Jump to content

Smartgauge Questions


rupertbear

Featured Posts

5 minutes ago, Dr Bob said:

Right, just been to W'spoons for a bevvy or 4 so response may be incorrerent ;).  Polyesters cure at 20°C no problem. Take the temperature lower and the crosslinking reaction slows down. Ideal MEKP level it 1-2%. At less than 15°C then you start having to add 2-3% MEKP or upping the cobalt oxylate level (normally in there anyway from the manufacturer...but more can be added). This then increases the reaction rate to get the thing to go solid....but the final crosslinking is compromised. When it goes solid you have about 10% of the final strength developed but the remaining 90% is dependent on the rest of the reaction going to completion. Trying to cure at less than 15°C is a bad idea.

Epoxies can be cured at 10°C and lower by choosing alternative curing aids but again this sacrifices the ultimate strength. For any of these systems wait until April.

Trust me, I am a doctor......and the duck agrees. Abbot is a nice pint!

Sorry, wrong thread, thought this was the Smartgauge thread, not advanced resin techniques:)

  • Haha 1
Link to comment
Share on other sites

3 hours ago, WotEver said:

So if I want a little more working time with epoxy wood filler I’ll be better off using it in the unheated shed than in the kitchen?

Or is that just a bad idea?

If you keep the two components cold then you will get a longer working time but if kept cold then it may not build up the full physical properties. Keep them cold so you get the best 'pot' life but then get some heat in - bringing into the kitchen, hair drier etc to get the full cure. Full cure on an epoxy is usually over 24 hrs rather than 1hr so keep the heat on for a day. For a 'filler' however, it is unlikley you need the 'full' cure so temp might not matter. The only problem with keeping the two parts cold prior to mixing, is that the viscosity is high so it doesnt flow or mix as well.....but in many cases that doesnt matter. If you really need full physical strength on epoxies or polyesters, then post cure at a higher temp, ie put in an oven at 60 or 80°C.

Once you have applied it, the thicker the section the more heat it will develop and therefore the better it will cure. Keeping thin sections only helps on application. Be careful if it is too thick or else it can build up too much heat and crack....in which case you should have used less accelerator.

Edited by Dr Bob
Link to comment
Share on other sites

5 minutes ago, Dr Bob said:

Once you have applied it, the thicker the section the more heat it will develop and therefore the better it will cure. Keeping thin sections only helps on application. Be careful if it is too thick or else it can build up too much heat and crack....in which case you should have used less accelerator.

Edited just now by Dr Bob

Think you should be called Dr Gougeon, not Dr Bob from now on!

Link to comment
Share on other sites

4 minutes ago, rusty69 said:

Think you should be called Dr Gougeon, not Dr Bob from now on!

Who the heck is Dr Gougeon? Did a google search and he died on 17th July last year. Was he famous? I once caught a gudgeon when I was a lad, but that was a while back so can't remember much about it. The Duck can't help either, He doesnt like gudgeon.

Link to comment
Share on other sites

1 minute ago, Dr Bob said:

Who the heck is Dr Gougeon? Did a google search and he died on 17th July last year. Was he famous? I once caught a gudgeon when I was a lad, but that was a while back so can't remember much about it. The Duck can't help either, He doesnt like gudgeon.

Geez Dr Bob, thought you was a-poxy expert. Look to the West and you will see the famous Gougeon Brothers (perhaps you need a telescope like wot I have got)

Link to comment
Share on other sites

Since I think the OP's topic has been adequately answered I don't mind going off topic. I use Epoxy resin for structural repairs to grp gliders, (not araldite, I mean proper epoxy resin!) and two things: One is that I am advised that if it's cold, it is a really good idea to warm the resin when mixing. This is so that the chain linking starts to take place. Even if it then gets colder, since the process has started it will tend to continue (slowly) whereas if it is all done cold, it will never start. But anyway, normally I cure at 25C for 24 hrs and then a further post-cure at 50 - 55C for 8-10 hours. This latter post-cure is something to do with raising the glass transition temperature, which I think is the temperature at which the resin will revert to a softer form (which would be a bad thing for an aircraft!).

Link to comment
Share on other sites

Thought I’d post an update about my smartgauge issues.

I’ve changed the settings on the Victron multiplus via the Dip switches. Adaptive charging has been turned off and fixed mode selected. The charge voltage options suitable for my Victron deep cycle AGMs are 14.4v absorption or 14.7. I’ve set it to 14.7v.

so this morning SG was showing batteries at 71%. On starting the built in generator the charge was 14.7v and 55amps. After 2.5 hours SG was showing 100% and the charge was 14.7v 9amps current.

so in short the SG wasn’t faulty at all. Quite the opposite, I wasn’t understanding the warning signs it was giving. It was a simple case of the multiplus combi factory settings being incorrect for the batteries and our off grid scenario. 

 

 

Link to comment
Share on other sites

FWIW, epoxy wood filler goes off really fast and at normal room temperature the instructions say to sand it after 15 minutes and no longer than 30 minutes or it will be too hard. This means that you have less than 5 minutes to use what you’ve mixed. Hence my query about slowing the reaction time. 

1 minute ago, Cloudinspector said:

so in short the SG wasn’t faulty at all. Quite the opposite, I wasn’t understanding the warning signs it was giving.

Result :)

Now, would you mind not interrupting our discussion of two pack resins?

  • Greenie 1
  • Happy 1
Link to comment
Share on other sites

17 minutes ago, Cloudinspector said:

Thought I’d post an update about my smartgauge issues.

I’ve changed the settings on the Victron multiplus via the Dip switches. Adaptive charging has been turned off and fixed mode selected. The charge voltage options suitable for my Victron deep cycle AGMs are 14.4v absorption or 14.7. I’ve set it to 14.7v.

so this morning SG was showing batteries at 71%. On starting the built in generator the charge was 14.7v and 55amps. After 2.5 hours SG was showing 100% and the charge was 14.7v 9amps current.

so in short the SG wasn’t faulty at all. Quite the opposite, I wasn’t understanding the warning signs it was giving. It was a simple case of the multiplus combi factory settings being incorrect for the batteries and our off grid scenario. 

 

Excellent, well done for sorting the Victron DIP switches. I don't have one but every time I read the manual I find it confusing! I can talk to my Mastervolt Combi via my laptop or via a display panel I have, much easier!

So is that +1 point for the Smartgauge?

Link to comment
Share on other sites

16 minutes ago, WotEver said:

Now, would you mind not interrupting our discussion of two pack resins?

No.:giggles:

 

34 minutes ago, nicknorman said:

Since I think the OP's topic has been adequately answered I don't mind going off topic. I use Epoxy resin for structural repairs to grp gliders, (not araldite, I mean proper epoxy resin!) and two things: One is that I am advised that if it's cold, it is a really good idea to warm the resin when mixing. This is so that the chain linking starts to take place. Even if it then gets colder, since the process has started it will tend to continue (slowly) whereas if it is all done cold, it will never start. But anyway, normally I cure at 25C for 24 hrs and then a further post-cure at 50 - 55C for 8-10 hours. This latter post-cure is something to do with raising the glass transition temperature, which I think is the temperature at which the resin will revert to a softer form (which would be a bad thing for an aircraft!).

Once epoxy has cured to a solid cheesy type texture it is only 10% of the final physical strength. To get the full crosslinking, and thus full strength a bit of heat certainly helps. In a factory environment, you would put it in an oven at 100°C for 24 hours. Your 50C for 8-10 hrs is not bad and will get most of the crosslinking done so as good a job as possible. Its not about a 'glass transition temperature' as strickly speaking, thermosets do not have a Tg, but the degree of crosslinking will affect its softening point and it flex and tensile strength. There is a psuedo Tg from side chain rotation over which there will be a softening of the composite. Bottom line is the cross link density but there is no real measure of this other than tensile and flex strengths which are both determined by destructive testing....not useful on a glider! Your post cure regime is going to get you to 95% of the ultimate cure which ain't bad .......unlike batteries!.....back on thread?

29 minutes ago, Cloudinspector said:

Thought I’d post an update about my smartgauge issues.

I’ve changed the settings on the Victron multiplus via the Dip switches. Adaptive charging has been turned off and fixed mode selected. The charge voltage options suitable for my Victron deep cycle AGMs are 14.4v absorption or 14.7. I’ve set it to 14.7v.

so this morning SG was showing batteries at 71%. On starting the built in generator the charge was 14.7v and 55amps. After 2.5 hours SG was showing 100% and the charge was 14.7v 9amps current.

so in short the SG wasn’t faulty at all. Quite the opposite, I wasn’t understanding the warning signs it was giving. It was a simple case of the multiplus combi factory settings being incorrect for the batteries and our off grid scenario. 

 

 

Will you come and set up my Victron combi. These dip switches are beyond me!

Link to comment
Share on other sites

1 minute ago, rusty69 said:

I recon Epoxy resin and the smartgauge are two fantastic additions to the boating world, and it was only a matter of time before they appeared on the same thread:)

If you epoxy your smartgauge to your boat, no one will ever be able to take it away from you!:)

I think one of them is a fantastic addition:giggles:

Link to comment
Share on other sites

13 minutes ago, Dr Bob said:

Once epoxy has cured to a solid cheesy type texture it is only 10% of the final physical strength. To get the full crosslinking, and thus full strength a bit of heat certainly helps. In a factory environment, you would put it in an oven at 100°C for 24 hours. Your 50C for 8-10 hrs is not bad and will get most of the crosslinking done so as good a job as possible. Its not about a 'glass transition temperature' as strickly speaking, thermosets do not have a Tg, but the degree of crosslinking will affect its softening point and it flex and tensile strength. There is a psuedo Tg from side chain rotation over which there will be a softening of the composite. Bottom line is the cross link density but there is no real measure of this other than tensile and flex strengths which are both determined by destructive testing....not useful on a glider! Your post cure regime is going to get you to 95% of the ultimate cure which ain't bad

The literature seems to disagree with you. (about Tg)  For example: http://www.epotek.com/site/files/Techtips/pdfs/tip23.pdf

As I understand it, the post-cure is not about increasing strength at normal temperatures, only at elevated temperatures. For a glider repair, one uses 50-55C. For a lght aircraft it is 80-85C, presumably because of the higher probable temperatures with there being and engine.

This is the product I use (well, the scheufler equivlalent), which makes reference to the strength improvement only at high temperatures.

 http://www.prfcomposites.com/store/image/data/PDF/RS-L285.pdf

Edited by nicknorman
Link to comment
Share on other sites

12 minutes ago, Dr Bob said:

If you epoxy your smartgauge to your boat, no one will ever be able to take it away from you!:)

I think one of them is a fantastic addition:giggles:

I was thinking of epoxying myself to the boat so no one can nick me!

Last time I used epoxy was to stick the balsa core on sailing boat,bloody brilliant stuff!

 

Now, where's that popcorn I had ready for yesterday?

Edited by rusty69
Link to comment
Share on other sites

47 minutes ago, nicknorman said:

The literature seems to disagree with you. (about Tg)  For example: http://www.epotek.com/site/files/Techtips/pdfs/tip23.pdf

As I understand it, the post-cure is not about increasing strength at normal temperatures, only at elevated temperatures. For a glider repair, one uses 50-55C. For a lght aircraft it is 80-85C, presumably because of the higher probable temperatures with there being and engine.

 

No I disagree. The example you quote agrees with what i said. The better the cure....ie the higher the temp (and the longer there) the higher the Tg. The Tg is a comparitive measure of how much crosslinking that has happened and hence proportional to the final physical properties ie tensile strength and modulus and flexural strength and modulus. The doc you quoted says that these are improved as you increase post cure temp which is what I said.

Tg measures if there is any molecular movement as your raise the temp. In an epoxy matrix, the matrix is solid ...as held by the crosslinked network.... but the side chains which are not crosslinked can rotate when the temp get high enough. This gives a softening effect but not that important and the matrix is inherently solid. Ok, for an aircraft you would always be below the Tg so you want the best cure you can. Post cure at temp is the way to do this. I am surprised there is a difference between gliders and powered planes.

The term Tg is usually used for the temperature at which thermoplastics change from being 'glass like' to a 'soft' plastic.

By increasing cross link density, as I said, you increase the physical props of the composite. This means at whatever temp your composite is at, the physical props will be better than if less crosslinked which was what I was trying to say.

47 minutes ago, nicknorman said:

 

As I understand it, the post-cure is not about increasing strength at normal temperatures, only at elevated temperatures. For a glider repair, one uses 50-55C. For a lght aircraft it is 80-85C, presumably because of the higher probable temperatures with there being and engine.

 

No, the better the post cure and hence increased crosslinking, the better the flex and tensile strengths  (and maybe the flex and tensile modulus) of the finished composite at whatever temp it is operated at.

Edited by Dr Bob
Link to comment
Share on other sites

Seems like it could be time to repeat my three main scenarios for batt ownership:

    Plan A for most (95%?) of boaters would be decent brand leisure batts.

    Plan B would be Trojans but only if they can be provided with the correct charge and EQ voltages, and required maintenance and monitoring. I expect this needs a genuine long term interest, hmmm... :mellow:

    Plan C is to use a less common battery make/type/chemistry/desulphators etc, but then you may be the guinea pig on that one. :unsure:

I guess relying 100% on a Smartgauge makes Plan A the best choice, and having a proper working understanding of 'tail current' opens up the possibility of Plan B?

So I guess the boater's knowledge of charging and monitoring needs to match the expense and charging needs of the batts. :)

Edited by smileypete
Link to comment
Share on other sites

1 hour ago, Dr Bob said:

No I disagree. The example you quote agrees with what i said. The better the cure....ie the higher the temp (and the longer there) the higher the Tg. The Tg is a comparitive measure of how much crosslinking that has happened and hence proportional to the final physical properties ie tensile strength and modulus and flexural strength and modulus. The doc you quoted says that these are improved as you increase post cure temp which is what I said.

Tg measures if there is any molecular movement as your raise the temp. In an epoxy matrix, the matrix is solid ...as held by the crosslinked network.... but the side chains which are not crosslinked can rotate when the temp get high enough. This gives a softening effect but not that important and the matrix is inherently solid. Ok, for an aircraft you would always be below the Tg so you want the best cure you can. Post cure at temp is the way to do this. I am surprised there is a difference between gliders and powered planes.

The term Tg is usually used for the temperature at which thermoplastics change from being 'glass like' to a 'soft' plastic.

By increasing cross link density, as I said, you increase the physical props of the composite. This means at whatever temp your composite is at, the physical props will be better than if less crosslinked which was what I was trying to say.

No, the better the post cure and hence increased crosslinking, the better the flex and tensile strengths  (and maybe the flex and tensile modulus) of the finished composite at whatever temp it is operated at.

The point I was disagreeing with and citing evidence to support, was your comment " Its not about a 'glass transition temperature' as strickly speaking, thermosets do not have a Tg..."

I'll need to read it again but I think your last para also disagrees with the literature in that the primary advantage of a high temperature post-cure, is the elevation of the Tg - any gain in strength at normal ambient temperatures is minimal. And of course in a composite, it is not all about the resin, it is also about the reinforcing fibres (glass etc) and the integrity (no air gaps).

Link to comment
Share on other sites

54 minutes ago, nicknorman said:

The point I was disagreeing with and citing evidence to support, was your comment " Its not about a 'glass transition temperature' as strickly speaking, thermosets do not have a Tg..."

 

The link you put in - the company is using Tg as a measure of how cured (or cross linked) the thermoset is. Tg is not really a measure of degree of cure but in a specific system it can be. The key property is the degree of crosslinking. The more, the better. Tg is just a property that will increase with state of cure. The cure and the level of the strength (tensile and flex) is the key. These are the most important properties.

 

54 minutes ago, nicknorman said:

 

I'll need to read it again but I think your last para also disagrees with the literature in that the primary advantage of a high temperature post-cure, is the elevation of the Tg - any gain in strength at normal ambient temperatures is minimal. And of course in a composite, it is not all about the resin, it is also about the reinforcing fibres (glass etc) and the integrity (no air gaps).

Then that literature is wrong. As crosslinking increases ....so cure increases, the tensile and flex stregnth at all temps (well at least the range we are interested in) will increase. I think you have read it wrong as actually the literature agrees with me. .......and you are right in that its so important to consider the fibres that make up the matrix.

Edit. The term tg is usulally use for thermoplastic polymers not thermosets. Have a look at

http://polymerdatabase.com/polymer physics/GlassTransition.html

Above the Tg, the glassy polymer becomes soft and rubbery. Look at the polymers they quote. All thermoplastics. Look at the M.Wt stuff. The link company you provide are using Tg as a measure of cure as there is a small softening due to side chains.

Edited by Dr Bob
Link to comment
Share on other sites

15 hours ago, Dr Bob said:

Edit. The term tg is usulally use for thermoplastic polymers not thermosets. Have a look at

http://polymerdatabase.com/polymer physics/GlassTransition.html

Above the Tg, the glassy polymer becomes soft and rubbery. Look at the polymers they quote. All thermoplastics. Look at the M.Wt stuff. The link company you provide are using Tg as a measure of cure as there is a small softening due to side chains.

Nick, I have been doing a bit of digging and talking to our composites expert and you are right in some of what you were saying. Cure is obvioulsy the most important thing in an epoxy laminate and increased cross linking creates that cure and the degree of cure will increase physical props at all interested temps as I said. However, Tg is often used (as you said) to indicate level of cure and the accepted design info now is that the Tg should be at least 30°C above the design temp of use. Tg however to is only an indicator to level of cure and in a properly fully crosslinked matrix (after high temp post cure) will be difficult to see or measure (ie the Tg is not an important issue when fully crosslinked). For a fully crosslinked matrix you will instead look for the softening point...or the heat deflection temperature which is then the key physical parameter when considering high temperature application. To accurately determine state of cure, you heat the sample on a DSC machine and look for an exothermic peak above the heat deflection point and the size of the peak will give an indication of how much 'cure is left' (keeping it simple).

I am from a school of polymer chemists that see Tg as a property of plastics (ie thermoplastics) rather than a property of thermosets. For plastics, Tg is a critical performance property and signifies the temp at which the whole polymer chain moves. For thermosets, the chains are crosslinked so they cant move so the Tg is far less important....but is being used to indicate extent of crosslinking. For a fully crossilinked matrix (which actually is unlikely unless a full high temp post cure can be achieved) a Tg will hardly be visible and far more important is the heat deflection temperature. That's why I tend to ignore Tg for a composite. To try and debate this anymore will require us to delve into polymer structure and properties which is just beyond the capabilities of this forum:)

Link to comment
Share on other sites

18 hours ago, Dr Bob said:

Will you come and set up my Victron combi. These dip switches are beyond me!

My missus used to read the instructions, tell me what sequence to switch and we'd double check together. (Her calmness has curbed my impatience over the last few decades!)

  • Happy 1
Link to comment
Share on other sites

4 hours ago, Dr Bob said:

Nick, I have been doing a bit of digging and talking to our composites expert and you are right in some of what you were saying. Cure is obvioulsy the most important thing in an epoxy laminate and increased cross linking creates that cure and the degree of cure will increase physical props at all interested temps as I said. However, Tg is often used (as you said) to indicate level of cure and the accepted design info now is that the Tg should be at least 30°C above the design temp of use. Tg however to is only an indicator to level of cure and in a properly fully crosslinked matrix (after high temp post cure) will be difficult to see or measure (ie the Tg is not an important issue when fully crosslinked). For a fully crosslinked matrix you will instead look for the softening point...or the heat deflection temperature which is then the key physical parameter when considering high temperature application. To accurately determine state of cure, you heat the sample on a DSC machine and look for an exothermic peak above the heat deflection point and the size of the peak will give an indication of how much 'cure is left' (keeping it simple).

I am from a school of polymer chemists that see Tg as a property of plastics (ie thermoplastics) rather than a property of thermosets. For plastics, Tg is a critical performance property and signifies the temp at which the whole polymer chain moves. For thermosets, the chains are crosslinked so they cant move so the Tg is far less important....but is being used to indicate extent of crosslinking. For a fully crossilinked matrix (which actually is unlikely unless a full high temp post cure can be achieved) a Tg will hardly be visible and far more important is the heat deflection temperature. That's why I tend to ignore Tg for a composite. To try and debate this anymore will require us to delve into polymer structure and properties which is just beyond the capabilities of this forum:)

Thanks. It's getting a little beyond my pay grade but I think I conclude that I will carry on doing things as I have been doing!

Link to comment
Share on other sites

9 minutes ago, nicknorman said:

Thanks. It's getting a little beyond my pay grade but I think I conclude that I will carry on doing things as I have been doing!

That's the conclusion I came to when you and Wotever started on a few months back, but I must admit ,I'm on minimum wage anyway.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.