Simon.O.

This a design of mine based on the vessel “Cable & Wireless adventurer” designed by U.K architect Nigel Irens. A variation of Parsons “Tubinia”.
It is 700mm long and 65mm wide on the main hull
Flat bottom with a draught of 25mm.
Stock 540 motor with a 7”x5” prop
Tamiya 60A Fwd/rev esc
Stock 2000mAh 6cell pack

This has gone through a few changes in the last couple of days.
Air steer with the small rudder was no good
I enlarged the rudder with a piece of coreflute and it turned well, however it also had a horrible tendancy to heel over during full power turns and try to dip one of the outer hulls. That would cause a capsize and be all bad news.
I have now ditched the large air rudder and fitted two water rudders that run flat with the bottom to avoid weeds and surface debis.
These I knocked up in about an hour using old rc car suspension arms etc.
It still has a tendancy to heel so now I am adding some depth the stabilizing hulls, and will ditch the air rudder all together.
It runs very well in a straight line and would outrun the “toy type” rtr boats. The bow wave almost reaches the deck as to be expected of a wave piercing hull.
I will continue to develop it and report back with my findings.
Things to try……..stabilizing foils, moveable trim foils, spherical sub-surface bows for the outer hulls………………I need a beer

Justaddwata

My Feedback: (3)

Nice concept boat - is this the hull she is styled after?

I snagged this shot last year in Auckland when she was on display at the boatshow.

Mr Cajun Gator

Kinda like the canard style hulls. To use air rudders, dual rudders will work best. With dual rudders, they can be pitched and/or toed, this will control which direction the boat leans in a turn. It would take some playing around with to know just how much angle the rudders will need.
Nice work

Simon.O.

I was thinking along those lines and put it in the two hard basket for now. The water steer rudders are o.k for now.
I like the idea of twin canted rudders and will make up a test bed to trial the idea with.
The pic above is of the NZ built, local to me, "Earthrace" That is the same design concept.
I have extended the outer hulls and am now waiting for the paint to dry so I can take it for a run.

Simon.O.

o.k so last time I ran it there was a serious issue with stability, it went fast in a straight line but wanted to tip over under hard turns.
It also had a tendancy to lower the bow as the stern tried to plane, and given that it is a flat bottom that was unusual.

I shifted the sponsons forward to counteract the nose dive and the cornering stability was still an issue.
I then extended the sponsons both in length and depth and this solved the stability problem however produced too much drag.
I then lifted the sponsons up 10mm and the result was amazing, less drag, more speed and great stability.

I then fitted an uprated 540 motor which was very fast but I was not able to use full power as the nose began to dip again. Run time was down so I have decided to go back to the stock 540 can.

Off to the pond again tomorrow and will report back with new findings.

Selph-Inflicted

I feel that if you had a rake on the center section that it would help keep the bow up and not from wanting to plow.

Nice work! Any chance of any videos?

pinky_d_brain

Nice design reminds me of Crispyspa Ghost project
http://www.rc-airboats.com/gallery/v...lbumName=Ghost

For the rolling in the terns i think you could have moved the pontoons out to fix this problem as well. For the diving dues the boat dive the hole time or just tell you get on plain or dues it plain off at all? I think what you need to fix this would be more length to the front of the boat, if you plan to mod it you could put a step hull up front to redoes drag and lift the hull out of the water some.

Think of your boat like a L shaped lever where your prop is one part and the hull the other, if you apply force to the upper lever how much force is needed to counter aced this on the lower lever (the hull) if this is not baleens out then the hull will ether dive or take flight. Remember that the water is only going to push up on the hull so much so we can not increase this that much but if we lengthen the hull less force Is required to baleens them out works the same as any simple machine.

You could try a small wing on the vary front of the boat as well but this will only work at hire speed and have no effect at low speed meaning if you cant get up to speed then it will not work at all.
Anyway just my 2c hope it helped

Simon.O.

No video bit I'll see if I can get some good photos today.
I'll keep in mind your comment on the bow..................a cat may be coming soon.

pinky_d_brain

Yes i thick a small rake would help some to like in the RL boat above if you look at the back part
Don’t get rid of much hull up front this is what i think is casing most of the diving problem. Its a bit like one of them long drag cars where the length is mint to keep the car on the ground where we want to keep it above the water, longer = les force required. Moving your motor back will also help

Simon.O.

I have taken in all the comments and suggestions so far including a few from a local well know mariner.

The next development is to form a vee on the sponson hulls and to taper the stern section of them, at the same time I will introduce a small amount of rake at the bow of these outer hulls.

I will also make adjustments to the thrust angle and produce a little downward thrust to the rear to prevent the bow drop that has been occurring.

I am looking to extending the stern in a ducktail shape and running one foil shaped rudder to reduce the stern turbulance and smooth out the water flow. Remember that the existing rudder set up is temporary as a result of the air-steer system sucking big time due to the hull length.

After that some of the ideas are to fit a subsurface bulbous bow to the main hull and possibly to the sponsons too. I am however reluctant to this at the moment as the main purpose is to be able to run in water that has a floating surface debris and the protruding subsurface bows will catch the weed worse than now.

I have gone back to the stock 540 can and am getting a satisfactory run time and speed.

Mr Cajun Gator

Your bow design is the best for running in places with a lot of debris. Around here the local fisherman use the same style of hull. Inwhich this hull design pushes the debri around the hull and prevents the hull from climbing on top of it. Making the sponsons a little wider will also help. A small bow rake will help it to get on step, but don't bring it up to high so that it removes the orginal idea of the hull.

pinky_d_brain

Only do one mod at a time this way you can tell what is working and what is not
Making the sponsors wider would help but slow you down simply bring them out farther form the main hull to provide more stability, if you need more flotation make them longer.
Angling the trust from the prop down will create lift on the back of the boat making the front dive more, angling the thrust up may help but normally it just pushes the entire hull into the water. Brining the sponsons forward will help but this would be more like a normal 3 pointer, which i think you are trying to get away form. The biggest thing that will help the diving problem is increasing the distends form the front of the prop to the front of the boat. The other is alien the prop more with the COG this is difficult with most set-ups the only way i think you could accomplish this would be get a smaller diameter prop with more pitch or blades or both and lower it down the best you can

Simon.O.

I have now cut the vee into the sponsons and tapered their sterns.
I have also made a false stern that is tapered to a point.
This is in fact a sealed box section that is just hot glued and taped to the main hulls transom as a trial unit.
There is now 1 rudder instead of 2

As suggested I am moving slowly and trailing each idea to see which makes improvements or drag.

I have had suggestions on how to reduce air drag over the alloy tubes that hold the outer hull. *** !! this thing only goes 10 – 15 km/h at the moment. Air drag ---- my shiney butt!!

Pics of trial unit taped in place ready to go.

Simon.O.

O.k the trial went well but I established that the rudder was a little on the small side and rough, hey that's trial rudders for ya, so I now have to make a nice foil section one that has enough throw for this length of hull.
More work
More trials
More pics to come.

TERBObob

My Feedback: (21)

NIce seeing that someone has to ambition to do these "out of the box? ideas and keep with it , rather than toss in the towel .
Keep posting so we all know the goods verse the bads .
BTW - the idea is very unique and hope it comes out better than expected when all is done and finished .

Simon.O.

Well it is still under going development and here is the latest.
I have now fitted ( temporarily ) a long bulbous bow, I will replicate it into a permanent one soon.
This breaks the water prior to the bow and produces a far smaller amount of water up the sides as was previously happening
It now has a much smaller wake and I think it goes a little quicker.
Here are a couple of pics of it running today.
If you look closely you can see the protruding bulbous bow under the water.

BTW this boat is now 950mm long overall which is a jump up from the original 700mm !!

pinky_d_brain

Vary nice would love to see a vid of it running whit the changes you have maid if you can [8D]
Did you solve the problems you where having

mrfixitwhite

wow how daft am i ! just read yuor whole build and only noticed on the last pics its an air boat!
can i ask if you've tried different style props? i.e the orange type slow fly props?
i built a hydrofoam and bought an apc9x6 prop -suggested for the motor but after running it there wasnt enough power to get it off the floor
showed it to a friend who flew various craft an suggested i try a slowfly type prop
full power and up she went -and eer crashed ...but thats my fault lol!
they just have the same pitch but maybe half the weight so much less power needed to spin them.
mayabe im wrong but £1.50 for a prop is maybe worth a try?
looking nice though ! i saw the earthrace boat pics a while back but its a bit beyond my build skills at the minute
would be good if someone could video it for you ?

retaobcr

WOW! Posting #16 with the pictures, can't say enough. Congratulations! You're turning out to be a guru! More power to you!

Rowboat

Nice build Simon.O
It's good to see you tweeking untill you get the boat doing what you want. I was going to sugest moving the motor forward to just infront of the sponsons. This might help keep the bow up on top of the water. But you have overcome the plowing bow problem. I like the pics , they show that she moves through the water with not wash .Good work M8.

Will Sgarlat

Simon, I really enjoyed viewing your progress in this design, it's unusual and you carried it through to a nice conclusion. I love the backward slanting lines in the last photo. Great stuff - keep the creative juices flowing!

Simon.O.

Sorry for the slow reply. Been in hospital for the last 6 days again.

Thanks for all the positive feed back guys.
The backward slant on that last pic is a result of my dodgy photo taking skills

I have not run it for a while but now that I have high speed net acess and a better camera, I'll see if i can get some video of it.
Be patient as I may not be boating for a week or two yet.