Ice thickness

This'nThat · 01-25-2009, 10:35 PM

Quote:

Originally Posted by BoulderBronco

I figured with these temps we would see a solid 14-16" everywhere by now. Wouldn't these temps yield about 1" per day of new ice?

No. The 1" per day of ice formation only occurs when temperatures are a constant 15 degrees below zero, with no snow cover. Otherwise, it's considerably less than that.

Mink Islander · 01-26-2009, 07:37 AM

We've got about 12-14 inches (measured) on the North side of Mink Island. First couple are snow ice. The rest is good solid black ice. So by my rough calc's we've been making approximately 1/2 inch per day of ice so we should have nearly 20" by derby weekend if it stays cold.

Saturday's wind blew a lot of snow off the lake and drifted/packed the rest, though the riding should still be ok, but not great. Noticed a fair amount of surface water (slush under foot) passing through Cattle Landing on Sunday. There's usually an expansion crack in the general area off the white boathouse on Dolly Island across to the mainland and near there is pretty damp. I didn't have a auger with me so I could check the thickness. There was 7+ inches through there last week so other than any gaps that will appear if the weather warms, it should be fine through there- particularly on sleds. Not sure I'd drive a truck through there, however. Always an area to be a bit more cautious.

Been pretty quiet on the lake overall near me. Over the past two weekends I have seen a few groups of sleds heading north around Bear hugging the shoreline, some heading between Jolly and Camp heading NE and a few heading East towards the Broads. Ample sled traffic through Cattle Landing and south towards Governor's/Meredith. I expect traffic will pick up this coming weekend as the Derby nears!

BoulderBronco · 01-26-2009, 10:26 AM

Quote:

Originally Posted by This'nThat

No. The 1" per day of ice formation only occurs when temperatures are a constant 15 degrees below zero, with no snow cover. Otherwise, it's considerably less than that.

No kidding. So those years when we had 20"+ it must have been crazy cold for a while. What kind of ice do you think the lake is generating these days? 1/2" a day? 1/4" a day?

I seem to remember having a derby, probably about 20 years ago, that we had 30" of ice halfway down Meredith bay. Can anyone remember that year? Whats the most ice you guys can remember?

Mee-n-Mac · 01-27-2009, 02:14 PM

For all the years we've had people, snowmobiles and various cars and trucks go through the ice I've often wondered if there wasn't a "good" way to measure the thickness in hopes of preventing all but the most foolhardy from taking a cold bath. I did some looking a while ago and tried to find a cheap and easy way to allow a person to make that measurement. I looked at doing it with sound (ultrasonics) and that doesn't seem viable. The problem is one of many layers of ice, snow and air all of which are in some unknown combination contributing to many reflections with varying timings through each layer (time correlating to thickness and density). I haven't given up on the idea but put it on the back burner as a result. I know airborne ground penetrating radar has been used but that seemed neither cheap nor easy. Electromagnetic induction coils have been used but that method depended on the salinity / conductivity of the water underneath. That's not going to work on a lake. There's a simpler variant of the radar method, detailed here, that seems to work. I don't know if 15 years advancement in electronics and signal processing would allow it to be "cheaply" though. The simplest answer would seem to be a small cordless drill attached to the end of a walking stick. You could get fancy and automate / instrument it to give a nice digital reading but I'd think color banding the bit would be sufficient. It doesn't help the sledders or truckers, unless they bother to stop and take a reading, but walkers might benefit. Of course they've already done a preliminary test just standing on the ice .....

Thoughts anyone ?

Mink Islander · 01-27-2009, 04:26 PM

Once you have drilled all the way through, how would you know at what point the bit hit water? Also, would need quite a long bit -- 2 ft of ice is not unusual. I suppose if you just wanted to test whether the ice was at least, say, 5 inches, you could use a shorter bit, mark the bit with tape or paint at the desired depth and drill to that level. If no water is found, then you know it's at least that thick. The problem is that you won't know how "good" the ice is using that technique -- meaning how much is slush ice vs. black ice. Just seems hard to get away from a handy manual ice auger -- might only need a 4" to be able to see where the black ice begins. Then I use a marked stick with a nail sticking out at 90 degrees to hook the bottom edge of the ice and measure up.

Google the Nimrod Ice Auger adaptor. It let's you use a cordless drill to connect to a number of brands of manual auger bits. Not sure how well it would work in extreme temps.

Webbsatwinni · 01-29-2009, 09:52 AM

All of this is good advice, the one main part that was stressed to me last year while learning about ice safety was about ice picks (I included a picture below). We wear them around our necks when ever we are on the ice. Knowing the ice depth is great, but what if the ice is thinner than you assumed and you are already on it?

I also added a picture we took two weekends ago, we cut a block out of the ice to see how thick it was, it was very solid ice (it is next to a hammer to provide scale). It was 100 ft into the broads off of Rattlesnake and it was a good 7-8 inches deep. Also, we checked the hole the next morning and there was over an ice of ice in less than 12 hours.

NHDOLFAN · 01-29-2009, 12:04 PM

Have you seen a lot of activity on the broads? I need to go to Rattlesnake via Wolfeboro Bay and want to make sure it's safe. I am on the Alton side of Rattlesnake.

Webbsatwinni · 01-29-2009, 01:22 PM

We were up last weekend and there was a steady stream of snowmobiles driving across the broads. We didn't, but there were many out there. And there is one lone bob house right in the middle of the broads straight out from Rattlesnake.

So to me, it looked safe just based on the activity.

NHDOLFAN · 01-29-2009, 01:43 PM

Thanks for the info. I can see the lone bob house from the Wolfeboro docks. Can't wait for the derby...

01-26-2009, 07:37 AM	#2
Mink Islander Senior Member Join Date: Apr 2004 Posts: 753 Thanks: 59 Thanked 271 Times in 129 Posts	Ice Thickness We've got about 12-14 inches (measured) on the North side of Mink Island. First couple are snow ice. The rest is good solid black ice. So by my rough calc's we've been making approximately 1/2 inch per day of ice so we should have nearly 20" by derby weekend if it stays cold. Saturday's wind blew a lot of snow off the lake and drifted/packed the rest, though the riding should still be ok, but not great. Noticed a fair amount of surface water (slush under foot) passing through Cattle Landing on Sunday. There's usually an expansion crack in the general area off the white boathouse on Dolly Island across to the mainland and near there is pretty damp. I didn't have a auger with me so I could check the thickness. There was 7+ inches through there last week so other than any gaps that will appear if the weather warms, it should be fine through there- particularly on sleds. Not sure I'd drive a truck through there, however. Always an area to be a bit more cautious. Been pretty quiet on the lake overall near me. Over the past two weekends I have seen a few groups of sleds heading north around Bear hugging the shoreline, some heading between Jolly and Camp heading NE and a few heading East towards the Broads. Ample sled traffic through Cattle Landing and south towards Governor's/Meredith. I expect traffic will pick up this coming weekend as the Derby nears!

01-27-2009, 02:14 PM	#4
Mee-n-Mac Senior Member Join Date: Sep 2003 Posts: 1,943 Thanks: 23 Thanked 111 Times in 51 Posts	Measuring ice thickness For all the years we've had people, snowmobiles and various cars and trucks go through the ice I've often wondered if there wasn't a "good" way to measure the thickness in hopes of preventing all but the most foolhardy from taking a cold bath. I did some looking a while ago and tried to find a cheap and easy way to allow a person to make that measurement. I looked at doing it with sound (ultrasonics) and that doesn't seem viable. The problem is one of many layers of ice, snow and air all of which are in some unknown combination contributing to many reflections with varying timings through each layer (time correlating to thickness and density). I haven't given up on the idea but put it on the back burner as a result. I know airborne ground penetrating radar has been used but that seemed neither cheap nor easy. Electromagnetic induction coils have been used but that method depended on the salinity / conductivity of the water underneath. That's not going to work on a lake. There's a simpler variant of the radar method, detailed here, that seems to work. I don't know if 15 years advancement in electronics and signal processing would allow it to be "cheaply" though. The simplest answer would seem to be a small cordless drill attached to the end of a walking stick. You could get fancy and automate / instrument it to give a nice digital reading but I'd think color banding the bit would be sufficient. It doesn't help the sledders or truckers, unless they bother to stop and take a reading, but walkers might benefit. Of course they've already done a preliminary test just standing on the ice ..... Thoughts anyone ? Attached Images __________________ Mee'n'Mac "Never attribute to malice that which can be explained by simple stupidity or ignorance. The latter are a lot more common than the former." - RAH

01-27-2009, 04:26 PM	#5
Mink Islander Senior Member Join Date: Apr 2004 Posts: 753 Thanks: 59 Thanked 271 Times in 129 Posts	some quick thoughts Once you have drilled all the way through, how would you know at what point the bit hit water? Also, would need quite a long bit -- 2 ft of ice is not unusual. I suppose if you just wanted to test whether the ice was at least, say, 5 inches, you could use a shorter bit, mark the bit with tape or paint at the desired depth and drill to that level. If no water is found, then you know it's at least that thick. The problem is that you won't know how "good" the ice is using that technique -- meaning how much is slush ice vs. black ice. Just seems hard to get away from a handy manual ice auger -- might only need a 4" to be able to see where the black ice begins. Then I use a marked stick with a nail sticking out at 90 degrees to hook the bottom edge of the ice and measure up. Google the Nimrod Ice Auger adaptor. It let's you use a cordless drill to connect to a number of brands of manual auger bits. Not sure how well it would work in extreme temps.

01-29-2009, 09:52 AM	#6
Webbsatwinni Senior Member Join Date: Sep 2007 Location: Lebanon Ct and Rattlesnake Island Since 2007 Posts: 610 Thanks: 180 Thanked 137 Times in 72 Posts	Bring your ice picks! All of this is good advice, the one main part that was stressed to me last year while learning about ice safety was about ice picks (I included a picture below). We wear them around our necks when ever we are on the ice. Knowing the ice depth is great, but what if the ice is thinner than you assumed and you are already on it? I also added a picture we took two weekends ago, we cut a block out of the ice to see how thick it was, it was very solid ice (it is next to a hammer to provide scale). It was 100 ft into the broads off of Rattlesnake and it was a good 7-8 inches deep. Also, we checked the hole the next morning and there was over an ice of ice in less than 12 hours. Attached Images

01-29-2009, 12:04 PM	#7
NHDOLFAN Senior Member Join Date: Jan 2007 Posts: 73 Thanks: 0 Thanked 0 Times in 0 Posts	Have you seen a lot of activity on the broads? I need to go to Rattlesnake via Wolfeboro Bay and want to make sure it's safe. I am on the Alton side of Rattlesnake.

01-29-2009, 01:22 PM	#8
Webbsatwinni Senior Member Join Date: Sep 2007 Location: Lebanon Ct and Rattlesnake Island Since 2007 Posts: 610 Thanks: 180 Thanked 137 Times in 72 Posts	We were up last weekend and there was a steady stream of snowmobiles driving across the broads. We didn't, but there were many out there. And there is one lone bob house right in the middle of the broads straight out from Rattlesnake. So to me, it looked safe just based on the activity.

01-29-2009, 01:43 PM	#9
NHDOLFAN Senior Member Join Date: Jan 2007 Posts: 73 Thanks: 0 Thanked 0 Times in 0 Posts	Thanks for the info. I can see the lone bob house from the Wolfeboro docks. Can't wait for the derby...