Krick - AVANTI - Test bed boat!

       

  Running name "PAM".
Semi-scale inshore shallow Vee race boat for electric for 540 electric motor.
Kit cost (discontinued) ....36
Accessories.. (motor, speed control & batteries) + radio.

AIMS

  I selected this kit on the basis of it's good looks alone. I already had two other electric boats, the
MFA PIRANHA and the Graupner HYDROSPEED, the latter was much faster so I wanted another boat to match it. In a couple of model boat books boats very similar to the AVANTI are used in electric competition races and as the AVANTI looked fast on the box's lid I bought one!


STYLE
  The hull is a very shallow vee with a racing deck and cockpit. The top  cowling could almost pass as a tunnel hull as the two are very similar in appearance, which first gave the idea for the outboard motor. In the model world this type of deck also serves as a self righting mechanism (SReMECH ala Robot Wars). This type of boat is seldom seen these days but is a predecessor of today's tunnel hull racing boat. Inshore racing tunnel boats are designed for outboard engines, high acceleration and possess phenomenal cornering. Lets see how the model matches up to the real thing.

I've built and rebuilt this kit five times in five different configurations,
 which are:

Mk I Electric outboard, 10 Cells.
Mk II 1.7cc IC engine.
Mk III Electric inboard, 10 Cells.
Mk IV Electric inboard with gearbox 10 cells.
Mk V 2.5cc IC engine with Airscrew.
 

THE MODEL

The kit is all ABS and will therefore produces a boat that is light and strong. The boat is quite small at 620 x 200mm but ideal for the designed electric set-up. There are three main parts to this kit, the hull deck and cowling or canopy as referred to by the plans and  was a relatively simple kit to build. The plan showed all details clearly laid out, it even gives two internal layouts for 7 or 10 cells.  Use only Stabilit Express or Devcon 'Plastic Weld'  two part epoxy or a good Superglue during construction of an ABS boat. Although I did silly things to the boat construction can only take a few  hours if I had stuck to the plans.
 

PAM Mk I
The plans showed the motor set-up of a 540 motor driving a submerged propeller, my initial plan was to build the boat with an electric outboard engine hanging on the back. Graupner, Kyosho & Robbe all make electric outboard units incorporating 540 motors, I bought the Robbe / Kyosho 'Jackson' outboard as it was the cheapest.

As I was intending to do strange things at the back, the transom would need strengthening in a big way. But how do you strengthen a wedge shape gap to make it strong enough to take through bolts?!?  After a bit of head scratching the answer came while sanding down car body filler on another boat, 'this is hard work' I thought, 'this stuff has dried as hard as concrete', and there was my answer.

 The inner surfaces were first reinforced with 2mm ply and glued with Stabalit to stop the ABS tearing. I then filled the gap between the inner and outer transom with 'Isopon',  car body filler which was compacted as much as possible. The cured filler allows the bolts holding on the outboard on to be tightened on to it without crumbling. Looking back, this was the only ideas I had that actually worked on this boat!

The hull and deck components form an airtight compartment for buoyancy,  but for extra safety, put in some polystyrene blocks in the voids just in case. The hull to deck joint is a little different compared other ABS kits, the joint is a flange type and will end up below the water-line so it must be made extremely carefully to prevent leaks. As the joint is a little tricky to get right, use liberal amounts of Stabilit after making SEVERAL trial fittings. Clamp together with clothes pegs or bulldog clips when you're happy. I used too little glue in the joint and mine started to leak after a few outings. (To rectify this I inserted a knife into the split and opened it up until I found where the joint was solid again. A flat needle file was used to remove the old glue and then cleaned up with meths and a good strong batch of Stabilit was liberally stuffed in.  The repair wasn't to hard but it's easier to make the joint properly in the first place.)

The internal plywood bulkhead was moved forwards  to 150mm forward of the transom to allow the radio box first used in the
SHG SHADOW to fit directly into the AVANTI. A frame of 9mm wood surrounds the radio box making a snug fit only needing a rubber band to hold it down. The radio box leaked in here the same as it did in the SHADOW, I never could make this box waterproof.....

With the hull complete I looked at the top. The cockpit was a little  bare - a Koala bear actually! - Get it? - A little bear?.... All right I'll forget the jokes. A drivers head was bought from the model shop, it's from a electric car kit and is roughly the right scale. A body was carved from balsa one evening in front of the TV when nothing much was on as usual.  When I had finished, I put plasters on all my cut fingers and was chased out of the living room when the Mrs saw the wood shavings over the carpet. The body was screwed to the cockpit and the head screwed to the body, Stabalit fills the gaps and secures it. A face was painted on in the avant-garde style, avant-garde-a-clue more like.

I finished the boat in gloss black using car spray paint, trimmed with  yellow and green lines then 'Tufcoat' to protect it. The colour choice was in honour of the Jamaican bobsled team that gave us such a laugh in the winter Olympics a few years ago by coming down the run on their heads!! Well done lads it was a great effort especially as some of them had never seen snow before!



 

I now started to diverge from the plan by installing an electric outboard motor. The Jackson outboard is available in two sizes, 380 or 540, the only differences between the two is the motor size and the size of the prop. I bought the 540 for the extra power. The outboard is all metal apart from the cowling and thus quite heavy. The drive line consists of metal spur gear reduction from the motor to the main vertical shaft and then metal bevel gears turn the drive at right angels for the final shaft to the propeller (fig a). I had found out the hard way that propeller size is very important and a new boat might need changing three or four times before you get one that works well. The Jackson has a dog drive fitting for the prop but I didn't have any of these types of prop so the shaft was cut down and a 2BA thread cut on to allow me to use ordinary propellers of which I have many.

One of the first thing I do with anything I buy is to strip it down to  see how it works and the quality of the product. My mum always used to tell me off for this when I was a kid but now I get paid for doing it as I repair computers for a living and generally people like them to work again after I've pulled them apart so I've learned how to put them back together again so they still work!. If you do strip the outboard down,  lubricate liberally with Teflon or `PTFE' grease. The outboard can be run in by connecting up a low voltage of say 3 or 4v.


A square was cut from 3mm ply to match the outboard's fixing plate and is  used as a spacer to give the tiller arm more room to move. The unit was held on with long M3 Allen screws that passed right through the outboard, transom, an inner reinforcing brass plate and secured with nuts inside the boat. The outboard was positioned so the anti-cavatation plate just level with the bottom of the hull. Steering is via two Bowden cables from the forward servo to the outboard tiller arm. Because of the short length of cable, it was sufficient to drill a hole through the transom and use Superglue to hold the outer plastic tube, no further support was needed. A
coil type speed controller was fitted to the ply bulkhead and a link taken aft to the aft servo. Lubricate the wiper contact with silicon grease to help prevent arcing. A beam of wood bridged the compartment at the front to support a set of speaker connectors to hook up the batteries as I was still using the cell packs I had made up for the PIRANHA and HYDROSPEED. The main cells were fitted as far forward as possible to keep some sort of balance in the boat as the boat was becoming very tail heavy.

I may be describing this a simplistically but it took ages to guess where everything should go as I only external pictures of racing mono hulls with an outboard engine. As I didn't have a prototype to model it off, I decided to go for aesthetics and build it so that it looked good.  Well it looks good to me!
 

SAILING Mk I.
Down at the lake, things were still looking good. With the boat (now  named PAM to please the misses), sat on a stand, the batteries were connected and wedged in with foam plastic. A X40 propeller was fitted to the outboard motor, the radio checked and the boat placed on the lake. The boat sat low at the stern due to the weight of the outboard. Hopefully as soon as the boat got on the plain this would no longer be a problem.

There now comes the moment that all modellers most look forward to and dread at the same time -how will it perform? You can make all the calculations  you want but it's only when you hit the accelerator that you'll find out how good she is. I opened up the throttle full - if the boat is going to do something spectacular, I want it to happen straight away and get it over and done with.  The motor started up and we were off...

Well, had hoped that the boat would leap out of the water and fly at a low attitude across the water but it didn't........  It sort of whined, revved a lot, swaggered around a bit and moved off slowly forward with the bows high in the air. It was working but the words "electrifying performance" didn't immediately spring to mind. The boat seemed to be trying to go but despite my careful draughtsmanship and precise computations, taking  into account Newtons laws of motion, Einstein's theory of relativity, and a hearty breakfast, the performance was rubbish!

Everyone needs a motto to work by, mine is "If it looks good, it must work good". (OK so it's not good English, but it's not an motto for speaking English!). My motto is borrowed from Jack White of Harrow college of higher education who tried to teach me basic mechanical engineering many years ago. He was a great mentor to me in an  engineering sort of way, thanks Jack.

Most successful designs mostly seem to have simple, clean lines and mechanisms like Concord, suspension bridges and sea sharks 'all look good' and work well, but although my boat looked good, my lack of applying elementary boat building principles made the boat under-powered and tail heavy.

At first I didn't think the balance problem was too serious and pressed on regardless hoping that I could increase the power enough to get the boat on the plane. All sorts propellers and adjustments were tried but the best performance I could attain would be best described 'lame duck'.

Back home on the work bench, I looked very critically at my modifications.  The Kyosho Casablanca boat uses two Jackson outboards and that works fine. The Casablanca uses the outboards in surface drive mode but with the outboard so low in the water on my model, the propeller had no chance of breaking the surface. I had allowed room for the outboard to be moved up and down which was soon done but a new hole had to be drilled for the steering cables, the old holes being filled with Stabilit.  I managed to raise the motor unit by 18mm, the length of the slots in the bracket. I also fitted a better car racing motor in outboard to increase the power. after leaving the new motor and unit to run in for a couple of hours she was ready for more sea trials by the next weekend.
 

SAILING Mk I again.
The improvement was hardly noticeable even with all sorts of different props. After a long while of tweaking this and that I noticed the hull was starting to sit very low in the water and decided to bring it in for investigation, I put the boat into reverse and the propeller promptly unscrewed itself and fell off. "Blast!" I had forgotten to tighten the nut on the propeller. The boat slowly drifted out across and down into the lake. This subsequently turned out to be due to the split in the join I described earlier. I was glad of the polystyrene buoyancy fitted which kept the boat from going totally under but only just. I eventually recovered the boat and the radio room was completely flooded and required the replacement of a servo but the rest survived.  Everything was rectified and I persisted with a few more outing but with no more success. A snap decision was made and the  whole idea was shelved. "Why did I chicken out so quickly?" When you know you are beaten in chess, sometimes it's better to give in and start a new game, ( that almost sounds intelligent!!! - sorry about that!).


PAM Mk II

About 3 months later after building another model I started thinking  about the AVANTI again. I had bought a second-hand HP12 IC engine that was going to be used in a later model but I thought it could be utilized here. Well I knew that an IC powered ABS hull could work (
Graupner ARROW), so maybe I could do the same again, but this time without the help of a tested design.


Back in dry dock
A small flat aluminium plate was made up to mount the engine and to fit  the front end of the battery compartment. Even with the aircraft type silencer fitted to the engine, there was still enough room to enable the engine to line up with original shaft position on the plans. The glow plug sat about 85mm from the font wall. The plate sat on two  wooden blocks. Liberal amounts Stabilit was used to hold the wood bearers down and then loads more was spread around just to make sure, Stabilit was the only thing that was holding the engine down. A couple of self taping screws held the plate on the two wooden blocks. I hadn't removed the skeg from the bottom of the hull during initial building and this proved useful. The kit came with a shaft and this had brass bearings so it was good enough to fit in place with a HUCO plastic universal coupling. (Shafts with plastic bearings are to be avoided no matter what the application due to there poor durability and high friction). A small blue SLEC tank was fitted in between the shaft and side wall and wedged in with Polystyrene.

What to do with the exhaust presented a real challenge. I don't like just  throwing the exhaust over the side in a non-scale manor, I like to throw it out the stern where it looks like it's helping to push the boat along. To run the exhaust out the transom was too difficult in this boat and going through the side would mean breaking the integrity of the air tight compartment so I started to look upward. Due to the cowling's design I couldn't fit anything to it permanently because it's has to be lifted to gain access to the interior. I decided to fit a short length of 10mm brass pipe to a spare Meccano bracket on the middle bulkhead and arranged to protrude out of top of a new hole in the middle the cowling. Silicon tubing of suitable size connected the two together. This tube tended to kink due to the sharp angle it had to turn so a couple of 10mm springs were forced along the silicon which kept the tube open.

A small brass rudder and the rudder shaft taken up through the radio box frame and over the top of the radio box and a single arm tiller fitted to the top above a suitable spacer. The tiller arm was a tight fit but I managed to get it in after a little jiggling about. A water pick-up was made from small bore brass tubing and a hole drilled 15mm left of the rudder. The speed controller was obliviously removed and a longer link made to connect up the servo to the carb. I fitted hinges and magnet to the cupper cowling, the same as on the
Hydrospeed, the magnet fits under the drivers dashboard to hold the front down. Not very practical but nothing showed on the outside!
 

 

Not Mine but some else had the same idea with the IC engine!
( Found on eBay )

SAILING Mk II.
So far so good. At the lake a silly oversight came to my attention as  soon as I started the engine up. The exhaust was pointing upward and as I was looking down on the boat to start it, I quickly got a new hairdo just before I dropped everything on the jetty while wildly rubbing my eyes. After a couple of tries i learned to start the engine while leaning way off to one side...... is that what's called stand-off scale?

The engine was very hard to start at first but eventually got going and needed very deft adjustment to get it running smoothly. I put in the water and let go.  Well it did work, but again I wasn't impressed! Slow plodding runs, nothing like the "scared cat" speed I wanted.

Because I had been spoilt by the success of the Arrow, I was expecting a much better turn of speed from such a light / small boat with an IC engine but this was not the case.

My usual plan for poor performance boats swung into operation, try every prop in the box, adjust the mixture from lean to rich and back again, change the fuel, change the plug, etc. etc. The best speed I got was respectable for an electric boat but at least it was riding the water at the right attitude with it's nose slightly up. Trouble was the engine kept stalling in a similar way to the Arrow but by now I was on my smallest  prop, a P35 and it still didn't have enough power to turn it. Maybe the engine needed more running in.

Back home I removed the engine from the boat and was soon annoying the  neighbours by running the engine in with an air prop late into the evening. After a few tanks of fuel the engine was as ticking over much better and now seemed quite powerful. The engine was fitted back in the boat and so back down to the lake but only a very marginal performance increase was noted. It would run well for a short time then conk out.

I got bored of this very quickly and came to the conclusion that the AVANTI wasn't going to be successful in this mode either, promptly gave up and retired the boat....anyway I was fed up with getting a face full of exhaust every time I started it up. It was just as well I
gave up because when I got home I found out that the motor had started to a tear free from the ABS floor. It had fractured partly from oil, heat, fuel etc. but mainly because of the load of pulling on the starter belt in rather an exuberant manor!
it.

The epitaph to the MkII was I never tried scale type props with lower pitch angle on the blades which might have worked. Also because of the large skeg a small 35mm prop might not have been getting enough 'clear' water to bite into thus with increasing speed would cause different engine loading problems which can't be checked while the boat is stationary. A larger but shallower pitch three bladed prop might have a better bet as more of the prop would be in clear water. I'm just guessing here but that's what I'm best at!
 

PAM Mk III
After completion of yet another boat kit, curiosity got the better of me again and I returned to the AVANTI, such a nice looking boat MUST be must be able to run well. I took the plans into the study and scanned the plans carefully. The plans showed the boat should run on a 540 motor with a straight shaft and submerged propeller, so as my plans had failed I would try following the instructions. I pulled the chain and left the study.

Dry Dock Again

The compartment floor was repaired with off cuts of ABS and a brass motor  mount was made. A standard 540 motor was fitted with double HUCO couplings down to the shaft fitted in the Mk II stage. The original speed controller was refitted and the motor connected up to 2x5 cells (12v). Getting the batteries and motor was a bit of a squeeze but I got it all in eventually. The rebuild didn't take very long, that's one reason that made me keep coming back to this boat, new ideas could be incorporated without too much difficulty.

SAILING Mk III.
Running was very mediocre, about the same as the Mk II but quieter. The boat got on the plane but was not flying over the water, it seemed under powered. I still wanted a more speed and thought it must possible without fitting loads of batteries or expensive motors. After all the Hydrospeed worked well with it's surface drive, single motor and 10 cells. I now had the same amount of power but the speed was nowhere near the same. I wanted to fit a strudder but the radio compartment layout prevented me running a shaft to the transom without major surgery, so that was out. I kept the boat in the Mk III format for a few months while I worked on different projects and a summer building break. I had spent so much time on the boat that I couldn't remember my wife's name so spending more time with her was in order as I can't afford a devoice..... I might loose my boats!
 

PAM Mk IV
One week later, not really. After a while I decided against the better  judgment of myself and wife to have another go at the AVANTI. She actually said "Not that stupid thing again!" But I could see through her reasoning and she actually was goading me to persist with the boat!!!

I've read that an electric motor likes to 'unload'. Now I should know  what that means seeing as I've got an 'O' level in physics ..... but . 'Trial & Error' will have to suffice.  Anyway according to some books, electric motors become more efficient the higher they are allowed to rev e.g. a motor might take 10 amps to rev at 10,000 rpm, but only 15 amps to rev at 20,000 rpm. I'm not sure how technically correct but you get the general idea.

There are two ways to increase the rpm from a given motor;
1 - use  small or fine pitch racing propellers, or
2 - use a gearbox.

Small or fine pitch racing props are not made by anyone at the time and would be very in efficient anyway. I went out and bought a 3-1 Graupner gearbox as used in my
Graupner Hydrospeed.

RECALLED TO THE DRY DOCK
Fortunately the gear box comes with a set of reducing bushes to cater for different size shafts, one almost fitted and only needed a little help. The gearbox was secured to the shaft fitted for the IC so that the gearbox could sit on the floor without any packing.

A cross beam at the front was refitted and supported the speaker  connector and the resister for the wiper type speed controller, again as used in model cars. I tried a wiper  resister controller this time to see how they compare to resister coil types, (coil types tend to drain the batteries if not returned to dead centre every time and get Very Hot!). A long tenuous link connected the controller to the rear servo through a steadying brace. As you can see with the gearbox, batteries and controller it was a very tight fit at the front end but the boat was now in balance. The set-up was left to bed-in over night on a low voltage.

SAILING Mk IV
At last a much better performance, the boat was getting on the plane without difficulty but the boat still seemed to be hiding it's full potential. It wasn't as fast as my
HYDROSPEED but could out pace with my PIRANHA. I kept the AVANTI in this mode for quite a few months as I thought it was good as it was going to get. ............ I again changed my mind after a short while, but what now?


PAM Mk V
I had now decided that the AVANTI was teasing me in that I suspected that if I could find the right set-up I would be able to get the speed I wanted. During the summer I saw an air boat down the local lake and although it was unstable and hard to control the speed was really impressive! Anything that moved quickly impressed me when compared to my AVANTI.

An air boat is usually a flat bottom style with an air propeller at the back and air rudders behind the prop. As nothing but the smooth hull of the boat is in the water they are used to skip over weed, muddy and shallow waters. Back home I dug deep down into a few old boxes and found an OS15 aero-engine and propellers that I had forgotten about.

RADICAL REFIT IN DRY DOCK
I gave up on the Tandy radio box idea as it was leaking more than a  cabinet of MPs and made up a ply platform to mount the servos. The batteries and receiver was stuck in any convenient spot . I wasn't too worried if the radio got a little wet as I had a sneaky feeling I wouldn't be keeping the AVANTI in this mode very long.

The rudder was still in place and the water pick-up that had already been removed  in the Mk III electric version. A yellow SLEC tank was fitted as far forward as possible inside the hull and two fuel lines run out through the transom, one for the engine feed and the other to pressurize the tank from the exhaust pipe as the fuel would have a long journey up to the carb. A long aluminium engine plate was cut and shaped as shown in the photo. A ply square wedge is sandwiched between the transom to allow clearance for the engine mount bolts. The engine itself is bolted to a standard plastic aeroplane mount. The throttle is controlled by a Bowden cable in a 1/8 brass pipe taken through the transom. The silencer in a Mardave car silencer modified to take a hose-clip type clamp to hold it on around the engine, any gaps were filled with 24 hour Aradite. The smallest 'pusher' propeller for this size engine was meant to be a 8x6 which would leave a lot of the propeller below the water line so it was slightly adjusted by removing the tips with a hacksaw and then checked for balance. This set-up looked rather weird but I had high hopes for it. The AVANTI now looked like a cross between a motorbike and a dragest! But would it work?


SAILING Mk V
The engine started up with some difficulty due to the height of the engine above the tank but I got it going in the end. I ran the engine till warm on the boat stand and everything looked good. While running the engine up to speed it started to push the boat and stand across the jetty, this reassured me that there would be enough power. I put the boat carefully on the lake ...............Whoosh!

Water sprayed up in all directions completely covering me, the jetty and anything else in a 5 meter radius! The boat shot forward a few feet before staling! Failed again.

The fault seemed due to the fact the back still didn't have enough buoyancy to support the weight of the engine and hold the propeller up out of the water which was the original problem I had with the Mk I version.

I re-drilled the engine plate and managed to raise the propeller by another 15mm. I couldn't find a smaller pusher propeller so I bought another prop of the same size and milled out half of the two centre sections with a flat electric wood drill bit so that when placed together I had a four bladed propeller. About 40 - 50mm could then be cut of the end of each blade, smoothed of and the whole thing rebalanced and still retain roughly the same blade area!?!?!  The new hub was then glued with Stabilit to provide a little more strength and clamped together on the engine shaft.  It fact Mike Elson of the Peterborough Model Centre almost passed out when I told him what I had done. I like Mike he's a helpful sort of bloke if not a little jumpy because his greater experience!

In all I gained about an extra 50mm under the tip of the propeller. I went down to the lake on the next weekend and waited till nobody was about. I was extremely cautious when starting the engine with the new propeller, Mike had put the frighteners on me. So for safety reasons I planed to start the boat from inside the car with all windows closed and the doors locked but my arms weren't long enough to reach the boat  on jetty. feeling brave I got out of the car to start her up in a more conventional manor. Once the engine was started up, the propeller seemed steady enough with no noticeable vibrations.

On the lake the 50mm didn't prove enough. I was again covered in a huge amount of high speed spray much to the delight of people that had sneaked up behind me while I wasn't looking. I said 'It was meant to that!' but I didn't fool anyone. This was captured on video much to my continual embarrassment.

I needed more height at the transom, I know I'll fit floats. I took a  trip to a large toy shop with a letter the wrong way round and bought two small toy boats. Now this is a really silly idea, but then again an air drive IC engine on a shallow vee boat was a silly idea. I tried it again at the lake, the propeller was still too low and I got a third drenching. Not the best way to get a bath.
 


CONCLUSIONS
Well I eventually gave up on PAM, the boat not my wife! It was been striped down to the bear hull and put in storage awaiting further development. The AVANTI has been a disappointment to me as it didn't live up to the speed it's looks promised and never proved faster than an average electric boat. Don't get me wrong, I not saying it doesn't work, it does what the makers  say it will do but I was after much more and I will get it one day! It did look good with the Jackson electric outboard on though.

I should have  fitted surface drive to the boat with a long shaft to the transom before giving up.... but then again I already had this set up in my Hydrospeed. But I could have tried an  IC engine!!!!!  I might do it one of these days, watch this space.

If you have built one of these boats I like to here how you got on.


PERSONAL RATINGS (out of 10)
Value ................................. 7 (Comes with usable running gear)
Kit Quality ......................... 8 (Clean, sharp mouldings)
Kit Design......................... 5 (Good appearance, questionable performance)
Ease of Building .............. 8 (Goes together easy enough)
Finished appearance ..... 7 (Good but needs good paint job)
Handling ........................... 5 (Nothing spectacular)

Next .......

All the boats I've built so far have been on the small size with a maximum engine size of 6.5cc so how about a big, mean off-shore machine, the Hydrafibre ATLANTOR sounds good, it needs a 10cc engine!

 

"Well  all  of this is just my opinion,  but what do I know!"