General Boat Chat Thread, r/c boat newbie in Ships & Boats; Hi, I am new to this fab looking forum.
30+odd years ago as a lad, an avid modeller, I was ...
r/c boat newbie
Hi, I am new to this fab looking forum.
30+odd years ago as a lad, an avid modeller, I was given a grp cabin cruiser hull which had previously had nitro in it, it is near 40 inches long. I intended to electric r/c it and started collecting bits together but at the time it was relatively very expensive! and floundered.
I now have my own kids and am working on this hull having got together more parts. I am not using the even older Taycol motor, new with instructions figuring it is too nice to use in this boat!
I have an 850 motor to run on 6-12V, a 12v 7.2a/h lead acid battery which weighs a bit but it is a large boat so should be fine. The old taycol motor was of course heavy!
I have a nice esc for the control of speed and this will power the r/c through the bec system.
The shaft is a new water sealed one I intend to fit and a brass rudder.
Being very new are there any essential tips I should know, siting/fitting the rudder servo etc? battery siting? propeller shaft siting and angle,
Prop size?? going to start with a 50mm racing prop and see what happens!
I am not after a racing boat, being into real boats too one that handles/maneovers well would be nice. I figure the 850 motor will offer a good turn of speed and get her on the plane if wound up but throttled back will plod nicely and offer a good service life with the largish battery.
Hi Petrolhead and a warm welcome to the scale models forum, nice to see another RC Boat enthusiast here.
For me your first steps are ballast experiments. Get your hull in the test tank (Bath) with as much stripped out of it as possible. Weigh the hull on the kitchen scales after assuring the missis that it is spotlessly clean and won't make a mess of the kitchen. Then put it in the bath and add weights until the boat sits at the correct draught fore and aft. Take it out and reweight it again. The difference in the two weights is obviously the ballast you require to get the boat down to it's marks.
Next job is estimate the weight you are going to add in putting the model together such as the superstructure, drive systems, battery, electronics etc. You need to get this as accurate as possible to be then able to take this weight away from the 'ballast' figure.
This will finally give you a weight that you need for actual ballast. I wouldn't put permanent ballast in to this amount as you have worked on estimates and you need to give yourself a bit of breathing space so I would go for about 60-70% of this weight as 'permanent' ballast. The remaining requirement would then be added at the end of the build to get the trim and ballasting perfect.
Some people actually prefer the entire ballast weight to be removeable, especially for large models but smaller ones definately benefit from having a proportion permanent and low down so possibly a metal plate in the base of the boat or lead shot encased in resin in the base. Some people also like to make the most of the ballast as battery weight so that has to be taken into account as well. My two recent builds both have permanent ballast, the Ben Ain steamer has two large metal plates encased in resin in the base of the hull with the steam plant all held down onto a brass plate and my Revell U-Boat has lead strips cut up and embedded in the keel with resin poured over the top.
That would be the starting point for me before even contemplating the build as amendments based on these experiments might make you change your mind as regards motors, batteries etc.
When you are happy with all this start the build. Keep us informed though and post some pictures as you go along.
“Dirty British coaster with a salt-caked smoke stack, Butting through the Channel in the mad March days"
Hi and thanks for the input. I have probably gone a bit cock hat at it but will try and build around what I have. I recall the ballast bath job 30 years ago in Mums bath! and will do it again before starting work. It still has rock hard plasticine over the holes in the hull!
Originally Posted by Bunkerbarge
It has a planing hull, with a medium V forward but running into quite flat aft section as opposed to deep V (I'm into real ones so ok on hull shapes!) so its waterline is quite shallow. Being flattish from midships back it can take quite weight without lowering its level in the water far.
I am keen on the biggish battery for extended use with family, but suspect the boat was quite light originally with nitro and no obvious signs of ballast.
Only pic I have attached, red blob rubbed off with thinners and will be repainted properly after it is together structurally and "pond trialled" with windows
Last edited by petrolhead63; 08-01-2009 at 09:53.
Hi Petrolhead and welcome to the site too,
I will certainly agree with Richards comments above re the ballasting - My HMS Active has cut up steel strips about 1/4" thick secured with fibreglass at the bows and the stern. The remaining ballast is the battery which fits nice and flat amidships.
For your boat - the Hull sounds the same sort of shape as my Scamp - Deep V on the front but almost completely flat at the back. On this boat the motor is mounted in the front, as this is probably the lightest part. It has an inboard prop and the brass rudder is fitted rear most behind the prop for best effect. To plane properly, I have the battery fitted just after midships towards the rear as this seems to be the best spot. I don't think you will really need any other sort of ballast in there as you want this one nice and light to plane properly and of course to enjoy the speed too !!
I am using a slightly larger battery than I should be doing, but the nose does come up nice and she will plane perfectly - the only thing I have to watch is dumping the nose after a speed run as she will stop quickly and the wake will suddenly wash over the rear deck. (This is due to the slightly heavier battery which I do intend to change, The boat is well sealed so the wash is not a problem). I have seen someone using a similar boat who immediately accelerated after dumping the nose and the boat promptly went under !! followed by a bit of swearing !
I am also using an X35 racing prop on mine on a 540 motor. My Scamp is probably only about 18 inches long and is quite light, so the X50 prop may be ideal for your size boat...always worth experimenting with different sized props though as a smaller one may well be fine too.
You can see my Scamp and another site member's one on this link:
Originally Posted by Bluewavestudios
The sinking in your own wash is quite normal. I mentioned being into real boats too. when we had instruction on our first boat which was a 19 feet planing fast cruiser one of the big lessons was how to crash stop in an emergency. The instructor demonstrated the effect of the wash nearly swamping over the transom and taught us in case of a sudden stop to throw the helm hard over at the same time as pulling back the throttle so as to face your wash. We had to do this as part of our examination.
I will be playing in the bath soon, my battery is heavy but if sited near the middle will have little effect on the trim of the boat. with under powered real boats it is not unusual to move passengers forward to get over the hump and then back to trim up correctly.
Now there is an idea having ballast on a motor driven ratched you can trim up and down the boat...perhaps the battery! one for later I think.
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