Boats ans Seagulls.

Talk about and buy or sell boats that are suited to Seagull outboards here

Moderators: John@sos, charlesp, Charles uk, RickUK, Petergalileo

User avatar
Collector Inspector
Posts: 3845
Joined: Sun Jun 29, 2008 4:32 am
Location: Perth Western Australia
Contact:

Re: Boats ans Seagulls.

Postby Collector Inspector » Mon Nov 20, 2017 11:33 am

I like all of these................

BnC
Just took a leaflet out of the letterbox, saying that there's no reason I can't have good sex at 65.

Brilliant - because I live at no. 49 so it's not far to walk home afterwards!

Liam2k3
Posts: 87
Joined: Mon Oct 23, 2017 3:30 pm
Location: Lancashire

Re: Boats ans Seagulls.

Postby Liam2k3 » Mon Nov 20, 2017 10:57 pm

Thats a really nice mix of boats. Im looking at building something with a little bit more for next year so its given me some ideas.
Thanks for posting

headdownarseup
Posts: 2485
Joined: Thu Apr 04, 2013 2:26 pm
Location: bristol

Re: Boats ans Seagulls.

Postby headdownarseup » Sun Jan 07, 2018 2:00 pm

I've often wondered how much work is involved with fitting an expansion pipe to a century/102 style seagull.

Question for the NZ racers now.
Is it possible to do something with the ordinary seagull exhaust tube so it behaves in a similar way to an expansion pipe? I don't really like the look of an expansion pipe looking obviously different to how a seagull should look.
And what about a set of reed valves? How would you go about incorporating some of these onto a century style block, or do you use a 125/170 block somehow with a modified inlet manifold.

Has anyone tried "playing" with a 102 cylinder before?
I have some ideas of my own, but i'd like to hear how some of the guys from down under do it.

Jon

User avatar
Oyster 49
Posts: 2899
Joined: Tue Oct 26, 2010 6:55 pm
Location: Erfurt, Germany

Re: Boats ans Seagulls.

Postby Oyster 49 » Sun Jan 07, 2018 8:31 pm


headdownarseup
Posts: 2485
Joined: Thu Apr 04, 2013 2:26 pm
Location: bristol

Re: Boats ans Seagulls.

Postby headdownarseup » Mon Jan 08, 2018 12:25 am

Not quite the sort of answer i was looking for, but thanks anyway Oyster.

What i was thinking was to utilise the existing exhaust tube of the seagull and build an expansion pipe inside of the normal exhaust tube.Essentially a plain jane pipe on the outside with all the trickery going on inside. Cunning eh!


Jon

User avatar
Nudge
Posts: 673
Joined: Sun Feb 15, 2015 2:43 am
Location: Auckland, New Zealand

Re: Boats ans Seagulls.

Postby Nudge » Tue Jan 09, 2018 10:39 am

Has anyone tried "playing" with a 102 cylinder before?
I have some ideas of my own, but i'd like to hear how some of the guys from down under do it.


No! But you can spill the beans on your ideas!
"THE KING OF BLING"!
Is it better to over think, than not think at all?

headdownarseup
Posts: 2485
Joined: Thu Apr 04, 2013 2:26 pm
Location: bristol

Re: Boats ans Seagulls.

Postby headdownarseup » Wed Jan 10, 2018 12:13 am

I'll try!

Most of us that have a basic understanding of how to extract a bit more power from a 2 stroke engine will know about things like piston clearance,reed valves,crankcase matching etc.
Fairly easy(ish) things for most people to have a go at on a square block seagull engine,and many have done it before with great success.
Not quite so easy on the 102 cylinders though is it, as there's not really that much anyone can do to these cylinders, or is there? :?:


Just an idea at the moment as one of our resident racers had given me this idea some time ago, but how about trying to simulate a similar layout in the combustion chamber of a 102 cylinder so it resembles the same as in a square block cylinder head. Or another way, try to optimise the 102 combustion chamber for a tighter clearance. I must have stared at the inside of 102 cylinders for too long now and not given it much thought until now. I reckon i could do something here but it could take me a while before i have anything worth testing as i need to find somebody to do the necessary alteration to the cylinder along with all the required prep work.

I'm also thinking of making my own set of reed valves somehow incorporated into a custom inlet tract , but i need to do some research into this.

I'm currently putting pen to paper with a home built tuned pipe but the mathematics is quite complicated to get my head into at the moment.
I have this idea i might be able to physically hide this expansion pipe inside a stock seagull exhaust tube, all stealthy like 8) Wouldn't want to give the entire game away first time out on the water now would i!
The overall idea being that i end up with what looks like any typical 102 would do,maybe with an anti cav plate for good measure but with a few hidden surprises elsewhere.
I've got a few more questions about this and what things i need to be aware of (possibly a chat with Chas.) but i think i have enough to work with on paper for the moment before i break out any heavy tools and commit fully to it.


Before anyone asks, i'm not going racing and haven't gone to the dark side or anything weird like that, i'm just interested to see what is reasonably possible from a garden shed perspective without using any expensive tooling or fancy and expensive machinery and fairly limited funds.

Having a faster seagull is one thing, but the boat that you're using this outboard on also comes into play, so i'm toying with the idea of building a small hydroplane. The boat must also fit on top of my car's roof so it's going to have to be small and lightweight.


So, now you know...


Jon

User avatar
Nudge
Posts: 673
Joined: Sun Feb 15, 2015 2:43 am
Location: Auckland, New Zealand

Re: Boats ans Seagulls.

Postby Nudge » Wed Jan 10, 2018 5:40 am

So, now you know...


Not really!
try to optimise the 102 combustion chamber for a tighter clearance.
how do you plan on doing that? I know how it could be done on a square block, but a 102? you would need to fill the cylinder with something? how would you hold it in there??

I have thought about it and hit a brick wall!
"THE KING OF BLING"!
Is it better to over think, than not think at all?

Liam2k3
Posts: 87
Joined: Mon Oct 23, 2017 3:30 pm
Location: Lancashire

Re: Boats ans Seagulls.

Postby Liam2k3 » Wed Jan 10, 2018 11:43 am

I have also been thinking about hydrofoils. To reduce the resistance of the boat in motion. But tge ones they use on surf boards are far too expensive to buy but they seem to be the right kind of idea. If only i knew someone with a hydrofoil board i could measure and copy maybe scale it up to fit the boat and add some kind of control surface. I had thort joy stick controls like a plane. Up down left right with a twist grip for throttle

User avatar
Charles uk
Posts: 4267
Joined: Wed Feb 27, 2008 4:38 pm
Location: Maidenhead Berks UK

Re: Boats ans Seagulls.

Postby Charles uk » Wed Jan 10, 2018 11:52 am

Look up Moth sailing dingy on you tube.
Make it idiot proof and someone will make a better idiot.

Liam2k3
Posts: 87
Joined: Mon Oct 23, 2017 3:30 pm
Location: Lancashire

Re: Boats ans Seagulls.

Postby Liam2k3 » Wed Jan 10, 2018 11:52 am

Replace the upright member with the seagull engine. Put some little sides on the board or make a super light dingy
You do not have the required permissions to view the files attached to this post.

Liam2k3
Posts: 87
Joined: Mon Oct 23, 2017 3:30 pm
Location: Lancashire

Re: Boats ans Seagulls.

Postby Liam2k3 » Wed Jan 10, 2018 12:07 pm

Those moth dinghys look good

headdownarseup
Posts: 2485
Joined: Thu Apr 04, 2013 2:26 pm
Location: bristol

Re: Boats ans Seagulls.

Postby headdownarseup » Thu Jan 11, 2018 2:27 am

Nudge
This might be a long reply, but bear with me here :P

My idea for a "sporty" 102 goes something like this.

As you say "fill it with something", well i was thinking of firstly boiling the cylinder in degreaser to get rid of any oil residue that will almost certainly be in the metal itself,(we're talking microscopic levels here within the grain of the cast iron) then somehow braze some extra material into the combustion chamber to fill up any wasted/dead areas in order to resemble something like a square block cylinder head, thus getting nearer to what we might call a tighter "squish".(i know it's not the correct term but you understand what i mean here for a tighter clearance to the piston crown itself) I think a clearance gap of anywhere from 2-5mm should be more than ample for this, but seeing as the "extra"material can be removed or added at any time by machining (somehow) or re-brazing, there should be plenty of wriggle room to play with for safety's sake. A plasticine "mock up" could be used to acquire a better idea of what needs filling and by how much.There will be complications with the spark plug hole being positioned towards the lower portion of the combustion chamber, but i think it's workable. Ideally if i could get a cylinder with its plug hole more centrally drilled this could work out even better for what i have in mind. I have a number in my head of close to 100psi on the compression but this might need to be played with depending on what i find when i come to test it out for real. As you've mentioned already, keeping this "added material" firmly fixed into position and at the same time trying to avoid any warpage to the bore during this process is something that needs a lot of careful thinking about. Maybe some sort of heat resistant insert inside the bore could help with distortion but it still needs to have enough access to the combustion area of the cylinder during the brazing process. Of course it would be much easier if a 102 had a removable combustion chamber in the first place just like the square block models, but due to design this isn't going to happen so some ingenious ways of getting around this problem need to be overcome first if this idea is ever going to get off the drawing board. Ideas anybody? Even if the cylinder modifications seem like a non starter there are a few other places to look for improvement.



The use of an expansion pipe will probably be a massive step forward for a 102 aiding the cylinder filling for a more complete burn of fuel/air and hopefully a bit more power with less unburnt fuel/air mixture getting pushed straight out of the exhaust port before its had a chance to do its thing. It might also help to increase the engines maximum revs a bit too before it runs out of puff. My idea of hiding this expansion pipe inside the bone stock seagull exhaust tube might need a bit more thinking as i don't know how well a pipe inside a pipe is going to work when it comes to heat build up and how that heat will affect the way the expansion pipe will work within a desired rev range. I've seen vids and pics of other 102cc seagulls with "power pipes" fitted whichever way they seem to fit as they've probably pinched the pipe straight off the nearest 2 stroke motorcycle with similar displacements and they look ugly in my eyes but perfectly functional. In this instance those externally mounted power pipes are to some extent air cooled and probably quite noisy too. I'm thinking that if the "belly" of my homemade expansion pipe is similar in size to the ID of the stock seagull exhaust tube there won't be much room for the water delivery pipe to fit, so i could run this externally of the stock exhaust tube with a small cut out at the top of the tube so it still connects to the water fitting at the base of the cylinder. Once i've worked out how long the expansion pipe needs to be and in which specific rev range i want it to work i can better work out if this seagull will need to be a standard or longshaft to get the expansion pipe to fit inside the stock tube. Stealthy but without giving too much away 8) but at the same time looking like a typical 102 .The expansion pipe itself i can work out the basic dimensions, but the flange that will connect it to the port i'm having trouble working out the best way of transitioning from a rectangular shape (exhaust port) to a round shape (the header of the expansion pipe) has me a bit confused. A bit more reading and i'll have a better idea of where i'm heading with it.



Reed valves in a 102 i reckon could be a fantastic way of reducing any (my words again)"blow by" back out of the carb as they work like a one way valve basically, and so with a more intense filling of the crankcase with little or no "blow by" there's more fuel/air mixture previously drawn into the crankcase to get burnt and make power. In essence i'm trying to minimise the amount of wasted fuel/air that gets vented to atmosphere before its had a chance to do anything useful, something an old 102 needs a lot of help with i feel. To the best of my knowledge i'm not sure if anyone has experimented with reed valves in a 102 before but in principle i think it has a lot of potential. If i can get the humble 102 to breathe a lot better than they do already i think i could be onto something. Again, will i need to do something to the crankcases for a stronger vacuum (or what i call "draw"), i don't know- but as and when i come to test this beasty out for the first time i should get a better feel for where things need to be. Baby steps and all that.


Carbs are another area i've thought about. The later 400 amal's seem quite good for what they do in a stock application, but i'd like to see if there's anything a bit better with more adjustability for changing jet sizes for that perfect tune. Ideally for me something that has a mixture screw fitted to it for tweeking on the move like some of the cart racers do. Some mini bike carbs look quite good for this and they're fairly cheap to buy with plenty of jets around to tinker to your heart's content. Being able to richen or weaken fuel mixture to some extent whilst on the move i think could help with some fueling issues under hard continuous full throttle situations for extended periods.


Ignition systems are something that comes down to personal preference, CDI's to me at any rate seem to be a good way to go especially when used with a recoil starter for quick getaways from the start line :lol: :lol:
Variable ignitions could have a benefit here too, but baby steps and a healthy dose of caution here. With this proposed higher compression there's going to be more heat inside the combustion chamber, and it only takes milliseconds for some dodgy brazing to become unstuck and wreck a 102's piston and cylinder so this brazing mullarkey has to be spot on the first time around. With higher temperatures you run into problems with detonation and if the ignition timing is too far retarded/advanced it could prove deadly for a modified 102 being pushed higher than it was designed to go :shock:
There's a few "racers" on here that have had experience of pushing things too hard before now. I'm trying to learn from other folks mishaps but at the same time acquire a working knowledge of where those boundaries are with some of these old school seagull engines.

As someone once told me it's about "more bangs per minute" if you want to go faster. If i can get a humble 102 engine to run at higher revs without destroying itself in the process , make better power than it already does and stay reliable and in one piece without the need for constant rebuilding, i will have reached my goal and i will be a happy Jon. In practice it's probably not as simple as it sounds but what the heck, i'm up for a challenge. Importantly though, if i'm going to go ahead with this project of modifying a 102 engine it cannot have vast amounts of cash thrown at it. It has to be kept at a grass roots level and within the reach of most people's abilities when it comes to seagulls. There's a lot of people in seagull land that have access to well equipped workshops, not me i'm afraid and as a result i have to make do with what i've got by way of power tools and hand tools. Just keeping it real for a lot of us here that have an interest in going faster with their seagulls but don't want to spend a small fortune on something that could go horribly wrong very quickly.

It's not just the engine that will need some attention, the gearbox and prop will need some fettling as well if they're being pushed harder than they were designed to go. I have ideas here too, but a work in progress for later i think.


I've watched many videos of your boat Nudge and it seems to be fairly well set up and pretty fast for what it is.(how fast will it go on a good day?) Like me i bet you've wondered just how far you could reasonably push things with the dear old 102. Many folks like to fettle a square block seagull purely because they're much easier to modify, but the dear old 102 doesn't get anywhere near enough the attention i think they deserve. I'm very passionate about 102's as you can probably tell from previous posts. If anyone has got anything they'd like to share please feel free as all of what i've mentioned here is just ideas at the moment. Nothing has been put into practice yet.



The boat i'd like to build is a hydroplane NOT a hydrofoil. You must have seen this design before now (minimost or minimax sometimes called a sea flea) in varying lengths. I've also considered another design but can't find any plans for it yet,similar to a 3 point hydro with sponsons.Either way it needs to fit onto a car roof rack with ease and be lightweight.
https://www.youtube.com/watch?v=g4ovCCGhmaA
Going by the video this guys motor looks to be somewhat comparable to a modified seagulls power capabilities. Difficult to judge how fast this is going but 4 horsepower of Johnson's finest gets this little boat moving very well all things considered. If i can manage to get a 102 to do the same (maybe better and faster) i'll be more than happy with my achievements. Here's hoping anyway!

I hope this explains things in better detail Nudge :P


Jon

User avatar
Nudge
Posts: 673
Joined: Sun Feb 15, 2015 2:43 am
Location: Auckland, New Zealand

Re: Boats ans Seagulls.

Postby Nudge » Thu Jan 11, 2018 7:53 am

but the flange that will connect it to the port i'm having trouble working out the best way of transitioning from a rectangular shape (exhaust port) to a round shape (the header of the expansion pipe) has me a bit confused. A bit more reading and i'll have a better idea of where i'm heading with it.


Welder, gas torch,flat plate, pipe and square bar.
1) cut a taper on the square bar
2) heat the pipe till it is red, while still red bash the square bar into the pipe.... now you have a square ended pipe!
3) weld or braze the flate plate onto the square end of the pipe.
4) cut square hole into plate the same size as the square on the pipe
5) extend the round end of the pipe to the size required.

I've watched many videos of your boat Nudge

Thats good! because I cant see or find any of the ones I put on photobucket (even if I try to log into the account)
"THE KING OF BLING"!
Is it better to over think, than not think at all?

Liam2k3
Posts: 87
Joined: Mon Oct 23, 2017 3:30 pm
Location: Lancashire

Re: Boats ans Seagulls.

Postby Liam2k3 » Thu Jan 11, 2018 11:27 am

Would you be better to build up the piston rather than the cylinder?


Return to “Boats Suitable For Seagulls”

Who is online

Users browsing this forum: No registered users and 2 guests