Jeremy_H

Self adhesive paint masks mate, varying from Frisk Film and another better one I forget the name of, fine line masking tape, and a particular removable flexible sign vinyl I use. Nowadays I cut the masks on a sign plotter, but for twenty years or so I cut them by hand, there's a way to do that quite accurately. So the mask is cut off the job and applied to it using a transfer tape. If you pop over to racairboats.net forum there's a far more detailed build thread on there, the masks are shown.

After a day of signwriting it's now ready for lacquer:

arcdude

Thanks for the tip rcairboats.net Jeremy, I have visited the site before. That is top quality workmanship! vid please....

Jeremy_H

I'll see what I can do to make a vid later .

Jeremy_H

Shiny bits!

Jeremy_H

Final Lacquer:

arcdude

Looking great there Jeremy, You can lacquer right over the decal material without any issue, bubbling and so on?

Jeremy_H

So long as the lacquer is not over thinned it's fine, if you wet apply the decals leave a day for moisture to escape. This is a new lacquer to me and I've had a few issues, but the only decal on this boat is the rc airboats logos and they are OK

Jeremy_H

A few hiccups with the lacquer, but good enough to crack on with it. Back to the hardware now for fitout.

arcdude

Looks fantastic there Jeremy, you could have yourself a part time job there excellent quality. What are you planning on using for servo's and control rods?

Jeremy_H

I did used to do custom paint for a living, I'm looking into doing other folks boats and have a couple of club members race hulls at the moment, I'm looking at practicality right now as I need a proper spray booth if I'm going down that road, doing these guys boats and mine is helping to identify whether I can take it on. I already do stuff in my own time for extra income in the machine shop, but it's always nice to have other strings to the bow as this is how I like to source funds for my hobby's.

For controls I've deviated in a big way from the drawings. The balance point seems to be something that's not well defined, I can imagine that engine weight and thrust levels would mean that each will be quite different, but there does seem to be a wide scope of balance points that will work judging by reading various folks reports, with a suggestion that a slightly nose light boat is the optimum. I'm not going to get that, but I can edge towards it more readily by shifting all of the radio gear to the back of the boat, hence the access hatch in between the pylon, and none in the cockpit/radio box.

If there's one thing that bugs me about controls it's those that don't neutralise accurately, and the best way to achieve that is by having stiff direct links with nothing in between. I can do that to a degree with the servos in the aft end, but bellows will need to be there for sealing. As it happens the control rods are what I made up yesterday, these are Carbon Fibre, threaded and epoxied into ferrules (tested with 10kg load) for adjustment of ball end connectors. After some hunting around I found some nice bellows that are 9mm wide at one end tapering down to a 2mm hole the other, these allow the side to side movement of the rod created by the arc of the control movement without binding. The hull side of the bellows is fixed to ferrules I made which will be epoxied into the transom for the rudder, and on the deck just inside the pylon for the throttle:



The throttle linkage will be almost vertical from the deck up to the carb.

For the throttle servo I'm using a classic HiTec HS81, a quite fast mini servo with 2.6kg/cm pull. I'm using the plastic gear version as the forces on that link are minimal, frankly the bellows will put up more resistance that the carb barrel will.

For the rudder I'm trying an Allturn AAS-750MG, an 11.2kg/cm high speed servo with metal gears. Seems too cheap for the claims they make, we'll see.

I want to anodise the ferrules before fitting, but I want to make up the turn fit parts first to complete the aluminium parts, I'll then anodise the lot including re-doing the rudder and turn fin bracket to a deep black.

arcdude

I knew there had to be some professional background at play for the quality of workmanship. Judging from video's that I've seen I would have to agree to the light front end and thrust angle to keep the nose down, at least it offers adjustability to find the best angle. I have spoken to many giant scale flyers and they report no problem or failure using the 256 plastic control rods which somewhat surprised me. I too will be using a HiTec HS81 servo for the throttle as I already have it from another model. I'm not familiar with the Allturn brand of servo's, but that seems to exert enough Kg for the steering and transitioning to carbon fiber rod should eliminate the heat and cold related expansion seen in plastic ones. Nicely done Jeremy

Jeremy_H

Re anodized the aluminium parts today, that's everything needed bar the hatch to finish the boat:

arcdude

Beautifully done there Jeremy.

Jeremy_H

Quite an easy process to be honest arcdude, just some nasty chemicals to control.

Radio install is complete, and the rudder and turn fin bracket are final fitted:

arcdude

Looks great! Jeremy what is the container under the motor mount with what appears to be a screw on lid?

Jeremy_H

That does kinda look like a plastic container is these pics. It's the radio box in the tub, which is capped with a 6mm thick Acrylic plate lid with a bottle top epoxied to it for switch and charging access. a foam strip will surround the hatch edge to stop vibration. Sorry for the naff pic, but it's clearer in this one:




The hatch will be sealed with profiled sign vinyl. I've not cut them yet, but here's the same principle on Miss FivePoint, the vinyl is the same colour as the paint, but you can just make out the edge where it's over red paint:


I figured putting a hatch under water on that happy accident boat would be a good test

Cheap and cheerful waterproofness

arcdude

I had considered a similar idea by cutting the top off a screw on cap container, it seems to be one of the safest ways to assure water tightness and ease of charging and so on. I don't quite understand how you fastened it to the radio box, there is no obvious fasteners visible, how is it removed to make changes or repairs? It does look like a very clean install and water tightness shouldn't be an issue.

Jeremy_H

This is clearer...

I use the tops of a particular type of plastic drinks bottle. There's plenty like this around, they have collars around the neck like a flange, which makes them dead easy to fit and seal. So this one is just epoxied into a holesaw cut hole. The bubble you can see in the Acrylic is a milled recess in the underside to clear the servo cables coming out of the receiver, they just rubbed against the lid before. The lid is held down with a single piece of sign vinyl. Stronger than hatch tape, needs a sound surface to stick to. I put in a little tab at the rear to aid removal.



The boat is now finished and ready to run this weekend:

arcdude

I'll tell you Jeremy that looks like it belongs on a show room floor on display, beautifully done! I like the idea of the vinyl to seal the radio box and I agree it certainly looks better than tape. I look forward to the video, enjoy the maiden voyage.

Jeremy_H

Thank you

Turns out it works too

Here's the Maiden/Still running in/Shakedown run, first time in the water. A better vid is to follow.

https://www.youtube.com/watch?v=i_0iIfQuLzc

arcdude

That looks like it scoots along quite nicely, I'm guessing by the speed you were taking it easy. Is there a turning issue I heard you mention you need more rudder. All in all it appears to be a very successful project, well done.

Jeremy_H

Yeah I'm still running the motor in. I use temperature to monitor this and it's getting better every run, i.e. I can sustain full throttle longer each time without getting too hot. Sam's same engine took about an hour of running to loosen up, this one is following the same pattern. Also, there's no doubt about my driving abilities here, threading this two foot wide thing through the buoys is quite tricky for me.

It's too soon to say what's occurring with the steering for sure, but it seems that the bite off the outside sponson which provides a lot of reaction force to turn is lost at lower throttles, it starts drifting at the front whilst the rear of the tub digs in at lower throttles, so there's a bit of resistance to turning at those speeds. Throttle it a bit and the bite is there, but too much and it'll flip, it's a balancing act .

Early days, but yes, it's very pleasing and can only get better. Here's a better video which does show some faster stuff, and a couple of boo boo's

http://youtu.be/WvSlm7Hwr3o

arcdude

Spectacular wipe out! That is a nice machine for sure. I kind of got the same idea in regards to the digging in at low speed, by design the engine thrust push's it up onto plane and req's adequate speed to keep it there, run her wide open lad and get used to it, great fun!!

Jeremy_H

Went out again today, rough conditions but learnt some more. The power/sponsons thing is a little different, because the thrust forces the bow down, the sponsons are depressed into the water providing an edge to work with to resist side movement, at those speeds if you throttle off the push on the nose is gone and the boat rides up fully, literally on the trailing edge of the sponson bottom. So now there is no sides in the water to resist slip and it feels like a Deer on ice . The boat needs little power to plane, once it's up a high idle will keep the deck clear of the water.

However, skipping over ripples is making it worse, at far side of the pond it was sheltered from the wind and it was much better over there. So its performance in winds is good for a three pointer, I'm looking forward to some calmer waters to explore it more. Right now attention is all about turn fins.

Some pics from today:



To be honest there's a lot more to this boat than meets the eye. I've found it prompting changes to my own designs, hidden in its apparent simplicity there are some clever things going on. I'm going to put my building attention to the twin engine boat now, but I'll be fiddling with turn fins in between. The guys on rcairboats.net have given me some good pointers and I've made a start, but there's plenty more to look into to see if this boat can be made to accommodate our small lake better. I also want to be able to turn right reasonably well with a fin on.

And yeah the wipeouts are usually good viewing . I've had a fair few today with it blowing a hooley, even simply having the boat blown over whilst cruising, but I've not got the stage of a full 360 and carry on with engine running bit right yet!!

arcdude

One thought on the turning fins that I've been thinking about is a fin on both sides with a curve inward that way it should hold the turn on the inside and the outside fin should ride up being curved and assisting in the turning in either direction.