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Inboard engine catamaran
Nov 07, 2006
 The boat accelerates. The front points
upwards and the wet area of the hull is reduced to the last step.
I wanted to try a calm nitro boat. My preference is
clearly the cats, and I wanted a complete boat (all in the box - upgrading and changing
will arrive later, I'm sure), so I had a limited choice.This boat is
really attractive. Nice graphics, perfect hull (Kyosho quality is unbeaten), ABN engine
and a complete set of hardware.
 A high speed turn. The outside sponson barely touches
the water.
If there is a boat in which everything fits perfectly, this is the one. The hull
is so perfect and sharp that I'm sure it will run nicely. It doesn't promise to be very
fast, but other engines fit on that space (.21). I'll run it with the original engine and
then we'll see...
- The boat is fun. It handles as if on rails with tight turns at high speed. It
comes with two turn fins and trim plates that really help the handling.
- However, the vibration is enough to loose all screws in the hull, so a locking
product should be used on all of them. This boat can be described as a high performance
screw ejector...
Tips
Get rid of the
original propeller!
If you want to get the most out of this boat, substitute the original propeller
as soon as you can. It is a plastic propeller equivalent to an Octura X460, but the
effectiveness of plastic propellers is much lower than their metal counterparts. The
plastic flexes under pressure and they loose grip, causing the boat to run slower.
The sport boat manufacturers do things on the safe side. Imagine a fast boat (really fast)
on the hands of a beginner...
Anyway, the boat goes as fast as you want (that's why we have a throttle stick...). My
experience tells me that you can put some more load on the engine installing a bigger
prop. Unfortunately the choice of 4mm propellers is not very good (unless you are in
Europe and can get Mocom props), so a small adaptation is needed for
using 3/16" propellers. See below.
How can you
use 3/16" propellers?
 Cut a piece of brass tube with 4mm inner diameter (this boat is all
metric, and the propeller shaft is 4mm) and with the length of the prop boss. You'll see
that the outer diameter of the tube is a little higher than 3/16". Using a lathe, a
Minicraft or Dremel tool and trim the excess material till the brass tube fits tightly on
the inside of the propeller. Now you can use all sorts of excellent propellers on the
boat.
How to
avoid problems with the motor mount?
After some attempts of engine starting (beware, the engine is very prone to
flooding), the engine mounts on the tub tend to break (especially the ones on the right
side, looking from the front of the boat). I noticed this problem too late, when the
engine started to vibrate like hell. You can prevent this applying some fiberglass and
epoxy before mounting the hull, over the holes where the rubber mounting blocks go. This
reinforcement is more than enough for avoiding this unpleasant problem.
Prepare
to substitute the plastic tank mount.
After a major overhaul of the boat I was going to put the tank in place, when I
noticed a crack on the tank mount. A close inspection revealed that this mount was
completely covered with cracks (I think that the heat inside the boat does this kind of
stuff to the ABS). I made a new mount from the excess ply of the base of the boat. It was
brushed with epoxy for fuel proofing and the tank was mounted from below
the mount (or else the hatch will not fit, because this mount is thicker than the original
one).
Substitute
the bushings for ball bearings.
This was a crucial modification in two respects. The friction is much lower than
with the bronze bushings, and the fact that the shaft fits tightly on the lower bearing,
avoids water getting inside the hull by the shaft, and believe me, this means a lot of
water...
You'll need two types of bearings - 2 units of 4mm x 7mm flanged, and 2 4mm x 8mm.
Boca Bearings and Duratrax make this kind of ball bearings but the Duratrax are much
cheaper (there must be a difference, isn't it?)
Be
careful with the clearance of the thrust bearings on the shaft!
You need to be extra careful with this clearance. There must be at least 1 mm
clearance between the end of the shaft and the inner part of the outdrive. If not, when
you turn, the friction will slow down the engine noticeably, and the plastic part of the
outdrive may melt (even underwater, and it happened to me). When correctly set up, the
loss of speed will only be due to dynamic causes (hull drag) and not to unwanted side
effects. If the friction is too high the pin on the universal joint may break !
Running
| Day 1 |
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The engine starts easily. I notice a high vibration in low RPM.
After checking all the moving parts, it seems that it's a characteristic of this engine.
Later, after reading a review of the boat my suspicion was confirmed.
I had some problems with engine tuning (a new engine , a new boat, what could I
expect?).
The three runs were made with a moderate acceleration just to break in the engine. |
| Day 2 |
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The engine is running OK. The speed is lower than expected. But
the handling of the boat is too good to be believed. The jumps are very
"elegant" and the stability is awesome. |
| Day 3 (15-Nov-97) |
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After reading a review of the boat and with the results shown when
a decent propeller was installed on the Nitro Vee, I decided to
go to a larger propeller (OCTURA X440/3). The boat comes with a plastic propeller
equivalent to an OCTURA X640.
WOW, what a difference! The speed increases amazingly and the boat
turns fast and on rails.
If the jumps were nice on the second day, now they're even better. I've seen worse
flying planes...
I made a few runs with (against) the Nitro Vee and on the turns the speed is more
or less the same, but on the straight the Nitro Vee can't keep up. I still have the engine
on the rich side and I'm sure I can get more out of this beauty.
I've installed a two blade Prather S220 highly sharpened (I made a
few finger cuts just installing it). This prop has only 2 blades, but the diameter and
pitch are 43 mm and 66mm which would make it roughly
equivalent to an OCTURA X543 (if it exists). |
| Day 4 (22-Nov-97) |
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The new prop gives even better performance. The engine revs easily
with this prop and the speed is higher. A good 2 blade prop is very effective. I'll try a
Octura X645 to see if the performance increases with it.
Check all the grub screws before going to the water. I've lost
one, and it was tight (I thought it was...). |
| Day 5 (7-Dec-97) |
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A fun day until all radio control was lost... I was really
lucky because this happened in a tight turn. The controls freezed on this position at full
speed.
I was unsatisfied with the duration of the runs (6 to 7 min.) but seeing the boat
go round and round for 5 minutes seems like an eternity... Finally the turns started to be
disturbed by the boat's own track and it stopped on some bushes close to the water. No
harm done. A check at the radio system at home revealed a crystal with random problems. A
cheap piece of equipment could have cost me an entire boat and a couple of months waiting
for a new one to be finished. And this is unbearable. |
Present config.
| Motor |
Kyosho .18 |
| Fuel |
10% nitro, 16 % synthetic oil, 4% castor |
| Propeller |
Prather S220 (sharpened like a blade) |
| Receiver |
Futaba F118 |
| Throttle |
Cirrus CS90BB low profile |
| Steering |
Cirrus CS90BB low profile |
| Radio pack |
Futaba Ripmax 1200 mAh |
Review
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The construction is very simple. The superb hull is complete and the shape and
details are excellent. This is a two step hull and the sharpness of every strake is
amazing. This is not an ordinary ABS hull! |
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The tub for the engine is screwed in place with lots of self tapping screws. I
found that they are "ejected" with the vibration... |
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The hull was painted with white resin paint just to match with the hatch color
which is substantially different from the hull color (the hull has a yellow coloration) |
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The shaft installations was made after the engine installation, just to be sure
that everything is aligned before gluing.
The bronze bushings were changed by ball bearings I bought from BOCA
Bearings. Two (flanged) on the extremities of the main shaft and two on the
outdrive. |
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The decals were applied with soapy water, and I the result is outstanding. Very
good set of decals (there are so many decals that you'll need a couple of hours to put
them all in place) |
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On top of the engine tub, comes the radio box. Easy fit, and again a lot of
self tapping screws to hold it. The radio box cover is also hold in place with screws
(these Japanese guys want to be sure...) |
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I like |
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The hull, oh boy what a piece of work! |
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The handling of the boat. The double turn fins make it impossible to spin. Just
open the throttle and do whatever you want at full speed (and with the prop I have is
really high speed) |
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I
don't like |
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The turn fins are hold in place with 3 screws each (again...).
Well, the holes are a endless source of water to the interior of the boat. And I mean a
lot of water. So, be sure to seal them with silicone on the inside and on the outside.
The method is simple. Before putting them in place, spread a fair amount of
silicone sealant on the area of the fin (even over the three holes) and screw them in
place. When the sealant is dry no more water will get inside the hull through those holes.
However, the big amount of water gets into the boat through the propeller shaft. If
you put the original bushings, lots of water will get inside the hull. The clearance
between the lower bushing and the shaft is enough for the water to go up the shaft into
the engine tub. The pressure will cause this. Then the water drains to the inside of the
hull through the tub hole for the shaft.
If you change the lower bushing by a ball bearing with less clearance (virtually
none), no more water will get in. |
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The engine tub cracks on each screw hole. Cyano won't work. Unless
you use a radical method to fix them (like fiberglass and epoxy), this tub will be
worthless after a few hours of vibration. Take care. |
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And that's all folks... |
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