minutes and open it the flow goes crazy for about 2 minutes. I believe the trees are creating pressure in the system and with no where to go it builds up. When I open the valve there's a rush of "Vacuum" that sucks the sap out.

So with what I obsevrved and what you are thinking I think we may be onto something here....

Dr. Tim? Any Thoughts on that? I could pretty easy rig up an acuator to close the valve say every half hour for 10 minutes...

[Starting Small]

NO Do NOT vent.....unless you'd like 33-50% LESS sap. The sap will run slowly in an unvented (tight) system, but that is what creates the vacuum. You will get some natural vacuum, but you need at least 30' of fall in elevation to develop good vacuum.

So is natural vacuum still possible if you do not have the 30 feet of drop? If the land is flat can the tubing act to prevent sap flow? I have about a 8% drop but seem to not get much sap. Only 6-7 gallons from 35 taps today when others around are posting getting close to 3/4 gallon per tap.

[shane hickey]

Alot of it is location

[DrTimPerkins]

If I close that valve right above the bucket for 10 minutes and open it the flow goes crazy for about 2 minutes......So with what I obsevrved and what you are thinking I think we may be onto something here....

The actuator is actually just a vent that you open and close. Take a straw....fill it with water....put your thumb on top and hold it upright. No flow or little flow. Take your thumb off, the water runs out. The same thing is happening with the tubing. When it is full and NOT vented, the sap will move very slowly though the line. That is fine....you're getting some small amount of natural vacuum. Put a vent in there, all the sap in the lines runs out fast, then it'll slow down so that it'll only come out in a small trickle. When it is vented, it is pulling air with microbes through the system into the tapholes. The result is that with vents, you may get your sap a little faster, but the tapholes will dry out much faster, and you'll get 33-50% less sap. DO NOT VENT.

[DrTimPerkins]

So is natural vacuum still possible if you do not have the 30 feet of drop? If the land is flat can the tubing act to prevent sap flow?

Yes, but it won't be much. It is the weight of the sap pulling on the sap/air in the tubing system that creates the vacuum. One ft of water (sap) in a pipe flowing downhill is equal to 0.88" Hg vacuum. If you don't have the height, you don't get the vacuum.....sorry, but you can't break the laws of physics.

Can sap in tubing impede flow....yes.....if the tubing doesn't go downhill at least a little. With an 8% slope you should be able to achieve the rules of tubing...tight, straight, and downhill. You may need a level, but it can be done.

As far as not getting the same amount of sap as your neighbors....quite a number of factors can affect that. It could be tree size, how open your stand is, whether your bush is normally warm or cold....and about 100 other things.

[not_for_sale]

With that said then, wouldn't it be better to use plastic spouts and buckets on the ground rather than hanging buckets for sap yield?

[West Mountain Maple]

i think dr tim misunderstood your actuator valve idea, but you absolutely do not want to be backing sap up in the system , just let it flow, you get what you get, and unless your bush is mountainside, you can pretty much forget about any relevant natural vac

[DrTimPerkins]

With that said then, wouldn't it be better to use plastic spouts and buckets on the ground rather than hanging buckets for sap yield?

Marginally. The best vacuum you could achieve in that way would be the length of your dropline to the bucket x 0.88" Hg/ft. So with a 3' dropline, under optimal conditions, with good flow, you might get 2.6" Hg vacuum. Most of the season the flow would not be high enough to get that, so over the entire season you "might" be lucky to average 0.5" Hg above a bucket on a tree, which means about 2.5% more sap.....not really noticeable.