lightengine Posted August 12, 2016 Share Posted August 12, 2016 (edited) I am attempting to make a river bridge using polystyrene as a starting place and former. I need to roll out 3 pieces of Das. 1 as the under bridge piece and 2 as the arched shape side pieces. Do I need to produce all 3 simultaneously and fit them all together? This way the edges can be moulded together whilst damp. Or can I shape 1 piece at a time? Fitting 1 piece before making the next? Or will joining the 2 edges together be hard to obtain a decent finish? Edited August 12, 2016 by lightengine Link to post Share on other sites More sharing options...
RMweb Premium jamie92208 Posted August 12, 2016 RMweb Premium Share Posted August 12, 2016 I've used a lot of DAS on viaducts and have always used several pieces. I roll it out and then roughly shape it with a knife and then put PVA on the bridge structure and place the DAS onto it. I try to form corners at the same time. It is possible to put several pieces on whilst it's wet and some excess PVA helps you to smooth out the join. It depends as to whether you are working the surface wet or dry. I work it wet if I want a rough stone finish and dry if I want a smoother finish. If I'm working it wet then you are limited as to the size of the sheet that you can work before it dries, which goes quicker the thinner the sheet is. Hope this is of help. There are some photos of using DAS to cover a house that I'm doing on the latest page of my layout thread. Some of that has been worked dry and some wet depending n the type of stonework. Jamie Link to post Share on other sites More sharing options...
lightengine Posted August 13, 2016 Author Share Posted August 13, 2016 Jamie, what minimum and maximum thickness of das should I aim for? Link to post Share on other sites More sharing options...
RMweb Premium jamie92208 Posted August 13, 2016 RMweb Premium Share Posted August 13, 2016 Jamie, what minimum and maximum thickness of das should I aim for?I generally go for about 1.5mm, any thinner it flakes away when you carve it. One tip is to roll it out on a flat board that has a couple of strips of 60 thou plasticard glued to it these then act as size guides if you roll the DAS between the strips. The thinner it is the quicker it dries. Jamie 1 Link to post Share on other sites More sharing options...
HLT 0109 Posted August 13, 2016 Share Posted August 13, 2016 I have found DAS to be very user friendly. If you find it taking longer than expected to get a piece to the size and shape you want, and that it is drying out too quickly, it will respond to the addition of a little water. In fact, if you add too much water, it will turn into a paste - which also has its uses from time to time. It is possible to reconstitute old stock from a part-used pack if desperate! Harold. Link to post Share on other sites More sharing options...
lightengine Posted April 28, 2017 Author Share Posted April 28, 2017 I finally got around to producing something. Starting point was a piece of packaging polystyrene. Already broken it needed reconnecting and shaping slightly. Link to post Share on other sites More sharing options...
lightengine Posted April 28, 2017 Author Share Posted April 28, 2017 (edited) Started work on the over part of the bridge today. A kit of girders for the ends and some salvaged back scrubber parts. Edited April 28, 2017 by lightengine Link to post Share on other sites More sharing options...
lightengine Posted April 30, 2017 Author Share Posted April 30, 2017 Bridge structure has now been joined fully and covered in plastered bandage. Link to post Share on other sites More sharing options...
lightengine Posted April 30, 2017 Author Share Posted April 30, 2017 The 2 parts placed together for a preview. Link to post Share on other sites More sharing options...
lightengine Posted May 8, 2017 Author Share Posted May 8, 2017 Latest update on bridge. Girders have been primed and some have been given a further coat. The stone sections have been primed and given 2 further coats. Weathering next. Link to post Share on other sites More sharing options...
Campaman Posted May 12, 2017 Share Posted May 12, 2017 Thats looking really good, proper sratchbuilding useing stuff you would normally chuck out (not in my house though) Link to post Share on other sites More sharing options...
lightengine Posted May 1, 2019 Author Share Posted May 1, 2019 I finally decided to roll some DAS and stick it on the bridge. Having smoothed it out on all 3 surfaces I started scribing whilst wet and in about 3 hours it was complete. Drying out is now taking place and hopefully the DAS will remain in place. 1 2 Link to post Share on other sites More sharing options...
RMweb Gold chris p bacon Posted May 1, 2019 RMweb Gold Share Posted May 1, 2019 Bridge looks good, but from a constructional point of view the arch is a bit flat. It should be semi circular or with a continuously sweeping curve as that is where it gets it's strength for the deck. 1 Link to post Share on other sites More sharing options...
lightengine Posted May 1, 2019 Author Share Posted May 1, 2019 10 minutes ago, chris p bacon said: Bridge looks good, but from a constructional point of view the arch is a bit flat. It should be semi circular or with a continuously sweeping curve as that is where it gets it's strength for the deck. Yes, agreed. My thought processess overlooked that. Link to post Share on other sites More sharing options...
RMweb Gold chris p bacon Posted May 1, 2019 RMweb Gold Share Posted May 1, 2019 3 minutes ago, lightengine said: Yes, agreed. My thought processess overlooked that. Brunel had a thing about 'flat arches' so I wouldn't worry about it. 1 Link to post Share on other sites More sharing options...
APOLLO Posted May 1, 2019 Share Posted May 1, 2019 3 minutes ago, chris p bacon said: Brunel had a thing about 'flat arches' so I wouldn't worry about it. Yes he did - This one at Maidenhead on the GW mail line Brit15 2 Link to post Share on other sites More sharing options...
Pete the Elaner Posted May 1, 2019 Share Posted May 1, 2019 34 minutes ago, APOLLO said: Yes he did - This one at Maidenhead on the GW mail line Brit15 That is not flat. The fact that it is still an arch makes a huge difference to its strength. 1 Link to post Share on other sites More sharing options...
lightengine Posted May 1, 2019 Author Share Posted May 1, 2019 Originally built by the Roman Mechanical & Engineering Legion the bridge crossed a fairly small river in a fairly deep ravine. The continual pounding of elephants weakened the construction unnoticeably. In later centuries the bridge fell into disuse except for the occasional fire chariots but the river widening scheme of the early 19th century brought it back into use. Global warming required more room for glacial water run off and the continued erosion of the chalk ravine meant that the bridge was split into 2 halves. Each part being dragged backwards for several metres (Belle Tout lighthousestyle) and major engineering took place using carbon fibre strengthening and some Gaffa tape. A large inserted centre piece was cleverly constructed in reinforced fibreglass and dressed in similar style to the original stonework. During the reconstruction period nobody was killed and a replacement bus service took pasengers on a 75 mile detour. 2 Link to post Share on other sites More sharing options...
RMweb Gold chris p bacon Posted May 1, 2019 RMweb Gold Share Posted May 1, 2019 I put an estimate in for the work but never heard anything....it was cash only so that might have been a problem.. Link to post Share on other sites More sharing options...
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