Hydro pros..........need help, PLEASE!!

[Make-a-Wake]

This is my first Hydro(miss Elam 1/12) after many Vees and i am having some trouble getting her to run well after several times out. A hydro is surely a different hull from what im used too, but i loved the look and wanted one.

Anyways, she has her moments of glory, but mostly not. Any and all suggestions are very appreciated as i am feeling a bit "beaten" by her.

I have been told to use an "M" prop, and to give the prop some positive angle. Running an x642.

Only got to 3/4 throttle once at about 1:14..........ran good right there til i slowed.
Thanks again in advance...............:biggrin:

The madness begins at 0:27

http://www.youtube.com/watch?v=VNvg19xML8M

[Make-a-Wake]

Just realized i posted in "building"............sorry mods.:o ..........i did build it though..........

[domwilson]

Try raising the prop till it's level with the ride pads. That would be a good place to start. Also run the prop level.
Where is your COG? Jesse on this forum as well as Darin have good advice on setting these up.

[domwilson]

Der...Didn't see the pic for the COG. Try moving it forward to 1 1/2" behind the sponsons.

[Jesse J]

Hey Carl, based on how she ran in the first half, I would suspect the turn fin came loose. This has happened to me and once that goes its like loosing a tie rod in a car.... That turn fin is your best friend and worst enemy. make sure everything is tight.

This is still pretty stock? do what ever you can to get weight forward, but that isn't your wigglywobbly problem. Check for loose stuff then if nothing loose come back and report. In the mean time I will study your pics in OP.

J

[Jesse J]

She looked real good at first. As for COG, you are a bit back, but that will only really become a problem at higher speeds. I think the strut is stock low like that to compensate some for the rearward COG. My buddies is over 3" back... I need to make him leave it in my shop so I can do some doctoring (probably what yours needs as well).

Darin added adhesive weights to the front and it supposedly helped out.

Last run on my avatar hydro, the whole strut came loose and was floppin like a fish held by its tail (I should post the poor mangled prop - its a trophy).

I was also told by a very credible source that cupping the prop some will help tame down that tail end.

If all else fails, you may need to redo the stuffing tube so you can raise up your strut some more. mine is probably about where Dom suggested and is pretty standard starting place. Remember, that prop is in equilibrium when riding at the surface and will try to achieve that. so if you have it too deep, it will keep popping up the back end. You will be perfect when you have a touch of hop, but it settles into the turn nicely.

Don't get discouraged, hydros are the hardest to tune, many variables - change one at a time.

[Make-a-Wake]

Thanks guys............................the cog is as far forward as i can get it.

As for the turn fin..............when it comes in, i dont notice it at a different angle..........seems tight. I think i'll try it tomorrow without the turn fin and go easy on corners while testing. Is the prop too big.........is it torquing the hull and lifting the left sponson?

I had a 5 ounce weight in the front left side and it didnt really help. Hmmmmmmmmm?

[Jesse J]

DO NOT TAKE OFF THE TURN FIN - it will not turn at all!

Try stuffing the ESC into the cockpit and the batteries into the sponsons. The more I think about it, the more I want to get your strut up higher. How much can you raise it? you may need to bend the stuffing tube (very gently as it is cheap brass and will break pretty easily). I cut mine off flush with hull inside and out then retrofitted it for .078" wire drive. But that should not really be done unless you are ready for the "overhaul".

These are the best looking hulls out there, but at a price. To get em to perform, you gotta tear into em.

oh, and the prop is perfect! you are not torquing the hull, it is sponson walking, frustrating little stunt they do when the back end is bouncing all around.

[Make-a-Wake]

OK............wont take the fin off. The strut is actually higher than it is stock already from what i've seen.

"you are not torquing the hull, it is sponson walking, frustrating little stunt they do when the back end is bouncing all around."

OK, so whats the cause of this? Back end too high as you have said the strut needs to be higher? I am at the end of the strut adjustment so i guess i'll ream out the slot for more travel up.

These suckers are tough!

[Darin Jordan]

It looks to me like it's fighting the turn fin. I think if you find my "Race Prep" thread for this boat, you'll should see an example pic of the turn fin I fabbed for mine. You can try rotating the fin forward or aft a little. I looks like it's pulling DOWN on the sponson, so rotating it forward a tad will eliminate that to a degree. I was never able to really make the stock fin work, so I replaced it.

This hull has a tendency to do this walking at speeds exceeding 45-mph when the water gets choppy, but you should be able to get it better than it is. Little adjustments.

[Make-a-Wake]

Thanks Darin! I was suspecting the turn fin myself, kinda why i wanted to run it without it, Jesse mentioned it wouldnt turn at all though.............with the cupping, it has to be perfectly aligned or it seems that it would pull down or push up. Gonna check your "Race prep" thread. I have been scouring your posts on the Elam.............even found the part about extra weight..........i think my COG is pretty close............?

[Darin Jordan]

To test the fin theory... go ahead and take it off and run the boat. You won't be able to turn very well, but you'll be able to test it for straight-line stability. Just slow down for the turns.... WAY down... ;)

[Make-a-Wake]

Well................off with the fin then!

I'll report back later today.....thanks again!

[befu]

I have tested this before also by replacing a curved turn fin with a small flat one. It will still help it turn slowly, but will not cause a digging or lifting in the straights.
Just make sure it is straight up and down.

Brian

[detox]

Here's Darin's fin.


I've made a new turn fin. Just about 1/4" longer, and a longer chord length to give it more area. It's made from .060" 7075 T6, and has two slight bends in it to hook it at the bottom, one 1/2" up and the second 1" up... Not quite as hooked as the stock one. Sharpened and drilled up. Should provide a bit more control in the corners when the water gets "racey".

[Make-a-Wake]

Thanks Keith.......................i have a couple of straight turn fins..........i my slap one on just to see how she does without the cupping.

[domwilson]

To me it looks like a combination of issues. The strut may be a little to deep and as Darin suggested, the turn fin is pulling the sponson down. possibly because of the angle of the fin itself. You may want to angle forward slightly so the curve is parallel to the way the boat actually rides.

[Make-a-Wake]

Thanks guys.................just got back from a quick run..........no vid man with me, but she ran SO much better! Threw a fin on from a big mono.................she settled way down. At WOT she wanted to "hop" off the water a bit every now and then......not one sponson lifting, just the whole boat up off the surface at times. I ran it with a bit of positive angle............im going out when the batts recharge here in a bit and try it with neutral...................right?

PS - she turns better to the left...........:confused1:

[dana]

Thanks guys.................just got back from a quick run..........no vid man with me, but she ran SO much better! Threw a fin on from a big mono.................she settled way down. At WOT she wanted to "hop" off the water a bit every now and then......not one sponson lifting, just the whole boat up off the surface at times. I ran it with a bit of positive angle............im going out when the batts recharge here in a bit and try it with neutral...................right?

PS - she turns better to the left...........:confused1:

hey what a cool idea! now i want to try it with my ul-1:popcorn2:

[Jesse J]

NOOOOOOOOOOOO, you took it off? Ahhh. ok, settling down (good wine at dinner). I am glad you have isolated the problem at the turn fin - at least you can replace that. it looked suspect the way it shook back and forth. Glad you took it off to test - my bad in telling you not too; I just have bad associations with when mine came off and she would NOT turn at all. Testing is a valid reason.

Cheers - well once you show us more vids -

wait... did you say she turns better to the LEFT??? What scale is this craft? and where did you put the turn fin? My buddy at the LHS keeps asking why we cant put two turn fins on hydros... tisk tisk.

I have hopping issues to solve myself. cupping the prop I was told.

still waiting for vids.

[Jesse J]

try it with neutral...................right?

Ideally you want a tad negative - 1 deg. this will keep the nose down when you are going mach 3.

[Make-a-Wake]

Hey Jesse, i used a straight fin as in the pic i posted above.............post #18. Its the standard 1/12 Elam.............28" or so.............

[Darin Jordan]

Ideally you want a tad negative - 1 deg. this will keep the nose down when you are going mach 3.


Just so you guys understand a little better... strut ANGLE mostly affects the BACK of the boat... lift increases as the angle increases at the back.

Strut HEIGHT affects the nose of the boat. The deeper the strut, the more it pushes the nose down.

Obviously the two aren't mutually exclusive, but in general, this is how it works...

[Make-a-Wake]

Thanks for the help Darin.................my strut is 3/4" below the hull bottom to the middle of the shaft..........its seems to be about where it would be stock..............i put an adj. strut on like you did. Little bit of Neg.........or neutral? I'll get some new vid when i can. Thanks again to everyone!

[Jesse J]

Just so you guys understand a little better... strut ANGLE mostly affects the BACK of the boat... lift increases as the angle increases at the back.

Strut HEIGHT affects the nose of the boat. The deeper the strut, the more it pushes the nose down.

Obviously the two aren't mutually exclusive, but in general, this is how it works...

Interesting, I was told the opposite. It makes more sense to me that the angle of strut, and therefore the angle of thrust, affects the force on the nose, whereas the depth of the prop, which wants to attain its surface penetrating position, will control the back of the boat.

This is the first time I have seen it stated to the contrary. Darin, why do you say this? have you some data to show that it is how you stated? I don't, other than my experience with trying to get my hydro to behave best possible. I have noticed that they generally behave as I stated, but am interested to hear why you have stated so decisively the opposite?

[Darin Jordan]

This is the first time I have seen it stated to the contrary. Darin, why do you say this? have you some data to show that it is how you stated?

Well... I may be remembering it backwards, but that's what Dick Crowe told me.

If you think about what angling the strut does (provides or reduces lift), WHAT is it "lifting"?? The BACK of the boat... When you leave the strut neutral, and move it down, it makes the back of the boat ride higher off the water, which forces the nose down.

Like I said, they aren't mutually exclusive, but in general, you push the strut down deeper in the water to help get the nose of the boat down, and you angle the strut more to get more lift at that back of the boat.

[Jesse J]

Well... I may be remembering it backwards, but that's what Dick Crowe told me.

If you think about what angling the strut does (provides or reduces lift), WHAT is it "lifting"?? The BACK of the boat... When you leave the strut neutral, and move it down, it makes the back of the boat ride higher off the water, which forces the nose down.

I am not convinced that simply lifting the rear of the boat does a whole lot to lower the front - it is being lifted as well by the air compressed under the tunnel. Whereas the angle of the strut will provide rotational force (stern to bow) around the center of mass axis running port to starboard, which will have more of an affect on the bow, and yes some but minimal affect on the stern.


Like I said, they aren't mutually exclusive, but in general, you push the strut down deeper in the water to help get the nose of the boat down, and you angle the strut more to get more lift at that back of the boat.

I agree that they are not mutually exclusive and it can be tricky finding a good combination, but I still think angle predominantly affects the front, depth the back. That said, I am very open to discuss the matter and am not in any way saying you are wrong - just not convinced. :Peace_Sign:

for the record, I definitely do not consider myself a "hydro pro" just a modeler interested in learning how to better tune these dang hydros.

[Darin Jordan]

I am not convinced that simply lifting the rear of the boat does a whole lot to lower the front - it is being lifted as well by the air compressed under the tunnel. Whereas the angle of the strut will provide rotational force (stern to bow) around the center of mass axis running port to starboard, which will have more of an affect on the bow, and yes some but minimal affect on the stern.



I agree that they are not mutually exclusive and it can be tricky finding a good combination, but I still think angle predominantly affects the front, depth the back. That said, I am very open to discuss the matter and am not in any way saying you are wrong - just not convinced. :Peace_Sign:

for the record, I definitely do not consider myself a "hydro pro" just a modeler interested in learning how to better tune these dang hydros.

It's possible I have it backwards. Your points on the thrust-line make sense. I tend to get stuff backwards when I try to remember it, and the more we "talk" this out, the more I question myself... NO WONDER I can't set a boat up!! :Sinking: :unsure: However, when you raise the back of the boat, the front has to go down. On and OPC, for example, the outboard height will raise/lower the tips of the sponsons because it changes the height at which the rear of the boat wants to run. Angling the outdrive may appear to have a similar affect, but it's actually pushing up/down on the back, the same as lifting/delifting a prop... This WILL affect the nose of the boat. Both will/can....

[Jesse J]

Hydros are certainly my biggest challenge and why I have cats and monos to console myself. I respect anybody that works with hydros and KEEPS doing it. they can be incredibly frustrating and hard-headed (the hydros that is); sometimes they are downright naughty!!

But they are definitely the most sexy and romantic of the water crafts in my mind. There's nothing like the shear speed and ability to turn at that speed, plus that wall of water?? oooooh, just makes the hair on my neck stand up. They are the closest thing to an airplane with floats.

[MarkF]

Lifting the back of the boat up by lowering the strut can lift the hull up evenly or it can bary the nose. It all depends on were the cg is. This is used for getting the ride heighth were you want. When you angle the strut down ( negative) it tries to force the back up but also the front down. Good for boats that are tail heavy or flighty. Can cause hopping in hydros though. Pointing the strut up ( possitive ) will help hold the nose up. Good for nose heavy boats. Also helps monos hold the bow up in the turns and helps get rid of hop in hydros. This is my basic understanding of how the strut works. Of course every boat is different and you need to play with the different strut angles to tune your boat.

Mark

Mark

[Jesse J]

nice Mark, I am glad you brought in COG, major player. Good points about how the COG influences the adjustment type. Your post highlights the complexity of how the variables can influence one another and are again, not mutually exclusive.

Thus the many factors to consider, then there is the type of prop - more vs. less lift, as well as hull type.

[wparsons]

Scorp, in regards to it turning better to the left. Do you mean sharper, or it handles turns better? If you mean sharper, its probably because you had some left trim, which reduces the throw to the right. Check to see how much throw you have in each direction before looking into it too much.

[tharmer]

I always start with the strut at 0 degrees. Then I move CG to find a spot where the boat appears neutral when it lifts off a roller. Then I adjust strut depth to get the ride height I want at the stern. A surface riding prop will always come to the surface almost regardless of how deep the strut is. This has the effect of pointing the nose down (not forcing it down) so that less air is packed under the hull, giving the impression that the nose is being forced down. After all this is done, I tweak the strut angle in very small increments to help the CG balance the boat at speed.
-t

[pda75]

I have the same approach (zero degre strut).... but I always have a central spanson on my rigger. Therefore the front angle sponsom does not depends on the strut depth.

I place the strut depth in order to have the prop at the standard position (when only the blade of the prop goes into water) and start with a low lift propeller

I then try to get the CG position which balance the rigger in order to be stable (no bumping) and then put some more weight on the strut (10% more). Than I adjust the strut angle depending on the prop lift.

Pierre

[Make-a-Wake]

Thanks for all the info guys.................and parsons, you were right about the servo trim............i had it cranked pretty far left.

[Make-a-Wake]

Here she is on glass! That darn stock turn fin was a real party pooper..............she runs like i never thought she would now that i had played with the strut and put a big mono turn fin on her!:bounce:

I went down to an x640 as one other change, but will now obviously go back to the 642.

Thanks so much for everyones help!! I'll post a new vid with the x642 tomorrow.

I'm pumped!:banana:

Ehml9rfNvrw

[Jesse J]

nice, glad to see you happy with her performance, much improved. keep at it!

[Make-a-Wake]

Thanks Jesse...................i'm stayin' with a straight turn fin................had no idea the stock fin could throw it off so badly if it wasnt set just perfect.

How fast was your Elam........................over 50?

[CircusCircus]

You should try a M435/3 blade Octura, I have found this to best all around prop for the proboats, if it feels like your topping out, jump up to a 437/3 blade.

[wparsons]

^^ He's not running the stock motor, so I don't think the M435/3 will be much good. He's running a low kv bigger motor on 8s (yes, 8!).

[Make-a-Wake]

^^ He's not running the stock motor, so I don't think the M435/3 will be much good. He's running a low kv bigger motor on 8s (yes, 8!).


:rockon2: :rockon2: :rockon2:

[Make-a-Wake]

Quick vid from today. Gettin' her figured out finally. Made a direct pass at my buddy who radar'd her at 48 mph. I have 3-5 mph left the way she sits due to my long rudder..................kinda sheepish to even show it. Its a rudder from Stevens store here and has the correct setback and so forth, just long. Gonna cut it down before the next run so it should reduce some drag.

EL3M8f2hxWk

[Jeepers]

hard to tell from the video, but it looks like its still dragging its tail.

[Make-a-Wake]

Probably cuz of the long rudder..................lemme cut it down to 3 1/2" or so and see what she does.