Aeromarine Sprintcat 40

[DISAR]

After a very nice Mean Machine I decided to build a bigger cat from Aeromarine (following also the suggestions of some members here). Here are a few pics until now. Rudder,servo,strut,stuffing tube installed.

Motor: NEU 1527/1Y, octura 8mm coupler, thrust bearing
ESC: MGM 25035 z-series or Hydra HV240
3/16 Hughey flex with 1/4 stuffing tube
Speedmaster 21 strut large extended
Top Secret rudder with extension
Prop: 648,450-452/3 etc...
Bats: 6-8s

Motor will be placed around 32% = 11.2" from aft. Any questions/comments are welcome

After the total rebuild, the motor was placed further forward at about 12.6" from transom and fitted the large extended strut which made the boat run very stable.

[DISAR]

One more photo

[jingalls007]

Love this hull, just got my 29" sprint cat yesterday. good luck!

[HOTWATER]

I have a .20/.40 Sprint Cat that I was thinking about converting over to brushless as well. How much will yours weigh ready to run? And what size lipos are you planning to use?

-Kent

[DISAR]

I will start with 6s2p and then 7s2p. The 7s will be a combination of 4s and 3s.

Total weight I estimate 4.5 kgrs = 145 ounces = 10 pounds

[DISAR]

Some progress with the motor mount installation. I place the motor with coupler-thrust bearing on he motor mount and install flex and checking for mount's angle and position for good allignment. At that place I glue some plywood and then Belzona (plastic steel) on top and place the mount (with motor) and keep it in the position until fixed. Then I take out the motor and apply more belzona and epoxy etc.. to glue the mount.
Now I need to figure out some way to support the motor from the other side. Any ideas?

[andym]

Are you realy going to run 6-8 cell with the Etti 150?

[DISAR]

I have the 2-7s ETTI and planning to use 6s initially and if temps are OK maybe go 7s with smaller prop. I have the extra caps too. If it dies, it dies.

[DISAR]

Some more photos, almost completed.
Closing also the cowl "turbine" opening.

[Flying Scotsman]

I have the 2-7s ETTI and planning to use 6s initially and if temps are OK maybe go 7s with smaller prop. I have the extra caps too. If it dies, it dies.

Therein, lies the problem if it dies a possible burnt and destroyed boat..The smell and the cost to buy a new more expensive high voltage/high amp ESC, if all is well. That is a big hull with big suggested props and motor

Douggie

[DISAR]

I don't understand why the ETTI will not handle it. It is for 7s, I will go 6s first, it is for 150A I aim to go about 100-130A.
The size does not matter.

[DISAR]

First test done, with 6s2p, 447/3, Etti 150 2-7s. This boat is really fast and dominates. Did not run it full throttle for very long because I had one "dive" and stopped after that. Luckily not any damage. What happened is that I was running half then full throttle and half again then no throttle and then the boat dived into the water. Don't remember exaclty but I saw the boat slightly up in the air and dived into the water with the fwd part. My COG is 34%, strut is level and bottom of strut 6 mm or 1/4" above sponsons bottom.
In half - full throttle the boat planed very easily and seemed running nice. Only back of sponsons touching the water.
Any recommendations to eliminate the "diving"? Shall I give a small angle on the strut upwards and adjust the COG to 32%?

[txboatpilot]

First test done, with 6s2p, 447/3, Etti 150 2-7s. This boat is really fast and dominates. Did not run it full throttle for very long because I had one "dive" and stopped after that. Luckily not any damage. What happened is that I was running half then full throttle and half again then no throttle and then the boat dived into the water. Don't remember exaclty but I saw the boat slightly up in the air and dived into the water with the fwd part. My COG is 34%, strut is level and bottom of strut 6 mm or 1/4" above sponsons bottom.
In half - full throttle the boat planed very easily and seemed running nice. Only back of sponsons touching the water.
Any recommendations to eliminate the "diving"? Shall I give a small angle on the strut upwards and adjust the COG to 32%?

Any gps speeds?? What temps were you getting on the equipment?

It would help to see video of your boat running,, to give advise on setup...

[Fluid]

That setup works great in 38" Q Sport hydros, with a smaller prop it will be great in the SprintCat. The diving was probably due to the varying throttle upsetting the attitude of the hull; a cat is not a mono and depends on air compression in the tunnel to 'fly' right. Keep the speeds more constant and you should be fine. Moving the CG back 1/2" woundn't hurt as long as the bow doesn't come up too far.



.

[DISAR]

Thank you Fluid and Txboatpilot.

Sorry but no gps nor video. It was the maiden "voyage" and my concern was on the boat's attidude first. It has a lot of potential and certainly very fast. Temps were cool after 1 min. but with very little time with full throttle. Then I started again but the "dive" came and I left to go to work.

I will follow Fluid's advise and move the COG back a little, also the big speed variations may cause this. (Like when you suddenly push the brake in your car)

Thanks again and when I have a video (I hope soon) I will post it