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.
|Thread: Vane Steering for Model Yachts|
Watch out Ray, I think Luddite was the word that got me into trouble last time.
I have to be careful what I say about Arduinos as I have been known to upset people in the past. The attraction in using them or similar devices to achieve some sort of automatic control is, to me at least, the challenge of making the system work and particularly making it work effectively. Its just another aspect of building the model like getting the scale, accuracy or painting done to the best of your ability. The fact that the control system might take away some of the skill or effort needed to sail the model is a secondary consideration. In practice the knowledge and understanding a person needs to acquire and apply to making an automatic system work would probably make that person a better operator of a purely 'manual' system.
Edited By Gareth Jones on 27/12/2019 09:52:15
Tim is quite correct in his description of a self tacking vane, The vane does not initiate the tacking manoeuver, that has to be done by the skipper or his mate on the opposite bank poling the bow of the yacht across until the jib sail fills and the vane then automatically flips over to the position appropriate for sailing on the opposite tack. The advantage that the self tacking vane gives is that the yacht does not need to be stopped to make a manual adjustment to the vane's position.
When the vane is broken it is held over on one or other side of its travel, partly by its weight assisted by the heeling of the boat, partly by the aerodynamic forces on the feather from the wind and also by a light overcentre spring. The spring prevents the vane from flipping over on to the opposite tack in the event of a gusty wind or choppy water. However the vane gear has to be set up carefully to ensure that when the boat is poled on to the opposite tack, the spring is not too tight and prevents the vane flipping over to the opposite side.
Its not unknown for boats to change tack inadvertantly and this phenomenon is exploited in guying when an overcentre spring is set up 'off centre' so the vane is held more positively at one side of its travel than the other. The boat is released on the tack where the vane is only lightly held in position. In the event of a change of wind speed or direction the vane flips over on to the opposite side and turns the boat. Because the vane is more positively held in this new position the boat should stay on this new heading. Its a useful tactic when you are near the finish line and don't want the yacht to go all the way over to the other side of the pond. However there is an element of chance in what will happen and setting just the right spring tension and offset requires great skill and experience.
I think every vane sailor is still learning, no matter how long they have been doing it. Its a big help in understanding vane sailing if you can find somewhere its practiced and watch and ask questions. Its a very sociable form of model yacht racing, much less aggressive than radio sailing. Unfortunately there are not that many sites where it is now possible as all round access to the pond or lake is required. The main centres nowadays are probably Fleetwood, Birkenhead, Bournville, Gosport, Hampton Court and possibly the Round Pond and Clapham in London - if I have missed anywhere out I apologize.
Tim - don't hold your breath, I may be a while getting started.
My plan was slightly different but also based on a staged approach
Step 1 was was to restore the yacht, which was essentially a wreck, and make it a dual control, radio or vane steered yacht. This was done and it was initially sailed under radio to get the basics sorted out and the mast in the right place. Then it was sailed as a vane boat, including a weekend at Fleetwood in their Vintage Marblehead competition. After about 20 trips each way down the pond over the weekend it was reasonably sorted and there is a picture of it below.
The next step is to fit the Arduino with a data logger and sensors to monitor what the boat is doing when being vane steered. Planned sensors are position by GPS, compass heading, rudder position to see what the vane gear is commanding and wind direction.
The third step is then to remove the vane gear and program the Arduino to try and emulate the vane gear. Its important to realise that the vane gear only attempts to maintain a constant heading relative to the wind direction and its a big assumption that the wind is blowing in the same direction all along the course you want to sail. One of the big advantages of the lake at Fleetwood is the wind is reasonably true. If you are trying to make adjustments to a vane steering system and the wind is being deflected by trees or other obstructions it gets very confusing and frustrating.
The next step is to develop the step three control system so it could be applied when tacking upwind.
The fifth step is to go one step beyond what a vane gear can do and that is to steer a course on a constant heading, in all directions relative to the wind.
Finally the aim is to get the control system to be able to sail a programmed course which would mean the Arduino would have to take control of the sailwinch as well as the rudder.
Hopefully I will make some progress on the project this year but I have got lots of other things to do so maybe it will stay on the shelf for a while longer.
You have set yourself a good challenge there. I have also planned to do something similar and bought an Arduino about 18 months ago. My objective was to try and make a self steering yacht with an Arduino processor replacing the vane gear and work up to a completely autonomous yacht that could steer along a straight course, emulating a vane steered model and eventually around a pre-programmed course setting the sails and rudder to the optimum positions. Unfortunately other projects have got in the way and so far I have only got as far as teaching the Arduino to turn an LED on and off. However its still on my list of projects and the Arduino is safely stored in the workshop. I planned to use a China Boy Marblehead as it has plenty of internal space and good access, There are several websites with information that would be useful to you.
At the moment I can't find my scanned copies of the Vane School articles and I might have to rescan them so it could take a couple of days to get them to you.
An Arduino is a small programmable processor that can be built up by linking it to other electronic modules. These can include sensors such as a compass, Global Positioning Systems, temperature, wind direction and also actuators like servos and motors The programming is also done in a modular way with lots of free to use modules available on the internet. There are lots of simple projects available on the web to get started with.
Dave, there is an introduction to vane sailing on the MYA website and a link to it here Vane sailing
In general vane sailing is done in a straight line from one end of the pond to the other, although the yacht will have to tack from side to side if sailing into wind. It would be quite difficult to combine vane and radio sailing systems on a yacht at the same time and switch between the two, mid lake, so to speak. However it is quite straightforward to modify a yacht so that it can be sailed either as a radio boat or a vane or Braine steered model. Many of the ones that my wife and I own are 'dual control' as there are few lakes near where we live suitable for vane sailing since they don't have the all round access required to cater for the unpredictability of a self steered yacht.
Edited By Gareth Jones on 24/12/2019 12:26:03
I am a member of the Vintage Model Yacht Group and have some experience of vane sailing with yachts ranging from 36R sized up to A class. There were a series of articles on vane sailing published in the Turning Pole, the journal of the VMYG a few years ago. I have scans of them and if you send me your email address by private message I will forward them to you,
There are free plans available on the web of an Ezi-build vane gear designed by Graham Reeves. I have attached a photo of the one I built to his drawings.
There is a link to the plans on the Llandudno model yacht club site here Vane gear
|Thread: Prop shaft vibration|
A single 'universal joint' coupling can only accommodate angular misalignment between the input and output shafts. It cannot accommodate any lateral offset, i.e. side to side or up and down misalignment of the shafts. A pair of couplings can accommodate lateral offset as well, the amount of offset being dependent on the length of the shaft between the couplings. However with a double universal joint, the couplings act as the locating bearings for the centre section of shaft. If there is any play in these bearings the centre section of shaft is liable to vibrate.
The geometry of universal joints is complex and subtle. For example many joints are not constant velocity, i,e, if the input shaft is rotating at constant speed, the output shaft will rotate at a speed which varies with angular position as the coupling rotates. This can lead to noise, vibration and wear. Obviously these effects are more significant with systems that are transmitting high powers at high speeds.
If at all possible its best to arrange the propshaft in your boat to be as straight as possible with the absolute minimum offset and angular misalignment.
|Thread: Snogg the sequel|
Sorry but I made a mistake in my post on the 17th, the normal motor in the Springer is now D3536-9 which is the same diameter as the proposed PT boat motor but about 12 mm shorter.
I did use a D2836-11 for a while and it was OK and safer as a have a go boat but a bit underpowered for fun sailing.
Sorry for the confusion, I had too many motors sitting on the bench when I was swapping things around.
Its difficult to provide the whole picture on the forum as there is no easy way I know of to display an Excel spreadsheet. If you would like a copy of the complete sheet with all the data I have collected, send me a PM with your email address and I will forward it to you. However a summary of the Springer data is as follows.
Graupner Speed 500E brushed motor, 7.2V NiMh 40 mm 3 blade prop driven at 3250 rpm (45% of unloaded speed) max load current 4.1 amps, This was the original configuration I used for the model, worked OK but a bit slow and the motor got hot with prolonged running at high power.
Turnigy D2836-8 1100KV brushless motor, 7.2 V NiMh 40 mm 3 blade prop driven at 5900 rpm (70% of unloaded speed) max current 12.2 amps. Not sailed in this configuration
Turnigy D2836-11 750 KV brushless motor 7,2 V NiMh 40 mm 3 blade prop driven at 4685 rpm (82% of unloaded speed) max current 5.5 amps.
Turnigy D3536-9 910 KV brushless motor 7.2 V NiMh 40 mm 3 blade prop driven at 5710 rpm (80% of unloaded speed) max current 9.9 amps. Standard working configuration now, also used with 11.1 V LiPo occasionally
Turnigy D3536-9 910 KV brushless motor 11.1 V LiPo 30 mm 3 blade prop driven at 10740 rpm (89% of unloaded speed) max current 9.4 amps Not sailed in this configuration
Turnigy D3548-4 1100 KV brushless motor 11.1 V LiPo, 40 mm 3 blade prop driven at 9540 rpm (76% of unloaded speed) max current 35.1 amps Not sailed in this configuration
Turnigy D3548-4 1100 KV brushless motor 11.1 V LiPo, 30 mm 3 bladed prop driven at 11630 rpm (89% pf unloaded speed) max current 17.5 amps Not sailed in this configuration
As a guide I work on the basis that provided the max loaded speed is at least 75% of the unloaded speed there is a good match of motor and propeller. Between 45 and 75% the combination is usable with care, i.e. provided the model does not need to spend long periods at high powers, eg a model narrow boat. Below 45% the motor is running too inefficiently and will quickly overheat if high powers are used.
I have sailed the Springer with a D3548-6 790 KV brushless motor on an 11.1 V LiPo but not measured its performance. However I did produce a rather blurred video of its performance and there is a link here supercharged springer
That's an interesting point about the drag from the un-driven centre propeller. Intuitively I would have thought that a fixed pitch propeller that was allowed to spin and 'freewheel' would create less drag than one that was held static. However I could be wrong. On another forum that I often frequent (PPRuNe) there was recently a similar debate about whether a seized turbofan engine would create more or less drag than a windmilling one. Opinions were mixed but there was some old flight test evidence that suggested a seized turbojet engine did create more drag than a windmilling one at high speeds. Since I spent over 40 years as an aircraft flight systems engineer, much of it working on the aircraft in question in the PPRuNe debate, I suppose I should know the answer. Unfortunately I don't. I think I know a man who worked at Rolls Royce Bristol who would know the answer but I suspect that he, like me, has been retired for some time - John Bewick, where are you now?
On Snogg in its previous incarnation the centre propshaft and propeller were allowed to freewheel and the overall performance was OK. Whether, and how fast the propeller rotated I have no idea. On the rebuilt model it would be relatively easy to try all three options, fixed, free and no centre propeller and see if there is a discernible difference. It would be easy to leave the centre propeller loosely threaded on the shaft for display purposes and remove it when sailing and that should clearly give the lowest drag. However it would be only a matter of time before I forgot to remove it or tighten it before sailing and lost it in the oggin. I will report back with some test results when the model is tested some time next year.
I should perhaps have added that although the original PT boats had three engines, Snogg the model will just have two motors driving the outboard shafts. The centre shaft and propeller will just freewheel for scale purposes. In the models latest incarnation the centre shaft will be much shorter and not extend fully into the hull as before, This will give me the option of laying the battery along the centreline of the hull rather than across as before.
Dave, thanks for the information about your Huntress. I think Snogg will be quite a bit heavier and draggier than the Huntress so it is likely to need more power.
Alas my snogging sessions have also suffered a marked decline over the years.
Edited By Gareth Jones on 17/12/2019 19:28:48
You are not paying attention, I explained this to Dave Milbourn a short time ago, admittedly in another thread.
The model is finished as a Royal Norwegian Navy vessel, originally build number PT602, which was built in 1945 for the USN or possibly the Marines, but did not see service in WW2. After the war it was sold/transferred to the Royal Norwegian Navy under a weapons aid program and was named Snogg, which is Norwegian for fast. Snogg was the first boat in that batch which were known to the RNoN as the Elco class.
Subsequently the RNoN have had several other batches of PT boats, several individuals named Snogg and from 1970 there was a batch known as the Snogg class.
The thread is called 'Snogg the sequel' because it follows on from the original article.
To bring the thread up to date the next step was to carry out a performance test with the proposed brushless motor. For many years we have had two Springers that have served us well as test beds and also have a go boats. One of these was sold at the last Blackpool model show but the other has been retained as a test bed and boat of choice for the Manx model boat club's hooligan competition at their Manannan event. It is normally powered by a D2836/11 motor (750 KV) which drives a 40 mm prop and gives quite a spritely performance but not PT boat speeds.
The chosen motor D3548/4 is a bigger diameter, but fits on the same mount and is an easy swap, just moved forward by about 12 mm. The installation was fitted up with my wattmeter and it was off to the bath to test it.
Driving the existing Springer 3 bladed 40 mm prop and using a 3 cell 6000 MaH LiPo battery, the motor gave me a prop speed of 9540 rpm and took 34 amps. This is above the rating of the speed controller which is a 30 amp Leopard unit. However it was OK for a quick test and survived unscathed. I have not got any photos taken during the test as it takes one hand to hold the boat steady, one to hold the tacho to read the prop speed and another pair of hands to operate the transmitter.
Driving the 30 mm PT boat propeller the brushless motor gave 11600 rpm with a current of 17.5 amps. By comparison with the original 700 sized brushed motor this is about 2% increase in prop speed but with only 73% of the current consumption and only 40% of the weight. Overall it looks a promising combination and I can now go ahead and design the mounts for the motor and the new propshaft and P bracket installation. I will probably replace the 30 mm props, which I think are standard Raboesch units, with some similar sized Prop Shop propellers which are a more accurate representation of the full sized ones. If necessary I could go up to 35 mm diameter without greatly compromising the scale appearance and still be within the 30 am speed controller rating.
Edited By Gareth Jones on 17/12/2019 18:03:00
Why bother removing the propshafts you may ask? Well there were several reasons. The drive shafts themselves had been lengthened to 420 mm to provide the required clearance to fit the 700 sized motors. This put the motors and overall boat centre of gravity further forward than ideal. The replacement motors are smaller and lighter and I wanted to install them further back.
The boat is fitted with 30 mm diameter 3 bladed propellers which are a good scale approximation to the real things which were 28 inches diameter. I have made many detailed performance measurements on the model and I know that I need around 11000 rpm with the 30 mm props to give good boat performance. However the installation was susceptible to vibration and probably some whirling of the propshafts so shorter shafts were desirable.
Finally the real boat has exposed drive shafts outside the hull, supported on P brackets, and I wanted to make the model more representative of the real thing.
Based on my experience with other brushless motors I had decided that a Turnigy D3548 sized motor should be powerful enough and the 1100 KV variant should give a fast enough prop speed. I might go up a small amount in prop size to 35 mm but even so this motor should perform OK. As a comparison the two motors are shown below. Note the brushless one is a lower KV but the same physical size as the one I plan to use.
As a comparison, the brushed motor weighs 390 grammes, the brushless motor 160 grammes. Both have 5 mm diameter driveshafts.
Some of you may remember an article I wrote for the magazine about 10 years ago, covering a major rebuild of a 1:24 scale model of an ELCO 80 ft PT boat. The article is still on the website and there is a link to it here PT 602
I have now started a second major rebuild and this is the first of an occasional look at what I am doing, As described in the article the original rebuild had a long string of propulsion problems, mainly due to my inexperience at the time, Eventually Snogg did achieve a good performance on a pair of Speed 600 motors as shown below.
Subsequently the model was fitted with a pair of Speed 700 motors (Graupner part no 7307) which ran much cooler.
Here is a picture of the Snogg internals as they were with the later motors and NiMh batteries.
Subsequently there was another weight saving exercise and a 6000 MAh 3 cell LiPo battery was used instead.
However time has moved on and the model was always ripe for a brushless conversion. There are also a large number of other potential improvements I would like to make adding more detailing and hopefully working roll off racks and torpedoes. However the first step has been to strip out all the internals and remove all the deck fittings so Snogg has now been gutted.
Everything came off OK without any damage but removing the propshafts was a bit of a challenge. I made up a wooden block drilled out 8 mm to be clamped around each propshaft with a pair of molegrips.
The prop shaft was then heated with a small blowtorch to soften the araldite holding it in the hull, being careful not to set the hull alight. A bit of twisting with the molegrips and all three propshafts were removed successfully.
A bit of cleaning up is required but so far so good.
|Thread: Spektrum MR200 receiver question|
Thanks for a very quick and helpful response. I will give it a go and cut back the screen accordingly. I have measured another receiver antenna and it is 31.2 mm long as best I can tell. I think I will put a length of heat shrink over the whole length of both antennas as the step where the screen is cut back does create a weak spot which flexes and eventually cracks the conductor. I will do a range test afterwards.
Edited By Gareth Jones on 17/12/2019 15:31:47
I have a Spektrum MR200 receiver which has worked faultlessly in a number of models. However as a result of multiple swaps between models the last inch or so of one of the two antenna leads has broken off. As I understand it, this last inch of un-screened wire is the antenna, the rest of the grey covered wire is effectively an extension lead.
Can I cut back this broken wire to reveal a similar length of un-screened wire to act as a new antenna or do I have to replace the whole antenna wire (assuming its possible to get one) ? If I can cut the wire back to make a new antenna how critical is it that I get the right length?
Any advice gratefully received.
|Thread: Kingston Peridot|
East Riding archives had a project to digitise many of the drawings of the Cook, Welton and Gemmell shipyard in Beverley where Kingston Peridot was built. They have a website called Trawling through time which gives a lot of information about the project and there is a link to it here Trawling through time
Kingston Peridot is one of the examples they show on the website and there is a link to the drawing here Kingston Peridot. I don't know if there is enough information for you on that drawing but there may be others or drawings of other similar vessels built around that time you could have a look at. You might need to contact or visit the archive centre at the Treasure House in Beverley to find out whats available or you may be able to search the records on line.
If anyone is thinking of building a model of a Hull (or Fleetwood) trawler I am sure there would be lots of interesting and useful information available on the Trawling through time website.
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