Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Pleasure boats, Sports, Race, Power and Leisure Boats: => Topic started by: cuppa on December 10, 2011, 12:02:32 pm
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Have just been told my wife has bought me an MFA Piranha kit for Christmas. So it will have to go the top of the 'build' list!
I was wondering if anyone could recommend as reasonable power setup for it?
My young grandson will be using it so it needs a reasonable turn of speed but does not need to be 'ballistic'. I would rather have longer runs at a speed that is entertaining rather than shorter 'fast as possible' runs.
Budget for the motor/esc is about £60 and I don't mind either brushed or brushless although i know very little about power systems as applied to model boats but have some experience of powered model gliders.
Thanks for any suggestions.
Cheers
Jon
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How about a 555 or 600 motor, 35mm prop and a 20amp esc. that should stand the test of time, as at least if he outgrows the motor, the esc wil take a further upgrade of both motor and prop.
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We have half a dozen in our club, all with different set-ups. We have basically agreed that a Graupner speed 600 Race with water cooling is the best all rounder. The hull isn't really design for brushless as it can't handle the much faster speed (I will now get shot down in flames {-)) We have tried brushless and although they're quicker, they can't handle the twists and turns so well as the speed 600. But of course, it's your decision in the end :-))
(http://www.gptsmbc.pwp.blueyonder.co.uk/p1020008%20%28600%20x%20450%29.jpg)
(http://www.gptsmbc.pwp.blueyonder.co.uk/dscf2001%20%28600%20x%20450%29.jpg)
(http://www.gptsmbc.pwp.blueyonder.co.uk/brian-piranha%20%28600%20x%20402%29.jpg)
(http://www.gptsmbc.pwp.blueyonder.co.uk/dsc00150%20%28600%20x%20450%29.jpg)
(http://www.gptsmbc.pwp.blueyonder.co.uk/ladyp_%28845_x_634%29%20%28600%20x%20450%29.jpg)
Hope this helps?
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Is the poorer handling on brushless power owing to a speed control issues?
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I don't think so, but we don't really know, I suppose with trim tabs and turn fins it might improve them, but built as per instructions to a standard layout for racing purposes, brushless has no advantage, not for us anyway...
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For a sports/fun run boat they should give more running time assuming the brushless motor is equivalent in power to the brushed version, with virtually zero maintenance.
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We need instant reverse though...most brushless esc's don't have this, and if they do it's a double de clutch to get it. Like I said before, we can only offer advice from actual experience of these boats and their performance. And as the OP doesn't want all out speed, the speed 600 race is as good as any, have you got a brushless in your Piranha, what does it go like for you?
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Thanks for the advice
I will go for a speed 600 - I have a Jeti 30 amp esc that should do nicely if I add water-cooling.
It should be fun for the lad.
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Yes, if you pay a little extra for the Race version, they are a bit quicker than the standard 600. We use 7.4v Lipos in them with a low voltage detector off ebay for a couple of quid. The 5000mah 2 cell lipo's last quite a time, but you can use standard 6 or 7 cell packs. A 35mm sub surface prop seems to work fine although some of the lads use a 40mm. Be careful of the X props though, they can burn out a smallish esc pretty quickly, most of us use 25a Mtroniks or better.
Hope this helps
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And make sure you fix the lid on well, also a watertight lid will stop it sinking when you overturn it.... ok2
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Thanks for all the advice.
It is much appreciated.
Cheers
Jon
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He will love that Jon. You'll be a star in his eyes. :}
ken
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He will love that Jon. You'll be a star in his eyes. :}
ken
Thanks Ken
He sure will love it.
Cheers
Jon
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I have now ordered a 7.4 volt 5000mah lipo pack, a low voltage alarm, speed 600 race motor, cooling coil and a motor mount.
Gosh - Lipo's have sure come down in price since my days with model gliders! I shudder to think what a 5000mah 2 cell pack would have cost a few years ago........
Must admit I am looking forward to building this and watching my grandson operating it!
It is wonderful that he is interested in making and operating models rather than spending all his spare time with his games machines. Probably I am old fashioned but I reckon it is far better that he has a hobby that requires imagination, teaches him practical skills and shows him the rewards of working at something........
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Be carefull the brushless set up does not suffer a dunking in the water!! You may get away with the standard ,nicad speed 600 and switch set up. mr biz
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I am doing the build with a mind to the kind advice I have been given here:
The piranha will have a taped-down watertight hatch at deck level so if he flips it over all should be well. So far all i have done is clean the hull to remove any release agent left from the moulding process, done a hull leak test (all was well) and opened up the slot for the propshaft.
Have assembled the aluminium and fibreglass motor mount and am currently working on a water cooling system for the 30 amp esc (In the end I am using a Turnigy 30 amp aircraft esc but it will be water cooled to keep the heat levels down. I don't want reverse on the boat at least at first because at the moment the lad has a habit of running rc boats flat out in reverse and swamping them!
I am also looking at the rudder post because I don't much like the plastic one in the kit (needs a large hole in the hull and I reckon we would be better off with a simple brass tube rudder post with a reinforcing plate in the hull.
When the propshaft and rudder are fitted (hopefully by the weekend) I want to make a fibreglass servo mounting plate. It takes me a long time to build things because i cannot use power tools for medical reasons and so everything has to be done by hand. Not a handicap though because I get there in the end - just takes a while.
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I had a airboat with a brushless set up and it turned upside down. I lost the lipo, the receiver,and just managed to get the motor working. A word of warning do not short the lipo as it will explode!! and the modern receiver goes on the blink with all those chips in it. mrbiz
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Well into the build now. The motor mount, propshaft and rudder are fitted. Have made a mounting plate for the battery and a mounting for the servo.
Will post some pics later.
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Here is a picture of the internal layout:
(http://i1205.photobucket.com/albums/bb430/cupoftea77/Layout.jpg)
The motor mount is a really nice bit of kit. Very well made and made the motor installation really easy. Battery mounting tray is 1/8 ply coated with epoxy. Servo mount is also 1/8 ply epoxy coated.
Next jobs are to open out the hatch in the deck, add the motor wires, fit motor supression and then attach the deck to the hull. So far this has been a very enjoyable and easy build.
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Hi Jon,
Nice work so far!
I can't see in the picture if you've used just resin to attach everything in the hull, or if some glasscloth is added to reinforce the joints.
If it's just resin, I strongly advice to add glasscloth, rough up the surfaces and degrease well before gluing.
I've been in the same boat a number of times and I've seen motormounts break loose due to the stress of running the boat in rough circumstances, followed by a sinking boat, as the motor coming loose tore the stuffing tube free from the hull...
Regards, Jan.
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Hi Jan
Thanks for the advice.
All the parts are fitted to the hull with glass cloth and resin. The hull was cleaned and the mounting areas were roughed up prior to glassing in the components.
Cheers
Jon
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Well - the deck is now fitted to the hull and I am trying to figure out how to do a neat job of fitting the plastic rubbing/buffer strip around the hull to deck joint. It seems to need to be pulled really tight in order not to 'crease' up on the corners. problem is that the instructions suggest gluing it on with silicon but the bond would not be very strong and would allow the strip to creep over time if fitted under tension. The alternative seem to be to fit the strip under low tension and slit it on the corners so that it will lay flat or to use a stronger glue such as epoxy. Ah well - I will ponder this one a while............ Any suggestions/advice will be most gratefully received...
In the mean time the driver figure is being painted and a transparent hatch is being made for the deck.
Cheers
Jon
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Jon,
Boil a kettle of water, put the rubber into a bowl and pour the boiling water over it. Let it soften up for a few minutes then remove it from the bowl. Dry it off with a towel and you'll find that it will stretch like a gud 'un. Where it raises up on the bends, apply some super glue and a clamp to hold it down, DON'T cut the rubber to size till it's ready to be joined with super glue :-))
HERE IS MY ADVICE FROM MY WEBSITE:
And finally, a tip!
The rubber fender is a hard plastic rubber that doesn't bend well. So boil a kettle, fill a bowl with scalding water then put the fender in for a few minutes.
Get a cloth and a tube of super glue and a few small modelling clamps together while it softens, oh, and a craft knife.
Remove the rubber from the water and using a tea towel or similar pull the rubber through it, drying inside and out, stretching it at the same time. The rubber goes floppy enough to bend it round the 3 corners, without having to cut it. Apply super glue and a clamp to keep it flat and it wont raise up.
Starting at the bow, bend the rubber in half, this gives you the spot where you must glue it, so you have equal lengths going down both sides and joining in the middle of the stern. I found that by doing this, I had about 2" of rubber that needed cutting off, 1" either end. If you try to put the fender on without softening and stretching it, you'll find it's barely enough to go round the boat......I super-glued it as I pulled and stretched it around, making sure it WOULD go all the way round as I did it.
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Many thanks Nige.
That would not have occurred to me in a million years!
Your advice is greatly appreciated.
Cheers
Jon
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Before you apply any glue, do a test to make sure you stretch the rubber long enough to go round the whole boat. A member in our club realised too late as he had glued it without checking and ended up with a gap at the back of the boat.. :-)
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Thanks Nige.
Could you post a link to your website? I found a link in an earlier post but it does not work for me.
Cheers
Jon
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Jon,
My site is off line as I'm totally furbishing it, is there anything particular you need off it? I can email you HTML pages if that's a help?
Nige
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Thanks Nige
I just wanted a look at your piranha build. No hurry - I can wait for the site to be back on line.
Cheers
Jon
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Nige's tip about heating up the plastic fender/rubbing strip worked a treat. It went on really well with no kinks and looks good.
Many thanks Nige!
Cheers
Jon
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Progress thus far:
Here is a photo with the 'lid off':
(http://i1205.photobucket.com/albums/bb430/cupoftea77/Piranha1.jpg)
And with the 'lid on':
(http://i1205.photobucket.com/albums/bb430/cupoftea77/Piranha2.jpg)
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Have made and fitted a speed controller watercooling plate:
(http://i1205.photobucket.com/albums/bb430/cupoftea77/Watercooling.jpg)
I cut away the heatshrink that was covering the speed controller's existing cooling plate and then fitted my home-made one on top of the existing plate with some heat conducting paste between the two to try and avoid any air gaps.
Not exactly sure if the watercooling is necessary but better safe than sorry.........
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The Piranha will be finished and ready for a test run this weekend.
The last jobs are to plumb in the water cooling and to wire up the motor followed by making a transparent deck hatch/cover to be taped down to provide a water-tight hull.
Have managed to buy 3 hardly used packs of 2s 5800mah lipos so we now have 4 lipo packs for it - excellent.
Made a stand for it by cutting a plastic food container to fit.
Must admit I am excited about seeing it on the water. In my eyes these 'vintage' boats have a visual appeal that is lacking in some of the more modern designs (Guess I am showing my age). The Piranha has a definite 60's look to it that I really like.
On to the next project.............(please don't tell the wife!).......... Now how can I smuggle another hull into the house?
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You could always try hiding it behind a big bunch of flowers [for the missus!] :-))
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You could always try hiding it behind a big bunch of flowers [for the missus!] :-))
Say it with flowers - buy her a Triffid! (Only kidding)
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Piranha is now operational. First test run soon.
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1st test run now done and it did not sink!
It has a good turn of speed and handles well. Run lasted about 20 mins and the 5800mah lipo was still going strong. Couple of jobs to do following the run:
1) Increase rudder travel a bit
2) There was a small amount of water ingress - I think from the propshaft.
3) Shorten flexible cooling tube run to improve flow - the motor was just warm to the touch and the speed control was cold but I noticed the water flow was nothing more than a trickle so it may as well get improved.
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Mods now done.
I have re-routed the cooling pipes and have a shorter pipe run.
Rudder travel has been increased and I hope the water ingress is sorted - we shall see..... When i took the propshaft out of the stuffing tube there was no water at all in the tube which makes me think that this is not the source of the water ingress so I investigated further and now think the source was the rudder tube so I have re-sealed it.
Overall i am very pleased with the boat and my grandson is over the moon with it. It is fast enough as is so I do not plan to do any mods to increase speed. Fast enough to be fun and still be something that my grandson can operate with success and learn the 'ropes' before moving on to faster models (he is keen to go racing at some point in the future).
Now on to project Genesis........... The look on my gransdon's face when the genesis hull emerged from its box was a picture! (In James May's words 'enough to make a small boy faint'). He spent about 5 mins just looking at it and then ran into the kitchen shouting 'Nanny quick - come and see what Bampy has got!'
The Genesis will be a long build though - he is not yet ready for a boat that fast and it will take time to afford the required motor and controller. Building boats is addictive and the more i do the more enthusiastic i become. Must admit I like sorting out the 'engineering and electrical' side more than traditional wood building and so am happy to potter on with the Genesis while running the Piranha. It's all good fun.
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Ran the piranha again this morning. It is now watertight with not a trace of water in the hull after the run. The watercooling is still not working well though. I am going to re-locate the pickup. At present it is as per the plan directly behind the prop and it is not effective. Am going to block it off and add a flush fitting pickup as per a mini-eco type boat. I hope this will improve the cooling.
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cuppa , i had the same problems back at the begining of last season . i found its better to have the pick up slightly to one side behind the prop , remembering to locate it to the correct side so water is forced in by the spining prop !
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Ah well - finished the relocation of the water pickup and then re-installed the electronics only to find that the motor has developed a fault. Time to order a new one. I guess the inadequate cooling took its toll on the motor.
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The tale of the Piranha continues.........
A new speed 600 race motor is now in place. I have replaced the cheap adapted model aircraft speed control with an MTronics 25.
Water flow through the cooling system is now much improved so hopefully the new motor will last a while........
The Piranha is currently my favourite boat - it is just such huge fun to run.
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First run with a smaller propeller :-))
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Yes indeed Martin
The prop that was included in the kit was an X35. The initial run on the new motor will be on a 32.5mm Graupner prop.
Cheers
Jon
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Ahhhh - that's better. Plenty of flow through the cooling system now and all is well.
Ran it on a 32.5 mm prop and then tried an S35 - motor and speed controller remained cool.