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[DJW]

Morning All


The plan is to build / develop a water skier for my Riva Aquarama currently in build, I'm keeping this thread separate to the main log.


So the broad outline is 1/10 scale, figure still to be decided but 6 to 7 inches tall, two skis. Second stage is to make it steerable... 


I've build one model skier in the past, its been running on and off for about 15 years, built around the Pink Panther figure from a happy meal... I'm the first to admit it's pretty crude. Last summer I played around with making it steerable, with promising results, so now ready to move to a new ski build.


Here's the Panther on the lake:





And on my desk:





I've found there are a few start points to get to a basic running stage:


1. The majority of the towing force is sent straight to the skis, with the line to the handle / figure just there for balance.
2. The ski's have to be a little wider apart than strict scale and held in position. I've used piano wire.
3. The ski's run parallel, but have to have a slight 'angle in', so they don't run flat. This seems to add stability.
4. The skier has to be balanced when stationary in the water so is in the correct start position to be pulled out of the water. So this means balanced on three points, that's the two skis, and the figure. The ski's are weighted / balanced so that the tips just clear the water at rest. The ski's are plywood, with brass fins, and brass plates at the tail end to get the balance right. The figure weighted / balanced with a buoyant lifejacket so at rest the head and part of the lifejacket clear the water..
5. The ski's are slightly longer and wider (+15%) than full size so they can operate at more scale like speed. (Slower)
6. CoG has to be low...


This pic shows the tow line adjusted to give a good running attitude for the skier:





Result is it's pretty reliable when running, pulls out of the water from rest without problems.  Just have to keep an eye where the ducks are so I don't decapitate them... 


All I have for the new build is this at the moment:





But if there's interest I'll keep posting as new build progresses. Regarding the steering... I tested the pink Panther by running two thin fishing lines down the main tow line, one connected to each ski, and in the boat, connected to a dual sided servo arm.  This resulted in the Panther changing its angle relative to the boat, but only a little movement from being central to the boats wake.  I added a couple of small fins to the inner edge of the front portion of the skis, this did make a difference.  The Panther was indeed sliding left and right of the centre of the boat wake.  Maybe pivoting the skis along their length for be best approach to change direction. BTW. the white cord above is the braided type with a centre set of filaments. I'm thinking that I replace the centre filaments with the two runs of fishing line to keep them hidden... 


Would be great to hear from anyone else who's tried and succeeded, or failed...


Aquarama build log is here: [size=78%]https://www.modelboatmayhem.co.uk/forum/index.php/topic,64276.0.html[/size]


Best regards
David.

[Shipmate60]

I am following this with interest.


Bob

[Tug Fanatic]

........................4. The skier has to be balanced when stationary in the water so is in the correct start position to be pulled out of the water. So this means balanced on three points, that's the two skis, and the figure. The ski's are weighted / balanced so that the tips just clear the water at rest. The ski's are plywood, with brass fins, and brass plates at the tail end to get the balance right. The figure weighted / balanced with a buoyant lifejacket so at rest the head and part of the lifejacket clear the water.....................................

I don't really understand this. Are you saying that the skier when stationary needs to be in much the same position as when moving ( with the nose of the skis slightly high) or that the skier should be ????????????

It is the reference to "balanced on three points, that's the two skis, and the figure" and "so at rest the head and part of the lifejacket clear the water" that I don't understand.

[ChrisF]

Interesting project David

I did read about someone else's build somewhere! May have been Model Boats magazine?

Chris

[Capt Podge]

This looks interesting - I'll tag along as well.


Regards,
Ray.

[radiojoe]

David there is always interest in what ever our members do especially when it's something different, of course I'll follow 


Joe

[ChrisF]

David, yes it was Model Boats - October 2019. You were ahead of the game!

Used a Barbie doll which does look good behind the boat.

Chris

[DJW]

Hi Everyone


Thanks for encouraging responses. 



@TF, Sorry if I wasn't clear, I did get a bit tied up trying to explain it...  When the skier is at rest, just the front tips of the skis are out of the water by about 3cm, then the skiers head with just a bit of lifejacket above the water, so maybe 3cm ish too. (These skis are 17cm long.) This is achieved by altering the overall buoyancy. Brass weight on the tail end of the skis keeps the tail ends down, naturally the skis want to float so the tips come to the surface. I used a bit of closed cell foam (pipe lagging..) for the lifejacket on the skier. So it's all about the balance at this rest state.  Then a gentle pull from the boat idling along gets the skis in the correct direction, followed by more power to pull the skier up and out. The main pull at this time is on the two skis, so they automatically get pulled into the correct position.


Here's a couple of pics to illustrate the attitude at rest, white line is water surface:





And being towed, the white line indicates water surface:





This pic also shows the three tow line in tension, so trimming these alters the towing attitude.


@ ChrisF. I didn't see that in MB, but will try to find the article, thanks. I have seen a few examples of model boat skiers on YouTube, but I'm keen not to use a rigid line, or a perspex plate between the skis, it can be done with a more conventional approach...  And the steering I've not seen, so am keen to try it..!


Basically its a fun and challenging project that I'd like to get right...   Aim it to run this in parallel with the Aquarama build, but get it on the water and tested so the skier is ready for the Aquarama.


Whatever happens I'll report back..!


Best regards to all
David.

[Tug Fanatic]

David,
That makes perfect sense now. Thank you.
Following.

[DaveM]

I've been asked to pass this on, so happy to do so.
DM

[DJW]

Hi Dave


Wow, that's an interesting document, and a few years old.  Thanks for uploading.


Best regards
David.

[SailorGreg]

BTW. the white cord above is the braided type with a centre set of filaments. I'm thinking that I replace the centre filaments with the two runs of fishing line to keep them hidden... 

Sounds an attractive idea, but I suspect that as tension comes on the towing line, the outer braid will stretch and compress, trapping your steering lines in a sort of Chinese finger trap.  But worth a little experiment to see if it works.

Greg

[DJW]

Morning All


Some progress with the skis, the skis were soaked, then clamped to get a decent shape and upturn of the tips:








Resulting in these:








Next step with the skis will be to shape some brass fins. Then a sealing coat of epoxy.  Eventual colour scheme to match the Aquarama, i.e. gloss mahogany topside, white and red accents.


I've ordered some 1/10 scale 3D printed figurines from a German supplier (recommended on this forum), two for the boat itself, and one to be the skier.  That one will need some surgery to get into a skiing stance, if I can make it work fine, otherwise plan B. The only plan B I have is a custom 3D printed skier, that's ideal from the skiing point of view, not so ideal from the wallet (and so wife) point of view.  Maybe I need a plan C...   


BTW. @SailorGreg. I've been pondering your point re the outer braid tightening, and agree you could well be right.  I think the solution would be to run a third fishing line down the inside of the braid, and tension so that the outer braid takes no real force, its just there to keep the lines tidy.


Best regards to all.
David.

[ChrisF]

Hi David

Will look really good when all painted up etc.

Where are you getting the figures from? I keep looking around for some 1:12 for my Fairey builds but haven't found any I'm happy with.

Chris

[DJW]

Hi Chris


I started a thread here: [size=78%]https://www.modelboatmayhem.co.uk/forum/index.php/topic,64880.0.html[/size]


And was recommended to this site for 1/10 scale: [/size][size=78%]https://www.dsd-uhlig.de/Figuren/M-1-10[/size]


They're not too expensive to give them a try, and seem quite lightweight. I'll put more details up when I get them.


But they're 1/10...  Not sure they will be of use to you.


Best regards
David.

[ChrisF]

Hi David

Thanks. I thought he might be 3D printing so able to do at different scales. The search continues!

Chris

[DJW]

Morning All


A little progress with the skis, shaping is now complete, I've cut out some brass fins, and created a slot in the rear tip of each ski to take the fins:





A sealing coat of resin has been applied and sanded back:





Here's the fins, I'll take the slot all way through and solder on a brass plate...  This will be stronger and provide the ballast to get the skis sitting correctly.



A bit of a go-slow til I get the skier...  Should be mid/end of this week.


Best regards to all
David.

[DJW]

Afternoon All


Bit of progress.  I now have 'Claudia', a 1/10 scale German lady. She's going to need a little surgery before getting on the Skis...





The skis need to run wider for stability, and her arms need straightening out...


Skis now have a couple of coats of white on the bottom.


I've also taken delivery of the piano wire and a few other bits.





I have a method in mind to control the direction / steering of the skier / skis using the multiple lines approach.


Reach for the Valium now... 


I'll try to get it mocked up in next update to illustrate, but two main points:


1. The skis will be slightly 'toe out', so closer at the tail end, then pulling from the boat on the right ski line will make right ski line up with the boat, and the left ski angle out further and so pull to the left.
2. Pulling on the right ski line as above will also lift the right edges of both skis...  So make them both want to go left.


Well that's the start of the plan.


Best regards to all.
David.

[Capt Podge]

Sounds like there will be some tweaking to be done during the trials - most intriguing... looking forward to your next update 


Regards,
Ray.

[Umi_Ryuzuki]

Your methodology is very similar to mine.
I did the same thing to a Gonzo muppet  happy meal toy.Formed the skis, and gave them a V shape and used a single line to tow, but
cemented between the skis to keep the towing point low.
In a turn, he would flop around freestyle and then come up and ski as the ride straightened.
The 1/10 scale should be fun. 

[DJW]

Morning All


@Umi, thanks for your comments.


Some slight progress with the skis, I've been a bit busy with planking stage of the Aquarama.


So I've created the two piano wire spacers, the forward one is slightly wider to give the 'toe out', and it has the two 'eyes' to lead the pair of tow lines through:





I've then clipped the uprights so they can become flexible joints when inserted into silicone pipe:








So this then allows the skis to pitch left and right, so here by lifting the right hand edge of both skis:





Trouble is it's not rigid in the fore / aft direction.  That will have to come from the skier, who will also have to not be solid mounted to the skis...


Best regards
David.

[DJW]

Afternoon All


Just thought this thread needed an update...  Not made too much progress on the actual skier, but have been busy with the Aquarama and making the mods to the boat that accommodate and control the skier.


My key aim is to make the skier steerable, so to that end I've made up a reasonably faithful to full sized ski pole for the Aquarama. It's brass but will be chromed. Its got a 1mm hole up the middle, and two servos underneath. They will give a push / pull to the left and right (fishing) lines that will provide the steering effect.  The ski pole is being mounted in same position as the full size build, so on the Amati build that's on the removable rear hatch, so that's now held in place by two 3mm stainless screws.


This shows some of the ski hardware in place on the boat build:







This the rear 'slipway' varnished and upholstered:





And the servos in place underneath:





I'm installing a FrSky RC system, one of the programming features allows automated movement of the servos, so on a switch they will alternate direction and I can use a custom curve to control the slalom motion...


This is described in this video: https://www.youtube.com/watch?v=Rj3ynymx54Y at around 5m 50sec.


The video also explains the plan for use of a hold heading Gyro to keep the boat in a straight line when the skier is moving around.


The boat has move on a shade from the above pics, varnishing is done bar the final polish, running hardware is installed, as are the motors.  Working at the moment with the electronics.








Anyway, slower than I'd hoped, but still aiming to get that skier up and running.


Best regards to all.
David.

[DJW]

Afternoon All


Time for an update. The Aquarama is coming along:








Slower than I'd hoped, but there we are...


For those who've not seen the main thread, the boat has now seen the water for some testing...





On the skier front, I'm remaking the ski pole as the first version was too thin, it was 3mm, now its 3.5mm which is correct for scale with a 1mm hole up the middle.  Silver solder needs some trimming in the lathe then a good polish. (And eventual chroming.)





At the base there's a keyway to stop the pole rotating and coming out of the boat (unless I want it to), and at the top, a small 1mm exit under the towing eye for the control lines.


And here's a test of the ski line with a pair of control lines inserted. I'm starting at 2m of 'ski' line, then shorten to optimum length when I get it on the water. The control lines seem very smooth sliding through the braided outer even at 2m, I think if most of the tension goes through the control lines the braid shouldn't close up too much, we shall see.  Control lines are 0.12mm 2 pound fishing line.


This is both ends at the moment:





And inside the boat, the servo arms will have a couple of washers and a bold to clamp the control lines and keep them adjustable or removable, then feed the lines over a roller guide and into the base of the ski pole.





That's it for now...


David.

[ChrisF]

Fabulous build David and looking forward to seeing how the skier performs.

You have certainly gone the extra mile with the control of the boat and skier and incorporated things e.g. the gyro that most of us wouldn't even consider.

For many of us our builds tend to take longer than planned. I should have got at least a couple of mine on the water this year but failed!

Chris

[DJW]

Hi Chris


Good to know I'm not alone in taking the summer off from building... 


Just got a tricky part out of the way.  With the control lines threaded through the main 'rope', I need to get the main 'rope' sorted out and attached at the boat end without trapping the control lines.  So the control lines have been broken out a few inches short, then a loop created in the 'rope':








And the end buried, with a small amount of glue... 





So now we have a removable ski pole, with a removable rope, with control lines that can reach the skier...





And in position on the slipway:





Going to get some progress on the skier next I think.


Best regards to all.
David.