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Author Topic: MFA 850 Torpedo in Dumas Chris Craft 1930 Runabout  (Read 692 times)

Hotglove

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MFA 850 Torpedo in Dumas Chris Craft 1930 Runabout
« on: April 29, 2018, 11:40:28 AM »

Hi, first post, absolute beginner, all comments welcome.
I have bought the Runabout ready-built and am very pleased with it overall.
Have been enjoying adding finishing details and seeing it on the water, but have a couple of queries.
There is a slight leakage through the propshaft (standard Dumas fit, well packed with Molykote 111 silicone grease) about 2 dessertspoons after 40 min running, mostly slow cruising, I put a tampon in the bilge and that soaks it up very well.
I have fitted an ESS One sound module, which is great at low speed, but at higher speed the electric motor is quite loud and detracts from the effect.
There is a guy at the club who has a boat about 2/3 the size of mine with a Darke Horse motor and it is amazingly quiet, I noticed that his connector is alloy and rubber, mine is the red plastic variety, and wondered if that might contribute to the low sound volume.
I changed the Dumas prop for a 40mm Graupner 2 blade and noticed an improvement in speed and planing but it still sits little low at the stern and "nose up"
Saw a video of a similar boat with a brushless motor, which ran extremely well but howled like a demented banshee, definitely do not want that!
Boat runs on 2 5000 lips and has a fan-cooled esc, after 40 min mixed running, mostly slow cruising with stops the motor is warm to the touch, batteries, esc and sound module slightly above ambient and voltage at 12v or just under.
So, all in all a well behaved boat that looks and sounds great except for a rather coarse motor sound at speed.
I would prefer to avoid drilling holes in the hull for cooling if possible.
Not looking to spend money for the sake of it but would be prepared pay significantly more than the cost of the MFA motor if it brought a noticeable improvement in performance, but most importantly, a smoother, more pleasing motor sound.
Thank you.   
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Shipmate60

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Re: MFA 850 Torpedo in Dumas Chris Craft 1930 Runabout
« Reply #1 on: April 29, 2018, 01:07:18 PM »

Try a rubber tube between the coupling ends.
So much more quiet.


Bob
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Hotglove

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Re: MFA 850 Torpedo in Dumas Chris Craft 1930 Runabout
« Reply #2 on: April 29, 2018, 03:33:28 PM »

Thanks for the prompt response, but a very ignorant newbie here, do you mean as a sleeve over the coupling?
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Perkasaman2

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Re: MFA 850 Torpedo in Dumas Chris Craft 1930 Runabout
« Reply #3 on: April 29, 2018, 05:31:28 PM »

A piece of silicone or rubber tubing replaces your red flexible coupling.
You need to place your batteries further forward toward the bow. This improved weight distribution change will help to bring the bow down and help the hull to plane properly. This will help to avoid the hull 'snow ploughing' with a low stern high bow attitude. Moving weight forward where possible helps to overcome this running condition. Some models have trim tabs fitted on the stern to overcome this problem.
Hope some of the above helps.
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Hotglove

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Re: MFA 850 Torpedo in Dumas Chris Craft 1930 Runabout
« Reply #4 on: April 29, 2018, 06:17:51 PM »

Thank you for the reply I will try the silicon tube as a replacement coupling, I can only move the batteries about 1 1/2 inches forward without modifying the battery tray, but will see if that small movement makes a difference.
I will also soon be fitting two crew figures who are made of solid pvc and will add a bit of weight to the front of the boat.

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