Something a bit different! Model Power Boating. RC Catamaran build thread.

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Hello!

So a couple of weeks ago I purchased this!

It is a 48" long "Orion" Catamaran boat produced by Dave Marles of Prestwich Models. When I posted it in the purchased thread, some showed some interest in a build thread. Well today, yesterday, and for the next 9 days I will be going into this at full steam. Maybe even squeeze in a test run next weekend! Lets see

On the flip side, if this thread dies on its butt, then mods can delete it

So without further a do! Let's get into it.

First up, I need to find the centre of the boat to fit the drive strut and then rudder, also make up a plywood based brace for them to screw to. Most boats come with one of these already, however this didn't, nevermind eh.

Made this up, fuel proofed and then fitted inside the hull against the transom.

With that in, I found the centre then proceeded to get the drive strut & rudder bolted on.

Next up, water inlets, outlets and handles.

From here, its ventilation. I have 3 air scoops to fit to the front for intake then 4 exhaust ports for the rear for air to vacuum out

Exhaust vents first.

Positions figured out, time to dremel.

Nasty stuff this carbin fibre.

And that about does it for now. I've got more to add, but I would like to get some better photos of the finished vents first

Anyway, that will do for a first post...

 

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Lots to add after another busy day in the shed but I've had some wine so I'll update tomorrow

In short

- the engine is in and hole cut for the propshaft
- started to build the braces for the fuel tanks
- figuring out layout for the radio box

To answer some questions...

Will you be doing fpv with it? That would be cool. I love it when I see it done on RC cars.

No. I think it would be too disorientating. I have some GoPro footage from my Sprint Cat which I don't think will be as fast as this and that looks mental as it is - I'll get that on YouTube soon

Are you going to run this brushless electric, or petrol / nitro?

Nitro. 15cc. I've got a CMB 91RS M-Line to put in it.

We had a catamaran mould once, never ever finished it though!
See you mention fuel proofing, why are you going nitro rather than electric?

I just find it more interesting from an engineering and technical perspective. Electric is faster yes, but my goal is not to be the fastest thing on the lake. Nitro is more fun as it's more involved IMO.

Tbh I don't like gas/petrol engines. They're too loud for my tastes.

Glad there is some interest here. I'll keep the thread going

 

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A) following because this is bonkers. Pretty sure I saw you say "50mph" in the other thread!

B) PLEASE start wearing gloves or at least a mask to work with CF especially if filing and sanding it. It really is nasty stuff and it'll get into your skin and lungs.

I am wearing a mask at all times when there is CF particles around. Rest assured. Haven't been wearing gloves unless dealing with certain solvents though. It's recommended for CF Dust as well?

And yeah I am expecting something like 50mph from this

 

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Sorry to bring my work hat to the table but please please please wear proper PPE if you’re grinding or cutting carbon fibre.

Exposure through inhalation is harmful and not to be taken lightly. A simple paper FFP3 dust mask can reduce exposure levels by 10x (assuming you’re clean shaven and wear it properly) and they can be bought in packs of 100 for a few £.

Looks like an epic project, I read the OP and already realise I know nothing about boats! Lots of words that were alien to me

No absolutely! Safety first. Maybe I came across a bit blasé in previous posts however ultimately it is messing around with power tools, chemicals and lord knows what else and we've been doing this since I was a kid with guidance from Dad and we're still here with all fingers intact for a reason

I did actually check with a friend RE the carbon fibre and dust particles before I began cutting into it the other day and he gave the same advice regarding a mask straight away.

The mask I'm using is paper based with an actual filter on it. I'll post a pic later.

 

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Indeed nobody ever died of wearing a dust mask when they shouldn't have

 

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OK build log update 2, I'll try to pickup from where we left off last time.

So the holes were cut for the vents, then I made a wooden fixture out of ply to go under each vent hole and to allow the vents to sit at a pretty flush fitting with the body of the boat. After these were stuck in, the vents were then screwed into them, the resulting finish I am very happy with.

Rear ventilation done, it is time to work on the front. I have 3 air scoops to fit to the front of the boat for intake, mostly fitted around the front middle of the hull, giving some downward pressure to stop the boat flipping and keeping it a bit more stable. Also with them being in the middle and the rear vents being spread across the back this should (I believe, in theory) create a vacuum and help pull the air through the boat.

Approximate position decided after trailing a few options, this was my preference.

First one fitted

Remaining fitted

Next up is autobailers. Typically I fit/have fitted just 1 per corner/spontoon but I am going balls to the walls with this so I have double up, fitting four in total. No boat ever complained of removed water too quickly from it right?

Initially my main goal was to get the external stuff done first as it generally generates the most mess and I am trying to protect the engine from flying particles unnecessarily entering the engine. That being said, pretty much all the externals is now done and its time to focus on the internals, which brings me to the engine.

Some have asked what will be going in it. I've chosen a CMB 91rs M-Line which is a 15cc nitro engine. I went with this for a few reasons...

- My brother has a gas engined, and frankly the amount of maintenance he has to perform on it every single week is off-putting. I am not in the UK often enough to maintain it properly, plus they're so loud you can't really hear yourself think when they're running. It is annoying to me.
- Electric whilst will be the fastest...is a bit too disconnected in this instance
- I have always wanted a CMB engine, they're the best in the business. Hands down.
- The CMB 91 M-Line is rated for 7.0bhp, the Tiger King 27cc petrol engines (like my brother has) are at 7.6bhp. There is also a significant weight difference between them, with mine being much lighter which I believe will make up the difference. Although frankly speaking, I am not trying to be the fastest on the lake anyway.

Speaking of the engine, here it is.

(ignore the fact the engine mounts are upside here, I did not realise at the time of taking and this has been since corrected )

Now, unfortunately I did not take any photos of the engine mounts being fitted to the rails inside the boat, they're pretty clear in a few photos time but after much measuring and double checking they went in and the engine is now "in"

From here the next step is the prop-shaft. This also involves cutting a strip out of the hull along the bottom to allow the prop-shaft to pass through to the prop-strut. One chance at getting this right *gulp*

Measurements taken, boat masked up for guidance and then moved outside due to pending carbon fibre dust...

One of these...

Safety first!

Now we have a hole!

Test fit with prop-shaft without brass holder

Angle looks good.

Overall view of the boat.

To fix the prop-shaft in place I really need guidance from Dad here, it is the only part of the boat I am just not sure or confidence in doing, this will be done tomorrow morning. In the meantime, I did a bit more and got the fuel tanks in place.

First I removed the engine (much easier to fit/remove tanks with the engine not in the way as they will sit directly behind/infront of the engine just under the air vents) - then I made a backplate out of ply and 2 additional front wooden guides to keep them in place. On the backplate I cut some velcro to fit then glued this into place and the front guides - this has resulted in snug fitting not moving but yet at the same time removable tanks (if needed)

I also fitted the mounts for the radio electronics box arm to hold it in place, quick test fit shows its holding well (I picked up the entire boat with just the radio box and it didn't move, good enough) (also totally forgot to photograph the wooden backplate before putting the tanks in, doh!)

While waiting for Dad to be able to fit the prop-shaft I can work on the layout of the radio box. I have been working on this on and off over the last 2 days. But first, a couple of things to note. First is the servo for the rudder, this is pretty special and certainly far from a "standard" one

It is a Hitec D956WP IP67 Waterproof digital servo. This has a crank torque of around 25kg - typical servos range from 1kg-5kg although for moderately sized boats an 11kg servo is pretty common. For those wondering, this is so when the boat is travelling at full speed you can snap the control stick left or right and it just will not hesitate in turning the rudder and moving a boat of this size regardless of the force of the water hitting it. If you ever build one, one thing you do not cheap out on is the rudder servo. It could be the difference between saving or losing your boat!

Next is the battery

I went with a LiFE battery over a standard one due to going for digital servos. Analog servos with traditional batteries "pulse" 50 times a second, however digital ones pulse 300 times a second, this is comparable to framerates on your monitor, more pulses equals smoother and more precise operation. To achieve this, you need a battery which can deliver this power requirement. The downside to these batteries if they are a bit err...delicate. So I made a holster for it inside the radio box.

Lined with bubble wrap so it does not feel any sharp impact and a tight fit of the fixed wood either side ensures it has a snug fit. You can actually pick up the radio box via the battery once its pushed in, meaning its unlikely to come lose during travel.

Also, to charge these you have to remove them from the boat as they can be very unstable and explode without warning - using a holster in this fashion allows it to be seated properly and removed with ease as required.

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That is it for this build log. I didn't really work on the boat today as we were out for the day, however I'll be piling more hours into this both tomorrow morning and evening (while taking other boats to the lake during the day! ) so I'll have more updates soon, the next one should be with the prop-shaft in place

Hope you're enjoying and thanks for reading!

 

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Side note, I've got time this evening. I'll see about getting some GoPro footage up from my other boat.

 

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How do people tend to rescue these in the water if the engine cuts, spark plug burns out etc? A friend used to run a pretty expensive electric one and whilst a lot of fun, I always wondered how he'd fetch it if there was a problem. Guess you could swim

Swimming isn't really an option, especially at this time of year. The waters are too cold and without the proper gear you could end up in trouble very fast!

Each decent club *usually* has a rescue boat, which often is a plastic bathtub of a hull and battery powered outboard engine, so if it cuts out....you jump in and go and get it

Before rescue boats or places without them people either bring fishing rods or you can now buy electric rescue boats which have big open arms on the front (think of SpaceX and Mr Steven) to go and push it back to you.

 

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Cheers Yadda

I was just totalling up, I think I've put around 40 hours labour into it so far - I could have cut some corners to save time but I wouldn't have been happy with the end result, so it suits me

Jobs left to do

- Prop-shaft, being done tomorrow
- Finish the radio box then installation (this is arguably the biggest job)
- Float tank install (I will get this done tomorrow as well)
- Lid fasteners (10min job)
- Sensor installation (RPM & Engine Temp)
- Plumbing

I would say with the exception of painting it the boat is around 65-70% completion - touch wood, all being well its going in the water next weekend.

 

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EDIT: Broken link, hang on.

 

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https://www.youtube.com/watch?v=aE228-ir9sQ&feature=youtu.be - this is better. The last was stuck at 720p.

 

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It's a lot more stable than I thought it would be, especially when crossing the other boat's wake.

That's a bonkers scale speed though. It doesn't hang around, does it!?

Hehe what amazes me is the acceleration of these. They can go from standstill to full speed in a couple of meters

And yeah, a few weeks back I had this in the water with 4 other boats at the same time, some others much bigger than this one and it cuts through the wake just fine. Incredibly stable boat considering its size of 42" - shame I did not have the GoPro on that time though. Maybe tomorrow will bring something. Lots of club regulars will be at the lake so it should be pretty chaotic at times

 

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Not a hobby I have ever seen much about but this looks like a really interesting build and those boats are insanely fast

Is there many crashes at the clubs?!

Funny you mention that. There was one crash today and one very very close call. I have the close call on video, I can sort that out later.

If you were to take into account the amount the boats are used Vs the amount of crashes there are, its practically nothing...then you have some days where it just keeps happening.

I'll do a proper build log update later. But today the propshaft was fitted (thanks to dad) and I did more work to the radio box. I fitted the power switch and breather.

Tomorrow I'll get the propshaft to finalized (the epoxy takes a full 24hrs to harden) and fit servos for the throttle and fuel mixture. Then if all continues to go well, begin making the mount for the rpm sensor.

 

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Time for another build update...

I'm finding this weirdly fascinating. I want to see it jump a big wake

Good! I'm glad its providing some interest to some

Picking up from the last build log, on Sunday morning we were in the shed early and Dad set about the propshaft job, the one job I just didn't know where to start with.

A few key things I was not aware of here, the brass part of the propshaft had to fit inside of the prop strut (which makes sense now i look back and think about it) - but as the brass section supplied did not slot inside it, we had to use pieces of a slightly smaller diameter brass tube to fit inside it, which would then slot into the prop strut. Once this fitted well, Dad proceeded to bend it into shape, how he did it...experience is patience is all I can use to describe it - we gradually, bit by bit, bent the brass tubing using his thumbs, hands and chest...very very slowly a bit at a time and check it constantly as he went...

Once you have the shaft in such a position, you then insert (oo er) the propshaft itself and secure it into the engine, then epoxy the whole lot together. This results in the propshaft being perfectly aligned with the engine reducing resistance and loss of power through unnecessary and movement between the engine & propshaft.

When it comes to applying epoxy, I taped up the bottom of the boat first to create a base, here is a shot half way through taping.

And applying the epoxy.

I left this to set overnight, and in the meantime continued work on the radio box. I added the waterproof power switch and breather port.

Continuing today the epoxy had set perfectly.

(you can see the piece of wood added, known as a skeg, to provide support to the propshaft against the water)

After this, I fitted the float chamber. This is to maintain consistent air pressure in the system regardless of the fuel content. This should provide more consistent powaaahhh

This has been fitted at a slightly forward facing angle to try and keep it more level when the boat is in motion.

Now comes the exciting bit, fitting the electronics. I got the throttle & fuel mixture servos fitted

After this I spent the rest of the afternoon linking up the rudder servo. Which involved cutting & drilling holes in the hull & radio box and fitting fixtures to allow the control arms through but keeping it watertight (oh and I fitted the receiver, its in the above photo next to the blue servo on the right) - I finished this up around 5pm and frankly for the radio its the most complex/hardest part of it.

Here is a short video of it working.

https://photos.app.goo.gl/1o3KVdxXUM4kk1hL7

I left it this evening with another layer of epoxy on the bottom of the boat, that should be it after that.

Tomorrows jobs should be:

- Link the throttle & fuel mixture servos to the radio
- Fit the temperature sensor (a very quick job)
- Fit the finished exhaust holder
- Fit the lid & fasteners
- Plumbing
- Balancing


....It is damn close to being finished now

 

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Today's work done so far

- Link the throttle & fuel mixture servos to the radio
- Fit the temperature sensor (a very quick job)
- Fit the finished exhaust holder

These are all complete.

Started the plumbing, now to fit the exhaust which has its own seperate complication (the angle of the manifold is now right) - so currently at Dad's workshop to see if it can be adjusted

 

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Will reply properly later Dereksdontrun

Along with a build log update. Boat is ready to hit the water tomorrow!

 

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OK so I have plenty to share on here including the final build log update but I know you're more excited to know how today went...

I have 2 statements from today

- It is fast...very...VERY fast
- It crashed!

Let me run through how it happened as I remember it and what transpired afterwards.

So we're at the lake. Todays objective is for the Orion to go around it and get it running as new engines and boats are often a bit of a nightmare to get running properly. Anyway, we're at the lake as you see above and Dad begins to set the boat up, he configures fuel mixture to run it very rich to ensure we do not start blowing glow plugs and to keep plenty of fuel in the engine. He checks it over, tries to start it, it fires instantly, throttle response is good, nothing else for it. He throws it in the water, I am with the controller.

It hits the water and instantly leaps out, I can't quite describe it. He throws it forward the engine has so much torque it goes from standstill to maybe 20ish mph in the space of about 2ft and actually jumped out of the water doing so and it began to skate forward quickly. Throttle is set to 50% and it is already going as fast as my other boat at full speed (confirmed 45mph)

Instantly check steering, we're good. Not as response and sharp as I would like and am used to with my smaller cat but I put this down to the sheer size of the thing. So start making laps around the lake, checking temp from the onboard sensor, its good. Here is where the problem started.

From my position the boat is at 12 o clock I try increasing the throttle marginally but its not making any difference, the engine is running too rich, understandable. Start to turn right as the boat is now at 2 o clock, and suddenly...explosion of noise, the engine has picked up and come on the exhaust pipe, and now is blasting along and I mean really really going, easily 50+ mph. I reduce throttle, no response ****! The speed is still increasing and I've lost steering, double ****!

Picture it, the boat is now travelling at roughly 55mph in a straight line towards the far right corner of the lake!

BANG

Boat hits the brush, engine is screaming. Try cutting throttle from the radio, nothing. Drop the controller and began sprinting down the lake towards it. All I am hoping is that the engine keeps going, if it stops suddenly then it's blown a conrod or similar and we're done for.

I made it to the boat and stuck my thumb over the carb to suffocate it and stop the engine.

The boat is looking a state at this point - the front of the boat has split open horizontally and one of the fuel tanks is on the ground infront of it, the other hanging out of the front, still attached. So the force of the impact has dislodged the tanks and with them being 500ml each and pretty much full the boat came to a sudden stop and they kept going and forced the front of the boat in two

Anyway, picked up the pieces and brought the boat back to the dock and began checking the engine. Compression is perfect, engine seems totally unharmed! Thank god for that - that was my biggest worry, the rest is nothing in comparison, if it had gone it would have been 850eur to replace it.

We put the boat in the car and continued the day at the lake (we took 4 boats overall) and decided to look later.

Fast forward a bit after a brilliant day at the lake. We got it home and investigated.

Here is what we think happened, and of which, its all totally my fault (live and learn!)

- The linkage between the throttle servo and carb was completely disconnected, like someone had pulled it apart. So this wasn't secure enough, also the carb on these are spring loaded to spring open to fully open. This explains the sudden explosion of power and accleration

- The rudder has 2 bolts in it, a thick metal one to hold it on and a small soft brass one to keep it facing downward. The idea of this is if the rudder were to hit a solid object the brass bolt would snap and it would avoid ripping it from the transom. When I was building it I accidentally sheered the brass bolt myself and FORGOT TO REPLACE IT - doh! It is entirely possible that as the boat sped up, the sheer force of the speed & water just pushed it upright. This explains the lack of steering

So yeah, lessons learned. Here is the front of the boat where all the damage is.

After getting it home, I removed all the hardware and cleaned it, the entire boat and all components were just completely covered in fuel thanks to the tanks and their little vacation they took. Afterwards Dad took a look at the damage. He gave it a thumbs up and said its an easy repair, he'll also reinforce the front of the boat in case we have any future mishaps

The sad note...I fly back to the Portugal tomorrow, so this thread will be a little quieter until January, which is when there will be more test runs. Also, there was no video footage, everyone was just a bit stunned at how it was moving and forgot to pull out a phone. The plan is for Dad to repair the hull in my absence and I'll reassemble the boat when I come back.

We are also discussing entering next years tournament. The boat shocked us all with its speed and agility enough to make us consider it. If that happens I'll keep this thread running with our antics from that

 

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Well, at least the engine should be run in.

Shame you're away until January. Thanks for the updates, I look forward to more when you're back.

I said this to Dad afterwards in the shed!

"Well thats probably run the engine in by now" - he laughed and commented saying on his one (he is going to order the same engine) he is just going to do the same as part of the run in process.

I might have some more info to share tomorrow, right now the boat is indoors drying out and tomorrow the repairs *should* begin before I fly back

 

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The thing is, if the engine had cooked, I would have been very annoyed at myself, but its fine. So I sit here now and laugh & smile about it. Understood where I went wrong, so we will repair...then have another go

With this hobby you have to take it with the not "if" you lose control but very much "when" you do. It IS going to happen at some point.

 

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Ah man, that's bad luck. One of my boats I could never get the electronics sealed (pressure tests and submerged in a bucket over night all good, but in use not good) so after 10 odd minutes of racing, would go out of control and up the bank. Always messy.

What was the radio box made out of?

We have 2 other boats which have radio boxes made from fiberglass with perspex lids and they have been awful. Consistently damp/wet inside even with breather holes made and its just rotting the components inside. Tonight we actually made the decision to change these out for something else. Too unreliable.