trim tab angle

I am using my Fast Tech sort of a learning boat, i dropped in a more powerful motor/ESC ( Leo 4072 2000kv, Seaking 180a), using stock prop,( ProBoat metal) gained 8.5 mph. From 30 mph to 38.5 mph. I know people using stock are getting better speed than I am. But, that is ok for now since i have alot to learn. I have read many posts and are aware of the necessary mod in setups, my question is the trim tabs, they came measured 90* but if I put a ruler along the bottom of the hull, then the trim tab looks it is pointing downward (holding the ruler perpendicular to the surface of the bottom, the edge of the ruler can not be flush with the bottom of hull because the tabs are "pushing" the ruler away from the hull. ) When setting up mono-V , what is considered as a neutral setting? If i bend them up so they form a straight line from hull to tab would that raise the bow so the boat runs less wet? The battery position is really too much in the front and I don't want to mess with removing the trays, would bending the trim tab help to raise the bow?
Thanks

Have you got a video of your new powerful? :w00t:

no, I go alone and can't take video, I ran the boat with the trim tab bent up so it is even with the bottom if you place the ruler as i described from the OP. I moved the batteries so the front is in the tray and the back extends out. ( ThunderPower is too long to fit in, either have to position so the front over hangs or the back over hangs and since i removed the tupper ware box that is no problem). Gained another 1.4 mph, it clocked @ 39.9mph. But I didn't like how the boat ran , she was neither stable nor graceful. I further moded the trim tab, added "dog-ears and I also bent the turning-fins per Darin's recommendation. I will test tomorrow and report back. Hopefully one of these days I will have a video, thanks for showing your interest.

ok but if you want more speed with your configuration try with the octura x642, i've got one and i' m happy with it! later i want to try the 1800kv from proboat because i remain in 4s.

Here to report that yesterday was a disaster: I rolled/fliped the boat in 5 seconds after putting her in the water. Don't know why?! I bent the turn fins just like the pictures here on the forum. Anyway the violent tumble ripped the sealed hatch, boat looked like a shark fin in the water till I finally was able to push here in with my rescue boat. Now waiting for new hatch and trying to dry everything out. I noticed there are green corrosion everywhere, even the balance tabs from the lipo, I think my good TP lipos are toasted, even the ESC and servo plug had green corrosion.
I was careful, never rough on the rudder so this came as really a surprise. I was basicaaly driving a straight when this happened. Wish I had a better report...

Put WD40 on all parts that can rust after each browser, that is what I do! Your set up is not to hard for this boat?

Thanks! I run 4s and never had a problem, I originally thought bending the turn fins would make the boat more sensitive and therefore didn't do it since i wasn't running a race. I don't know what got into me and decided to bend them, anyway, that maynot even be the reason, because I wasn't steering the boat at the time...might be something in the water? I was concerned if the set up was too hot therefore I used the stock prop. Temp was always good. One time I ran until lvc and motor?ESC were 113*, batteries 110* more or less ( temp gun)
Thanks for the tip!

Hi, did you use the x642 with the stock motor? I got a p/bx642 but am afraid to use it with the Leo 4074 2000kv motor, I put the boat back to stock configuration with the exception of motor/ESC, runs better but I think I upset something and is not as stable as i first ran her with this motor. She turns right for no reason, could it be the port side trim tab is a bit too high?

yes I use an x 642 with my stock motor 1500kv Because it's the best prop for this set up!

For the 2000kv X440 uses a stock or the prop, the pitch is less important!

Thanks!! I have a x440 , will try!

HI, Thanks for suggesting the x440, it seems to let the boat run smoother and I don't have to worry too much. Losing a bit of top speed is ok. I have a question, my O/P was to ask what is the best trim tab angle, well, now that I have restored to stock setting, the point is moot. However, the boat would bank to the right on a straight run and "hooK". If I don't let up the throttle then it will roll, I looked at how the boat runs and it is always the starboard side , I raised the trim on that side but it chine walks a bit. Do I need to futher fine tune the trim so it will neither hook nor chine walk?

The Fastech was my first brushless boat. Had lots of fun with it in the neighborhood ponds, but I don't ever run it anymore. I also did Darin's mods and it was running great! Checked the trim tabs and they are raised about 3mm from level. With that hooking and rolling, you are running too wet, or the tabs are forcing the front of the boat down. Where is your COG? Adjusting the trim tabs up should raise the nose, then put the batteries all the way back and see how it runs. I removed the back of the battery trays and also about an inch of the parallel brace so my batts sit and inch or so back of the original position. Ran a X642 and was getting mid forties out of it with the stock motor and Turnigy 120 esc. It's a cool little boat when you get it running right.

Wow, I read your post with envy and admiration! I did once raise the trim tab but the boat ran unstable, I did the dog ears and also the turn fin per Darin's mod, i guess I did something wrong. I bent the fins to high, I noticed Darin said "mark the chine line and bent from there". The boat ran much worse. The best run I got from a stock metal prop was close to 40 mph. Anyways, I know i need to move the bat. tray more to the back, just didn't know how to get the wood out, guess will have to Dremal it out? Thank you very much for the informative tips. didn't know the batteries have to go that far back. ( I removed the tupper ware box so it shouldn't be that difficult, hopefully). I wish I could have seen your Fastech run. Thanks again!

I know this is an older post but I was wondering if you had ever got to run your fastech after sinking it? I have the exact same characteristics with my fastech. I actually never run her anymore because I am afraid of sinking it. It constantly chine walks and wants to hook and roll over, scares the hell out of me every time I take her out. I cant ever give her full throttle. I am running an x642 with everything stock otherwise. I have done all of the turn fin mods, the trim tabs are bent up with the small 45 degree bends in them. No matter where I adjust the strut this damn boat keeps hooking, I have had it roll over several times on me thankfully ending back upright so far each time, almost as if it is a self righting hull. Anyways was just wondering if after removing the back of the battery trays helped? I really want to run this boat, I love the way it looks. I watched a youtube video of a fastech running with a blackjack and man did that fastech fly, I could never dream of running mine full throttle because it will ALWAYS hook to the right and want to roll but I let off the throttle before she does. Very frustrating, almost want to sell it because right now I am afraid to run her!

Just to be clear: the boat ran ok with stock set up (X442) . It was actually very stable. I installed a Leo 4074, 2000 kv w/o any mods, ( x440) still was ok, then I bent the turn fin and adjusted the trim tabs, problem started ---- Shouldn't have adjusted two aspects at the same time. Lost all reference points. I don't think the bent-up turn fins were the culprit. I shouldn't have touched the trim tabs as the factory setting was a bit "negative", I raised it in the hope that the boat will run a bit drier. YOU NEED TO TUNE YOUR TRIM TABS CAFULLY, FIGURING OUT THE SWEET SPOTS FOR THE PORT AND STARBOARD SIDES. I got it back, this was the trickiest part because they are like ailerons on an airplane.This being a sub-surface drive prop I think the boat has its particular character. I bent the trim tabs down and was a bit calmer, but I liked the straight turn fin as its parasitic drag during a turn will slow the hull down and I don't get carried away.
Those that race will tell you I am nuts, but I am a sport boater, pleasure is my goal, not white knuckles.
I have since moved the 4074 motor out of the boat and installed the Proboat 1800kv/Proboat ESC with x440. Runs ok but like you, I love the look and the gel coat is starting to get hairline cracks i probably will have a shelf queen.
Never removed the battery trays though. The hull is too thin and flexible for a surgery like that, IMO.

Yeah, I'm not looking to break any speed records with this boat. I just want it to be stable.....which seems damn near impossible. So you truly believe its all in the trim tab angle? I have read SO many threads on tuning this boat and yet I just cannot seem to get it right. I have my impulse tuned perfectly, that boat screams! So you basically put the turn fins and trim tabs back to stock settings? Did you bend the little "tabs" on each trim tab? You should check out that youtube video on the fastech racing a blackjack, that fastech in insanely fast for what it is and I dont see that one hooking at all! This boat definately runs wet and I cant seem to get it right at all. Looks great up on my shelf though! I guess I will have to just keep playing with the tabs, just debating whether I should put the turn fins back to original settings.

I also think that the x642 generates alot of torque, hence the hull leans---torque roll, with the stock 1500kv motor and a 42mm ( I used x442, less pitch, however) the amount was tolerable, once the motor is faster and more powerfull, 42mm prop may not be the best choice. In retrospect I think a x642 ( wish I had tried that combo) and the original 1500 motor would have been a happy marriage. I was a newbie and didn't know ( still don't) what I was doing.

Yes, I did bent the corners of the trim tabs, but since I too wasn't looking to set speed records, and like a squirrel crossing the road, I made a "dash" back where I came out sensing danger ahead! :lol::lol::lol:
I restored everything.
That other post said moving the batteries rearward helped, since my hull won't take this operation, I wonder if I put some lead weight as ballast would help.

I tought the same thing with the weight, maybe leave the batteries in the stock location but add some weight to the rear. I have access to automotive strip tape weights that we use on wheels to balance them. I should try weighting down the rear of the boat and see what happens. Did your strut height seem to make any difference at all? It really didnt do anything for me, raising or lowering the strut, the boat still hooks. What I cant understand though is that from reading all the posts on this boat, this problem doesnt seem to be that prevelant. Really not many are having this issue? Only have I read that you had this problem enough to cause the boat to capsize? I can tell you I actually had two fastechs, I sold one, that one had the same problems also. Ive had my eyes on a genesis, maybe I should just sell this thing and buy a genesis, that too is a sweet looking boat. Thanks for trying to help me, I am just so frustrated with this thing.

Well, I bought this one way back and although I didn't have running issues I did have a water intrusion problem, that was before I found out this forum and didn't think about putting a piece of silicone tube at the stuffing tube in the hull. Anyway, I say this to tell you I probably had the first batch.
I could not change much in terms of strut height or angle because the design of the assembly did not have margin to be moved about. At that time I tried the Proboat metal props with the original 1500 kv motor and ran well, but that is a heavy prop and although I was led to believe that it is balanced out of the box. The little remaining inbalance quickly translated to accelerated wear on the bushing.
Now, when I ordered a replacement strut, it was shorter than my original one and I can def move the angle, the shorter length allowed room for it to move w/o binding the prop shaft. I have a bit of "positive" angle dialed in. In terms of height adjustment, not much can be done, the exit of the stuffing tube is encased with the hull and only a short distance to the strut, I tried to set it as high as I can.
I agree it is a sweet looking boat and if you can keep it, should keep it, IMO. I know the moment I let go of something i regret and start all over again to acquire it, well, I am hopeless!
Good luck with tuning your boat, love to hear/see how it works out for you.

T-

Just to restate: you are running a 2000kv...so I would think a 42mm is too much... For reasons you stated. The torque roll is bad with that size prop... I have the stock setup and a prather 215 (similar to the X642) and the thing rips! The dog-ears STOPPED the chine walk. The angled stabs STOPPED and roll in the turns! Make sure your CG is good! Strut angle on mine is about +2 degrees... It took some tweeking, but that thing should handle high 30's low 40's like on rails! I have mine set up so that I can make a 10 foot diamter turn at full throttle and NEVER roll...

The one time I rolled was on a straight, and a plastic bag wrapped around my prop... That boat rolled over like nothing I have ever seen.... And my boat sank...but I swim like a dolphin and got it :rofl:...But follow the advice Darin has on here about mods. It does work super well... But if torquing is still and issue, i would suggest a X440 or maybe even a X638-X637... I know it's small, but if you have it, it might work out... I run a DF 26 on an 1800 Aq motor... and I love the handling on the X638. i get like 10 mph more on my X642, but the torque rollin is not managable... and my run times are 2x better on the smaller prop...

Quote:

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Originally Posted by sanyijr

T-

Just to restate: you are running a 2000kv...so I would think a 42mm is too much... For reasons you stated. The torque roll is bad with that size prop... I have the stock setup and a prather 215 (similar to the X642) and the thing rips! The dog-ears STOPPED the chine walk. The angled stabs STOPPED and roll in the turns! Make sure your CG is good! Strut angle on mine is about +2 degrees... It took some tweeking, but that thing should handle high 30's low 40's like on rails! I have mine set up so that I can make a 10 foot diamter turn at full throttle and NEVER roll...

The one time I rolled was on a straight, and a plastic bag wrapped around my prop... That boat rolled over like nothing I have ever seen.... And my boat sank...but I swim like a dolphin and got it :rofl:...But follow the advice Darin has on here about mods. It does work super well... But if torquing is still and issue, i would suggest a X440 or maybe even a X638-X637... I know it's small, but if you have it, it might work out... I run a DF 26 on an 1800 Aq motor... and I love the handling on the X638. i get like 10 mph more on my X642, but the torque rollin is not managable... and my run times are 2x better on the smaller prop...

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:iagree: I did go down to a x440, and ran with stock trim tabs and turn fins, I don't think I had them adjusted well, but I took the motor out because I got a PB 1800kv motor, now using x442. No torque roll. Mine also sank once and I lost the hatch, good thing at that time they had a few left at Horizon. The reason I no longer run this boat is that I really love the looks of it and the hull is just at the threshold of developing hairline cracks, I would like this boat be a shelf queen.:o