Arowana 32" self righting hull

[Old School]

I have purchased two of these hulls (one in my possession, one soon to be intransit) from an eBay seller "thebuild-rc". The build quality looks very good with an immaculate glossy white gelcoat finish, however, I am sure that achieving self righting capabilities will take a lot of experimenting in the bath tub.

A quick check revealed the chamber leaks inside the hull (probably to be expected as I did intend beefing up the hull). Secondly, the chamber is extremely small occupying no more than about 750 cc. The Arowana 32 is well known for its stability when the hull is inverted in the water due its large flat deck, so I feel that additional lead weight will be needed to be added inside the float chamber towards the rear, plus biasing the battery to the left side.

I had hoped being a production hull that the flood chamber volume had been sorted out but it seems that I need to do a lot of homework to eventually achieve a self righting hull. Fingers crossed that a new inner wall will not be needed closer to the keel centreline to gain additional volume.

[rol243]

sounds like a good size 4s class mono hull. any pics of this ?

[Old School]

As requested

[Old School]

Also. Hull is 80 cm in length and 24.5 cm width.

[rol243]

Thats not a bad looking mono hull atall. wounder if this seller has non self righting hulls available as well.

[Old School]

This is his selection of hulls from his website -

http://thebuildrc.com/rc-boats/hulls.html

[boatsrnew2me]

i have eyes these hulls before as i love a self righter but i am not a builder . i wasnt aware they sell them on ebay .they do list almost ready to run ones but they are never in stock .

[Old School]

Personally, given that my hull flood chamber leaks I would not trust buying an ATR model. I think that any hull will need rectification plus some fettling to get the hull to self right as the flood chamber is I believe too small a capacity.

[denboy01]

Pursuit-inside.jpg

Photo shows a Pursuit hull setup for self righting

[martin]

The Arowana is the same hull bottom as the Pursuit, but with a different deck & hatch.

[rayray9]

denboy01, does that actually work on the Pursuit?

[denboy01]

The boat in the photo has an almost full length flood chamber and 4oz lead at the c of g between the speedo and battery. With this setup the boat selfrights easily.
With heavier speedos and batteries the lead might not be required.
.

[denboy01]

Youtube has a few examples of Pursuit hulls that self right

[rayray9]

Any pics of the flood chamber?

[denboy01]

Hi Ray, i'll try and get some more pics on tomorrow

[Old School]

After extensive reading I believe the Arowana stock flood chamber is woefully undernourished. My measurement of 750 cc (stock) is about one third of what is required. I feel that I have no alternative other than to rebuild the chamber bringing it out almost to the rails, but even then the volume may still be only about two-thirds of that required.

Offsetting the battery and ESC will help as well as compensating for torque roll. Reading back over a long thread on another site the small flood chamber was introduced back in 2014 and comments were that a lot of additional weight would be needed to self right the hull. The hull was then sold by R2 Hobbies.

[martin]

A couple of guys over on RC Groups forum fitted flood chambers to their Arowana's a few years back, both of them said the chamber wall needed to come inboard right over to just shy of the motor mount. Other wise the chamber's volume is just to small to self right the boat.

[Old School]

A couple of guys over on RC Groups forum fitted flood chambers to their Arowana's a few years back, both of them said the chamber wall needed to come inboard right over to just shy of the motor mount. Other wise the chamber's volume is just to small to self right the boat.

Many thanks. I read all 45 pages of the thread on the Arowana and it seems around 2300 cc volume is needed plus offsetting the battery and ESC to the chamber wall. With only 750 cc stock I need a lot more volume inside. The main issue seems to be that the hull is too stable when upside down.

[785boats]

My old Arowana was one of my favorite boats.Why did I sell it?

They are available with motor & hardware, or with hardware only at 'tobsd hobbies'. Although the motor & prop supplied are too small for a 31" boat in my opinion.
No flood chamber in these ones though.

http://tobsd.com/ViewDetails.aspx?ProductID=1020
http://tobsd.com/ViewDetails.aspx?ProductID=959

Here's mine running cheap Himodel 3674 8xl (2074kv) on 4s lipo, & an x440/3 prop.
Good Lord. Was it really 6 years ago?

[properchopper]

Here's an Arowana I built for a customer in 2011 (man I'm gettin' old) with a Leo 4074 2200KV on 4S2p. Boat ran nicely with a modded 447/3 in rough/windy conditions. This didn't have the flood chamber IIRC and had a very tall hatch :

https://www.youtube.com/watch?v=mwzDzBUPn60

[denboy01]

Air-exit.jpgChamber.jpgRear.jpg

More pics of the Pursuit flood chamber.

[R2315]

It's Not the same boat and I'm not sure how wide yours is or if this would help at all.. but here are a few pics of my flood chamber in my 30" mono, maybe they can help. This works well with just one 1/4" hole for air release.

_DSC1898.jpg_DSC1892.jpg_DSC1897.jpg_DSC1899.jpg_DSC1902.jpg

[Old School]

Your hull has a wide chamber extending past the hatch lip. This is basically what I intend doing to increase the chamber volume. Reading online it seems that water alone may not be enough to self right with many adding lead weights inside the chamber.

Apparently, if one can get the hull to flip so it is vertical then the torque reaction from the prop will finish the job.

[R2315]

Your hull has a wide chamber extending past the hatch lip. This is basically what I intend doing to increase the chamber volume. Reading online it seems that water alone may not be enough to self right with many adding lead weights inside the chamber.

Apparently, if one can get the hull to flip so it is vertical then the torque reaction from the prop will finish the job.

With one lipo strapped to the flood chamber beside the motor and one closer to the front but still to the left of center it drives well and flips over every time. Different story if your only using one pack though.

[Old School]

Many thanks. Early designs with smaller length hulls had a larger cabin so the hatch lid became very bouyant, assisting the hull to self right itself. Alas, the stock Arowana is stable when upside down. Perhaps a larger cabin as on the Pursuit (they share the same hull) would assist.

Edit: the second hull arrived in just two days and as expected the chamber also leaked into the hull. Other than that the quality matches the previously received hull.

Edit #2 : the Arowana is 240 mm in width at the transom. I have decided to run a fillet of epoxy along the stock chamber wall inside the flood chamber to ensure that the chamber is sealed (particularly near the bow as this is where the factory hull is leaking into the hull from the flood chamber on both hulls. I will then glass the inside wall of the chamber. After curing I will cut access holes through the chamber wall to allow water to flow into a chamber extension, basically doubling the stock capacity. The chamber extension will be built using 2 mm carbon fibre strip and 2 mm plate. The joins will be reinforced with an epoxy fillet.

[Old School]

I have progressed these hulls the last few days. I reinforced the flood chamber wall with fibreglass tape and fillet filled the join inside the chamber. I then applied fibreglass tape to the longitudinal keel and then overlaid with carbon fibre. The right side hull join was reinforced with tape. Unfortunately due the stock flood chamber I am unable to reinforce the port side join. The transom was also reinforced with two layers of carbon fibre. Once the inner flood chamber wall is installed I will then apply another layer or two to the transom. I may fit two-part expanding foam to the forward under deck area as the stock deck flexes when pressed.

I have ordered some carbon fibre strip and square tube and utilising 2 mm carbon fibre sheet that I have I will build up an inner flood chamber wall, hopefully doubling the size of the factory chamber. Once this is installed then I can proceed with fitting the internals.

I am building two boats at once as I intend posting off one boat to my son once he receives his final posting in central Queensland. He will have access to an immense freshwater lake to run the boat. Being self righting then he hopefully will not need a rescue boat and be able to enjoy what he likes most - SPEED!!!!!!! My choice will be to build two speed demons or perhaps a fast boat for him and a not so fast (less expensive) boat for me. Being self righting will give me more confidence in running.

For the fast boat perhaps a 4092 (or TP equivalent) with a 180 amp ESC, running 4s. Perhaps a prop around 44 mm - 47 mm running through a 3/16" Speedmaster stinger. The slower boat perhaps a cheaper motor and ESC.

Edit: criticism of the original non-righting Arowana was that the stock cab moulding was relatively fragile and prone to split open on impact. While this current model is not the same shape as the original I still decided to reinforce the cab interior with two longitudinal and one lateral layers of fibreglass tape.

[Old School]

As I will be building two boats almost simultaneously, the first will need to be the guinea pig to sort out my ideas. I was thinking a TP Power 4050 motor and did not have the confidence in the stock fibreglass mounting plate, so am thinking that the TFL aluminium mount should be capable of retaining the motor (used on 40 series motor mounts in Zondas). The ally mount would be bonded to the fibreglass mount plus affixed to the hull, with the motor mount bolts passing through both mounts.

I still need to install the inner flood chamber wall which will come close to the port side longitudinal fibreglass rail, limiting access to the traditional motor mount bolts normally used with the alloy ring type motor mounts. Thus I feel that access to end mounted motor mount bolts will be more practical. If the alloy mount is not enough then I would need to look at a forward mount install or perhaps a simple 'rest bracket' for the motor to sit on.

I have drilled holes in the modified factory installed flood chamber wall to allow water to flow into the additional inboard flood chamber yet to be built. The transom will be modified to enable water to exit both interconnected chambers when power is applied. Most likely I will fit wheel weights inside the new chamber as I am not confident that I can build sufficient chamber volume to successfully self right the hull.

[rol243]

Looks like a nice neat layout inside. hey i have a new 4050 t.p. motor with cooling jacket fitted 4 sale , only selling as i want a smaller motor for a particular hull.

[Old School]

As yet I have not settled on a particular motor, possibly a TP for my son's boat and something with a little less performance for myself. I was thinking a motor on 4s around 1800 - 2000kv. Because of the offset battery location (aft port side against the flood chamber wall) I really am limited to 4s.

[rol243]

the 4050 i have is a 2310 kv.