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

[Jeff Wohlt]

Many BL motors will stop completely when thriottle is off so the prop then becomes kinda like a brake. Feigos may not as they turn very easily at off. You will never see a drag boat just pull off the throttle...they come off slowly. I guess the stopped prop could cause some transom to lift. Combine that with a fast reduction of tunnel air and yes you could almost go end over end in some cases.

For my bassboat coming off some serious speed (near 70 in an 18 ft boat) you always watch the third hop if you are taking some big waves. That is my experience with fast real boats. It can stuff you real damn fast. Just the right combo and it then pushes the transom up and in you go. I have come very close. I did spin it out at around 50 and almost broke my ribs. I was trimming down as I went into the turn...that is a no-no. IOGP/Formula One boats (Seebolds that I get to be around ) used 24v down trim systems.

[DISAR]

Interesting experience, I wish I had a real fast boat. It must be the sudden speed reduction that caused the diving.

[Jeff Wohlt]

That or a combo of three good waves that you went over and the last one threw the transom up and stuffed it.

Yes, a buddy was behind me and said all he saw was a big spray and actually thought I barrel rolled it.

Charger bassboats do not like trimming down thru a turn and it is because it has such a deep v at the front. Had I stayed trimmed up I may have been ok just some porpising. We actually run them thru turns pretty damn fast. I do not have the kahoonas but at Truman Lake is is nothing but 15 foot wide channels as you get backin the arms and fish for spawning bass...these guys fly thru there and all you see is a big rooster tail coming thru the woods since it is nothing but trees in the lake. Two boats meet and no kidding you can give them a 5 smack holding your hand out and they hardly back down below 40 mph. If you get out of the channel you can go from 15 feet to 3 feet in nothing flat. Already replaced one lower unit on mine from hitting bottm. All you can do as you see the depth finder getting very shallow is keep it wide open and trimmed all the way up...never come of the plane as you will bury it in the rocky bottom....I not only took the lower unit out but actually hit the bottom with my boat at around 40 mph so I figure I went in to about 1' of water. Only a $3500 screw up.

Here is a friend of my sons little weekend catch.

[bustitup]

Just a heads up
there is a guy on ebay selling the molds for this boat...hull, top, cowl, radio box

[Fluid]

Just a heads upthere is a guy on ebay selling the molds for this boat...hull, top, cowl, radio box

Nope, a completely different boat. It's 42" long (not 34" like the SC40) and it is definately NOT an Aeromarine hull. I don't know what hull it is a splash of.


.

[Joern Markset]

The size does not matter.
That`s not what I`ve heard.... http://content.sweetim.com/sim/cpie/emoticons/00020148.gif

Interesting to watch your project, I have pretty good experience with this hulls but powered with .45 nitro. They can be incredible fast with a proper setup.
I have plans for building an electric cat in that size my self, just don`t have the time at the moment...
Keep on posting, and provide us a video when you`re done :thumbup1:

[DISAR]

New test today on 6s2p with 447/3 again with cog about 32-33%. It was a bit windy and choppy and did not run at full throtlle only once or twice for about 2 secs. No dive today which I believe was due to sudden speed decrease, but quite the opposite. The boat has the tendency to be air-borne when I hit full throttle and quite loose on the water. Only aft part touching the water but the bow lifts quite a lot. Maybe I have to transfer the cog a bit fwd again 34-35% or add some weight somewhere to adjust the cog easily. Because of the hull's design the batteries are quite difficult to reach and have cut some part of the rails and deck edges. I have the following questions:
a) Does anybody know where the cog should be for this boat? Joern?
b) My bottom of strut is above 1/4" from bottom of sponsons shall I lower it or lift it to keep the boat on the water?
c) Or shall I change the angle of the strut, now I have it parallel.

Needs some more testing but not much time.

[EPower]

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.

Your Etti will handle it just start with a small prop i was told that a Hydra 120 could handle that motor LOL i bet you the Hydra would go up in smoke first :rofl:

[DISAR]

You know what, I took out the ETTI and put a HM200A 3-7S (my last one) which has worked satisfactorily till now in my other boats. See how it goes and then put the ETTI in. I don't have the money to go for an expensive one now.

[Joern Markset]

I was running my cats with about 33 - 34 % cog. I had a 16 oz fueltank in front and the .45 engine was mounted right behind the fueltank. Bashing around throttling up and down makes this boat dive in the end because of the very low bow. Your struthight seems fine to me, maybe you should try a slightly positive angel. It is no problem to run in the 60`s and still become stable. Just get yourself experience with this boat and you will be satisfied. Hours and hours with testing will get you on the top :thumbup1:

[DISAR]

Many many Thanks, appreciate Joern.

[Jesse J]

Disar, when I get mine together Im gonna try small props until I learn how to drive it. I wonder if you propped back some and found a less windy day, if that would help to get the feel of how she handles, then prop back up once you have her dialed. I'll be curious to see how things go, good luck!

[DISAR]

Are you going to build a Sprintcat? That will be nice.
I know that the conditions were not good for testing but I wanted to see first the temps of ESC,motor & batteries. Everything was cool. Handling was of secondary importance which will be now first. The 447/3 is considered quite "small" for this setup and I think I can go upto a prather 235-240, 452/3 for max.speed.

[Fluid]

a) Does anybody know where the cog should be for this boat?

This depends on the speed and weight. The faster the boat, the further forward the CG needs to be. On 80+ mph SAW passes my SC40 needed the CG near 35%. With 4S power and 50 mph, 32% was good. If the CG is too far forward the boat may hook in the turns.


b) My bottom of strut is above 1/4" from bottom of sponsons shall I lower it or lift it to keep the boat on the water?

You will probably need to raise the strut to keep the boat down on the water - between 5/16" and 3/8" worked well for me but it is prop-dependent. The deeper the strut, the higher the boat rides, and usually when the strut is that low the boat tends to skip over the water rather than ride on it.


c) Or shall I change the angle of the strut, now I have it parallel.

The angle will probably need to be between flat and two degrees up at the prop end. Set the boat on a flat surface to measure the depth and the angle, don't 'eyeball it'.




,.

[DISAR]

Mr.Fluid I don't know what to say:bowdown::bowdown::bowdown:

Thank you very much for your excellent advice:tiphat:

[bustitup]

Any updates here

[DISAR]

No updates at all. I've been very busy with work and I am overseas now for quite a long time so no possible to touch the boat.

[DISAR]

Total rebuilt, and runs very stable now. The large extended Speedmaster strut made the difference! Propeller is further back (abt 3.9" from transom) and it makes the boat much more stable, Thank you knpc for your advise!
I Cut the rails and fit platforms in the sponsons (on top of foam) (also knpc's advise) and fit the lipos in there, also moved the motor further forward to 12.6" from transom in order to leave more space for additional lipos and flexible cog adjustment. Added also carbon-aramid fibre on the tunnel and platforms, I like the look. Tested with ESCs MGM 25035 and Hydra HV240, a good ESC over 200amps is necessary to run this boat. Total RTR weight is 11lbs which might be too much but I'm very happy with the boat, Thank you, Jay and Kevin!

[knpc]

Nice that everything worked out and you got her dialed in. I had mine out this morning in windy conditions and it was still runnng fast and stable. If you get a chance post some pics of the inside layout and hardware. I'd like to see your setup.

Kevin

[D&D]

I ran this boat for years (nitro) and built several. Push the back of the boat down on a flat surface with the strut loose. While holding the boat (as above) push the strut down flat and tighten. This is the correct setup for the strut, however; CG will vary with each different Sprint Cat hull and that is probably causing the hull to fly up and then they are famous for nose dives. Good Luck

[DISAR]

Oh yes I had a couple of nasty nose dives before with the small strut, but with the new extended large strut no dives any more. I have the strut 10mm above, have not tried with even yet.
Added some transparent plexiglass for watching the gps without removing the hatch and modified also the aft part for taping down more easily.
Some photos

[D&D]

DISAR, I like that extended strut, if I could figure out how to post a picture I would show you a picture of my 60 Spint Cat in my album on this site. Then you would be able to see the extended strut that I worked out and how much weight I had up front in the boat with an .67 OPS, an 16oz fuel tank, etc., etc..... Seeing your build sure makes me want to build another Sprint Cat - electric this time.

[DISAR]

D&D, I saw your pics in your album and you have very nice boats. With what colors did you paint them? An electirc conversion is easy.

[D&D]

DISAR, The red color of my cat boats (these are actually four different boats) came as ordered from Areomarine, the black and white were many sanded and polished coats of Krylon (sp?) rattle can. Even running 60% nitro I never had a problem with the Krylon.

What I like about your new "big strut" is the setback it gives the boat which makes the boat handle as though it is longer. I am looking forward to learn how your boat is running, have you captured mph yet?

This is a test to see if I finally figured out how to post a picture:

16870

16870

[D&D]

Well I guess that is one way to post a picture, but how do you guys get them to open up? Do you take them from youjr posted album on this site?

[DISAR]

In the "Quick reply" box you click "Go Advanced", then further down you click "Manage Attachments" new window opens click browse and select the photos that you want from your PC, then wait and when they are attached you close that window and post reply.

The colors are very shiny, did you use varnish-lacquer-clear coat?

[DISAR]

Ok today tested some propellers 646 detongued, 225, 648, 235, 447/3. My best one was the 235 for good handling and speed of 44mph. I run the boat in sea water where conditions are different from ponds and speeds are less I believe, I have not compared speeds between fresh and sea water since there is not any pond here! The 646 d/t was also very good and 40 mph. I didn't like the 648 which made the boat quite unstable for me. 447/3 also good but with similar amps as the 235 but less speed. I am not into racing chasing speed I just want a reliable and nice handling fast boat. For the exact amps I don't know, only comparing, because the MGM black box sometimes gives me !@#$%!.
The boat is very nice.

[D&D]

DISAR, That's what I did to post the pictures and the pictures are OK, but I see all of the other pictures that open up into a nice sized picture for viewing when you click on them (OK, it might just be my "old age" desires). As to the shinny paint on the boats, that is just a lot of elbow grease, 1200 grit sand paper, polish, and wax. Also please note all the work on the inside of the boats, all sanded out and recoated with a red tinted resin. Yep, I was certifyably nuts! But I just loved it when the other boaters came to look at my boats and just walked away shaking their heads.

[D&D]

DISAR, I'm really surprised that the Octura 447-3 didn't work for you. As I thought about building a boat like yours that would have been my first selection. But, of course, I don't know nothing about the electronics and how props affect them. My 60 nitro ran a cut down 455-3 and three bladed props always ran the best on the 40/60 hull.

[DISAR]

The 447/3 was good also but I think the 235 better. From the props that I tested I will run the 646 d/t for general purpose and when need more speed the 235. Next thing is to measure the exact amps before going any higher. Very important in electrics in order to blow your ESC (expensive) or motor- also expensive. With the above props. everything was cool.

You can either have my setup or this
http://forums.offshoreelectrics.com/showthread.php?t=8680&highlight=sprintcat

Neu 1521 1.5D, 4s2p, hydra 240 which may be better and a bit cheaper

[DISAR]

final arrangements here, one twin, following Rumdog's idea (2xhpi 2200, 2xturnigy 180,4s,442) boat runs excellent even in windy and choppy conditions (better than my monos)
and another one with the 1527 1y, also runs great, on 8s it screams

[DISAR]

I finished my new twin sprintcat, 2 HPI tork2200kv, 4s, Turnigy 180, 442-447, speedmaster struts and rudder

[bonewar]

Very nice work there my friend.:thumbup1:

What have you used to reinforce the floor in the boat. Hybrid cloth ??
I think this 1 will be a very nice boat to drive.

Also love that gold and carbon cat in post 46
It looks Awesome. :rockon2:
How fast is she.

Thanks

Bonewar :rockon2:

[DISAR]

Many Thanks!

it is carbon kevlar 180gr and underneath carbon 160 gr on the tunnel, I have not tested them yet. I tested the red one once and it was very nice and fast to drive but did not like the shaft temperatures, therefore I built the white one. Time for testing now....