Simons Bigger Cat.

[crabstick]

pointy bit forward with a squarish trailing edge, i should draw you a pic, A Guy in our club runs one on his 122kph Gas Shovel and its made the difference from a boat that used to blow over all the time to one thats quite stable for 100+ kmh heat racing

a bit rough, but you get the idea



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[Simon.O.]

I ran it today with an air-dam in the front of the tunnel.

I gathered a lot of info from the first half dozen passes. It is now a lot more settled on the water and would not blow off on a parallel wake crossing like before.
It was running so well that I hogged in at least 10 passes before it all went quiet.
I was hoping for an esc thermal once the tow boat bought her in but the news was not that good.
Another Mystery 200 to the smoke god ! dang that is 3 now ( with differnt hulls) and I am half way to the cost of a C.......

Another will be on the plane soon !!

Here is the kicker, It is smooth and fast and stable but it just needs a bit more.
I'll pull the esc from the big rigger and give it a run here.
The strut is close to perfect but the air dam need s to go forward or be thinned a little.

I'll get this right one day.

[crabstick]

Good to hear the Air dam helped.

[Simon.O.]

Matt The air dam will get reduced as it is too tame now, I will give it a run with the dam further forward and see how that pans out.
I can always reduce the dam size and put it back where it is now.
There is a lot to learn again with the air dams.

[Simon.O.]

An idea.

[crabstick]

reducing the height of the Air dam will reduce its effect also

[Simon.O.]

9XL dead !!

Last week she stopped in the middle of the pond with what was at the time a rooted esc, no big smells just dead.
I dragged out the spare esc this morning to give this a run and found some very uncool things. It will free spin but any load causes all kinds of noise from the motor and the esc gets warm fast. No run there !!

At home i spun it up on the bench and found the same thing, I grab an old 7XL and load test it to show the esc and packs are fine and the short story is the 9XL is now a paper weight.
Overheated too many times and now demaged ! There is a long story to my diagnosis but I am sure you all know how it pans out. The motor is dead and I need to do something about that.

Well as it happens I have been thinking about twin driving this one for a while.
It should have been twinned from the start as two rudders and one prop is just a cop out, it looked cool and ran well but not any more.

It will now get twins and the motors are still undecided but I will order something tonight.

Here are a few pics of a bit of work I got done today while it is wet outside. Some of you may recognise the wooden rudder standoff.

The motor mounts are made but as I have not got a motor to fit they are undrilled and look very boring so were not in the photo lineup.

[Simon.O.]

Yay ! i joined the twin-cat club today !

I managed to get a run in despite the dodgy weather.
It was all good as nothing broke, bent, smoked, flooded, flipped or sunk.

The setup is a pair of 1600kv Outrunners of 36x50mm size. Capable of 1500W
Props. K40 Carbon Graupner C/R with them rotating inwards.
5S 4500mAh Turnigy 30C 135A capable feeding both esc's
Esc mystery style 100A air cooled.

The struts were set to give me a fairly neutral attitude.
1 deg positive with 9mm from the table to the shaft centre line, (6.5mm under my struts)

It has a bit of torque rool from take off if I pin it and this was a bit of a surprise for a twin prop, but there ya have it.
On the plane it was stable and if I punched it from a low planning speed the acceleration was impressive.

Overall she was running very wet , about the same as the one video clip I have.
I anticipated that and can now dial in a bit more angle on the struts to give me about 2 degrees positive.
The last time I ran it with 2+ was on a single with Cg at 29% and it was a blowover queen.

I now have my Cg at 30% and there is very little room to adjust so I will work the struts to get a nose up attitude.

Overall I am happy with the twin setup and have found a few good things.
The outrunners sound beautiful as a pair. Twins are just asking for OR motors, for a single cat I am still undecided.
The 100A esc's were barely warm after about 6 80m (250') passes, packs were the same and the motors just warm.
42mm carbons are on the way soon !!

I am happy and I'll keep this thread updated.

Some pics.
Yes the HW needs tidying up and the rudder rods will run lower down at the next "refit"
The internals are a bit busy but that is as I have jemmied this one together for testing.
The packs (3S+2S)sit crossways at the front of the compartment.

[Simon.O.]

I got another run in today.
This time I had the struts set at near 2 deg for a bow up run.
It was very windy so I was hesitant to run it at wot into the wind.

After a few passes, wot downwind and 3/4 upwind I decided to open it up.
Once it got on the run into the wind it was well flighty and I am now at the point where I can set the AoA for windy or calm conditions.

I use a set of blocks under the front step to set the AoA, and now have a good set of measured blocks so that I can run in windy or calm conditions.

I had a play with wot off the line. That was fun. It is very random.
Once it launched like a TAH drag boat, totally flat and airborne for about 2' and then away at wot, very cool
Another go got a bit of torque roll and one prop bit more than the other and it went................well I have no idea where it went initially but out of a ball of water came the Cat for a stern first landing, not so cool.
One last punch from a standstill got a very wobbly but not unspectacular launch.

I have now decided that it is better to punch it from idle as that seems to work well.

The new strut settings got me,
Warm packs
Warm esc's
Kind of hot motors, they are OR's so that may be ok

A tail riding cat that looks and sounds very nice. Remember that was part of the design brief for this hull.

I may push it with 442's but that will have to wait a while until I need an overseas order.

[norbique]

video please :) very nice progress Simon! keep up the good work.

[crabstick]

video please :) very nice progress Simon! keep up the good work.

+1 on the Video

[ace028]

+2 on video

[fmarcelo]

Very nice work!

[Simon.O.]

There will be no video unless someone films it for me.

I got some new props yesterday, a pair of K45 Graupners.
I went down to the pond this morning to try them out.

A bit of history first. I have been a a mad fan of rpm and pitch to get speed and this has got me some good results with the riggers. for cats it appears that a bit more blade is good.
So far this hull has been good to go with a 640 or even a 642 on a single and was very cool on a pair of K40 props as a twin. I even got to add a bit of positive (bow-up) on the strut to get some speed and had a rare blow over.

Today
It was quite windy but at least it was blowing the way I like it if there is wind.
On with the K45 props and 1 deg of pos on the strut.
Into the wind to the narrow end of the pond at about 50% power and then turn, line it up and give it a bit of throttle.
Holy fark, that is nuts !!
I did not get to wot on the straight as it was starting to lift the nose like never before and was hauling like I had not seen this hull do.
Turn at the bottom end and run 50% past me to the narrows for a turn to downwind again.
Line it up at 50-75% power and then pin it !!
Shiate !! off the water and landed at wot and ran nose up for 80-100m at a speed that I can only guess as close to my bigger rigger.

I need to spend a lot more time on the pond with this hull to get the best out of the K45 props. I will go back to 0 deg on the strut and start again, preferably on clear flat water.

I can now say that rpm and pitch is good but there is also minimum prop dia for a hull. Mine is somewhere over 40mm and the 45 is just nuts. I like them and will keep them and will tune the setup to suit.

I have done a lot of calculations and given that the gear was warm after 2 mins I guess I am well over 40mph and somewhere in the high 40 low 50 area.

It looks good and that is all I need.

[norbique]

Good News Simon! Keep up the good work. Let us know how the 0 angle turns out.