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.