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Old Mar 22, 2016, 04:37 AM
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Build Log
Aquarius Aquacat Racing Inflatable, 1/6th Semi Scale, Scratch Build

Built this a while ago but would still like to upload a build log as this is my first scratch build boat that I have built.

Project started a while ago when I went with a friend to the local model boat club. One of the members, who is known to make interesting creations for fun, had a model of an inflatable boat that he built out of a pool toy and an outboard motor that he built using gears from an old printer. It worked pretty well and was the inspiration for my build, however I wanted to do one better and build a model of a racing inflatable.

MY DUKKY (1 min 28 sec)


The Trans-Aguhlas boat race is a local race that is known to be the 'World's Toughest Inflatable Boat Challenge'. IT takes place every year over 5 days along 700 km of South Africa's south coast, starting in Plettenberg Bay and ending in Gordon's Bay.

http://www.trans-agulhas.com/index.php?dirname=home

I chose one of the boats used in the race, the Aquarius Aquacat, which has won numerous titles in South Africa, including the Constructors Championship for the last 10 years.

http://aquariusinflatablesna.com/Specifications.html
http://www.aquariusinflatables.com.a...ccessories.php

The project kicked off when I found, by chance, a Grauper GTX-650 at my local hobby shop. Armed my newly purchased outboard and a little bit of research including the dimensions for the Aquacat, I drew up some plans.
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Last edited by Melbran; Mar 23, 2016 at 01:15 AM.
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Old Mar 22, 2016, 06:33 AM
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I do not have the skill to make the hull inflatable so I decided to make the hull out of foam, plywood and fibreglass.

I chose to use a material called ISO-board, it is a high density foam that is used as household insulation. It is easily sanded and shaped unlike polystyrene.

http://isoboard.com/insulation/

Cut the ISO-board into strips and did some basic cuts to start shaping. Used an old can with the ends cut off and sharpened to start getting the strips into a tube shape. Final shaping was done by hand with sandpaper.

The pontoons came out fairly symmetrical considering they were shaped by hand.

Cut some plywood for the deck, transom and nose.
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Old Mar 23, 2016, 09:50 AM
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Change of Scale

When I drew up the plans originally I had not yet purchased the outboard motor. I chose draw the plans in 1/10th scale for simplicity and that I had no other scale restrictions.

By the time I bought the motor I already had started built the pontoons, deck and transom. Sizing the motor to the partially built hull it was grossly oversized.

My solution to the problem was to put the plans on the photocopier and enlarge them. At 1/10th scale the length of the hull was 40 cm so I enlarged it to 60 cm. Unfortunately I got the maths for the sale a bit wrong, resulting in a final scale of 1/6.75. The motor is still slightly oversized, but it is mainly just the cowling.

It wasn't too difficult to re-cut the transom and deck or shape new pontoons. I used an old broom handle to make the lower highriser pontoons.

I still have the parts for the original 1/10th scale model, which I might build as a static model in the NSRI colours to match the other boat I am building.
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Old Mar 23, 2016, 10:02 AM
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Completed the hull and mocked up the motor. Looking good at this stage but means I need to start the part of the project that I'm looking forward to the least - fibreglassing.
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Old Mar 23, 2016, 10:15 AM
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The project stalled for quite a while for a couple of reasons; didn't know how to fibreglass properly, started a new job, and moved to a new house in a new country.

The build got going again after my colleague showed me how to fibreglass. The fibreglassing turned out relatively well for my first attempt. Not sure what I enjoyed less the fibreglassing or the sanding.

Used some modeling clay to help shape the lower highrise pontoons. Normally they are created by the PCV being stretched tight by the inflatable pontoons.

In hindsight I should have used a lighter material as the boat is heavier and slower than it should be, but it does have a nice scale wake.
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Old Mar 30, 2016, 07:43 AM
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Motor Modifications

In between the months it took me to finish the fiberglass I made some small modifications to the Graupner GTX-650 outboard. Used a piece of brakeline with a flare for the watercooling outlet / telltale.

The outboard came without a motor so I fitted a Turnigy Aquastar 3660-1700kv Water-cooled Brushless Inrunner. The motor is a bit overkill as it is a 1800w motor that can run on 6s. I am only running the motor on 3300mah 3s 45c battery. I can probably get some more speed out of the boat on a 4s with a different size prop, but it is fast enough for me on 3s.

http://www.hobbyking.com/hobbyking/s...ess_Motor.html

I am using a Turnigy Aquastar 120A Water-cooled ESC as the motor requires 90 Amps. Again well over-speced as the ESC doesn't even get hot after 15-20min at full throttle without water cooling.

http://www.hobbyking.com/hobbyking/s...ming_Card.html

Choices for electronics here in Botswana are limited as there isn't a Hobby Shop and the prices in South Africa are ridiculous. There are just no cheap electronics sold at local hobby shops.

Fitting the motor was a bit of a challenge as I had to bore the coupling from 3.5mm to 5mm. Turned out to be much more difficult than it should as the Lathe bored off center, resulting in having to braze to fill it in the hole and re-boring, and tapping for the grubscrew, after the lathe had been trued.
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Old Mar 30, 2016, 07:54 AM
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Finally completed the fibreglass and painted the boat in a simple black and white colour scheme. I can add stickers/decals later if I want to make it look more like a race boat.

Mocked up the electronics box. Not many options for the electronics as they can't be hidden below the deck or in the pontoons or nose.

Started building the servo mount that will be hidden under a faux fuel tank. Slightly larger than scale to hide the servo. Wires for the motor will be run from the electronics box through the fuel tank to look like a fuel hose.

Fitted a tiller arm, the first of the scale details to be added.
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Old Mar 30, 2016, 10:09 AM
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Grumpa Tom
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Really quite awesome what you have built!
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Old Mar 30, 2016, 10:13 AM
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boat butcher
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Runs really well . Nice lake also.

Mark
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Old Mar 30, 2016, 11:11 AM
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Do you have a video of your boat with changes running? Jerryj98501
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Old Mar 31, 2016, 02:38 AM
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Quote:
Originally Posted by jerryj98501 View Post
Do you have a video of your boat with changes running? Jerryj98501
I have some cellphone videos of it running at a local lake and most recently in a storm water drain after some heavy rain. (Coupling came loose during the last run so my fun was cut short)

I need to edit and upload the videos. I will do this in due course (trying to keep things in order) as there was a lot of testing and a few mods to get the trim right, will discuss this in the in the build log.
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Old Mar 31, 2016, 06:57 PM
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Thank you. jerryj98501
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