Paulekins

Hi all so the build begins . . . .
first off we will start with the engine mount for this I used mild steel rods which were braised
together to form a small tower with diagonal braces
I built the sides first then mounted the engine to make sure I got the distance between the sides correct for the engine then braised in the first of the diagonal braces then removed the engine so I didn't damage it with the heat while I put the rest of the bracing in
re mounted the engine and fitted the prop just to make sure I had got the height correct
once checked I then fitted the base plate and gave the whole thing a coat of paint

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( don't know why only one picture thumb nail came up instead of all of them )

there that's the engine stand sorted

Paulekins

Hi all
now what's next ah yes the air boat body
OK let's make a start first I (with a little help from my friends ) set to working out the dimensions of the air boat using a template I found on Google and started to draw the air boat to scale on a large role of paper not an easy thing as I am no draughts man (I prefer chess)
once completed I used some wall paper paste and pasted the whole thing onto my ply wood sheets (3mm) and left them to dry over a couple of days
now the fun part (lol)cutting the lot out which is just a matter of following the lines on the paper (well not that easily) until I had all the pieces laid out on the floor
at this point on the last one I built I started gluing the whole lot together but this time to try and make it a bit lighter I am going to use a hole cutter to cut holes in the ribs but not too many that it weakens them but enough to help lighten the frame work a bit similar to an aeroplane wing now to start gluing it all together and leave for a day or two for the glue to really dry
next is to bend the base up to the frame to give me my bow
to do this I turned the boat upside down over the edge of the bench and weighted it down so it cannot move
next is to use a wall paper steamer to soften the ply by slowly introducing the steam under the hull to help in the bending being carefully not to melt my glue holding the frame work together
also I attached a weight to the edge of the bottom ply to help pull the ply down into a nice curve
this is one of the times when patience is a virtue as this dose take a bit of time to get the bend to stay once it has all cooled down once cool I glued it to the frame work
again leaving it for a couple of days for the glue to set
next is to fix on the sides starting at the stern and working my way forward gluing each rib as I go stopping at the last rib from bow as from here on is going to be bent inwards and upwards at the same time I will let the sides dry first as there will be a fare amount of pulling on those rib joints when curving the bow
ok the ribs have dried and now to curve and glue the bow I have a couple of clamps that I will use to hold them in place for a few days while the glue goes off i will trim the excess off when i have the deck fitted

NEW222

What glue are you using on your build?

Paulekins

hi I am using two glues
the gorilla glue for the main body and ribs as it foams up and gives that little extra support
and the 30d which is a quick dry for all wood work
i might use a two part epoxy on locking down odd bits
and the metal frame for the engine are braising rods

Paulekins

hi all i have just been trying to work out the scale of my air boat
from stern to the tip of the bow including the reed lip ___/ it comes to 40" long
so by my calculations this works out to be 1:2 scale for a 20' boat
can some one confirm this for me please

Got RPM

Your boat is 1/6th scale.

20' X 12" = 240"
40"/240" = 1/6



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Paulekins

ok thanks i must have my maths wrong some where
yours adds up
but so dose mine
so which is correct i am confused

Got RPM

You are not correct, that is why I corrected you. There is no confusion, a 1/2 scale model would be 10 feet long. Line up six of your models and they will stretch for 20 feet, the length of the full scale boat. Your model is 1/6th scale.


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Paulekins

i dont want to cause trouble but i did not say it was 1/2 scale but 1:2 scale as referred to by Wikipedia, the free encyclopedia see link
https://en.wikipedia.org/wiki/List_of_scale_model_sizes
and scroll down the list and you will see why i am confused 1"=6" in real life

Got RPM

Read Wikipedia more carefully. One foot = 6" or 1/2 scale, which with your boat is not the case. Your boat is 1/6th the size of the real one which is 1/6th scale or 1:6.


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Paulekins

sorry i was wrong you are correct

Paulekins

ok now where are we up to just finished putting the base of the hull together
next is to put in the posts for the rudders in at first I made them the same height as the propeller
but I decided I did not need them so tall so I cut them in half the positions of the posts were placed about half way across each blade on each side
I also put in some blocks for mounting the engine plate to under the deck
next is to put in the wiring for the servos and an extra cable for extras such as lights etc at a later date
once I had done this it was time to put the rest of the decking on
I made the deck slightly bigger than needed so I could plane and then sand the edges to get a neat edge to the hull once completed I gave the whole air boat a coat of fibre glass resin to seal the hull and give it that extra boost to the strength
ok now to make a quick box to house the electrics in the idea this time is to have all electrics above deck to solve any problems of water ingress and fit a water proof switch on the side of the box for switching the power on and off
the servos for the rudders I mounted on top of the rudder posts one on each post and used a y cable to join them so that they will work in unison
for the throttle servo I have mounted the servo on the engine frame again to keep things out of the water also it makes making the linkage a lot simpler
last is to fit the Battery, BEC and the receiver and connect everything together bind it to my DX6I
and set up the controls
all that is left to do is fit the fuel tank, lines, pump and tune up and fit the engine but that's another day

Paulekins

well that's the electrics all finished now on to fitting the spray rails and the chine's
spray rails are the ones that are fitted to the sides of the hull and chine's are
mounted just on the edge of the hull where it changes angle to the side of the hull
a bit complicated to explain so have a look at the drawing for more clarity
ok that done just do a quick mock-up of the air boat just to check I have every thing
and that it all fits before I start the painting and hey am I glad I did
I found that the brace I had put in in-between the rudder masts would have stopped me
from starting the engine as it was in the way of the spinner
so I had to cut that out and move it up to on top of the servos which in a way was a good thing because it would help steady the servos as well
phew that was a close call I would have hated to start chopping things once it was painted
as you can see in the pictures I have painted the servos red to make them look more like
hydraulic rudder controllers and the servo wires yellow to make them look more like hydraulic
pipes the wood frame work is painted grey to look more like steel box section (ran out of silver)
and the control box I am going to make that look more like a cooler/fridge (for keeping the
fish I caught in and some where to put my beers in lol)
next is to sort out the fuel system
this time around I am going to use a Perry pump with a check valve the reason for this is that the engine already had a Perry carb and there is a hole in the side of the crank case for a nipple
( can I say nipples on here without offending any of the ladies )
to screw into which means I don't have to have the fuel tank level with the carb any more
I have placed the fuel tank on the deck and used a combination of plastic pipe and copper pipe
for the fuel line also looks a lot neater and saves having fuel line blowing around
so now the fuel tank is vented no need for back pressure from the exhaust manifold
the fuel pipe now goes from the fuel tank to the check valve to stop any back flow to the fuel tank when the engine stops so no need to try and get fuel all the way back up to the carb when next starting
after the check valve it goes into the pump then on into the carb and there is a pipe from the base of the pump which goes to the crankcase to power the pump unfortunately the previous owner of the engine drilled the hole in the crank case to 5mm instead of 3mm so now I am waiting on a 5mm nipple to arrive before I can go any further
but just to make sure the engine runs I have put a bolt just into the hole and used a standard fuel set up (no pump and pressurized tank by the manifold)to get the engine running and all seams well

while I wait for the nipple to arrive I have made a start on the seating as this is such a big boat I thought it deserves a single pilot seat and a two seater passenger seat
as you can see from the pictures I started off with a drawing of what I was going to make then set to with the wire cutters and the brazing torch and built the frames next is to put the seat bases in and the step for the pilots chair
and that's as far as I have got to date just waiting on the nipple and a bit of vinyl for the seats

Got RPM

Looks good Paul, keep it up!



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Paulekins

thanks looking forward to getting it onto the water

Paulekins

the vinyl has arrived so I set too in cutting and shaping some blue rigid foam to fit the seats
and then cut the vinyl to fit using evo stick contact adhesive to glue it down to the foam
then used the same glue to glue the cushions down onto the seats looks quite good if I do say so myself ( I might make up some seat belts I am not too sure yet )
one thing I did for get to mention before is have you ever tried to get a 2 1/2" three blade pusher spinner ? they are like gold dust no one seems to sell them so I have ordered a standard three blade plastic one and a aluminium one the idea is to practice cutting the plastic one until I get the cut shape right then once I know what I am doing I will then cut up the aluminium one
but in the meantime I will use the two blade pusher prop with a spinner that I have hacked to fit
all the paint has now dried so I can now put the name on the boat one on the bow and one on the stern along with some other lettering on the fuel tank and the throttle servo (see pic's ) you will also see in this pic that I have had to cut the exhaust in half and angle it down this is because before it was pointing forward (as you can see on previous pics)against the direction of travel which not only looked odd bit would have messed about with the engine tuning
I have now finished to control box cover too and put some lettering on that (see pic's )
something seems to be missing from the front ?
Ah! it is the reed rail for pushing the reeds and other plant life out the way of the bow so I have made one and fitted that while I waited for the nipple and the 3 blade spinner to arrive

Got RPM

Looking good!



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Paulekins

they have arrived at last the nipple and the spinner
now to get this spinner cut up and fitted and see if I can get it to start and tune the carb with this pump should be fun because you can alter the amount the pump puts out which would mean you could put too much fuel to the carb or not enough fuel to the carb causing all sorts of problems when trying to tune the carb
well after a lot of messing about I have got it running without spewing fuel all over the place it will need fine tuning but it is running

one thing I might do is extend the exhaust output pipe closer to the stern but I am not sure how that will affect the performance of the engine if any it would mean extending the pipe by 3" (see pic)
I have also refitted the carbon fibber rods for the prop guard with some bracing and i might put a bit of fine aluminium mesh around to finished it off

I have also put a bump guard around the edge of the hull for when I get a bit too close to the bank, dock etc
I also spotted an action man search light on E-bay which I got for a tenner I thought would look good on the bow at the moment it is a little bit bulky and runs off a 4.5 volt battery in its base lighting a standard light bulb
so I am going to cut the main part of the base off that holds the battery and power it from the main battery on the boat and put a led bulb in it and I will be able to switch it on and off through the receiver just need to think about what colour to paint it ? as at the moment it is a dull green

well i think i will go with the two greys the head of the light will be the blue grey of the cool box and the stand will be the grey of the rudder supports and i will paint the disc at the base silver
just need some dry-ish weather now to take it down to the pond for its maiden voyage
and my right thumb to heal as i have cut the top off on a circular bench saw (owch!!)( a stupid thing to do just that split second of not thinking)

Paulekins

well i have been tuning the engine and i just seemed to have no air movement well not as much as i thought i would have

then it dawned on me with putting the fine aluminum mesh on the top and sides and partially across the back of the fan guard it was to fine and was stopping the air flow

bol**ks to put it mildly

so i set to in removing the mesh but as the carbon fiber rods were at there limit of bend when i tried to remove the mesh that had been glued on boing went the carbon rods so now i have to start again making a fresh fan guard fortunately i still have enough rods to make a new one

i have also had to replace the battery that i was using 3c11v lipo as it was too heavy up front and put the balance point of the air boat about half way down the boat but it wants to be 1/3rd of the way from the stern which also meant that i had to remove the search light from the bow as well dam!!
ah well such is life the maiden voyage will have to wait a bit longer

Paulekins

update

well i finished the fan guard with out the wire mesh this time and all was looking good
but as always with building models some thing else has to fail
and fail it did the wire cage that supports the engine started to break around the points that had been brazed
that is what happens when you do things on the cheap i had used coat hanger wire to build the frame
and it just wasn't robust enough and metal fatigue took its toll
so i ordered some new steel rods and have just finished remaking the engine stand
i will hopefully get it all put back together this weekend and finish off tuning the engine
then out for its first run later on this week if it stops raining long enough

Paulekins

well here is the first video of the MK II but as you will hear the engine starts to struggle after a couple of minutes and wont rev up

until it finally gives up and dies half way across the pond

fortunately there was just enough breeze to bring it back to shore

once i got it home i found that the rubber seals had perished on the carb and it was chucking fuel every where except into the engine

now getting seals for an old Perry 60 carburetor aint that easy as the new Perry carbs are made from plastic

but i found theses on flee bay

http://www.ebay.co.uk/itm/3220795289...%3AMEBIDX%3AIT


and i am hoping there will be a couple in there that will fit the carb
any way heres the video
https://www.youtube.com/watch?v=zibsKd_Ue0U

Paulekins

bank side video coming soon

Paulekins

ok here is the second video taken from the bank

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

Paulekins

hi all
i think i have found out what my engine tuning problem is
and it was not the seals

if i tune the engine on tick over it runs sweet at low rev

quick rev up sweet
but getting to top rev a problem
at top rev the prop (pusher) is sucking against the venturi

and pulling loads of fuel out of the carb and spraying it all over the place

which is why when i have the engine tuned to run properly at top rev (with loads of fuel every where)
at low rev it is way too rich hence lots of smoke and eventually floods and dies

dose any one know of a cowl that i can put around the mouth of the carb
there doesn't seem to be enough of the venturi to put an air filter on also

i don't think this would solve my problem as air would still be sucked away from the air filter

what do other people use on pusher props

Got RPM

I have trouble believing that is your problem. There is more air flow over the venturi when the engine is mounted as a tractor, and a large number of pusher airboats have been built without this issue. I suppose it is possible, but I suspect a carburetor problem, too much prop or an engine with excessive timing as more probable.



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