Here is a list of all the postings Gareth Jones has made in our forums. Click on a thread name to jump to the thread.
|I have just measured my wife's Moonbeam and it's 67 inches (1.67m) from the bottom of the keel to the top corner of the top gaff sail and boom. I don't know what the scale would be since its a replica of a pond yacht rather than a real yacht but, based on the height of the ships wheel above the floor of the cockpit I would guess about 1:32.|
|Thread: Shemarah II|
Having made the decision to go with the original plan of lead ballast and not try and complicate things with a pumped water system, I have now installed the ballast supports. There will be 4 main areas of ballast. There are 2 pads, one either side of the motor mount which will probably take the biggest proportion of the ballst. The hull currently weighs around 5 kg and that will probably double when all the rest of the model is added so I guess I will need around 10 kg of ballast. I guess around 3 kg will go either side of the motor mount and 2 kg at either end of the centre section.
The ballast mounts were made from 6 mm ply which is screwed on to 10 mm square pine bearers which in turn are glued to the internal frames. The photos below show the 4 areas and a typical pad. A single 4 mm screw has been fitted in the centre of each pad to act as a stud which will retain the ballast. Individual sheets of lead will be added in all 4 positions to get the boat level at the correct waterline. Around 17 will be needed either side of the motor to give a total weight of 6 kg here. ( I weighed one of the initial cut sheets on the kitchen scales) I have used this method on other models and it works quite well allowing accurate balancing to be achieved by juggling the size and number of lead sheets in each location. My source of lead sheet is the remains of a roll of lead flashing, originally purchased about 15 years ago to repair our roof valleys. There will be plenty left, even after Shemarah is finished.
The aft ballast pad is shown in the photo below with the rudder servo mount which has also been fitted in its final place. While the front and rear ballast would not be so easy to fit while the boat is in the pond, the two centre blocks and the battery will be accessible so it should be possible to reduce the weight of the hull to around 12 kg if needs be, when I get old and infirm and can't shift the complete hull.
The planned next step is to fit the kort nozzle and propeller and temporarily install the radio and speed controller so that the whole of the propulsion system can be tested. I will have to cut quite a few more ballast weights to make the overall weight reasonably realistic then its off to the pond to see if the model performs OK in the water before proceding too much further.
Its been a while since I updated the build log for Shemarah but don't despair I have not been defeated by sanding down the fibreglass resin. That job is now just about complete with just a few minor spots to fill and sand. I will probably have one more round of filling and sanding before the hull will be ready for the next stages prior to priming.
After some consideration at the Haydock Park model boat show I decided to purchase an Action Electronics Noisy Thing sound system and after discussion with Dave Milburn the speaker will be mounted in the floor of the superstructure and be removed with it. This leaves the interior layout free for all the rest of the gubbins, by far the heaviest of which will be the ballast. There is some confusion between the Model Boats article on Shemarah and the plans. The editors note in the article says the model should weighh 19.6 kg, whereas the plan says 31.4 kg.
The full size vessel displaces 301 tons or near enough 301,000 kg. The model is to a scale of 1:25 on linear dimensions. The scale factor for any area is therefore 1:25 x 25 or 1:625. The scale factor for any volume is 1:25 x 25 x 25 or 1:15,625. Since the model must float at the same waterline as the real vessel it must therefore displace proportionally the same volume of water. The weight of the water displaced by the real vessel is 301,000 kg therefore the weight of water displaced by the model (and hence the weight of the model) must be 301,000 / 15,625 = 19.26 kg. One up to Paul Freshney there then.
There has been some scepticism about operating a boat of this weight, 19.26 kg is around 43 lb. My plan has always been to move the model using a build in handle and fit the superstructure when it is on the water. To test this theory Shemarah was ballasted up with 7 house bricks and weighed on the bathroom scales at 46 lb. Just to satisfy myself it is going to be possible to lift it, and the handle is not going to break, heres a photo of the model, and my arm being tested.
|Thread: Tiny Passenger Liner|
I have found that tweezers are really useful for some of the smaller fiddely items. The days of my youth when I could manipulate Meccano nuts and bolts in all sorts of confined spaces are long gone. Your mention of vibrating motor ships reminds me of another reminiscence from my past.
Immediately before I retired from Brough, which is now part of BAE Systems I had to have a medical examination. This turned out to be just a hearing test and I guess it was intended to make sure you could not sue BAE Systems for an industrial injury if you subsequently lost your hearing. Most of my work was carried out in a relatively quiet office but occasionally I went out on aircraft engine runs for one reason or another. Anyone who has seen a Phantom running in full reheat will realise that working directly under the engine is a pretty noisy environment.
At the end of the hearing test the nurse in the medical centre said " Mr Jones, I am pleased to be able to tell you that even though you are 60, you still have the hearing standard of an 18 year old. I can also tell you that nowadays a typical18 year old apprentice starting work here has the hearing standard of a 43 year old because they have already deafened themselves with IPods, computer games, discos and rock concerts"
I just dont know how Bob can make these finely detailed models at such a small scale. My fingers and eyes can't really cope with anything smaller than 1:24.
Straying slightly off the original topic on to company canteens, I started work in 1970, at Brough in East Yorkshire for what was then Hawker Siddeley Aviation. There were 6 levels of canteen on site. The lowest of the low was the 'Works' where it was self service, you had to provide your own cutlery and the sauce bottles were never more than 1/4 full. The next level was 'Weekly Staff' which was also self service but cutlery was provided and the sauce bottles were up to 1/2 full. Next was 'Monthly Staff' which was waitress service and the sauce bottles were full. Then there was a 'Silver Grill' for executive managers which you had to be invited to join when you had reached sufficient seniority, and there was a 'Golden Grill' for directors. There was a separate restaurant for visitors known as the Flying Club. After about 20 years working my way up the Technical Department I was eventually invited to join the Silver Grill but turned it down on the basis that I thought all this discrimination was divisive. Maybe that's why I never got promoted any further in the next 20 years.
|Thread: Shemarah II|
After a few more hours work one side of Shemarah's hull is now sanded down and filled where necessary.
Hopefully the other side will be quicker, and no doubt after the first coat of primer lots more areas will be revealed as needing filling, but thats normally the case.
As a bit of light relief I have made the rudder servo mount and linkage today. The servo is mounted on a piece of 6 mm ply which will be screwed to two cross beams. These are 12mm x 6 mm pine strips which run the full width of the hull and will be glued to the frame webs at a suitable height. Nothing has been fixed yet, the beams are just clamped in place. The rudder servo is a Futaba S3014 high torque servo. A standard servo would probably be OK. I just happen to have this one going spare at the moment and its the same size as a standard servo if I decide to pinch it for some other application later.
The rudder pivot tube has been made long enough so that the top is above the water level to minimise the risk of water seeping up into the hull by that route. I like to use a push-pull double linkage for rudder controls as it give some degree of dual redundancy and it minimises the side loads on the rudder. In most cases its easy enough to engineer it into the space available.
I am not keen on the idea of plating the hull, its yet another step into the unknown and I dont think it will give the look of an all welded ship. I think I will stick with the sanding block for this one - better the devil you know.
I have the Spurn lightship pencilled in as a possible future project. That's got lots of joggled and rivetted plates and might be the test bed for your suggestion. You will probably have to wait till around 2013 before you see any results though.
Thanks for that John,
it seems like a good plan.
Thanks for that John,
I think I will abandon the power sander and just do the job by hand.
What is slightly more worrying is that there are quite a few small areas where there has been an air bubble in the resin/tissue layer and these are now coming to the surface leaving a crater. The question is do I keep sanding till I reach the bottom of the crater or just leave them with a reasonable resin layer around them and fill the crater afterwards?
I am a bit concerned about water getting under the resin in these areas.
I will follow your advice on the strips when I finish rubbing down the hull (if I ever do)
I am no expert in marine engineering but I assume the half round bars are to protect the relatively thin skin plating from damage in the areas where the heavy weight bits of the trawling gear are hauled aboard. Nobody has told me what the two big doors in the transom are for yet.
I know part of next weekends show is now at Haydock but I assume the smaller concurrent show is still at the Birchwood sports centre ( I never did understand the relationship between the two shows). I see guest of honour at Haydock is Paul Freshney, we had all better be on our best behaviour or there could be a big expose in a future Model Boats magazine.
Back to the sander,
Not much visible progress over the last few weeks due to holidays and some major DIY work as a result of having a new central heating boiler and hot water cylinder fitted at home. Shemarah is now being rubbed down to achieve a good surface finish on the fibreglassed hull. This is going to take a while, there is obviously a knack to getting a smooth finish at the resin application stage which I dont seem to have. Its just a matter of plodding on using an electric sander where possible and wet or dry paper where not. I have found that the electric sander is best with a light touch to avoid the resin melting and clogging the paper. You have to be carefull on the corners so that you dont go completely through to the wood. Wet or dry paper used with some soapy water is best once the biggest lumps and bumps have been removed.
I guess there are another couple of weeks or so of this tedious job before I can move on to something interesting. However I can at least look forward to some retail therapy at the Birchwood show next weekend where I will be on the lookout for a sound system and some advice where to fit the speaker. I am also planning to work out how much half round styrene strip I need to make the reinforcing bars which cover the back end of the hull so I can aquire that - it may not be as exciting as rivets but it is hull detail to keep Bob happy.
|Thread: STILL FOR SALE|
We are fine. Thanks for the info but it would have been too big for us anyway.
How long is your yacht hull and what is it made of? - my wife may be interested.
My wife built a Victoria a couple of years ago. We fitted the radio gear pretty well exactly as the instructions describe. We used a Spektrum receiver with the short aerial mounted vertically and the longer one running horizontally aft through a short length of plastic tubing to restrain it. The servos were Futaba and there is some additional information on these in another post in the RC and Accessories section of the forum, entitled Which Servo. The last post in that thread was on 1/2/2011 so you should be able to find it OK. Unfortunately I did not take any photos at the time and my wife has now sold it and moved on to bigger and more expensive models including a Moonbeam and a Marblehead.
|Thread: Shemarah II|
I have had a look at some of my photos of Shemarah and in one of them which shows her on the ship lift at Fraserburgh you can see some weld lines so maybe I will add that detail after all. However I will need some better photos to get them all in the right place.
I have now covered about 70% of the hull exterior in glass fibre tissue and learned a few lessons in the process. I found that the dosing ball from the top of Persil non bio washing liquid is a good disposable measure for the resin as its calibrated at 35 and 52 ml. Mixing up 35 ml is about the most I could cope with. I tried 52 ml and was left with a gooey lump in the bottom of my paper cup as it set before I could use it all. 35 ml of resin covers around one square foot of tissue so you have to work as quickly as possible in relatively small areas at a time. I used the minimum amount of hardener to get the maximum working time. I could tell when the resin was starting to get too tacky as the brush tends to start picking up fibres from the tissue and gets quite hairy. Dunking the brush in cellulosce thinners immediately after use seems to preserve it reasonably well. I'm still on the original brush but I wont be using it for painting in future.
I tried wrapping the tissue around the keel but that did not work well at all as it inevitably pulled away on the inside corners leaving gaps underneath. I found the best method was to cover each side of the hull with separate pieces of tissue, starting by clamping the end of the sheet to the keel with bulldog clips and leaving about 1 cm spare on the edge. Resin is then applied to the hull to within about 1-2 cm of the keel and allowed to go off. The next lot of resin is then applied up to the keel and into the corner so that the tissue gets worked well into the corner. The photo below shows this stage of the process. Finally the top can be trimmed and folded over for the next application of resin.
I think I will also apply some tissue and resin on the inside where the hull is planked rather than covered in ply sheet. In some areas on the corners the planks are pretty thin where they have been sanded and they could do with some reinforcement.
I am going to apply two more coats of resin on the exterior and the comes the joy of several days sanding the hull to get the final smooth surface finish, and probably several more iterations of Isopon filling as well.
|Thread: Motor and Prop Survey 2020 Update|
I know time has moved on, the article has been published and most of you have lost interest but for the anoraks among you here is another variation on a theme of TIDs. My TID has had is Speed 900BB torque surgically removed and transplanted into Shemarah II. Its replacement motor is a Graupner Speed 720 BB torque, and here is the performance data.
Name TID13 (I know there never was a TID 13 in real life)
Scratch built, ply plank on frame hull
Length 900 mm
Breadth 230 mm
Draught 70 mm
Weight 6.4 kg
Motor Graupner Speed 720BB torque (type number 6372)
Propeller type 4 blade Rivabo brass general purpose
Propeller diameter 55 mm
Direct drive, no gearing
Battery 12 volt 7 amp hour lead acid
Duration not known but well over an hour
The motor takes 4.7 amps at full power of 54 watts into the speed controller.
Battery voltage was 11.65 at this condition.
Prop speed was 2140 rpm which is about 52% of the free running speed of the motor.
The static thrust from the propeller was 720 gramms max.
The attached photos show the motor installation and the tug running at full power on the pond at Goole today. I have not tried towing anything yet but it looks quite good at full power, much more realistic than with the previous motor. Note the picture of the tug on page 1 of this thread is not at full power, its much less.
|Thread: Wiring problems|
I am not sure how have plugged in your bow thruster and water pump to the receiver. I would have thought there would need to be a speed controller for the bow thruster and switch for the fire monitor pump as you could not connect either device directly to the receiver. Can you draw a simple diagram to show how these have been connected?
It sounds as though they are both just taking the power from the receiver power supply. The receiver alone could not control either of these devices, just provide power on the centre and outside pins of the receiver connectors.
|Thread: Shemarah II|
I think rivets had gone out of fashion by 1995 when Shemarah II was launched and at a scale of 1:25 I dont think you would really be able to see the weld lines, so the answer to your question is probably not. From the photos I have of the vessel, the most obvious hull feature is the way the plating 'pants' between the frames but I cant see any way of reproducing that realistically on the model. There are lots of half round reinforcing bars to protect the aft end and I will be fitting those.
OK Bob, its a bit subtle for me but was that a hint?
Anyway here is a bit more about Shemarah but more along the lines of 'Great Eastern the cable layer' than 'Shemarah the model'. I have always been fascinated by machines, the more complicated, the more interesting and I always like to try and understand how they work. A couple of years ago I built a Mountfleet Osprey armed drifter and there were two pieces of equipment fitted either side of the superstructure that I could not understand. They looked like old fashioned cast iron radiators but the drawing only showed one view of them, the instructions did not mention them and the photos were too small to see the detail. Eventually I found the magic word to type into Google which turned outo be Oropesa, the type of float used to suspend the end of the minesweeping cable. The 'radiators' turned out to be the kite and otter which were used to pull the front end of the cable down and rear end out sideways. Eventually I found suitable pictures of the real thing and was able to make a better model as a result. I also learned a lot about how minesweepers work, which is always useful when anyone askes me questions about the model. I suspect I may have fitted WW 2 kites and otters on a WW 1 minesweeper, but I am not too fussed about that. One thing I never did find out was how did they get the kites, otters and oropesa floats in and out of the water, there were no suitable davits or cranes on the model, was it just a case of manhandling them over the side or is there something missing from the model?
However, back to Shemarah II, there are two similarly puzzling aspects of the real vessel which maybe someone can explain to me. She is a twin rig trawler and I can see how the three main winches will pull the trawl wires (warps?) and the power block on the rear gantry is presumably used to somehow haul up the net at the end. However, the cod end hatch is forward of the main superstructure on the starboard side. Presumably therefore each of the two nets has to be somehow manoeuvered around the side of the ship to get it over this hatch. I wonder how they do this. It seems a bit of an awkward layout but maybe some naval architect or fisherman can explain why the ship is laid out like this.
Secondly in the transom there are two large rectangular doors with a roller at the bottom edge, suggesting something is hauled into or out of this area. The net drums are up on the shelter deck above this, so I am puzzled about the purpose of the transom doors - does anyone know the answer, maybe Donald Moodie the skipper of Shemarah II could enlighten me.
As far as the model is progressing I have spent the last couple of weeks filling and sanding the hull. Its just about ready for the application of the fibreglass tissue and resin, probably starting in the next few days.
|Thread: Exciting development!|
I am glad you are enjoying the Shemarah build. Progress is a bit slow at present as the main job at the moment is filling and rubbing down the hull prior to application of glass fibre so there is not much to see. I am also occupied with holidays and redecorating after a major plumbing job (replacement of central heating boiler and hot water cylinder) which is currently the priority task.
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