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Old 23-05-2020, 09:21 AM   #141
Thundercat guy
 
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Country: Scotland
Location: Isle of Lewis
Occupation: Skipper
Boat make: Thundercat
Engines: Yamaha 70ces

Join Date: Apr 2014
Location: Isle of Lewis
Posts: 470
Engine is running well with less timing, lots of testing done. Rebuilding again now though, due to one of the wee bolts from the choke flaps coming loose...


Tested the motorbike windscreen, worth about 0.57 knots. Modelling the boat on CAD too to try do some CFD aerodynamic tests. Not something I know much about

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Old 26-05-2020, 01:40 PM   #142
Thundercat guy
 
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Country: Scotland
Location: Isle of Lewis
Occupation: Skipper
Boat make: Thundercat
Engines: Yamaha 70ces

Join Date: Apr 2014
Location: Isle of Lewis
Posts: 470
Finally getting somwhere with the CFD. Took a long time to get a solid model in Rhino which I could use. Cd, drag coefficient is around 0.438, now to try and reduce it


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Old 07-06-2020, 05:44 PM   #143
Thundercat guy
 
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Country: Scotland
Location: Isle of Lewis
Occupation: Skipper
Boat make: Thundercat
Engines: Yamaha 70ces

Join Date: Apr 2014
Location: Isle of Lewis
Posts: 470
Now thinking simply rounding the front of the cowl a bit would help more than the windscreen I was using. Shape of the screen would generate downforce, which I don't need.
Backed the timing right off to 13 degrees, which seems to agree more with the pistons. Been out in the boat a lot since the lockdown was eased, no issues so far.



Ordered a 53L fuel tank as the 21L doesn't last long! Still plenty of testing to do, just waiting for dead calm conditions. Going to test the 90hp carbs again
Carbon cowling is coming along nicely, should be 3kg lighter than the original which was 5kg
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Old 18-12-2020, 11:33 AM   #144
Thundercat guy
 
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Country: Scotland
Location: Isle of Lewis
Occupation: Skipper
Boat make: Thundercat
Engines: Yamaha 70ces

Join Date: Apr 2014
Location: Isle of Lewis
Posts: 470
Bits and pieces done to the boat, got more props to try just need some decent weather. Gearbox is getting a nose cone added on so will have to re test props anyway
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Old 09-01-2021, 09:07 PM   #145
Thundercat guy
 
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Country: Scotland
Location: Isle of Lewis
Occupation: Skipper
Boat make: Thundercat
Engines: Yamaha 70ces

Join Date: Apr 2014
Location: Isle of Lewis
Posts: 470
Engine sadly didn't last long with the modified gear box...
Thinking it lifted too high, lost water pressure and cooked the top piston. Fortunately didn't damage the block so will get it back together soon enough. Going to remove the nose cone from the gear box, have ordered a low water pickup version which should solve the issue. Whos stupid idea was that anyway



Managed to quickly test the Forge V2 before the engine blew, very happy with how it went. Still got 5 more props to try but will have to wait a while. Going to do a couple other jobs on the engine while it's apart. Cleaned up the cylinder head, printing some new velocity stacks for the 90hp carbs. Might get some nylon engine mounts made up for it, and maybe a lick of paint for the leg.
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Old 15-01-2021, 10:25 AM   #146
Thundercat guy
 
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Country: Scotland
Location: Isle of Lewis
Occupation: Skipper
Boat make: Thundercat
Engines: Yamaha 70ces

Join Date: Apr 2014
Location: Isle of Lewis
Posts: 470
Doing some more bits and pieces, the play in the engine was from the swivel tube bushes. Getting some brass ones made up which should last longer. New stacks are made up, also designed some reed block stuffers. Took a few days and 7 versions to get them how I wanted but they're a really good fit.


Also cut down the air intakes on the cowling.

Going for 185/195/195 main jets to start with, playing it safe! Also drilled out the needle valve seats, they were 1.6mm now 1.8mm. Ordered a bigger fuel pump, from the Yamaha v6 two stroke.

Flowed the exhaust and sandwich plate, removed some restrictions from there. This does mean the engine isnt UIM legal any more but I don't mind. If I go to Coniston again it will likely just be for a performance certificate rather than a record. Would prefer to go for the worlds fastest thundercat.
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