My thundercat - Page 22

spartacus · 10 March 2021, 19:45

Does this engine use stock reed valves, or are they upgraded to Boyesen?

What are the advantages?

Roflhat · 11 March 2021, 09:20

Being the 70ces, competition version of the 70hp it actually came with carbon reeds as standard from Yamaha.

Main advantage is if they break they won't damage the pistons or bores. Slightly more crisp throttle response too

GuyC · 11 March 2021, 17:22

Do you have a mermaid in your family by any chance?

spartacus · 11 March 2021, 21:08

Quote:

Originally Posted by Roflhat

Being the 70ces, competition version of the 70hp it actually came with carbon reeds as standard from Yamaha.

Main advantage is if they break they won't damage the pistons or bores. Slightly more crisp throttle response too

Thank you. I was toying with idea of adding Boyesen reeds to my Tohatsu which is already upgraded to 70hp, but it's running sweet as a nut just now, so it may just be tinkering.

Roflhat · 12 March 2021, 07:55

Quote:

Originally Posted by GuyC

Do you have a mermaid in your family by any chance?

I do indeed. Will be an episode of this series featuring the thundercat on March 30th

Quote:

Originally Posted by spartacus

Thank you. I was toying with idea of adding Boyesen reeds to my Tohatsu which is already upgraded to 70hp, but it's running sweet as a nut just now, so it may just be tinkering.

Can't hurt having carbon reeds, it's been that long since I ran an engine with standard reeds I can't remember how much difference they made. No top end difference but the acceleration is a bit snappier

Roflhat · 22 March 2021, 18:22

Spent far too many hours on this... New design of head and a fancy cover plate. Going to see if I can get one CNC'd

Iankristy · 23 March 2021, 17:25

Quote:

Originally Posted by Roflhat

Spent far too many hours on this... New design of head and a fancy cover plate. Going to see if I can get one CNC'd

Led zeppelin fan/ bass player?

Roflhat · 23 March 2021, 17:39

I am a led zep fan but that's not where I got the idea! Just thought it was a cool design

Iankristy · 23 March 2021, 22:10

Quote:

Originally Posted by Roflhat

I am a led zep fan but that's not where I got the idea! Just thought it was a cool design

[ATTACH]136661

New it straight off lol

Roflhat · 04 April 2021, 08:35

Finally got out for a run and some testing yesterday. Gearbox isn't properly painted yet so it's back off for that now. Engine running beautifully and stayed that way which is always nice!
Speeds are up about 1.5 knots on average per prop from the last test. Plan now is to remove some weight from the boat, carbon cowling, replace the grabner lifejacket with a formula which is 1kg vs 2.2kg. Then the billet cylinder head and maybe try lift the engine up some more

Head is finished and should be here next week

Been thinking more and more about switching to an Aquarius hull just can't bring myself to spend the money...

smallribber · 04 April 2021, 09:34

Now you are a chap who likes to hone the best out of things

spartacus · 04 April 2021, 12:42

Recognise your anchorage Rolfhat. Possibly the best natural harbour, anywhere!

Hope to be back soon once this bleed'n lock-down eases.

jwalker · 04 April 2021, 13:17

Wow, that head looks good, I hope it performs as well as it looks! Saw you on the telly tother night. It's good that yous kept the places secret, social media would have a thousand folk there in no time....

Roflhat · 04 April 2021, 20:32

Quote:

Originally Posted by smallribber

Now you are a chap who likes to hone the best out of things

I do try! Something very satisying about tuning to get the maximum from a piece of machinery. Would be far cheaper to buy a faster boat

Quote:

Originally Posted by spartacus

Recognise your anchorage Rolfhat. Possibly the best natural harbour, anywhere!

Hope to be back soon once this bleed'n lock-down eases.

Had to make the most of the one good day I had at home! Back to snow for this week

Quote:

Originally Posted by jwalker

Wow, that head looks good, I hope it performs as well as it looks! Saw you on the telly tother night. It's good that yous kept the places secret, social media would have a thousand folk there in no time....

So do I! Was debating whether to go for offset or centre combustion chamber. Offset would give cooler temps but centre in theory has higher hp. Sort of a hemi design with a flattened section at the plug to keep the spark closer to the piston.

It's a fine balance, arguably Skye has gone too far with having an influx of tourists and holiday home owners each summer. At least here the number is restricted by Calmac, can't physically move many more people to and from the islands

Roflhat · 11 April 2021, 20:11

Had some decent conditions today, a bit windier than I hoped but nice and cold. Did about 15 top speed runs, some 2up and then some with just myself and a 30kg water ballast. Performance is the best it's ever been, managed 78.1mph on one run! 67.8 knots, even faster than I went at Coniston. Still a couple things to try

Allye · 11 April 2021, 20:14

You’re mental. Love it!

jwalker · 11 April 2021, 21:41

Quote:

Originally Posted by Roflhat

Had some decent conditions today, a bit windier than I hoped but nice and cold. Did about 15 top speed runs, some 2up and then some with just myself and a 30kg water ballast. Performance is the best it's ever been, managed 78.1mph on one run! 67.8 knots, even faster than I went at Coniston. Still a couple things to try

Well done! That's serious speed for the little boat... I'm waiting for it to take off... No joke!!

Roflhat · 12 April 2021, 07:09

So am I to be honest! Felt pretty light yesterday, wouldn't want to catch a gust of wind at that speed. Don't know how much more is possible but have to try anyway

ThundercatRob · 12 April 2021, 07:15

Is the goal to break 80mph?

jwalker · 12 April 2021, 13:44

Quote:

Originally Posted by Roflhat

So am I to be honest! Felt pretty light yesterday, wouldn't want to catch a gust of wind at that speed. Don't know how much more is possible but have to try anyway

Yes, I was thinking exactly that, just a gust of 10mph and your wind speed will suddenly be about 90mph!!