Wednesday, December 7, 2011

Pier Street Christmas Market 2011

Over the last few years I have been selling my sundials through various third parties with moderate success. Being once removed from the customer I lacked the feedback necessary to understand why things sell (or not) as they do. I felt it was inevitable that at some point I shall have to try the direct approach. So last Sunday, supported by my wife, I took the plunge.

Some weeks ago we applied for a table in the most prominent of the Christmas markets in our town and was granted one. I was not going to go crazy, I thought one day would be enough.

I was determined to go into this fully prepared. I spent extra time in the workshop to make sure the stock was adequate. My wife (without whom I would never have attempted this and who put in a mammoth amount of work) went over all the details with me in a painstaking fashion to make sure the table looked right on the day, the packaging was just right, there was enough information material etc., etc. I was sure on the day that we were ready.

Sunday was a beautiful day with sun shining ( a rarity here) and a Santa parade in town which brought the citizenry out in force. I thought our table location was near perfect, certainly compared with what some others had to put up with. We got our McDonald's breakfast, got to the market in good time and set up well ahead of schedule.



We had a couple of jewellery stalls, a cosmetics stall, knitted articles and novelty dog food in our immediate vicinity.

To cut a long story short, the outcome is best described as "we are richer for the experience". Here are some of the observations:

1) Considering that the weather and circumstances seemed ideal, the actual turnout appeared low.
2) Given that this is a town where I know several hundred people (and they know me!) I identified exactly two individuals the whole 5-1/2 hours.
3) 99% of the attendees passed my stall with their eyes glazed over. There was no opportunity to engage (which my wife was ready to do at a drop of a hat - her being Steve Jobs to my Wozniak to use the Apple analogy).  There was no curiosity.
4) I cannot blame this on lack of originality: Mine were items unlike anything remotely present in the market. The most curious were the children and I ended up giving out quite a few of my "How the sundial works" handouts to them.


5) The question of workmanship did not even come up - the minority who commented were universally complimentary. The creative process was enquired about by only one person. The prices were not mentioned once.
6) Observing the other stalls there seemed minimal sales off all of them except the novelty dog food; That did roaring trade!

After digesting the experience for a couple of days I came to the conclusion that I have been dealing with the wrong demographic compounded by the poor economic climate. Pre-2008 I was selling my dials which were considerably inferior to my current standards with little difficulty. Admittedly this was in the neighbouring town where the demographic is somewhat different. As recently as June the same dials sold in Vancouver at significantly higher prices (the gallery there takes 50%!).

There is always the possibility that since June people came up with a better way to tell time but I suspect this is unlikely :-)

I intend to spend the next 3 weeks in reflection on what to do next as well as updating my workshop. I could:

1) Cut my ear off and start painting sunflowers. However, I do not have a rich brother.
2) Change my line of products completely. Somebody on a forum I belong to suggested good results may be obtained by making items for the S+M community. This no longer seems so far fetched...
3) Explore ways and means of getting through to a different demographic.

To continue with the Apple analogy I would like to follow the late Steve Jobs maxim "Screw the market research, how do they know what they want till you show it to them?" a bit longer.

Wednesday, October 26, 2011

Oil-based versus water-based finishes and stains

I have always used oil-based wood stains and finishes. This is fine in summer when the temperatures are just right but try it in an 8 degree garage and bad things happen. I tried to make a spraying station in my bathroom but was unable to contain the fumes in the improvised "booth". Therefore, I thought I would investigate water-based products.

The "green" regulations have had the beneficial (?) effect of more research going into water-based paints in general so there is now more choice than there was even a few years ago.

I really wanted to know a) How good are water-based stains and b) How good are water-based finishes when applied over oil-based stains.

I tried a water-based Varathane stain, new on the market. It was a disaster. The stain would not penetrate the wood and was easily removed by even light sanding. Varathane water-based finish over it sloughed off quite easily. I returned to my favourite Varathane gel stain. I let it dry for 48 hours and then applied Varathane Diamond water-based finish to half the pieces and the Varathane Professional Clear finish to the other half. Both produced acceptable results. A tape test showed good adhesion of both. The water-based finish is not as lustrous and rich but the difference is apparent mainly when viewing the pieces side-by side (see picture).

Given how well the gel stain behaves particularly on the end-grain it will be while before I am persuaded to try water-based stain again. I hear good things about water-based stains produced by a Quebec company called Saman. We shall see!

I was happy that water-based finish can be safely used over an oil-based stain. However, in the process of doing the trial I developed a method whereby I can use the oil-based finish inside the house without contaminating the atmosphere beyond what is acceptable: Keep everything warm until the last moment, then dash out into the garage, spray and dash back in with all the pieces and cans!

Next I shall see if this works for metal finishes...

Saturday, June 11, 2011

Woodstoves

One of my many life-time interests have been primitive and survival technologies, especially related to firemaking, cooking etc. Recently while researching another subject I came across some information related to new and improved types of woodstoves. Many of these could be improvised from cans, scraps of metal etc. Some incredible claims were being made for these stoves and I decided to investigate. After all, if one lives on a fault line one might be called to make one of these for real at some point.

There are many sources of information on these woodstoves on the net. There seem basically two kinds: The Downdraft Gasifiers and the Rocket stoves. The common principle is complete combustion of the fuel (often referred to as "biomass") which increases the calories available form a given quantity of fuel while at the same time reducing polutants such as smoke and carbon monoxide.

The best article on Downdraft Gasifiers is here:

http://www.waoline.com/science/newenergy/BioEnergy/Links/WoodGasStove.pdf

It explains the principle in some detail which I am not going to repeat. Suffice to say that burning fuel from top to bottom creates a pyrolysis zone below the combustion zone, wood gas is generated there which then rises and is mixed with secondary air and burns to provide the actual heat for cooking etc. There are many versions of these described on the net and many videos on You Tube. Not all of these are actually what they claim to be and in many of them the authors show only tenuous grasp of the principles in play.

The definitive source for the Rocket stoves and its many variations is here:

http://www.aprovecho.org/lab/pubs/arcpubs

The paper on design principles by Larry Winiarski is a must read. The Rocket stove is a more "linear" affair in terms of combustion: The design simply allows for a more complete combustion of fuel without the intermediate gasifier step. Again, there are many of these on You Tube etc. of varying quality.

I decided to have a go at building some of these starting with a small model to see what properties of these stoves are essential for correct functioning and how the various designs behave under different conditions.

Fig. 1
Fig. 2
I thought I would start with a Downdraft Gasifier stove. The simplicity of construction appealed to me as well as the theoretical ability to use a wide variety of fuel. I made one from two bean cans, 75 mm in diameter and attached their open ends to each other by cutting one in four places and sliding it into the other. I cut out one of the bottoms and deburred the sharp ends to make this the cooking end of the stove. I drilled holes in half of the bottom of the second can as well as one of the detached lids which I then riveted to the bottom thus providing myself with an air-flow regulator (Fig.1). More holes near the bottom and a row of holes about half way up the assembly to provide the secondary air intake, three legs riveted to the sides, and voila (Fig.2)

I tested the stove on top of my BBQ. The first fuel was the waste from my workshop - sawdust, chips and shavings. The result was disappointing. If enough of this "biomass" was loaded to fill the stove to the level below the secondary air intake the fuel burned very quickly and was used up in a couple of minutes. Loading the stove to the rim allowed the fuel to burn until the level of secondary air intake was reached and then the fire went out whatever one did . I interpreted this as lack of air flow through the primary holes. I increased the number of holes in the bottom (the air inlet regulator plate fell off later anyway - the aluminum rivet simply melted in half) and added few more holes around the priphery of the bottom. This made absolutely no difference to performance (Fig. 3 and 4)
Fig. 3
Fig. 4

 I figured then that the problem lies with the fuel which is too dense to allow the primary airflow (the author of the first article refers to difficulty he had gasifying pellets of 0.5 cm for that reason.)

I decided to try the stove with sticks cut from a "SPF" 2x4, guaranteed dry. The sticks were cut so the length which  corresponded to the depth of the stove. I crammed as amny as I could into the stove cavity and ignited them with a butane torch. Once the top part of the sticks burned through and the combustion zone reached the secondary air holes ther was a definite evidence of gasification in that a) there was no more smoke and b) the flames were clearly related  to the secondary air inlets (Vid. 1 and 2).


It took approximately 2 minutes for the stove to reach gasification stage. Disappointingly, the gasification stage lasted only about 7 minutes for a full load. The stove was re-loaded with cubes of the same wood appx. 1.5 cm per side. This revived the gasification but it was again short lived.

In the second video you can see an improvised shield made from aluminum foil. It did not seem to affect the pattern of the flame, it kept the wind out rather poorly. Many of the You Tube designs make much of the necessity of having such shield to pre-heat the secondary air. Whether my shield increased the temperature of the flames is impossible to determine. A boiling water test would be appropriate to determine its effect but this would require building an additional pot-holding fixture. That the nature of such fixture is critical to the stove's performance is explained in the Winiarski paper.

I did not use the "wick" as described in the first paper. It is not clear what effect, if any, adding the wick has on the stove performance. I have not seen the wick in use elsewhere and I simply did not have a suitable can to make it from.

The stove described in the first paper was, as far as can be determined, 12.5 cm internal diameter and 30 cm tall. My stove proportions were similar to that, consistent with the need to provide adequate space for the secondary air to mix with the wood gases and allow them to burn completely. Many of the You Tube variations have hardly any space above the secondary intake at all. I believe this shows inadequate understanding of the whole concept. The 3:1 ratio is also recommended by Larry Winiarski to achieve complete combustion in the Rocket Stove.

The authors had their stove burn for a total 37 minutes on a single load of fuel. It should be noted however, that at 20 minutes they reduced the primary air intake to only 20%. It is interesting to extrapolate from their graph to see what the duration of a full burn would be - I estimate it around 25 minutes. Given that the volume of fuel of my stove is about 1/4 of theirs the durations of full burn are consistent (assuming that the rates of burn is comparable which I suspect is not necessarily correct.)

The concept of restricting the primary air intake is problematic. Such restriction leads to incomplete burning of the fuel and therefore inefficiency. It also leads to increase of undesirable products such as carbon monoxide. The authors measured carbon monoxide emissions however they do not state at which point of the burn cycle. They do warn about "extingusishing the stove completely" because of this danger.

At the end of their burn cycle their stove produced a signinficant amount of charcoal. It is not clear to me what the direct benefit of making charcoal is. Howeve, presence of significant amount of charcoal confirms that at some stage the burning of fuel was inefficient. In my stove at the end there were only 4 small lumps of charcoal and I terminated the smoldering with water for safety's sake. There may have been even less if I let the stove go out by itself.

Larry Winiarski is quite clear that any air flow restricition is undesirable. The Rocket Stove regulates heat production by inserting or withdrawing fuel from the combustion chamber which, due to its design, is relatively easy to do. Such procedure in the case of the Donwndraft Gasifier is impossible, in fact refuelling the stove can be a problem while cooking.

Conclusions:

1) The Downdraft gasifier technology is feasible and easily reproduced from readily available material.
2) The design is fuel sensitive in that dense and packed fuel will not allow the stove to function.
3) The size of the stove is of some importance due to limited burn time. It took 8 minutes to boil a litre of water with the original design thus the minimum useful size of a stove for such purpose (as defined by the volume of fuel) would be at least double that of mine.
4) Refuelling the stove is relatively awkward especially if there is pot on the stove. Additional features to allow this would add to complexity of construction.
5) Regulation of heat output by varying the amount of fuel burned other than by restricting the air flow is impossible. I find the concept of air flow restriction problematic and undesirable for reasons discussed above.
6) The concept of pre-heating the secondary air is interesting and probably should be investigated if one considered this design to be of further use. It is certainly considered essential feature of the Rocket stove.
7) The effect of the "wick" is intriguing. Same applies.
8) Overall my impression is that although this design clearly works it has many drawbacks which render it of limited use in all but emergency situation where such design is easily constructed using little but a can opener.
9) The Winiarski concept of the Rocket Stove has solved many of the above issues. Its design is clearly documented and the design principles firmly established. Hence I will experiment with it next.

Saturday, May 28, 2011

On benefit of buying smaller eggs

It has been brought to my attention that eggs have been one of the items that has been affected by the recent price rises. This increase has been reflected unequally among the different stores, some charging considerably more for the same size eggs than others. Furthermore, there seems a disproportionate premium on "jumbo" size eggs. As a result my wife has started buying the eggs one size down - the extra-large ones.

Due to an occasion of needing to "look after myself" I have had the opportunity to purchase eggs in the store we frequent most (Save on Foods). I noticed availability of not only the usual 12-egg cartons but also 18-egg cartons, the latter only in the "large" category. A quick calculation led me to conclude that this should be a good deal compared with the same size eggs in a box of 12 (although these inexplicably were not priced). I decided to do an experiment. I purchased the 18-egg carton and proceeded to compare them with the 12-egg carton of  "extra-large" at home.

The hypothesis was that :

1) Buying slightly smaller eggs will lead to disproportinate savings without sacrificing significant nutritional content.
2) Smaller eggs are less likely to burst on boiling thus leading to further savings due to reduced losses.

Method:

The eggs in each carton were weighed on a kitchen scale reading to 1 gram accuracy. Some were weighed twice to assess repeatability of the measurment.

The mean weight and standard deviation for each sample were calculated.

The samples were compared using the unpaired Student's T-test.

The eggs were cooked using the standard soft-boiling method by immersing them in cold water and bringing this rapidly to boil where they were kept for 4 minutes and then cooled rapidly by running water.

Due to the curved nature of the shell the shell  thickness could not be measured reliably with the existing instruments (outside micrometer, calipers).

Results:

1) The mean weight of the extra-large egg is 65.08 grams. SD = 1.73 n=12
2) The mean weight of the large egg is 60.17 grams, SD = 1.95, n=18
3) The difference between the means is 4.91 grams or the larger eggs are 8.16% heavier.
4) The difference between the samples is highly significant with p<0.0001
5) The cost of the 18 large eggs was $3.99. This translates to a cost per dozen of $2.66.
6) The cost of extra-large eggs and a 12-carton of large eggs at Save-on Foods could not be reliably ascertained due to continuing lack of labelling and a verbal information thought to be unreliable at best. The cost of 12 large eggs at Quality Foods was $2.99, extra-large $3.29. Quality Foods do not sell jumbo eggs.
7) None of the extra-large eggs boiled in the fashion described burst during cooking and so far none of the large eggs have done so either.

Discussion:

The egg weights correspond to the modern Canadian standards for each size class. The extra-large eggs are significantly heavier by 8.16% than the large eggs. Survey of literature (such as could be accessed on the Internet) reveals that about 10% of the total weight of the egg is the shell, the yolk is about 30%, the white 60% of which 90% is water. None of the literature sources indicated whether these proportions are maintained across the weight scale. It would seem likely that with increasing size the proportion of the egg contents (yolk+white) would increase as the shell represents the surface of the egg and increases proportinately to radius squared whereas the content represents volume which increases with radius cubed. Whether the shell thickness also increases could not be determined due to lack of suitable measuring equipment (a point micrometer would be most suitable). Most cookbooks recommend adjusting the number of eggs for baking according to their size, however, the evidence basis for this is presumably empirical, based on the quality of cakes etc. In any case, assuming that the proportions are maintained the increase in the nutritionally active ingredients would only be of the order of  2.9 grams.

Although I was not able to price the eggs accurately at the source where they were obtained a representative pricing from elsewhere shows that the price increase from large to extra-large is 10%,  i.e. disproportionate to the 8.16% size increase. Anecdotal evidence suggests that this disproportion is even larger in the case of jumbo eggs. On the other hand buying large eggs in a packet of 18 is even more advantageous economically.

At the table this size difference was not obviously noticeable.

None of the sub-jumbo size eggs burst while cooking. This may be due to unusually resilient shell in our two batches or may in fact represent an increased relative strength of the shell in the smaller eggs. Some postulate air pocket in the eggs as the cause for the shell burst. However, air is already present as gas and as such follows the law of Gay Lussac stating that the pressure of gas in presence of a constant volume is proportinal to the absolute temperature. Thus increasing the temperature of the egg from 8 degrees C (281.15K) to boiling (373.15K) will increase the pressure of air within the egg by only 32%. However, air is compressible so it is not at all clear that this pressure increase is enough to cause the shell burst by itself. There is however, a significant water content in the egg, 54% of the total weight which, in a 60g egg is 32.4g. If this amount of water were converted entirely into steam it would render a whopping 54 litres of steam at 760 mmHg. It is unlikely that such complete conversion in fact occurs (otherwise all eggs would surely burst while boiling), however, I suspect that it is the steam formed during boiling the egg that is reponsible for the eggs bursting rather than the air pocket. Only 2% of the available water converted to steam will generate over a litre of steam.

The reduced amount of water in the smaller eggs is unlikely to play a role in the increased resistance to bursting as the available volume of steam is still appreciable. I feel the answer lies in the increased ability of the shell to withstand transmural pressure due to the reduced diameter. The egg, in fact, follows the Laplace law, P=2T/r, where P is the transmural pressure, T is the wall tension (here represented by the strength of the shell) and r is a radius of a sphere which the egg approximates. It is clear that a smaller wall tension will contain higher transmural pressure if the radius is reduced. This phenomenon is well described in medicine where e.g. larger aneurysms are more likely to burst than smaller ones.

The only indirect observation suggesting that the explanation is correct is that the larger eggs invariably burst only once the water reaches the boiling point, i.e. steam production inside the egg is ramped up.

An alternative explanation is that the smaller eggs have stronger shells. Thre is at present no way to ascertain this but there is also no reason to believe that this is so.

Conclusion:

1) Buying smaller eggs is economically advantageous as the price premium on size is disproportionate, particularly in the case of jumbo eggs.
2) The benefits of buying eggs in large quantities are also evident and consistent with most other grocery purchases.
3) The smaller eggs appear to have a better resistance to boiling-induced shell bursts. This needs to be confirmed by boiling other batches of both extra-large and large eggs to confirm this and determine the threshold level of this phenomenon. The scientific reasons for such resistance are discussed. Decreased losses from boiling-induced bursts, if confirmed, contribute further to the economic benefit of buying smaller eggs.

Comment:

At this time the eggs in BC are priced as above. The information available on the Internet suggests that the price of similar eggs in the USA is of the order of $1.75 per dozen. This difference is entirely due to built-in subsidies that the Canadian producers continue to enjoy as well as their protection from US competition by cross-border levies.

References:

Google it!

Acknowledgment:

The author wishes to express his thanks to his esteemed colleague Dr. Sheldon Cooper without whom such foolishness would not have been attempted let alone brought to fruititon.

Wednesday, May 18, 2011

Visiting the neighbouring fencing club - Part 2

I went to see our neighbours again, this time on my own. My wife was absent due to some strange notion that seeing her children once a year is more important than fencing. Here are some more lessons learned:

1) Walking is no substitute for anaerobic interval training.
2) Fencing, even a 60-year old woman, on a regular basis is better than not fencing at all (You will come back if you loooove me...)
3) Just because you beat someone one way on a certain day does not mean that you will do it that way next time. Do not be a one-trick pony!
4) At 59, fencing smarter beats fencing harder
5) Once you know you can win a fight do not concentrate on winning. Practice difficult moves even if you lose 5:0.
6) If you do lose 5:0 make sure you practiced the right moves correctly (this one is really hard without a coach).

Sunday, April 10, 2011

On decline of garage sales

Last year I noticed that the quality of the stuff available at local garage sales declined. This year the number of garage sales is down also. And I mean down! Whereas last year this time we would go to 10-12 events each Saturday, this year we are lucky if we see 5 or 6.

I suspect that there are two possible explanations:

1) Weather. It has been miserable and unstable. That global warming thing has not reached us yet: We have been seeing temperatures consistently 3 degrees C below seasonal average. Furthermore, predicting the weather has been problematic. The scientists employed by the Environment Canada are clearly not the same ones that confidently predict 2.5 degrees increase in average temperatures in the next 100 years. Ours, as reflected by the predictions on the Weather Channel, have the greatest difficulty deciding what the weather will be in the next 12 hours. In fact, the way the Weather Channel deals with this locally is to show different predictions every 6 hours. Presumably one of them will eventually turn out to be right.

Thus people are reluctant to hold garage sales unless they have the ability to go indoors in bad weather. It will be interesting if the numbers pick up in summer although "summer" is a relative term here on the Island.

2) Bad economy. I postulated this last year as the reason for poor quality stuff available. People in financial difficulty buy less new stuff and hold onto their good old stuff longer. This was also reflected in the local auction house. However, it is not clear what "bad economy" means here on the Island. There is some unemployment due to mill etc. closures. OTOH those who are employed or have their own businesses may not be as hard up as all that. For example I have tried to get estimates for some building work which I guess would be about $1500 worth. Of the four companies I asked two have not turned up and the two that did have so far failed to provide the quote, in one case for over a week. I figure that if you can turn down that sort of work you are not suffering.

I wonder what the garage sales experience has been elsewhere...

Thursday, April 7, 2011

What I learned visiting a neighbouring fencing club

Our Cyclops fencing club had an outing last night: We went to visit our neighbours in Comox. We have not been there for over 2 years. All in all it was fun. Here are some things I learned:

1) Pushing yourself is good even if you are an old cripple. It would have been easy to stay at home and watch another episode of Criminal Minds. It did not hurt nearly as much as I thought it would.
2) Aerobic capacity is greatly affected by the state of mind. I was gassed during the first few fights purely because I was hyped up going into them. Once I relaxed it was not nearly as bad.
3) A 60-year old woman can dish out beating to young bucks.
4) A 59-year old man will lose 5-0 to the same bucks if he fences them the same way he would fence a 60-year old woman.
5) A good strategy may compensate for poor technique and lead to victory (see *3*)
6) A crappy strategy with so-so technique will lead to defeat (see *4*). Also there is such thing as too much relaxation.
7) Some clubs do not teach offense. A determined attack in such places often pays off. Even if the attack is horrible (see *3*)
8) Tall people have long arms. Epee at the end of a long arm reaches farther than one at the end of a short arm.
9) Hitting arms is harder than one would like it to be. So is moving blades out of the way.
10) If you have any doubs that your epee needs re-wiring there is no doubt. Re-wire and quit bitching about lost touches.
11) You can improve your fencing even if your circumstances make it very difficult. You have to want to learn by any means necessary. Our club is a living proof.
12) A decent coach would not hurt, though. Coaching is much easier if you see your student as an observer than as an opponent.

Alll things considered we did not do badly (some did better than others - see *3* - again!) Let's hope we can do even better next time.