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Sep 17, 2003, 08:23 AM
and this wire goes where?
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Riva Aquarama

Hi, I'm about to embark on a scale Riva Aquarama. This is my first boat, around 850 mm long with a build based on the original hardwood planking.

I was going to go for 2 540's to power it. Anyone know what sort of ampage the pair will pull? I want to get this in the water reasonably low cost, so was trying to work out if it would be better to get 1 speed controller that can handle both motors, or 2 small, one for each motor.


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Sep 17, 2003, 09:38 PM
Sea Dragon-Lover
Umi_Ryuzuki's Avatar
I would guess that a typical 540 motor is capable of drawing
from 3.5 up to 7. 5 amps

I am not sure how big you are planning on building the boat,
but one 540 would be fine up to about 30 - 36 inches (91cm)
Sep 19, 2003, 08:30 AM
and this wire goes where?
Thread OP
hmmm... in that case twin 540's might be overcooking it a bit then - the boat is only 78cms long...

How about twin 400's, or even 300's? Basically I want it to have a performance to suitably reflect the pedigree of the original, which is known as the Ferrari of the boat world (which is odd, as it's powered by twin lamboughini engines!!)

I think it's going to be quite a heavy boat - it's traditional type build planked with 5mm thick Mahogany and lime stripping.

Any thoughts greatly appreciated
Sep 19, 2003, 07:11 PM
Tachikaze's Avatar

Riva Aquarama

I think that you are right with regards to it runnning a little hot with the 540 motors. Most of the Runabouts of that size are running on one 540 or 550 motor.
If you use a 380 or a 400 twin set up you should be able to move that boat really well.
As for your speed control, I run a 57" Italian destroyer that weights in at about 15lbs on two Pittman motors with 12V. This is one a single speed control, the older MCD speed control. But I have also run this boat off of a Tekin Rebel with out any problems.
If you are using the 380 or the 400 then a R/C car speed control that can accomidate 12V should not be a problem. What would work very well, but would be a little heavy is teh EVX speed control used in the Traxxas EMaxx. It is set up to handle twin 580's.
You can also decrease the weight of the boat by sheeting in 1/16" balsa, sand to take out any little defects ( do not worry about it getting thin when you sand) and then sheet over the balsa with thin mahagony or cherry, what ever you wish to finish the boat in. This way you are not using the heavier hard wood.
Also with a boat this pretty you WILL want to fiberglass it. Use a thin weight glass and do not goop on your resin.
Sep 23, 2003, 03:26 AM
and this wire goes where?
Thread OP
Well I've managed to get hold of some extremely light plywood for the main frame from an old cupboard. No idea what it is made from, but it appears very light yet extremely strong (5ply even though it's only 4mm thick!). so far with all ribs, runners and lower planking in place we have a total weight of just 230 g's (about 1/2 lb I think) so I dont think I'll worry about going for the balsa with thin hardwood. I have also decided on a pair of speed 400 for drive, and I'll keep my eyes on ebay for a speed controller that will suit.

Definitely going to glass it - not entirely confident my planks are going to be water-tight...

I do have another question though - Boyancy.

what would be the best way to add some? My Dad popped round at the weekend to view proceedings, and suggested using expanding foam between the ribs to ensure it doesn't sink on the first mishap. Any thoughts?!
Sep 23, 2003, 05:35 AM
and this wire goes where?
Thread OP
New Question!!

I was considering using 2 old speed controllers and 2 old 6 cell packs , 1 of each for each motor. both have forward & reverse and BEC. If I chose this route, how would I wire them up??!

The only reason for looking at this option was I have these parts and so no money needs to be spent, but I am concened mostly because both ESC's would be trying to feed the power to the receiver (would it be too much voltage?) and I'm also trying to work out the BEC's functions in this set up!!

Many thanks
Sep 23, 2003, 08:08 AM

Expanding Foam

I would highly recommend staying away from the expanding foam...I have seen hulls distorted by the use of this material if too much is put in. Also, it will continue to expand for a long time, sometime months. Exposure of the boat to warm sunlight and/or the heat from a motor can cause it to re-activate and continue to expand weeks after the initial installation, again causing distortion. It is also heavier than other choices and some brands actually absorb water like a sponge.
I prefer simple and cheap balloons. Just inflate them a samll amount, and stuff them in where ever you have open areas, replace as needed. I have found that they will hold air for several weeks.
Many people purchase small air bags used in packaging, but balloons are cheaper and perform the same.

Sep 23, 2003, 08:48 AM
and this wire goes where?
Thread OP
Thanks George - I actually have a large supply of those packaging bags - hadn't thought of that! when they eventually deflate I'll try some ballons.

Dont know if you know the Aquarama, but I am going to be a little tight on space to shove them - is it likely to be enough to just fill the bow with them, as I think I'll only get a couple in elsewhere?

Actually, come to think of it how do I work out what will provide enough boyancy? When you mentioned the bags my initial thought was to shove a few in a bag and then see if they could support a lump of metal the same weight as the complete boat, is there a more scientific approach?!
Sep 23, 2003, 10:50 AM


Trial & error is the only way I know of to calculate the needed amount of floatation. And in the case of some boats, you cannot get enough in to actually keep it afloat, due to space limits.
Another choice to get some into tight areas is to cut up styrofoam in pieces that will more or less conform to the areas that you have available.
Worst case, make sure that you have enough to keep the boat partially afloat, preferably by the bow, as that forms a natural air pocket. Then make sure that your electronics are waterproofed.

Put your receiver inside a balloon (9 inch round balloons work pretty good) and tie the end with a "twistie".
Servos can be waterproofed, remove the bottom of the servo spray in a product called "Corrosion X" and replace the bottom. This process should be repeated on a regular basis; i.e. once a month or so depending on usage.
ESC's preferrably use ones that are water proof from the manufacturer. Those are hard to find. Other than that there is no easy way to water proof them, can't use a balloon as the heat will melt the balloon. Only thing there, would be to build a small waterproof box to mount the unit in, but again heat may become a problem. SMC(?) makes a nice unit that is waterproof and good for up to 18 AMPS(?) and relatively cheap, and is watercooled. If you don't need reverse, has the best waterproof ESC on the planet and it handles up to 90 AMP draw, also watercooled. You can't destroy one of these except by wiring it wrong.
If fyou are using R/C Car ESC's and you get water in the boat, kiss them goodbye, they hate water, and a few drops will kill them.

Sep 23, 2003, 11:49 AM
Sea Dragon-Lover
Umi_Ryuzuki's Avatar

Re: Floatation

Originally posted by George Pfeifer

If fyou are using R/C Car ESC's and you get water in the boat, kiss them goodbye, they hate water, and a few drops will kill them.

George [/B]
It is interesting to note, what seems to be absolute "fear" in the model boating community of having one's boat sink.
Since I am one of the people that sail my ships with the intention of sinking others, there is always the risk of being sunk.

See the images from this years Nationals.

I and others have use various speed contols over the last 15-20 years. It is usually cross wired connections that mess them up, not the water. For instance my destroyer used a model car speed contol for over 12 years. It was the new motors that almost killed it. A friend managed to replace the burned Mosfets and it still works today. Those motors wer immediatly replace with 14 volt pittmans.
When one of our boats goes down, one of the first things that is done, is the dissassembly of the electronics. Rubbing, or Denatured alchohol is then poured thru the circuit boards. The the alcohol and water are blown out using canned air. (The alcohol displaces the water, and evaporates faster.) After a good period to let them dry the electronics can be reassembled and run.

My new LST got sunk on its second sortie. It was ready to run two hours later. We ran it a couple of times as the Tank on board was giving us range problems all weekend.

It is good to take safety precautions, but a boat with a leaky hull should get a little water in the bottom. Not sink on its first seven minute run.


NOTE 1: A 3/16"(4.7mm) hole will sink a 54"(1371mm) destroyer in 7 minutes if the bilge pump has failed.

NOTE 2: Most water tight boxes hold water very well.

LST construction page( for those that didn't see it already)

Since the LST is done, we are now building two models of the LA fire boat #2

If you keep your hardwood sheeting tight the boat will look awsome, and the fiberglass and resin will keep the water out. Rigid foam insulation from a building supply store is what we use for construction, and floatation.

Is the Aquamara a dual prop boat? I had the impression that it has a single drive.

[edited] Because of absolutely horrible spelling.
Last edited by Umi_Ryuzuki; Sep 23, 2003 at 11:57 AM.
Sep 23, 2003, 12:30 PM


What brand of ESC are you using?

Over the years I have used Tekin Titans and Novak Roosters and Super Roosters, when they got water on them I got large amounts of smoke, burned cases and wires. Not enough left to even attempt to salvage them. I still have that foul smell of burnt electronics in several of my boats after 2 years. All of that from just water in the boat, not enough to sink them.

I am considering coating my ESC's with 3M DP270 Epoxy over this winter, it is what Andy Kunz from RC-Hydros uses to waterproof his units, and seems to do the job. One of our club members has coated his Hacker brushless ESC's with this material and it solved the problem of water soaked units.

Sep 23, 2003, 12:40 PM
Sea Dragon-Lover
Umi_Ryuzuki's Avatar
I will answer this in the "sinking model boat" thread.

I do not want to "Hijack" the Aquamara thread.

Sep 24, 2003, 03:38 AM
and this wire goes where?
Thread OP
The Aquarama is a dual prop, it's earlier predecesor, the Triton, was virtually identical apart from the absence of the stern sun deck and single drive.

I am hoping that my planking will be nice and tight, however this is my first attempt at a wooden boat, so I'm prepared to be a little dissapointed!!!

I've got some glass cloth that is tissue-paper thin for use in model helicopters i thought might be OK to line it with?

by the way Umi, dont worry about hijacking the thread, I spend a lot of time on the Ikarus helicopter forum and they tend to wonder on and off thread like a Yo Yo!! makes for an interesting read in a way
Sep 24, 2003, 07:04 AM

Glass Cloth & Epoxy

As Tachikaze mentioned earlier (above) the glass cloth and epoxy would be recommended. I would put the cloth on the exterior with a light coat or 2 of epoxy, then sand to a smooth finish. I would also put a thin coat of epoxy resin only on the interior (no cloth needed) Polyurathane would olso work on the interior.
Epoxy is good because it adds strength as well as water proofing, but it comes at the cost of extra weight. You also need to be aware that most expoxies are not UV protected, but clear coats that are UV resistant can be applied over the epoxy.

In our club, the guys who build the Classic Mahagony boats insist that you need to put 7-8 coats of epoxy on the exterior, then sand and polish the finish to a bright shine. They start sanding with 150 grit paper and work down to 12,000 grit, then polish with jewelers rouge. They do end up with a nice deep finish, but the weight added is incredible. I personally prefer 1-2 coats of epoxy, followed by several coats of automotive clear coat, with sanding in between.

Sep 24, 2003, 07:21 AM
and this wire goes where?
Thread OP
Sorry if this seems like a really stupid question but if I glass cloth over the exterior, wont I just be hiding all the carefully prepared mahogany planking I'm doing?

As I say, might be a stupid question if I've missed the point, please forgive if it is I'm a bit new to this type of craft!!

Many thanks

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