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>> Home > Tags > stability

stability
compatibility
incompatibility
stability
HMS BRAVE BORDERER by RHBaker Fleet Admiral!   Posted: 1 month ago
Adjusted the transom flaps and reprogrammed the ESCs to the softest start settings, retested. Until now, the test runs did not have the duration or stability to really examine what was happening. Using 3 S batteries acceleration is rapid and a is plane quickly achieved. However, as the acceleration continues and speed increases, the bow digs in. A cloud of spray then surrounds the model as the plane is lost. Brushless motors do not modulate as smoothly as brushed and adjusting power tends to be erratic or exaggerated. This is a scale model and the propeller shaft angles are per the plans. The thrust from the propeller has two components, horizontal and vertical. The horizontal propels the vessel forward. However, the vertical component forces the stern upwards and, correspondingly, the bow down. Have moved as much weight as possible towards the stern to counteract this, limited by maintaining the correct displacement and waterline. The easiest solution is to reduce motor power, decreasing both speed and the lifting component. Decided to retry the 2S batteries as they give reduced power. A plane is again achieved, but as the motor response is more docile, it can be controlled. If the speed gets too high the bow lowers, as before, but the motor output can be more easily adjusted. Spent a pleasant half hour or so with the vessel accelerating onto and off a nice, controllable plane. Much less spray and drama than with 3S and much more controllable. Have now decided to revise plans and use 2S rather than 3 batteries. A further advantage is the motor noise is muted and now sounds more like a gas turbine than a dental drill! Finally feeling comfortable with the model. Will thus shelve further building until the late fall when sailing in Canada concludes. Want to enjoy the rest of my fleet in the meantime! Will summarize my experiences with brushless motors in another blog shortly for the benefits of others contemplating their use. After restarting the model will resurrect periodic build blogs to advise progress.

Vickers Vedette 1/96 scale by f4u7 Seaman   Posted: 2 months ago
Many thanks for your kind words, I've not sailed her yet, only test tank and had to up the water line a little bit for more stability, I also scaled up the plans to true 1/96 as the plan is around 1/100, the 1/96 fittings I bought from fleetscale were out of scale to the plan, and using the 1.1 water line length noted in the magazine article.

Windows, stoopid question. by Westquay Fleet Admiral!   Posted: 4 months ago
Doug, sorry, I should have answered you last time on that. A good impression of a dummy screw can be made in aluminium with a piece of tube sharpened on the end so it looks like a miniature leather punch. Obviously better if you can do it with something you've done in the lathe, in steel, but you don't have one. SO....PM me your postal and I will send you something I will knock up for you tomorrow in steel. That will last you into your dotage, when you will be found dribbling into the geraniums with this little tool in your mitts making impressions on the window cills of Frau Schmutterputz's Home for Englische Modelbauen. You will be able to "sharpen" it buy running it round on a stone lightly, rolling it as you draw it backwards. Can't add to Squire Turpin's words at all. I have a slide tailstock on my wee Taig lathe which makes screw forming easy as the thread takes the tap/die as it wants it, square and true. The piercing saw has clamps for much finer blades rather than the relatively big fret saw blades which generally have a pin at the ends. Sometimes you'll break a blade at one end. Then the adjustability makes sense as you just re work the length and re-use the broken blade. Tight wads like me appreciate such things. Car booked in tomorrow for repairs. About £300, so not as bad as I thought it might be. It's passed for the last two years. Busy boy today as I sprayed the Crash Tender grey on its upper works and by the looks of it it just needs a few areas of fine filler and a rub down on the toe rails and one more coat then it'll be ready for the gloss sides and the hull proper. Then I even used my brand new saw to mitre the corners of the topping to Chris's new garden pond casing. It's a stand up one to save our backs. So now, I am gonna sit and watch shite telly, even shiter than normal as it is all infested by ball kickers playing grown ups and failing miserably . G'night. Martin

Marblehead Sailboat by Ron Fleet Admiral!   Posted: 4 months ago
All done and ready to sail. I took it to an outdoor swimming pool at a neighbours and did a Sytems check; Stability; All was fine and I suspect this is going Go like a greyhound on the lake! Put in a new sail winch robbe #8336; rudder servo is HiTec HS-322HD

Sea Scout 'Jessica' Sea Trial - at last! by RNinMunich Fleet Admiral!   Posted: 5 months ago
Interesting Canabus! Not quite what you recommended last year 😲 If you now think the Propdrive 1000kV has "no guts" why did you recommend it to me?? Thanks for spoiling my mood 🤔 As far as I'm concerned you just devalued your currency! I'm happy with her as she is, balance and stability is OK and performance, endurance vs current drain is much more lively than she ever was in 55 years.😊 After all, she's supposed to be a Broads Cruiser and not an Offshore Power Boat.😉 I'm not into racing either. From time to time I'll fiddle with fittings detail and cockpit on Jessica. Time to get on with other projects now. Doug 😎

H.M.S BRAVE BORDERER by RHBaker Fleet Admiral!   Posted: 5 months ago
Looks like everything is set for the first open water test. Sun is shining, ice has gone and water smooth. Intention is to start the open water test program with a repeat of the pool test, except this time with everything wired correctly; the load cell positioned so the “pull” is more horizontal and ballast available to hold the propellers underwater if necessary. Hope these improvements help reading stability. To modify the “pull” arrangements, wrapped a light cord around the propeller shaft struts and fed the loose end above the transom shelf and out over the stern. The load cell was hooked into this and then tied to a fixed grating on the pond side. Started by measuring the electrical requirements for each of the three motors and the propeller bollard pull, using the 2 S battery. Found the bollard pull was up slightly at almost 3 lbs per propeller. Probably because they were now held at a greater depth in the water. Also blew several 20A fuses, so fitted 30, which seem to work. A series of runs showed adequate performance with plenty of spray, although the bow did not lift much onto the plane. The forefoot did raise almost above the water surface. Then tried a 3S battery. Although this was much heavier, the performance improved dramatically. The bollard pull was up to almost 18 lbs per shaft. The bow still did not lift much to a plane, although the forefoot was almost clear of the water at full speed. The battery was located just back from the bow, so it is suspected that it held the bow down. The impact of the transom flap down angle could also hold the bow down, but have decided to leave as is for the time being and avoid the temptation of making too many adjustment at once. Whilst it is still too early to draw definite conclusions, it seems as if a 3S battery will be required. The model sustained some slight damage due to the test arrangements, so will repair that and also fit the 2 bladed Hi Speed propellers. Will then repeat the program and report. Should be able to draw some definite conclusions then on the best power train. Neither of the batteries used, neither the 2 S nor the 3S are ones I would choose for this model. As a result the capacities and weights are not ideal. That must also be remembered in future deliberations.

Genesis 9000 by RNinMunich Fleet Admiral!   Posted: 6 months ago
Hi Peter very unusual problem with the switch😲 You could temporarily replace it with a bullet connector to continue trials. Glue one end down so that you can quickly unplug the battery one handed. OR: simply short circuit the switch and use the fuse as the 'switch'!? Boat looks a little heavy / tail heavy? Maybe shift some weight a little forward to give more stability? Happy trialling, cheers Doug 😎

H.M.S. BRAVE BORDERER by RHBaker Fleet Admiral!   Posted: 6 months ago
An unexpected opportunity arose to try the unfinished hull in a small pool. Whilst the performance envelope could not be explored, was able to try and measure operating parameters and get a “feel” for the model. Used an electronic scale and a combination voltmeter/ammeter/wattmeter to measure propeller thrust /bollard pull and motor power requirements. If it is necessary to fit different drivetrain components, or a 3S cell this will serve as the baseline. The model floated levelly and well above the waterline. At about 8 volts the motors drew around 20 amps each at full speed; so only about 35% of the potential output capacity was being used. Tested each motor individually and measured the bollard pull at just over 2 lbs. A considerable amount of spray and wash was created making stable readings difficult. For further testing, will add ballast at the stern to hold the propellers further underwater. Should help reading stability. Currently using 20 A fuses; which as one failed seem marginal. For sustained use think 25 or 30 Amp better. With these high-speed, low torque motors establishing the “dry” propeller rotation is deceptive. Found one motor to be reversed! Nevertheless, the model accelerates quickly and is sensitive to engine speed movements. Left the pool with a list of modifications to make before assessing the installation properly on an adequate body of water. Some conclusions can be made though. If it is necessary to add a second cell this needs to be located around midships, not in the bow or stern. Still hoping a 3S cell will not be necessary and that 2S may be adequate. The suggestion to do testing using the bare hull with a minimum of detail was a good one. For a models with a sophisticated power train think this is a good approach. Nothing worse that finishing a boat just to find the performance disappointing, then have to to rip it apart to make major modifications or adjustments!

Devil in the detail! by RNinMunich Fleet Admiral!   Posted: 7 months ago
I'm with you there Skydive 👍What Boatshed means is the part of the rudder in front of the stock. Thinks: are you building an Offshore Power Boat or a scale Lifeboat? If the former then follow Boatshed's recommendation. If the latter and the rudder is 'scale' then leave it alone. Any braking effect, which usually is only significant in a fast racing boat model or other fast planing types, can be diminished by reducing the rudder servo throw at the TX. One should also consider how the original behaved, maybe they did 'dig in' maybe not. There has to be a reason why such rudders were developed, and surely not just to annoy modellers 😁 One more minor point that struck me - Ouch 😭 Your prop struts! "not that it provides a huge amount of support but adds to the scale appearance." Even in a model they can be important. To help reduce potential whipping of the propshaft, especially if the model is overpowered. Actually in the originals they were vital, especially in larger vessels. The purpose of these struts, in larger vessels 'A' frames, is to provide support to the end of the shaft which carries the prop weighing several tons and, more important, to carry the bearing for the outer end of the shaft! Actually in the originals the shaft tube, or 'Stuffing Box' would not extend significantly beyond the hull. Thus the strut or A frame was vital for the shaft end bearing, fitted immediately in front of the prop for maximum stability. Attached pics of my HMS Belfast (sorry don't 'ave nutt'n smaller with this feature🤔) show the arrangement. Have witnessed such construction in various shipyards around the world. Last one in UK was the first T45, quite an experience! 😲 In the end she's your boat, if it feels good do it! 😉 I would leave the rudder alone if it is 'as fitted'. 👍 I make my struts and A frames from brass sheet and tube. Cheers Doug 😎 PS Stick with the brass Donnie! 👍

Vintage Aerokit Crash Tender by CB90 Fleet Admiral!   Posted: 7 months ago
Brought this vintage Aero Kits RAF Crash Tender for £50 from Newcastle area, it is the 34in version. To my surprise at home I found that it had a Bullet 30 motor installed these motors were the top drawer motor of early fast electrics in the early 1980's and its the only one I've ever seen, it can run on 24v and pull around 15A giving 300w not bad for a brushed motor. due to the power of this motor I have modified the hull under the water line with turn fins and trim tabs to reduce torque roll and improve turning stability, the underside is incorrect already as it only has one propshaft, where the original had two and I believe that both props turned in the same direction. The Pictures here show some of the work in progress I have remounted the motor and added a speed controller rated at 24v I have remade the stern compartment and rudder gear under it. I have blocked windows and foamed the front half of the boat. made missing parts and repaired delaminating ply. Note old ply is not as good as modern, the glue is not as water resistant. Have painted the hull and have just ordered the decals from Cornwall model Boats :-https://www.cornwallmodelboats.co.uk/cgi-bin/sh000001.pl?WD=... The 34in is 1/16 scale Fitting can be brought but many are cast white metal and can add weight to the boat, I have made two water cannons and plan to buy plastic fittings from this site. This has turned out to be a task that is difficult to assess how much effort and money to spend on a hull that has been built by someone else (say no more). Have just finished the steps for the stern compartment. Painted and now for the test run. the Bullet 30 motor ran well between 14 and 18v,

Too Powerful Brushless ? by jarvo Fleet Admiral!   Posted: 9 months ago
Hi Graham, all agreed with you post. But. The last photo looks like the blades are soldered or brazed on, that is a week point, but looking closely the blade appears to have sheared of above the hub. Your hull is not really a high speed hull, so a racing prop might cause instability, i would suggest a cast prop, (propshop) and possibly 3 blades 40 - 45mm with your 1100kv motor would give good speed combined with good run time. The 5mm upgrade is also a great idea. A rule of thumb is don't exceed the diameter of the motor. Mark

Sea Queen Spray Rails by Dave M Fleet Admiral!   Posted: 11 months ago
Yes some more recent models, predominantly made for racing do have moulded rails along the bottom. Two reasons, one to add strength, especially if of thin material and secondly to provide lateral stability at the high speeds encountered. When the Aerokits were designed in around 1960s plastic was not commonly available to hobbyists and models were designed using wood/plywood and the originals did not even have spray rails fitted. The running gear was also heavy and bulky resulting in much heavier models than are possible today so the hulls did not plane so easily and the rails were not needed for most models. Technology can now turn out hulls in bulk using extruded and formed plastic and the rails add to the strength to help keep the shape. You can see this on most plastic packaging used for consumer items

Sea Queen Spray Rails by IanD Sub-Lieutenant   Posted: 11 months ago
My Sea Commander "Jaydee" has spray rails about 3/16th inch square. Have a look at the Aerokits photo gallery. There is a picture of it out of the water and some in action. I believe rails are a must for stability in the turns when going at speed as well as helping lift the boat onto plane. Ian

Totnes Castle 1894 by hammer Fleet Admiral!   Posted: 12 months ago
I have posted this on another site, but will continue here if there is interest. I have a plan taken from a book some time ago. Drawn my own sections from experience, having built 2 paddlers before. T.D.B.W. on the sections is the true depth of hull. Increased depth for stability, as steam plants are top heavy, experience again.

M.V. TEAKWOOD by RNinMunich Fleet Admiral!   Posted: 1 year ago
Sure looks like it Mark! I'm beginning to wonder if this is to be a display model only, and the bolts are for the pedestals!? Or maybe to bolt on a 'stability keel' when sailing? Doug 😎