Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Pleasure boats, Sports, Race, Power and Leisure Boats: => Topic started by: Andy M on March 31, 2021, 08:12:14 pm
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I had a Robbe Proppy back in the 80s, fitted with radio gear and motor setup from a Tamiya Holiday buggy.
Sadly, I no longer have it.
Happily, I can make myself another one if I want. The original was moulded abs if I remember correctly, mine would be of different construction, and maybe a bit smaller.
I did some research online and couldnt find very much about it at all. I did find a few photos but not really a lot to use for producing a plan, I was hoping to produce something as close to the original model as possible but I suppose its not that much of an issue if I get it fairly close.
If anyone still has a Proppy or even a set of instructions, that would help me to get its proportions right.
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Have a look in the files section in 'model boat plans' group on facebook, I have seen similar design boats on there.
Also, check 'Aerofred' on the interweb, although mostly planes, there are lots of boat plans on there too and definitely some of similar designs/style to this.
Hope this helps.
Will
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Hi Will, I am not on facebook but I have some of the plans from aerofred, I also found some more useful Proppy pictures and an article from a french magazine too. There is some stuff out there, it is just a case of getting your search aimed in the right direction.
My project might end up looking slightly different as I cant mould anything near this size with my vacuum former.
I still have a few boats to finish off, this project is still in the planning stage. I have a lot of options to consider just now, I will narrow these down closer to building time.
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I will have a look through my plans and see if I have any similar ones.
If so, I'll send you a message.
Will
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Thanks very much. I have used one of the proppy pics I have to produce a cornflake box cardboard cutout at the rough proportions of the proppy. It is only a top view so far. I have a couple of ideas, I might use the same brushless setup that my 3 boat selection is going to use and scale the 'proppy copy' down a bit to suit it, but I also have a brushless fan unit of the same type as I use in a 2 metre span camera plane, it would need a slightly bigger version of the proppy as it is a bit of a beast. Not sure which way I am going to go yet, but I like to go through all my options first.
All help is much appreciated. Thanks
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No problem.
My plans are all PDF, so you would be able to scale one to suit the motor size O0
I'll have a look tonight when I get home and see what I have that may suit.
Will be in touch later.
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Brilliant, many thanks.
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Andy,
Check your messages.
Will
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Did you get my email Andy?
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Hi Will, I did get it, many thanks again, I have just had a quick look, they all seem pretty similar in plan view to the proppy and the cardboard cutout I made. I am unsure which one I would go for, I will adjust construction to suit what I have. It will probably be an average of the 3 plans, the proppy and my carboard sketch. As for size, I think my motor setup from Rorqual would be plenty for a hydro a fair bit/much bigger than the model sizes I am building at the moment. I was considering a possible depron version, but I will decide later.
Thanks again, Andy
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Here is the cardboard outline I made, based loosely on robbe proppy proportions. It is 66cm (26 inches long. Is this too much of a size jump for my Rorqual motor? After trying the Rorqual, I wouldnt say so. I could be wrong though.
I am probably going to do a depron version so the actual hull will be light.
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If the hull is going to be made of Depron, then no, definitely not too big.
In fact, I would think that you could get away with making it bigger even if you wanted to.
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I had a look at the plans I was sent, pretty similar outlines to the Robbe Proppy and my cardboard cutout plan view.
I have some 9mm depron, so I decided to draw round my cardboard cutout, using the nicest looking half, then flipping it over to draw the other half.
I drew up sponsons, using the outline again, then I modified them so that it will sit a bit closer to the water. Prop angle and motor position were decided. Motor mount is a tough bit of lite ply, or a light bit of tough ply. Anyway 3 holes were drilled for motor screws and shaft. Motor mount done.
Cockpit/hatch sides were made up from 9 mm at front and 6mm hatch sides, left to dry then glued in, motor and mount will be fitted a bit later.
Looking not bad so far. Weight so far.... 3 ounces! Looking as if it going to end up pretty light, still a fair bit of skinning to go on yet, it is 3mm depron, so not very heavy.
I will hopefully get a chance to get the framework all sanded up later, ready to accept the skins.
As it is going to use the motor setup from Rorqual, I know it has more than enough power, maybe try this one on 2s pack first. The hydro looks huge compared to Rorqual so I expect it to handle the power a bit better, it is much wider so shouldnt just torque roll to inverted. Hopefully! 😁
A lot of my models are experimental, built with me not knowing how they are going to perform. As I enjoy the build so much, if it sails (or flies or drives, in the case of planes and ground vehicles) well, thats an added bonus.
Anyway, will stick more photos on as it progresses.
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Managed to get the sponsons done, they have still to be sanded. Next job will be to make up propshaft mounting. I am going to use 2 layers of 1/8 liteply. This will be keyed into the hull and possibly extend up into a former to brace it up.
Also added small bulkhead piece where the nose/bow skin and the curved top side skins will meet. Nearly ready for skinning, bit of sanding and maybe a few more bracing bits around the front to keep the profile and stiffen it up a bit.
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You are extremely industrious Andy!
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Thanks, I build a lot of stuff when I am in the mood.
I realised I wasnt going to get actual plans for the proppy as it was a moulded hull, so I just went ahead with my own version, its ended up pretty close, enough to suit me anyway.
A few more bracing pieces glued in at the front end, once these were set, the front end got a good sanding over, ready for the front skin. Sponson skins were also sanded to final shape.
Not sure how it would form round the front, I intended to use one piece for the skin, it had to go round a fairly curved front shape, with a little bit of curvature at the rear to meet the rear side skins.
I was a bit worried in case I made a mess at this stage, using uhu por, you dont get much repositioning once it has grabbed when you use it as a contact adhesive. I had done my planning right, and also got the skin where I wanted before pressing it together around the bow. The rest flowed round the way I hoped, and I left it to set for a while before glueing on rear side 'decks'.
These went on very easily with a fairly good transition to the bow section.
Starting to look good now, even if I do say so myself. 😁
Photos show size compared to Rorqual, which I tried the power system in, finding out it was far too much for the tiny balsa boat.
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All the top skin edges have still to be trimmed and sanded to final shape.
Hopefully get my propshaft support made up tomorrow and see about getting the motor in soon.
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Although depron is known more as a material for building aircraft, I thought it would be worth trying a boat made from it. It has its limitations, but it has its advantages too, not least that it is not essential to paint it to waterproof it, the fact it is super light, and most of all.... I have some in my stock.😁
I did think about a swamp boat style model built from it and using a (very wild) brushless fan unit, but settled on the hydro. It isnt an exact copy of the Robbe Proppy, but close enough in style to remind me of the one I had in the 80s.
My original was painted matt black, this one should end up a bit brighter. Just need to think of a paint scheme.
There is still a fair bit to do on this model, hardpoints for rudder and propshaft have been built in. Motor and propshaft will hopefully be glued in later today if I get a chance. Liteply should be more than strong enough for these areas and still be pretty light compared to a 'standard' build using birch ply.
I dont forsee any need for buoyancy, the construction style I have chosen divides the hull into lots of watertight compartments, with a single, long open area that houses the motor, radio and battery. This is divided by a couple of additional bulkheads. I have still to decide how I am going to build the hatch, no rush, I will probably finish the hull first before I decide on the hatch details.
Very happy that I managed to glue the 3 top skin sections on without making any mistakes. There was plenty of opportunity for it to go pearshaped during the glueing. Good planning and an uninterupted building session helped get it together nicely.
It is a straightforward build resulting in a fairly light structure. Not as durable as a ply build, but way cheaper and relatively robust under normal use.
Depron seems to attract dents, but with some care, these can mostly be avoided. Not crashing will definately help preserve it, as with any vehicle. Worst case scenario is that I need to remove a damaged bit and splice in a new piece.
I gave the top skins a sand as well, so I am getting through my 'still to do' list steadily
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Rudder servo fitted, motor mounted and propshaft epoxied in place. Heavy duty thread to stitch propshaft end to support, superglued then epoxy to seal it. Might not need it but I want it to stay there.
I have to paint the propshaft support and rudder lower support plate before I can do any testing. I used slow setting epoxy as that was all I had. My shed is pretty cold just now, even with my stove on, so it is taking a while to set. The rudder tube is supported by the 1/32 ply lower plate, 9mm depron hull bottom, a 1/8 liteply plate on top of the depron and another 1/8 liteply plate 30mm above that, so hopefully its not going to move at all.
I managed to break a blade off my prop, waaah! Not too bad though, as I have a spare one since I cant find the shaft from my other propshaft set.
Hopefully my epoxy will have set by tonight so I can start painting the external wood bits. The inside wooden parts of the rudder support and propshaft support have had a coat of paint, I will do one more coat later if I am doing the outside bits.
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Propshaft support and rudder tube reinforcing plate have had 2 coats of paint, I fitted 2 liteply plates to hold my speed controller in place, this is cable tied on, through the 2 plates and 9mm depron bulkhead so it isnt going anywhere.
I had to make up a couple of 7.4v packs as I didnt have any with the same connector, the packs are split so they can fit either side of the inner bit of propshaft support.
It was now ready for a bath test, it sits nice on the water and has good rudder control at the low speed that bath testing restricts me to.
The weather is terrible just now so further testing will need to wait.
I suppose this will give me time to get some kind of paint scheme happening, I always find this a very difficult bit, actually picking a paint scheme I like. I will see what I can come up with....
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It looks amazing, what do you use to stick it all together ?
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Thanks very much.
I have used Uhu Por, its made for polystyrene, depron etc.
I have used about a tube and a half so far, about £7 worth. I could probably have used a bit less but I wanted to make sure it was all really well sealed.
Total weight so far, with all radio and ready to go with 7.4v 1500mah pack is 1 pound 7 ounces, not bad for a 26 inch boat.
It is experimental but I am pretty confident its going to go well.
The 9mm depron is a bit thick/heavy for flying models, at the size I have been doing anyway, so I figured this would be a good project to use it on.
It is a bit prone to dents though, I may have to add some balsa skins to the sponsons, or some alloy sheeting, the same stuff I used on my trailer. It might end up with quite sharp edges though, 1/64 ply would be better but I dont have any big enough bits.
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I have still to make up a hatch, not sure whether to try and copy the proppy one, I doubt I can get depron to curve that much without cracking or looking bad. I will see what I can manage, might just be flat topped for initial testing.
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Thought I would try some colour on it, not sure if I will keep going with this, its done the 'Blue Peter' way.... Sticky backed plastic, so it can come off if I dont like it. I didnt really plan it out very well as I am not sure if I have any more of it in my stock. Might end up with a different colour to finish it off, I will know tomorrow after an expedition to my attic.
As I said, I find that deciding on a colour scheme is really difficult, nearly as hard as picking what to build next. (or finish building😁)
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I managed to find more sticky plastic and finished off the main bit of my colour scheme. I still need to build a hatch, I would like it similar to the proppy, but I will be having a drinks bottle plastic cockpit which will end just in front of the start of the blue bit, probably a carved balsa front cone type front to it.
I tested the boat today, I had been told about hydros having a poor turning circle but this was definately not the case, I was able to turn in about 6 or 8 feet, at low speed obviously to start with. Might end up twitchy at higher speeds.
I can always turn it down a bit if required.
It ran nice up to about 1/4 throttle, getting up on the plane almost instantly and getting up to a higher speed than I managed with the Rorqual. No signs of torque roll even with sharp acceleration up to 1/4 throttle, why only 1/4 throttle?....
I thought it was drawing air in at the prop, it revved higher then the boat kind of slowed down sank in a bit and then it would go again up to about 1/4 again and do the same thing. I tried steering about to see if turning stopped it doing it. No difference, then with a very loud vibrating noise which buzzed water droplets into the air arround it..... It stopped moving, tried throttle again,, same. My coupling sleeve had separated from the shaft and come off, bit of damage to the hull but not burst through, need to check it later.
The boat looks as if it will be really quick, sits very stable on the water, accelerates really really quick to its coupling slip limited speed, once I sort this out, I will have a nice little boat that does look quite big. Good test though, very happy so far.
Another thing, I think the propshaft is too weedy, it is only 1.7mm with small nylon bearings, I think it is bowing with the centrifugal force then straightening out as the revs get up a bit. I might have to do some surgery, get the old shaft out and upgrade to a 4mm shaft. This would fit my coupling without needing to use the spacer I made up.
Need to submit a request to my financial manager (wife) and see if I can get one ordered up.
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That's one smart looking boat Andy and went together very quickly. Even with the increased build speed of depron, you sure don't hang about.
Glad to hear that the sea trials went pretty well. I'm sure that the 4mm shaft will sort things and as you say, the coupling won't need modifying then either.
A nice light, easy to transport model to throw in the back of the car and head for the water.
Look forward to seeing some action shots/video.
Will
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Thanks, I am going to try and improve my coupling and try and get a propshaft bush made out of nylon and pushed halfway up the tube to eliminate the bowing in the thin shaft.
I will get a pic of my improved coupling adapter, and propshaft mods. Shouldnt slip round, and I will loctite it as well.
Looks like it might end up too fast for the small bit of river we use. Turns really well tho, very impressed with that.
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Harry kindly sent me plans for building a Sea Rover, started on it last night. Not bad progress so far, looking forward to getting into a wood build after my depron one.
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I tried one of my 3d printed outboards on this boat, but it was extremely tail heavy, so I am going to fit a 4mm propshaft as I mentioned earlier, and get it running.
I am not sure which motor I will use, it may just be a 540 brushed. The boat is very light so a 540 might be enough. If not, there is always brushless.
The brushless I tried already with the 1.7mm propshaft went into one of my outboards on the Javelin, so I dont want to take it out just now.
I decided to leave the outboard bracketry on the hull to mount a rudder. The rudder is made from 2 bits selected from a bath panel and glued together with Tamiya plastic cement, the rudder bolts to a modified outboard bracket. It pivots on a 4mm brass pin and lines up exactly with the servo pushrod I used for the outboard.
There is a rudder tube in the boat already, but it is just a bit of transmitter aerial, I used the rudder on another project. I will just bung the end of it before use, if I remember. 😁
I have a propshaft that is close to the size needed but I will need to check it with the coupling and motor attached to know for sure.
If not, I will order one soon.
The hydro looked as if it was going to be quick when it had its maiden voyage and shook its coupling loose.
The outboard trial on it wasnt good so I have wanted to see it go properly.
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I originally built this boat as a quick build to try the original brushless setup. It had an air of disposability about it, like a polystyrene cup.
It has had some changes since building it, some balsa sheeting to try and reduce ding-ability and now heading on towards its 3rd power setup. I have removed the original mount for the 380 sized brushless and will make up a new one for the 540 brushed motor.
It does look its age, but it still runs nicely, I gave it a good clean out with contact cleaner and oiled the bearings before trying it. It hasnt had much use, so should be fine.
The ply mount came out relatively easily, I flexed the depron sides a bit and the epoxy let go enough to wiggle and snap it out . In normal use it would never flex that way so I am happy to do the new mount the same way.
I still get the feeling it is not really a 'proper' boat, and at times I have wondered if it is worth the effort, why not just do a proper ply version?
As it was my own design, and not having seen it going properly yet... (I dont even know if it can?) it seems a better idea to wait till I get the depron version working first before embarking on a more durable, maybe slightly larger ply version.
I think if I get this one running nice, I might be tempted to skip building a ply version. It would be a good bit heavier even at the same size.
I have my stretched Javelin twin motor project to build (not even finished my plan yet)
I have a lot of projects on the go at the moment and more lined up.
Projects can happen at any time......
I made the 'mistake?' of finding a plane wing in my storage area, looked quite good condition, so I cleaned it, looked really good condition, I repaired a tear in the solarfilm and it looks almost as good as new! Awesome.... But now I feel I have to build a plane to suit it...... 😁
Then I found another wing, which is the same chord, so it would also fit the same plane but is 2 feet extra span, effectively making a motor glider version, if I get round to building it.
Anyway, back to boats, I will get a motor mount made up for the hydro, I think my propshaft is close to the right length, depends on which coupling I have that I can use, but the process of extracting the original weedy propshaft has left an oversized hole. The ply propshaft mount/keel section is still very strong, so any loads will be taken by this, I really just need to seal the hole. Maybe a thin ply plate cut out to fit around shaft and keel.
I am not really that far away from getting it running.
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The rough painted blue bit is mostly under the canopy front edge, so not usually seen, just realised how rough it looks. 😁