Making a Dial in The Gambia. What materials to use?
Dear Friends, I seem to have talked myself into making a dial in The Gambia, about 13° north of the Equator. The design is fairly straight forward. In brief it is to sit on the ground on the south side of the swimming pool at the hotel. It will recline so as to be visible from the northfrom a lying position around the pool. The dial has been calculated for 45°N therefore 45 - 13 means that its plate will be sloping about 32° to the horizontal. The distance from the pool is about 10m, therefore it needs to be of some size. I am planning on making it about 2m across. The main problem seems to be the choice of materials. I have ruled out wood due to the termites in the area. I have also ruled out paint as the sun is so very hot most days - except for the 3 months of rains. It has to be constructed by local labour with minimal materials available. I am planning to be there to set it up and work out the delineation but I want to be sure that we have all the materials to hand to build it within a few days. At present my thoughts are to make it from concrete, preferablyoff site, so that it can be laid in position, and dare I say it?, enable me to make small adjustmentslater if necessary. This will probably mean that it will have to be made in up to 4 parts plus the gnomon. The ground on site is basically sand. I originally considered moulding in the hour lines, numerals etc. but think that this would be too much for the personnel involved. My latest thought is to make just a flat plate and apply the hour lines as strips - of wood? and house door type numerals. At least, when the termites eat these strips, they can easily be replaced! Therefore I am asking for any other suggestions that may be more appropriate. I am sure that several members of this list will have made dials for the tropics and eagerly await their comments. Regards,Mike Cowham.Cambridge, UK.
Making a Dial in The Gambia. What materials to use?
Dear Friends, Thanks for the suggestions so far received - mostly off the list. They are all sensible. However, I must stress that I have to rely on local materials or what I can take in a small suitcase on an airline - 20kg is soon used up. This rules out most of the exotic materials that I would like to have available. Another solution that I had thought of was to make the hour lines with sea shells. Even the numbers could be formed this way - either Roman or Arabic. However, as they must be applied to a concrete base so I must find some suitable adhesive. A twin-pack epoxy would have to stick to perhaps semi-wet concrete, unless I can find some paving slabs. It will also require a large quantity of 'glue' if shells are to be fixed. As far as maintenance is concerned, I will be visiting the site at least once each year and can fix bits that are broken off - between swims in the warm Atlantic. We are also involved with a school there, but vertical dials are of no use between the tropics. Has anyone tried an annalemmatic dial at this sort of latitude? Regards, Mike Cowham. Cambridge, UK.
Re: Making a Dial in The Gambia. What materials to use?
Hi Mike, I think Tony's idea of moulding the dial is a good one for DIY construction. As another alternative to cement, there are powders which make up to a stone substitute, like an outdoor plaster-of-paris. I have used it for small items and it is very good. Available from arts and crafts suppliers. For commercial dials that will last several lifetimes, I have been investigating vitreous enamel on steel. This is the technique that was used on garage advertisements for petrol etc in the 1920's, as well as railway signs. Not something you can do at home, but I got a not unreasonable quote to make some 1.5metre diameter dials. Good luck with the dial - we will expect a report and picture in due course! Regards, John --- Dear Friends, I seem to have talked myself into making a dial in The Gambia, about 13° north of the Equator. The design is fairly straight forward. In brief it is to sit on the ground on the south side of the swimming pool at the hotel. It will recline so as to be visible from the north from a lying position around the pool. The dial has been calculated for 45°N therefore 45 - 13 means that its plate will be sloping about 32° to the horizontal. The distance from the pool is about 10m, therefore it needs to be of some size. I am planning on making it about 2m across. The main problem seems to be the choice of materials. I have ruled out wood due to the termites in the area. I have also ruled out paint as the sun is so very hot most days - except for the 3 months of rains. It has to be constructed by local labour with minimal materials available. I am planning to be there to set it up and work out the delineation but I want to be sure that we have all the materials to hand to build it within a few days. At present my thoughts are to make it from concrete, preferably off site, so that it can be laid in position, and dare I say it?, enable me to make small adjustments later if necessary. This will probably mean that it will have to be made in up to 4 parts plus the gnomon. The ground on site is basically sand. I originally considered moulding in the hour lines, numerals etc. but think that this would be too much for the personnel involved. My latest thought is to make just a flat plate and apply the hour lines as strips - of wood? and house door type numerals. At least, when the termites eat these strips, they can easily be replaced! Therefore I am asking for any other suggestions that may be more appropriate. I am sure that several members of this list will have made dials for the tropics and eagerly await their comments. Regards, Mike Cowham. Cambridge, UK.
Re: Making a Dial in The Gambia. What materials to use?
Mike Cowham wrote: Therefore I am asking for any other suggestions that may be more appropriate. I am sure that several members of this list will have made dials for the tropics and eagerly await their comments. One possibility would be to make an 'incised' and reversed version of the dial using old fashioned cork lino' of the type used for lino' cuts. This stuff is easy to work, takes quite a deep cut and the various 'V' and 'U' tools required are available from art shops. If the finished result formed the bottom of s shallow wooden 'form' for concrete - or better still high-alumnia Ciment Fondu (that is the correct spelling if I remember correctly) - it could be poured to cast a permanent plate. I first met Ciment Fondue when used as a cheap substitute for bronze in casting statuary where it produced a superfine surface which could be wax polished. It must be mixed with exactly the prescribed amount of water or it 'rots' when exposed to a moist atmosphere as the roof beams of our local swimming pool proved where mixing had been by guesstimation. A thin layer applied by hand first would fill all the detail with plenty of agitation to avoid bubble cavities when backing up. Care would be required to stop the lino' floating upwards in the middle perhaps. I've not actually tried this technique but it might be worthy of experiment. Good Luck with this interesting project Mike. Tony Moss
