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I am currently building a skimmer (Dave M will be very familiar with the type). I propose to mount the motor as a pusher on the single pylon. To minimise clutter I was thinking of a single rudder, mounted centrally behind the motor. Most skimmers/airboats I have seen have two rudders, but do I really need two? Any thoughts? Thank you Steve
Hi Mate and welcome to the forum, (mad as hatters!!!) I have built the 46" and before you get to far in you need to decide if your having single or twin motors, and rudders, that way you dont fall foul of bulkheads, and shaft mountings, mine has Graupner 700bb motors on 3s lipos, but i am up-grading them to brushless soon, have the new ESC,s and the motors are on order. Great model to build and sail, attracts a lot of attention. Mark
Hi Steve Sorry, no I did not take photos of the build. If you have the Mobile Marine hull then I built a vertical wooden plate up through the top and strengthened with wood plates beneath the top moulding. If your rudder snake runs over the top make sure you allow for this when deciding how high to mount the motor/prop!! This works but flexes when power is applied so if I did another I would mount the upright to the base and make a slot in the top to allow it to pass through. I would also provide support, below the top, to the upright behind and right up to the hull sides. The force from the motor is truly awesome and plastic mouldings tend to (and do) flex. I use two rudders as other members have found they work better than one. I used 1/8" welding rods for the cage and did have some hard black netting at one time but have had no problems with just the frame. If I sailed in an area where the public had access then I would provide a cover. Just get the mount and prop sorted before you finalise as mine was too small!
Ok Is the weight and dimension the same as the Siren or 507? Looking at the rudder this looks like an after fit and does seem to be differently mounted (more vertical) than those on the website. The keel looks flat on the bottom. Has it been chopped in half? This would make the model very sensitive, especially in a gust. I'll wait for your response before adding more thoughts.
Hi All I was told to use plumber's tap silicon grease, which I have used for 3 years and only regreased once each year. I have added oiler/grease tubes to my rudders as well. Also you can get a silicon spray like WD40, but, with the silicon spray it crawls up the shaft. With the shaft out and the tube cleaned out(pipe cleaner works well for this) a shot of silicon grease in each end of the tube(only small amount). Hold your finger over the other end and install the shaft, this stops the grease coming out as the shaft comes through. A shot of silicon spray down the oiler tube and seal silicon fuel tube sealed off at one end. Canabus
This time I will try to remember to put in the ‘source’ information on the bits and pieces I use........... In the most recent piece I should have included exciters/transducers are Dayton Audio DAEX 25VT -4, 4 Ohms – 20 Watt pair, obtained from Sound Imports Netherlands and very quickly as well. The sound unit is a Mtroniks Digisound 5M diesel sound, available all over the place. Now to look at where I am at. Exciters are in place as high up the Hull as possible, but remembering the Deck level. Used the adhesive pads as supplied after wiping that part of the Hull with Meths and Silicone adhesive to keep in place as well as using the wiring tidies from Modelsport Ltd., for the cabling. (Pic 1+2) Before I start the motor and controller wiring I changed the platform ‘up front’ (pic3) with a piece of thin ply which I have given a couple of coats of varnish to waterproof. Then I thought to myself “why am I waterproofing this when, if it gets that wet, it will have gone to the bottom and be useless anyway”! (Pics 4) However, the platform gives a little more choice in terms of layout of other components and my plan for them is not really settled yet. I am concerned about the stern and possible swamping, but it currently seems the best place for the upgraded battery. (Pic5 ) Whilst talking batteries, I have gone for a separate battery supply for the receiver and hope to use the Bec supply for running other less critical items. Also the fitting of the battery in the stern bay drew my attention to the rudder servo for a couple of reasons. First is I am still considering increasing the size of the rudders and I am assuming that will increase the strain on the servo. The servo supplied is a standard issue and not water resistant so I have gone for an upgrade as shown(Pic6) That gives torque increase of 17Kg/cm over the Hobby Engine S1040C and has metal gears, metal control arm and waterproof for 20grams extra weight. Second is the closeness to the new battery position. So I was going to alter the servo arm setup anyway and the new metal arm suits this well. Maybe my ‘tutors’ will consider all this to be a little ‘over the top’ but I do so enjoy messing......................... New Servo DS 3218 by AYANI from Amazon. (Pics 6/7 ) Following that distraction, back to the front end and the Motor/Mixer placing and wiring. Now a little time ago I drew a plan to see what could go where and it came out that most of the ‘bits’ would go in the front bay with motors to be wired once power was brought forward, followed by the Esc/Mixer. (Pic 8) At that time I bought a P94 dual esc/mixer from Action Electronics and got the 20 amp version to be on the safe side................. My ‘guardians’ did point out this was ‘over-kill’ but I had already got it. Now, when placing the unit on the mounting board I found that the heatsinks made it too high to fit in the Hull! So being a spoilt brat only child I ordered the 10 amp version and as usual it came very quickly from up here in Bangor. ( Will keep the other one for the next project............Happy Hunter??) Unboxed it and it looked just the same, heatsinks and all. (Pic 9/10 ) So at that moment there was a bit of a set-back so I rang Component Shop at Bangor, they said “take the heat sinks off and you have a P94 lite”! Such a simple answer and such a nice chap. (Pic 11 ) Now a quick 'measure up' before I have a glass of wine (Pic 12) and does it all fit...? Well it appears to at the moment! (Pic 13) Next time really going to screw down the components under the forward hatch and wire it up. NPJ
[Score: 9/10] 35"/4500g CG-40564 Capable of 15mph and a runtime of 45mins Twin Propellors (4 Blade 50mm) Direct Drive to a 775 JOHNSON-TYPE 6-12V (4 Blade) Powered by NiMH (8.4v) 3Amp/h Batteries Controlled Through HOBBYWING (15Amps) ESC - Comments: DUMAS 1:14 USCG 40' UTB. REPRESENTING US COAST GUARD UTILITY BOAT CG-40564, WHICH CAPSIZED DURING A RESCUE ATTEMPT ON THE COLUMBIA RIVER BAR ON 17 JAN 1961. HER CREW WAS FORTUNATELY RESCUED. SHE WAS ASSISTING CG-52301, A 52' TYPE F WOODEN MLB, WHICH FOUNDERED WITH THE LOSS OF ALL HANDS. IT REMAINS THE WORST SMALL BOAT RESCUE DISASTER IN COAST GUARD HISTORY. THIS IS AN UNUSUAL SCALE BALSA PLANK-ON, COVERED BY 2 OZ FIBERGLASS. I USED MINWAX POLYURETHANE FOR AN ALTERNATE TO RESIN, WHICH TURNED OUT WELL, AND CAN BE DONE WITH MINIMAL VENTILATION. WITH BIRCH PLY DECK & CABINS, 1/8" SCRIBED SHEATHING COVERS THE DECK BOW TO STERN AND MAHOGANY TRIM LEFTOVER FROM ANOTHER DUMAS KIT IN MY SCALE SHIPYARD. STOCK D/C FITTINGS WITH SOME SUPPLEMENTAL PREMADE AND HANDMADE ITEMS. SHE FEATURES TWIN RABOESCH 4-BLADE WIDE FLUKE WHEELS AND MATCHING RUDDERS; WORKING HATCHES WITH STOWAGE AREA FOR ANCHOR & TOWLINE, LIGHTHOUSE 9V LED NAV LIGHTS AND FLASHING LED LAW ENFORCEMENT BLUE LIGHT (RC CONTROLLED). I'M ADDING A MOUNT FOR A SCALE BROWNING M2 50 CAL THAT I WAS ABLE TO PRODUCE ON MY 3D PRINTER. THAT'S AN ADVENTURE IN ITSELF. THIS WAS MY FIRST REAL PLANK ON BULKHEAD, AND BALSAWOOD CAN BE A LIL TRICKY, BUT WILL ALWAYS BE THE STANDARD OF WHICH I COMPARE ALL MY SUBSEQUENT BUILDS. MY FATHER BUILT RC AIRCRAFT, AND ALWAYS PREACHED THAT YOU SHOULD OVERBUILD IN ORDER TO SURVIVE A CRACK-UP AND FLY ANOTHER DAY! THAT'S MY CREED WITH BOATS. OVERBUILD!!! THANK YOU DAD! BTW-FYI-MR. ARNOLD PALMER WAS A US COAST GUARDSMAN (YM3) 1950-53
Finally obtained General Arrangement drawings for both vessels. Scaled them to the same size and superimposed the Teakwood hull drawing onto the Velarde. This confirmed that a conversion was possible and that much of the major rework would be limited to around the stern. The bow could be extended relatively easily and the bulwark heights trimmed and reshaped. One point to remember in reviewing the attached photographs, the Velarde hull plan is slightly oversize. Have noticed when printing plans the humidity affects the paper and sizes can change slightly. This would not be of much importance when building a kit, but should be considered in a hull conversion. With the two hulls superimposed and the Velarde adjusted to the correct size, considered the ways the hull could be adapted. Measuring sternwards from the revised bow profile found the correct LBP could be obtained if the Velarde rudder post was moved back about 5/16”. This would also reduce the stern rework and allow the use of my traditional bow strengthener of bent wire from a steel coat hangar. This slight bow extension would help to offset the stern profile, with the hull and LBPs remaining the correct overall lengths. In the photos the Velarde hull lines are black and the Teakwood red with pencil accents: they indicate the amount of bow/stern rework. The bulwarks are relatively simple, they only need lowering slightly. Next step is to examine the actual hull and compare it with the plan to see how accurate it is. Hopefully this will confirm of my investigations - of course, could always leave the hull “as is” and use it that way. I would be only person aware of the differences! Unfortunately, being something of a purist, this easy way out did not compute.
Sometimes I hate work it gets in the way but I've managed to get the first fix for the prop tube at last now to leave for a while as work and courses in the way again. I have also managed to open the hole for rudder guide and presume this needs a bit of expoxy resin to secure it in place? The oiler is also fitted and a bit of cleaning of the inner hull to remove some of the old paint ready for sanding sealer coat after I've mounted and aligned the motor - not looking forward to that at all if past experience is anything to go by. But now the old mount is out there is more space and the prop and shaft is at a much better angle thanks to Dave and Doug😁😁
Standard Saturday Mrs Mac decided I had other things to do before being allowed out to play but I think I've got there, just need to check it's right before gluing up. OK so I lied that I wouldn't be asking more questions on this topic😁😁 The hole has been opened out enough to achieve 3/4" but the photo doesn't really show it. It took some time to achieve it as well more time than I thought, even used my dremel at one point😁. But pmdevlin's tip on using a disc was a great help. The position of the outer tube on the hull needs a slight adjustment but nothing major and still achievable as no glue. I did have a check fit of the motor and came across another issue as there was no way I could achieve alignment of the shaft and motor which was made easier by Doug's universal coupling idea😁. I went for removing the last remaining piece of the old motor mount (should have listened to Dave a year ago) which took about an hour as it was glued in good and proper.😤😤😤😤😤 There is some clearance on the hull from the prop so think I'll be going for a 30mm prop as suggested by Dave as to my surprise mine is 40mm diameter. Hopefully the arrangement is all good and I can use Dave's and Doug's tips on getting it secured. I still need to blank off the water pick up and fit the new rudder tube. Also I think the motor alignment will still be interesting as after removing the last bit of the old mount the motor was interfering with the bulkhead behind it so removed so it. Also will possibly need to take some out of the hull centre piece to achieve a perfect alignment. Hopefully tomorrow will go well as will also fitting the oiler as seen on Robbob's Build Blog.
I'm after some advice on rudder position in my ever tedious restoration of a crash tender. After some great advice from DaveM and Doug I actually 'bit the bullet' and removed the old IC Engine Mount and lessened the angle of the shaft which will hopefully make motor alignment easier. I removed the rudder bearing tube and water pick up for ease of access whilst re positioning the shaft and then noticed the rudder and pick up were not centrally positioned on the hull. On looking at the plans for the 34" Crash Tender I found that the measurements of the rudder and water pick up tubes were also not positioned correctly. I am now presuming that I will be need to re position the rudder as a priority and possibly the water pick up?😤😤 Any advice on this one would be much appreciated from you the experts😁😁😁
Hi Neil, yes, very similar. Could be regarded to as a first step before applying Eze-Kote to give it a harder, knock and almost everything else resistant surface. Hammerite then sticks to it like the proverbial to the blanket and you have a super clean 'engine compartment' dead easy to keep clean. 😊 80 quid for a brushless !!! Do you want it gold plated or what? My Propdrive 2830 cost less than 20 knicker from Hobbyking and was delivered almost before I ordered it! Just make sure it comes from the UK or EU (still!?🤔) warehouse and not USA or Global. otherwise you might get stuck for import tax 😡 For the motor mount / shaft alignment: no one said it was easy, but Nothing's Impossible', maybe that's why I drive Toyota!!😁 back end is determined by the diameter of the prop you want to fit, which in the case of brushless motor should be roughly the same diameter as the brushless (outrunner). In my case 28mm motor and 30mm prop. This defines how far you can lift the aft end of the shaft, leave at least 1cm between the prop tip and the hull! This reduces unwanted interaction between the vortex from the prop and the lamina flow along the hull, result; more forward thrust and better rudder effect. (Didn't spend 30 odd years talking to shipyards for nowt😉) If you have plan (or at least a sketch - take some measurements if you don't have one of these and make a sketch) of the keel and existing motor mount; project back from the newly determined exit point of the shaft. Check how far forward you need to go to be able to comfortably fit the motor mount with good alignment and purchase a shaft of appropriate length. Cut a wood block to fit around the keel as the basic mount and 'fiddle' with it until your motor and mounting (e.g. the Robbe / Romarin 400 mount) aligns with the shaft line. Alignment is checked by running the motor at a fixed low speed with an ammeter showing the current it draws. Shim the motor mount up / down, and shift slowly from side to side until the current reading is a minimum. Then glue and screw everything in place quick before anything moves! Takes almost longer to describe than to do😉 The coupling type shown in my photo is called a 'Steg' coupling here in Germany (don't know the English🤔) and available from Krick Modellbau, for various motor shaft / prop shaft diameters, here the link to their English page- http://www.krickshop.de/?shop=krick_e Part number for the 3.17mm (1/8") to 4.0mm version I used is 63902. part number for the motor mount I used for my 28mm brushless is 42117. Advantages (to me at least!) they are not as long as the traditional UJ and Cardan types, they are resilient but don't flop about like the UJ types so are much easier to fit and align. Cos they are shorter you can use 'em for mountings in confined spaces. And they don't make no noise!! 😉 One final tip (may not be so useful on hard plywood built boats!). When I had this problem with my destroyer I sharpened the end of an 8mm alu tube (same as the shaft tube dia) and used it to bore back from the hull exit to the last bulkhead before the motor mounts. the bulkheads though were 1/4" balsa! Nice and soft man 😉 Hope this helps more than confuses, but it all worked for me! Cheers and happy fiddling, Doug 😎
Hi Neil, here's my 'twopenn'orth' on this subject w.r.t. the brushless upgrade in my 24" Sea Scout. I'm happy with the relationship between prop and rudder so am concentrating on the motor mount and coupling now. Pics show the motor removed and the new one, old and new mounts and new coupling. Alignment will be done with the help of an ammeter as usual. Minimum current draw = best alignment 😊 Insides have been cleaned up and sealed with Eze-Kote 1 part polyester resin. Lovely stuff, just wash out the brushes with hot water and you can use 'em again! When all is correct the 'engine compartment' will be painted with white gloss Hammerite. 2nd last pic shows old plastic prop (50mm) and new brass one (30mm) matched to the brushless. Have fun, Greetings Doug 😎
Hi Neil, (Old (Sea) Dogs can learn😉). My pleasure, happy to help. Today (quite coincidentally!) I ran across a mathematical dissertation on the relationships between prop, rudder and hull (Yawn!) done by Marin Corp. for a symposium on 'Fast Mono-hulls'. Primarily naval. Full of Froude numbers and Lord knows what. But the upshot was that the optimum distance between prop and rudder should be 0.47 x radius of prop. So with my 30mm prop and 17mm distance I'm a 'bit' off🤔 15x0.47=7.05. Shucks; where are my thrust washers? Need a couple more 😉 Never mind, I wanted to make a new shaft anyway, to fit the brushless upgrade mounting. Ho hum! Whatever - Have fun, Doug 😎
Well there I was with the Kingfisher motoring along on the pond when it suddenly lost power, nothing??? No forward no reverse. I could give the motor forward and reverse but no reaction. Fortunately the breeze blew the boat into shore along with me using the rudder control. Upon landing and a cursory inspection I saw that the universal nylon had broken off at the metal connection. But, upon the workbench it was discovered the motor mount had come off the hull structure. It was just totally free, it lifted right out of the hull after removing the speed control connectors. Maybe, it is time to replace the geared motor to a direct drive. Any suggestions? I use brushed motors.