---------------------------------------------------------- Europa-List Digest Archive --- Total Messages Posted Wed 01/30/08: 15 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:21 AM - Don Dykins book (Remi Guerner) 2. 03:28 AM - Re: Don Dykins book (craig bastin) 3. 03:35 AM - Re: Don Dykins book (Mike Gregory) 4. 06:30 AM - Re: Don Dykins book (Mike Parkin) 5. 07:06 AM - Re: bowden cables, sliders (Jeff B) 6. 08:04 AM - Re: bowden cables, sliders (ALAN YERLY) 7. 12:16 PM - Re: Don Dykins book (craig bastin) 8. 04:14 PM - Re: Don Dykins book (Mike Parkin) 9. 07:20 PM - Epoxy Measuring - Balances vs Digital Scale vs Ratio Pump (Roger Lowe) 10. 08:37 PM - Re: Epoxy Measuring - Balances vs Digital Scale vs Ratio Pump (jimpuglise@comcast.net) 11. 08:45 PM - Re: Epoxy Measuring - Balances vs Digital Scale vs Ratio Pump (Keith Hickling) 12. 08:48 PM - Re: Epoxy Measuring - Balances vs Digital Scale vs Ratio Pump (Fred Klein) 13. 10:38 PM - Re: Epoxy Measuring - Balances vs Digital Scale vs Ratio Pump (Fred Klein) 14. 11:06 PM - Re: Epoxy Measuring - Balances vs Digital Scale vs Ratio Pump (David DeFord) 15. 11:18 PM - Re: Epoxy Measuring - Balances vs Digital Scale vs Ratio Pump (Greg Fuchs (FB)) ________________________________ Message 1 _____________________________________ Time: 12:21:03 AM PST US From: "Remi Guerner" Subject: Europa-List: Don Dykins book Hi all, I have just read Don Dykins book =AB Understanding the aerodynamics of your Europa aircraft =BB and I am puzzled by what I read in the "Prototype flight test performance" section. Figure 1 on page 15 shows that you need more power to fly at a given airspeed at altitude than at sea level. I first thought it was a typo, but page 18 confirms this assertion: "more HP is required to fly at a given speed at 10,000ft than at sea level". The typical light aircraft cruises about 5 to 10 percent faster at 10000 ft than at sea level using the same power, and you can verify this with your own Europa as well. So Don Dykins is wrong. Unless he is talking about indicated airspeed. In that case, talking about performance, this is nonsense. I cannot believe someone who has contributed to the design of such a wonderful aircraft can be so wrong. Am I missing something? Please comment. Remi Guerner ________________________________ Message 2 _____________________________________ Time: 03:28:14 AM PST US From: "craig bastin" Subject: RE: Europa-List: Don Dykins book If you consider the fact that you need more power or a longer ground run to take off at high temps or lower pressures (higher density altitude) then Don's assertions are correct. Consider also that some aircraft were supercharged during world war 2 only to delay the onset of "coffin corner" and allow for a higher service ceiling. Well thats my 2 cents worth. Craig -----Original Message----- From: owner-europa-list-server@matronics.com [mailto:owner-europa-list-server@matronics.com]On Behalf Of Remi Guerner Sent: Wednesday, 30 January 2008 6:12 PM To: Europa-List Digest Server Subject: Europa-List: Don Dykins book Hi all, I have just read Don Dykins book Understanding the aerodynamics of your Europa aircraft and I am puzzled by what I read in the Prototype flight test performance section. Figure 1 on page 15 shows that you need more power to fly at a given airspeed at altitude than at sea level. I first thought it was a typo, but page 18 confirms this assertion: more HP is required to fly at a given speed at 10,000ft than at sea level. The typical light aircraft cruises about 5 to 10 percent faster at 10000 ft than at sea level using the same power, and you can verify this with your own Europa as well. So Don Dykins is wrong. Unless he is talking about indicated airspeed. In that case, talking about performance, this is nonsense. I cannot believe someone who has contributed to the design of such a wonderful aircraft can be so wrong. Am I missing something? Please comment. Remi Guerner 10:20 PM ________________________________ Message 3 _____________________________________ Time: 03:35:46 AM PST US From: "Mike Gregory" Subject: RE: Europa-List: Don Dykins book Hello Remi, Yes, the airspeed axis on page 15 Figure 1 is labelled "VEASKTS", standing for Equivalent Airspeed in knots, which is a more technically precise term than Indicated Airspeed for aerodynamicist's calculations. For practical purposes, they may be treated as equal for the flight envelope of the Europa. The reason why you need more horsepower at altitude for a given IAS is that, for a given efficiency, the engine is providing thrust to equal the same drag (which is dependent on IAS) but the True Airspeed is greater, so the actual distance moved in a given time is greater. Work = Force x Distance; Power = Work/time. The engine is therefore having to do more work in a given time at the same IAS at altitude, but this is more than offset by the gain in TAS, so cruising at a given TAS requires less horsepower at altitude. I do not believe Don Dykins is wrong, and I do not agree that it is nonsense to talk about performance in terms of indicated airspeed. As I understand it, he is showing his calculations of aerodynamic performance and comparing them with the results of flight tests, where IAS is measured. It would be interesting to know how the latest VP propellers compare in efficiency with his working assumption of 80%. Best regards Mike _____ From: owner-europa-list-server@matronics.com [mailto:owner-europa-list-server@matronics.com] On Behalf Of Remi Guerner Sent: 30 January 2008 08:12 Subject: Europa-List: Don Dykins book Hi all, I have just read Don Dykins book < Understanding the aerodynamics of your Europa aircraft > and I am puzzled by what I read in the "Prototype flight test performance" section. Figure 1 on page 15 shows that you need more power to fly at a given airspeed at altitude than at sea level. I first thought it was a typo, but page 18 confirms this assertion: "more HP is required to fly at a given speed at 10,000ft than at sea level". The typical light aircraft cruises about 5 to 10 percent faster at 10000 ft than at sea level using the same power, and you can verify this with your own Europa as well. So Don Dykins is wrong. Unless he is talking about indicated airspeed. In that case, talking about performance, this is nonsense. I cannot believe someone who has contributed to the design of such a wonderful aircraft can be so wrong. Am I missing something? Please comment. Remi Guerner ________________________________ Message 4 _____________________________________ Time: 06:30:21 AM PST US From: "Mike Parkin" Subject: Re: Europa-List: Don Dykins book Craig, I am not sure that is correct. 'Coffin Corner' describes the area of the flight envelope where stalling speed meets the critical mach no. This is a problem with high flying aircraft such as the U2. I don't think that extra power would help here. regards, Mike do not archive. ----- Original Message ----- From: craig bastin To: europa-list@matronics.com Sent: Wednesday, January 30, 2008 11:24 AM Subject: RE: Europa-List: Don Dykins book If you consider the fact that you need more power or a longer ground run to take off at high temps or lower pressures (higher density altitude) then Don's assertions are correct. Consider also that some aircraft were supercharged during world war 2 only to delay the onset of "coffin corner" and allow for a higher service ceiling. Well thats my 2 cents worth. Craig -----Original Message----- From: owner-europa-list-server@matronics.com [mailto:owner-europa-list-server@matronics.com]On Behalf Of Remi Guerner Sent: Wednesday, 30 January 2008 6:12 PM To: Europa-List Digest Server Subject: Europa-List: Don Dykins book Hi all, I have just read Don Dykins book =AB Understanding the aerodynamics of your Europa aircraft =BB and I am puzzled by what I read in the "Prototype flight test performance" section. Figure 1 on page 15 shows that you need more power to fly at a given airspeed at altitude than at sea level. I first thought it was a typo, but page 18 confirms this assertion: "more HP is required to fly at a given speed at 10,000ft than at sea level". The typical light aircraft cruises about 5 to 10 percent faster at 10000 ft than at sea level using the same power, and you can verify this with your own Europa as well. So Don Dykins is wrong. Unless he is talking about indicated airspeed. In that case, talking about performance, this is nonsense. I cannot believe someone who has contributed to the design of such a wonderful aircraft can be so wrong. Am I missing something? Please comment. Remi Guerner href="http://www.matronics.com/Navigator?Europa-List">http://www.matron href="http://forums.matronics.com">http://forums.matronics.com href="http://www.matronics.com/contribution">http://www.matronics.com/c ------------------------------------------------------------------------- ----- 30/01/2008 09:29 ________________________________ Message 5 _____________________________________ Time: 07:06:02 AM PST US From: Jeff B Subject: Re: Europa-List: bowden cables, sliders Jos, When I added the heater door to Baby blue, I used a universal push/pull (choke)cable assembly from Auto Zone. Works just fine... Jeff - Baby Blue 363 hrs josok wrote: > > Hi All, > The ventilation-heating system has been installed. It should work, as far as i can imagine. The difficult part for me is how to operate the selector valves. I ordered some cables from ACS, but these are way to stiff to flex nicely into the narrow spaces available. Bowden cables like in use on bicycles probably should do the trick, but then i need some buttons or sliders on the other side. I have no idea on what's available and from where. Anybody with some idea before i start machining something from scratch? > > Regards, > > Jos Okhuijsen > > > > > > > Visit - www.EuropaOwners.org > > > > > > > > > > ________________________________ Message 6 _____________________________________ Time: 08:04:57 AM PST US From: "ALAN YERLY" Subject: Re: Europa-List: bowden cables, sliders Jeff, They are pricey, but I use part number A-700 Button Lodck Dash Control. Red for heat and Black for cool if you have both. Usually the 6 foot is OK. I secure the .062 wire end with a Z bend and the spiral sleeve wrap with a "cable safe" PN 05-16250 both available through Aircraft Spruce. Bud Yerly Custom Flight Creations ----- Original Message ----- From: Jeff B To: europa-list@matronics.com Sent: Wednesday, January 30, 2008 10:02 AM Subject: Re: Europa-List: bowden cables, sliders > Jos, When I added the heater door to Baby blue, I used a universal push/pull (choke)cable assembly from Auto Zone. Works just fine... Jeff - Baby Blue 363 hrs josok wrote: > > > Hi All, > The ventilation-heating system has been installed. It should work, as far as i can imagine. The difficult part for me is how to operate the selector valves. I ordered some cables from ACS, but these are way to stiff to flex nicely into the narrow spaces available. Bowden cables like in use on bicycles probably should do the trick, but then i need some buttons or sliders on the other side. I have no idea on what's available and from where. Anybody with some idea before i start machining something from scratch? > > Regards, > > Jos Okhuijsen > > > > > > > Visit - www.EuropaOwners.org > > > > > > > > > > http://www.matronics.com/Navigator?Europa-List http://www.matronics.com/contribution ________________________________ Message 7 _____________________________________ Time: 12:16:18 PM PST US From: "craig bastin" Subject: RE: Europa-List: Don Dykins book Sure my use of the term "coffin corner" may not be correct, but it is a simmilar situation is it not?? If the approach to coffin corner is caused by a lack of power rather than a design limitation then it would be, wouldnt it? Say like trying to fly your Europa with 60hp at high altitude, you would end up in the same situation, can't go slower or I'll stall, can't go faster not enough power. Some of the heavier 912ul powered europa are flat out at around 120kts arent they, yet the design is good for about 165-175 kts. craig -----Original Message----- From: owner-europa-list-server@matronics.com [mailto:owner-europa-list-server@matronics.com]On Behalf Of Mike Parkin Sent: Thursday, 31 January 2008 12:26 AM To: europa-list@matronics.com Subject: Re: Europa-List: Don Dykins book Craig, I am not sure that is correct. 'Coffin Corner' describes the area of the flight envelope where stalling speed meets the critical mach no. This is a problem with high flying aircraft such as the U2. I don't think that extra power would help here. regards, Mike do not archive. ----- Original Message ----- From: craig bastin To: europa-list@matronics.com Sent: Wednesday, January 30, 2008 11:24 AM Subject: RE: Europa-List: Don Dykins book If you consider the fact that you need more power or a longer ground run to take off at high temps or lower pressures (higher density altitude) then Don's assertions are correct. Consider also that some aircraft were supercharged during world war 2 only to delay the onset of "coffin corner" and allow for a higher service ceiling. Well thats my 2 cents worth. Craig -----Original Message----- From: owner-europa-list-server@matronics.com [mailto:owner-europa-list-server@matronics.com]On Behalf Of Remi Guerner Sent: Wednesday, 30 January 2008 6:12 PM To: Europa-List Digest Server Subject: Europa-List: Don Dykins book Hi all, I have just read Don Dykins book Understanding the aerodynamics of your Europa aircraft and I am puzzled by what I read in the Prototype flight test performance section. Figure 1 on page 15 shows that you need more power to fly at a given airspeed at altitude than at sea level. I first thought it was a typo, but page 18 confirms this assertion: more HP is required to fly at a given speed at 10,000ft than at sea level. The typical light aircraft cruises about 5 to 10 percent faster at 10000 ft than at sea level using the same power, and you can verify this with your own Europa as well. So Don Dykins is wrong. Unless he is talking about indicated airspeed. In that case, talking about performance, this is nonsense. I cannot believe someone who has contributed to the design of such a wonderful aircraft can be so wrong. Am I missing something? Please comment. Remi Guerner href="http://www.matronics.com/Navigator?Europa-List">http://www.matronhref "http://forums.matronics.com">http://forums.matronics.com href="http://www.matronics.com/contribution">http://www.matronics.com/c href="http://www.matronics.com/Navigator?Europa-List">http://www.matronhref "http://forums.matronics.com">http://forums.matronics.com href="http://www.matronics.com/contribution">http://www.matronics.com/c ---------------------------------------------------------------------------- Release Date: 30/01/2008 09:29 10:20 PM ________________________________ Message 8 _____________________________________ Time: 04:14:58 PM PST US From: "Mike Parkin" Subject: Re: Europa-List: Don Dykins book Craig, What you are talking about is a stall - plain an simple. It is nothing to do with the "Coffin Corner". Please see http://en.wikipedia.org/wiki/Coffin_corner_(aviation) regards, Mike ----- Original Message ----- From: craig bastin To: europa-list@matronics.com Sent: Wednesday, January 30, 2008 7:45 PM Subject: RE: Europa-List: Don Dykins book Sure my use of the term "coffin corner" may not be correct, but it is a simmilar situation is it not?? If the approach to coffin corner is caused by a lack of power rather than a design limitation then it would be, wouldnt it? Say like trying to fly your Europa with 60hp at high altitude, you would end up in the same situation, can't go slower or I'll stall, can't go faster not enough power. Some of the heavier 912ul powered europa are flat out at around 120kts arent they, yet the design is good for about 165-175 kts. craig ________________________________ Message 9 _____________________________________ Time: 07:20:49 PM PST US Subject: Europa-List: Epoxy Measuring - Balances vs Digital Scale vs Ratio Pump From: "Roger Lowe" Hi, I've purchased a partially complete Europa a little over a year ago and had to put it storage until my garage/workshop was re-vamped in order to build the kit. It is now to a point to where I can start moving my kit into it and start working on it. I have question about the different devices used to measure the epoxy and wondering what most builders have done in the past. The cheapest of course is to make the Europa mechanical balance which should be no problem (is it quick and easy to use during a layup?) but I'm leaning towards either a Ohaus / Sartorius digital scale with a resolution of 0.01gm (do I need that much precision or can I get away with a lower cost 0.1gm unit?) OR a ratio pump like a Glenmarc Portionator MBT-JR from A/S which is the most expensive of the all the options (is it worth the cost for ease of use?). I live in Canada so I will be using Aeropoxy resin (100:27 by weight or 3 to 1 by volume). I would appreciable any feedback/experience that you have that would help me make up my mind! Thanks, Roger Visit - www.EuropaOwners.org ________________________________ Message 10 ____________________________________ Time: 08:37:39 PM PST US From: jimpuglise@comcast.net Subject: Re: Europa-List: Epoxy Measuring - Balances vs Digital Scale vs Ratio Pump Roger- I think you'll find that most people use a scale. I have an Ohaus which read to 1/100 of an ounce. Your mixing needs to be very precise and you will do it often, so an easy to use and accurate scale is important. I throw a sheet of plastic over it to protect it and put the cup on before it is turned on and use bottles like ketchup is served in in restaurants to dispense epoxy and hardener. If I go a bit over, a paper towel can be used to "wick" a little until it is just right. I think the scale is a little over $ 100 but well worth it. Jim Puglise, Punta Gorda, FL -------------- Original message -------------- From: "Roger Lowe" > > Hi, I've purchased a partially complete Europa a little over a year ago and had > to put it storage until my garage/workshop was re-vamped in order to build the > kit. It is now to a point to where I can start moving my kit into it and start > working on it. > > I have question about the different devices used to measure the epoxy and > wondering what most builders have done in the past. The cheapest of course is to > make the Europa mechanical balance which should be no problem (is it quick and > easy to use during a layup?) but I'm leaning towards either a Ohaus / Sartorius > digital scale with a resolution of 0.01gm (do I need that much precision or can > I get away with a lower cost 0.1gm unit?) OR a ratio pump like a Glenmarc > Portionator MBT-JR from A/S which is the most expensive of the all the options > (is it worth the cost for ease of use?). > > I live in Canada so I will be using Aeropoxy resin (100:27 by weight or 3 to 1 > by volume). > > I would appreciable any feedback/experience that you have that would help me > make up my mind! > > Thanks, Roger > > > > > > > Visit - www.EuropaOwners.org > > > > > > > >
Roger-
 
I think you'll find that most people use a scale.  I have an Ohaus which read to 1/100 of an ounce.  Your mixing needs to be very precise and you will do it often, so an easy to use and accurate scale is important.  I throw a sheet of plastic over it to protect it and put the cup on before it is turned on and use bottles like ketchup is served in in restaurants to dispense epoxy and hardener.  If I go a bit over, a paper towel can be used to "wick" a little until it is just right.  I think the scale is a little over $ 100 but well worth it.
 
Jim Puglise, Punta Gorda, FL
 
-------------- Original message --------------
From: "Roger Lowe" <rlowe@speedway.ca>

> --> Europa-List message posted by: "Roger Lowe"
>
> Hi, I've purchased a partially complete Europa a little over a year ago and had
> to put it storage until my garage/workshop was re-vamped in order to build the
> kit. It is now to a point to where I can start moving my kit into it and start
> working on it.
>
> I have question about the different devices used to measure the epoxy and
> wondering what most builders have done in the past. The cheapest of course is to
> make the Europa mechanical balance which should be no problem (is it quick and
> easy to use during a layup?) but I'm leaning towards either a Ohaus / Sartorius
> digital scale with a resolution of 0.01gm (do I need that much nd muc
________________________________ Message 11 ____________________________________ Time: 08:45:13 PM PST US From: Keith Hickling Subject: Re: Europa-List: Epoxy Measuring - Balances vs Digital Scale vs Ratio Pump Roger, I used the Europa balance, but modified by using 20 lb breaking strain nylon fishing line as the pivot, rather than the nail as described in the manual. The nylon line goes through the brass tube, and is stretched tight across the frame. This was a suggestion from Dr Martin Armstrong, technical director of SP systems (now Gurit) who make Ampreg resins. He pointed out that if you use a nail for the pivot, the brass tube tries to roll on the nail, resulting in a slight movement of the pivot point, and it also causes significant friction, both resulting in inaccuracies. I tested the balance against accurate pharmacy scales and found it was accurate to less than 0.02 g when balancing a 100 g weight with a 25 g +- small weights using the 4:1 ratio (ie 40 cm to 10 cm on the balance). In practical terms, I can easily detect the effect of 1 drop of hardner when nearly balanced. I expect that using digital scales would take longer, as you have to accurately measure quantities of both resin and hardner, whereas with the ratio balance you just pour roughly the amount of resin you want, then add exactly the right amount of hardner. Having now got close to the end, I have been amazed at the number of resin mixes needed - far more than I initially envisaged - so any time saved here is significant. I also always mixed the resin and hardner back and forward between the two cups, rather than simply pouring the resin into the hardner as suggested and then reusing the resin cup next time. I had thought, and Martin Armstrong confirmed, that this can result in significant inaccuracies, depending how long you spend draining the resin from the cup each time, as well as allowing water (vapour) and CO2 into the residual resin in the cup. I'll be interested to hear what others have found. Regards, Keith Hickling, New Zealand. Engine in, working on cowls. ----- Original Message ----- From: "Roger Lowe" Sent: Thursday, January 31, 2008 3:53 PM Subject: Europa-List: Epoxy Measuring - Balances vs Digital Scale vs Ratio Pump > > Hi, I've purchased a partially complete Europa a little over a year ago > and had to put it storage until my garage/workshop was re-vamped in order > to build the kit. It is now to a point to where I can start moving my kit > into it and start working on it. > > I have question about the different devices used to measure the epoxy and > wondering what most builders have done in the past. The cheapest of course > is to make the Europa mechanical balance which should be no problem (is it > quick and easy to use during a layup?) but I'm leaning towards either a > Ohaus / Sartorius digital scale with a resolution of 0.01gm (do I need > that much precision or can I get away with a lower cost 0.1gm unit?) OR a > ratio pump like a Glenmarc Portionator MBT-JR from A/S which is the most > expensive of the all the options (is it worth the cost for ease of use?). > > I live in Canada so I will be using Aeropoxy resin (100:27 by weight or 3 > to 1 by volume). > > I would appreciable any feedback/experience that you have that would help > me make up my mind! > > Thanks, Roger > > > Visit - www.EuropaOwners.org > > > ________________________________ Message 12 ____________________________________ Time: 08:48:34 PM PST US Subject: Re: Europa-List: Epoxy Measuring - Balances vs Digital Scale vs Ratio Pump From: Fred Klein > The cheapest of course is to make the Europa mechanical balance which > should be no problem > (is it quick and easy to use during a layup?) Roger, I've used the standard balance design with, I believe, excellent results. E04 will give you the proper lengths for Aeropoxy proportions. I excercised some care in building mine to minimize friction. I find it works like a charm. I like the fact that I can pour out as much resin as I think I'll need and easily match it up with the correct amount of hardener...the balance registers to an accuracy (of say, a couple drops of hardener) which I find astonishing. Happy building...welcome to the list, Fred -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. ________________________________ Message 13 ____________________________________ Time: 10:38:10 PM PST US Subject: Re: Europa-List: Epoxy Measuring - Balances vs Digital Scale vs Ratio Pump From: Fred Klein Roger...one further thought re: my post. I've not attempted to reuse resin cups as I found early on that as the weight of the used but (somewhat) empty cup varied enough to upset the balance point...rather than futzing w/ the location of the add on balancing piece (I've used a large flat washer) every time I do a mix, I zero out the balance w/ clean resin and hardener cups and once done, it remains balanced. Fred On Wednesday, Jan 30, 2008, at 20:45 US/Pacific, Fred Klein wrote: > >> The cheapest of course is to make the Europa mechanical balance which >> should be no problem > >> (is it quick and easy to use during a layup?) > > Roger, > > I've used the standard balance design with, I believe, excellent > results. E04 will give you the proper lengths for Aeropoxy > proportions. I excercised some care in building mine to minimize > friction. I find it works like a charm. > > I like the fact that I can pour out as much resin as I think I'll need > and easily match it up with the correct amount of hardener...the > balance registers to an accuracy (of say, a couple drops of hardener) > which I find astonishing. > > Happy building...welcome to the list, > > Fred > > > -- > This message has been scanned for viruses and > dangerous content by MailScanner, and is > believed to be clean. > > -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. ________________________________ Message 14 ____________________________________ Time: 11:06:56 PM PST US From: "David DeFord" Subject: RE: Europa-List: Epoxy Measuring - Balances vs Digital Scale vs Ratio Pump > > Hi, I've purchased a partially complete Europa a little over > a year ago and had to put it storage until my garage/workshop > was re-vamped in order to build the kit. It is now to a point > to where I can start moving my kit into it and start working on it. > > I have question about the different devices used to measure > the epoxy and wondering what most builders have done in the > past. The cheapest of course is to make the Europa mechanical > balance which should be no problem (is it quick and easy to > use during a layup?) but I'm leaning towards either a Ohaus / > Sartorius digital scale with a resolution of 0.01gm (do I > need that much precision or can I get away with a lower cost > 0.1gm unit?) OR a ratio pump like a Glenmarc Portionator > MBT-JR from A/S which is the most expensive of the all the > options (is it worth the cost for ease of use?). > > I live in Canada so I will be using Aeropoxy resin (100:27 by > weight or 3 to 1 by volume). > Roger, You will find people who swear by each of these approaches, so I won't try to tell you which is best. We used digital scales with 0.1 gram resolution and found them to be quite satisfactory, though I wouldn't recommend less resolution. Our original scale (an Ohaus Scout) died after a few years of excellent service, and we have used a couple of cheaper models since. For a staggering selection of scales, check out www.americanweigh.com. Even the cheapest pocket-size scales would probably have good enough accuracy, but you need a large enough weighing platform to hold your mixing cups easily. (You will often be in a hurry when weighing epoxy, and spills are a real pain.) Be sure that the scale stays on for long enough to zero the cup weight, weigh the resin, and then weigh the hardener (even with some interruptions) before it turns off to save its battery. Not a problem with AC power, but some of the small scales with tiny batteries get in a hurry to shut down. Keep in mind that absolute accuracy is not needed for mixing applications, only good linearity. This can be tested precisely even without accurate calibration weights. Just weigh anything and note the result. Then replace the first item with something else, and zero out the reading. Adding the first item to the platform should result in exactly the same reading that you got when weighing it by itself. The two objects together need only to remain within the scale's range. Remember also that you will frequently have to mix Redux/Araldite 420/??? with good precision, and it's ratio will be different from the layup epoxy, so a mixing pump or fixed 100:27-ratio balance won't do this job. A digital scale is a bit like the digital level or close-quarters drill that you buy for one specific job, and then find that you use it for many other things. Dave DeFord N135TD ________________________________ Message 15 ____________________________________ Time: 11:18:56 PM PST US From: "Greg Fuchs (FB)" Subject: RE: Europa-List: Epoxy Measuring - Balances vs Digital Scale vs Ratio Pump ------------- Keith Hickling wrote: "I expect that using digital scales would take longer, as you have to accurately measure quantities of both resin and hardner, whereas with the ratio balance you just pour roughly the amount of resin you want, then add exactly the right amount of hardner. " ------------- I have always used the digital scale. It is an Ohaus, with a resolution of 0.1 gram and does not suffer hysteresis inaccuracies like some do. Absolute accuracy is not important, since the accuracy error will factor out in a ratio, as long as repeatability is good. No need to bother with using the sample weights that come with the scale to make it accurate. With the scale, you never need 2 cups to mix the resin back and forth, and only have to carefully measure the hardener. I put resin pumps on the containers of hardener and resin, and leave them there(they can be obtained from the local epoxy supply, such as Tap Plastics, or probably Aircraft Spruce or Wicks), with a plastic bag over them when finished. Upon needing a batch, just grab both out of the temperature-controlled storage area, pull off the plastic bags, and start pumping. For example: Epoxy: Put a disposable cup onto the scale. Turn it on, and it will auto zero, excluding the weight of the cup from the equation. Dump in whatever amount of resin you feel like. It does not need to be measured, a wild-ass guess will do, but write down the final amount of the weight of the resin. Multiply this amount by 0.27 (Aeropoxy), and you have your hardener amount to add. Add that number back to the initial amount of resin measured, and you get the total amount of resin plus hardener needed. Simply pump hardener into the same cup until you get close to the final amount, then go drop by drop until you nail the reading to a tenth of a gram (resolution of the scale), and you got it! Its very easy and takes almost no time, and no need to mess around with pouring between the resin cup and hardener cup to use all of the material -just keep a calculator handy, and a pencil to tap the numbers to keep the calculator clean. Mix until you see a homogenous mixture, and you are done. It took a little while to explain, but it goes really fast. As a final check, keep a mixture lookup chart nearby and right before adding the hardener, verify that the calculated hardener amount to add is close to proper value. Araldite: Araldite won't pour, and needs to be scooped out with a Popsicle stick. It will adhere grossly to the stick. Hence in this case, put the stick and the cup on the scale before it zeros the value, to cancel out the weight of the popsicle stick too. Make sure it is always in the cup during measurement. Scoop out the araldite needed, and put the scooped amount along with the stick, into the cup. The measurement reading taken will be for the araldite only, since the stick was cancelled out. Make the calculation (multiply by 0.4, similar to the epoxy, above) Then pour in the hardener from a ketchup-like bottle which has the ability to dispense from stream to drops, depending on squeeze pressure (I purchased one from the local epoxy shop, and it is similar). Verify calculated amount with the araldite mixture lookup sheet (found on one of the web sites) to verify that the calculated amount is close, then mix. In the build manual, I write the resin amount measured, and hardener amount to be mixed, along with the total amount of the two, which is the important number, since you will add hardener until the total amount is achieved, then write how close I actually got to the calculated total amount. Almost always, the final resin + hardener measurement (actual) is the same as what is calculated. It is amazing how accurate the ratio scale can be if it is built properly, like using the fishing line technique that Fred described. And it is cheaper. For me though, the $100.00 digital scale which you can sometimes find for 35 or 40 works really well, is fast, and if carefully done and verified, will always make the proper ratio. Have fun, ~Greg Fuchs ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message europa-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Europa-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/europa-list Browse Digests http://www.matronics.com/digest/europa-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.