Miss Geico dialed in- strut modification

[hydro_pyro]

The higher you go, the more stern-lifting effect you get, at the slight expense of holeshot punch.

[Speedracer128]

@ hydro
If the higher the strut is the more stern lifting effect happens does that push the bow down as that happens?

[ozzie-crawl]

Been awhile since i played with boats so could be wrong but when raising the strut it should push the stern into the water further creating more stability.
By adding angle to the prop lowers (prop angled down) or lifts (prop angled up) the bow.

[hydro_pyro]

The propeller produces a cone-shaped thrust profile. When less of the thrust cone is below the surface, it results in a stern lifting effect. This allows the COG to be moved back. Angling the strut downward further amplifies the stern lift.

Angling the strut neutral or "up", or running the prop deeper does lift the bow, but it keeps the stern glued to the water, which causes the tunnel to pack too much air. When the air pushes its way to the back, the stern pops up and farts the air bubble out the back, and the bow drops. Then it starts all over again. Hop, hop, hop. All the while, it's itching to blow over.

By un-wetting the stern, the boat can ride smooth and fast without the hopping. The COG keeps the bow up, and lift provided by the prop keeps the stern up. Hydrodynamic drag is reduced. More speed, less hop.

[ozzie-crawl]

Did the strut mod with batts at 30%. Not lifting and dropping the front any more. Boat stays flatter and more planted but does bounce a little bit. Very stable tho and does not look like blowing over.
Tried the batts forward a little and was a about the same so tried moveing them back further and had a blow over.
This was on flat water. From my testing the day before a bit of chop will make in run spot on.

[AlanD]

hydro_pyro and tlandauer, can you guys post photos of the interior layout of your boats with battery packs installed? Pyro, I'm wondering if your use of a third battery pack upfront is keeping your bow more stable, whereas many of us are just using 2 packs, creating the need for a slightly different cog. Without going too far down the polar moment of inertia road, I'm curious if you have a different distribution of weight to us "2 packers." :)

[Speedracer128]

A third pack will def change the balance of the boat but I'd like to know how much a dif it makes also

Once I upgraded my motor and esc my MG blew over constantly, even with my strut angled down and packs forward. On one of the blow overs I had a seem split so I reinforced it with a heavy coat of resin with fiberglass strands in it and that totally changed the ride of the boat because of the extra weight. I know it slowed the boat down a bit but I like the extra weight up front. How it is now, even at high speeds she's not trying to blow over and the other great things is that when I hit waves and she goes airborne with the extra weight the boat stays level. So I'm much happier with how she rides now

[ozzie-crawl]

Not one of those you asked but Given mine a few short runs the last couple of days and have eliminated the bounce altogethor in slight chop. Useing the strut mod posted here and batteries are 35mm from front of battery tray. Cog is 205mm from rear of sponsons or around 29%.
Been fairly windy so not certain how it will run on smooth water.
Running a pb1500kv motor on 6s (2x3s 4000mah) with a detounged x642. Have not bothered temping any thing as motor and esc have hardly any warmth after a 4 min run.

[tlandauer]

Did the strut mod with batts at 30%. Not lifting and dropping the front any more. Boat stays flatter and more planted but does bounce a little bit. Very stable tho and does not look like blowing over.
Tried the batts forward a little and was a about the same so tried moveing them back further and had a blow over.
This was on flat water. From my testing the day before a bit of chop will make in run spot on.

hydro_pyro and tlandauer, can you guys post photos of the interior layout of your boats with battery packs installed? Pyro, I'm wondering if your use of a third battery pack upfront is keeping your bow more stable, whereas many of us are just using 2 packs, creating the need for a slightly different cog. Without going too far down the polar moment of inertia road, I'm curious if you have a different distribution of weight to us "2 packers." :)

@ AlanD, Just a quick reply before I have time to take pictures: I don't think a third pack in front of the motor is the answer. When the boat is dialed in with the COG at where it's supposed to be, there should not be a need for extra weight forward of the motor.

[Speedracer128]

Ozzie
What kind of speeds are you getting with that setup?

[tlandauer]

hydro_pyro and tlandauer, can you guys post photos of the interior layout of your boats with battery packs installed? Pyro, I'm wondering if your use of a third battery pack upfront is keeping your bow more stable, whereas many of us are just using 2 packs, creating the need for a slightly different cog. Without going too far down the polar moment of inertia road, I'm curious if you have a different distribution of weight to us "2 packers." :)

@ AlanD,
DSCN3423_3622.jpg DSCN3422_3621.jpg
I am ashamed to admit that it's been a long time since I ran my MG, I don't remember what was the exact spot. But you can see the range od adjustment on my battery tray is about 2.5". In order to get the so-called 30% COG , the batteries have to go to the rear like photo No.2.
I never made a science out of it, I will see how the water is and put them some where in between, drive the boat for 30 second and bring her in, adjust the batteries and go out again. What I found out was that with the sponsons trued and the strut up, the boat doesn't bounce and the forward COG is really to prevent unnecessary blow over should the wind and chop conditions are not favorable.

[ozzie-crawl]

Ozzie
What kind of speeds are you getting with that setup?

I would not like to guess and have not gps,ed it as yet. just got a new data logger to run bullets on (other has deans) but still need to order gps for it.
Here is a short video of the last few laps i ran this afternoon. http://youtu.be/GzE2-IP44M0
Video is a bit poor as it was of my phone and had the res turned down and zoom on.
The water had a decent amount of chop that the hull seems to really like but there was a decent wind as well. running into the wind (away from camera) i was taking it easy and the getting wot coming back but you here me get of the throttle a few times.
Had a short run on other side of lake were it was much smoother and it has a slight bounce but runs nose high and airs right out.

[kwiktsi]

Not one of those you asked but Given mine a few short runs the last couple of days and have eliminated the bounce altogethor in slight chop. Useing the strut mod posted here and batteries are 35mm from front of battery tray. Cog is 205mm from rear of sponsons or around 29%.
Been fairly windy so not certain how it will run on smooth water.
Running a pb1500kv motor on 6s (2x3s 4000mah) with a detounged x642. Have not bothered temping any thing as motor and esc have hardly any warmth after a 4 min run.

Hey Ozzie- what ESC are you running in yours?

[ozzie-crawl]

Hey Ozzie- what ESC are you running in yours?

Still just the stock one. It is just getting a bit of warmth in it after a 3-4 minutes of running. All plugs are 5.5mm bullets.
Will try get a some data logging done next weekend see what amps it is pulling.

[AlanD]

@tlandauer - thanks for the pics. My batteries are flipped 180 degrees from yours so our wires are in the same position as in your second photo. Yet my cog is right on the stuffing tube bulkhead which is about 30%. Its just the little bit of bouncing at WOT which I'm working out. I'll try your positioning later today and report back.

[Speedracer128]

It was choppy and it was still running good. Is that a stock blackjack on 6s with the strut angled down with this mod?

I need a GPS too

[hydro_pyro]

Remember to carefully bend the stuffing tube and re-shape it so it's aligned with the sleeve in the strut. Add more bend where the tube exits the hull, and straighten out some of the bend as it approaches the strut.

[kwiktsi]

Still just the stock one. It is just getting a bit of warmth in it after a 3-4 minutes of running. All plugs are 5.5mm bullets.
Will try get a some data logging done next weekend see what amps it is pulling.

Wow, can't believe the stocker is holding up on 6S. How long have you been running it like this?

[ozzie-crawl]

It was choppy and it was still running good. Is that a stock blackjack on 6s with the strut angled down with this mod?

I need a GPS too

Still stock except for motor and prop. Only thing else was the strut mod in this thread. Have not blue printed sponsons yet.

[ozzie-crawl]

Wow, can't believe the stocker is holding up on 6S. How long have you been running it like this?

Only had the boat a couple of weeks so its done about 1 hours worth of running. After a 3-4 minute run every thing is only just warm.
I reckon i could do a 7-8 min run with out any thing getting hot.

[BHChieftain]

Remember to carefully bend the stuffing tube and re-shape it so it's aligned with the sleeve in the strut. Add more bend where the tube exits the hull, and straighten out some of the bend as it approaches the strut.

+1 !!! else you'll see water shooting up the stuffing tube.
Chief

[Speedracer128]

What does changing the angle of the stuffing tube do to handling or performance?

I run my MG on 6s with a 4082 and a 642 or 646 prop. I haven't made any adjustments to my stuffing so I'm wondering if I'm missing something

[AlanD]

Ok, so I moved the battery packs to your position. Usual strut down angle. Slight breeze, pretty flat water. The boat ran so nose high at half throttle it was at risk of blowing over and still had a lot of bouncing. I pulled it out after 2 minutes and respositioned the batteries to their "usual" place and ran again. Now I'm back to really flat running with only a little bounce at WOT.

My deduction is that my motor must be heavy enough to warrant the cog being between the motor face plate and stuffing tube bulkhead. The lesson learned is that you have to do whats right for your particular setup to get what you want out of it. Here's my setup for what its worth.
picture004.jpgpicture006.jpgpicture007.jpgpicture009.jpg

[hydro_pyro]

To answer speedracer's question...

Notice in the 2nd photo above this post, how the strut shown is angled down, but the strut is not correctly aligned with the stuffing tube. You can see where the angle changes at the joint-- the tube turns upward, but then the strut angles downward. It doesn't affect handling, but correcting the mis-alignment will reduce stress on the flex cable and strut bushing, and help keep water out.

The problem is, the stock tube turns and meets the strut at a "level" angle, so it will turn upward when you raise the strut vertically. The modified strut will make this break angle even worse once it's angled down, unless you correct the angle.

With the strut removed, bend the tube so the curve is concentrated nearest to the hull bottom. Then straighten out the bend below this point, so the tube is angled downward as it approaches the strut.

Alan, correct the tube angle, then raise the strut vertically higher like in my photo above. The bounce will go away.

Here's the tube aligned correctly:

[hydro_pyro]

Once the strut is raised high enough and angled downward enough, you will have lots of stern lift effect. This will allow the packs to be moved back more without the blowover risk. Stern lift keeps the back end higher, which will allow the bow to fly higher without the tendency for the tunnel to trap air. Stern lift gives the trapped air an escape path. More speed, more stability, and NO bounce.

Note the pack position... No blowover tendency here on 4s.

[Speedracer128]

Thanks for the explanation hydro. I didn't realize the stuffing tube is bendable/flexible when the strut isn't attached

I understand what your talking about the air escaping from the tunnel by having the strut higher vertically, but I thought by having the prop deeper in the water was more stable. This weekend I ran my boat on 4s and 6s with the strut set low and angled downward toward the back to keep the nose down and my boat has never been this smooth riding at high speeds since I upgraded my motor. This weekend was ruff where I was running but even when I was going fast when the boat would catch air she stayed level while airborne. With 4s my batts were a out the same position as your pic above with 6s slightly further up. But on mine i made new battery trays that sit lower in the hull. I do know that when I reinforced my hull, the extra weight made my boat handle much differently. I think I need a GPS so I can exactly know how all different adjustments affect its speed

[hydro_pyro]

On some boats, "stable" just means it's stuck more firmly to the water. On a tunnel or catamaran, this traps air and increases the chances of a blow-over. When the strut is higher, there's less prop in the water, and thus there's a lower cross-section of the prop's thrust cone being exerted on the surface of the water. This reduces bow lift and pushes the back end of the boat up, allowing the air to escape out the back, which makes it handle a little more "loose", but more consistent because it's not hopping constantly.

[maxmekker]

https://www.youtube.com/watch?v=_Uln02dfrSs

This is my run from Sunday. Still a little bounce at high speed. OSE has a new upgrade strut which should be released this week. I'll be ordering that soon with the M440.

cool video man, that thing is fast :-)

[Mike Caruso]

Hi,
My son has been racing his Miss Geico (V2) in the p-limited offshore class, and we have it dialed in on stock setup with x642 prop. Batteries are just behind the front end of the motor (non-shaft side). Per the tips on the forum, I ground a wider slot in the strut, allowing a bit of negative angle. I have the strut up pretty high-- with the sponsons on the table the shaft does not touch the table-- close-- probably less than 1/8 above it (in the picture it looks like more, but that is just due to the camera angle).

In race conditions (ie, some race-induced chop in the water), the boat rides perfect, no bounce. In glass water, we get a slow bounce. I have not blueprinted the sponsons, and probably won't bother as the boat is doing great in race conditions.

Been too busy coaching my son through the races to get a video, but will try to get one next time.

Chief

Hey Chief,

Great info to help the guys with the same boats get flying and nice of you to put it out there! Makes me want to keep an eye out for one now.

[Shane_744]

Thanks for the information and pictures on this modification. It took about 1 hour to do this mod to my MG 29. Longest time was bending the stuffing tube correctly and keeping the strut lined up while tightening it. Took the boat out for a quick run and much better. I left the batteries in the same spot that I ran the other day. Bouncing was almost reduced but the bow did wanna lift at full throttle. Boat is otherwise stock. The packs are around the "middle" of battery placement. Ran that for about 2 minutes and the ESC let out some pretty white smoke and black bits.