HELP NEEDED WITH SET UP FOR 1/8TH SCALE HYDROPLANE MHR 8255

[TREVOR JENSEN]

Hi Don,

Sponson trailing edge is 26mm, Strut depth from hull bottom to shaft centre is 20mm.

Thanks

Trev

 

[Greg Wannamaker]

After viewing the LohringMiller boat in the NAMBA propwash I notice the tub area is much wider and no real sign of a offset tub so batteries can be evenly spread out in the hull.

Can you somehow convince me that 1.5kg of lipos suitated 1.5inches to the right of the centerline of the hull isn't apart of causing my issues with too much weight on turn fin side of boat.

Thanks

Trev

The offset weight of you batteries might cause problems but would be less problematic than having your front to back CG misplaced. Like Don says get your strut depth correct, test it, try some negative strut angle, test it, try some different props, lifting vs non lifting, tons of testing to be done here and again as all have said, only one change at a time - there really is no short cut, you will need to work it out, one step at a time, you'll find the solution eventually. Once you find its sweet spot and you are able to open it up and get max speed out of it without the fear of blowing it off then I would suspect you will be able answer your question surrounding the left/right weight balance. If it's an issue I expect it to rear its head in the corners by causing the right sponson to ride deeper in the water than you would want and might result in a hooking problem. However you might just find that inside weight may allow your boat torail the turns which is where races are truly won.

Stick with it and you'll find the correct set up for your boat.

 

[Don Ferrette]

Hi Don,

Sponson trailing edge is 26mm, Strut depth from hull bottom to shaft centre is 20mm.

Thanks

Trev

I really feel your strut is not deep enough, go to 26mm from hull bottom the centerline of prop shaft to start. I typically begin with strut depth (at shaft centerline) the same as sponson depth on all scale hulls regardless of who makes them, often wind up a little deeper. Also having more weight on the turn fin side is actually a good thing............

 

[LohringMiller]

The reason for offset batteries is to counter motor torque. Electric motors can develop more torque than IC engines, especially at low rpm. We ran a larger prop on the electric version which also increases the torque effect.

Lohring Miller

 

[GraysonTaylor]

Two kitchen scales, one under each sponson are good for checking left / right balance provided the rear is supported from the center.

 

[Duck899]

How many guys run struts with no angle? Yes, if you can design the perfect hull to carry the weight, have the fuel on the center of gravity, figure out the density of air under the boat for different temperatures and altitudes, then you might be able to run the strut with zero angle. This will give you the ultimate speed. Even riggers need downforce and run 1-2 degree's of negative angle. I would try this before glueing and sheeting the bottom of the hull.

Have you tried to put negative angle in the strut? Have you tried a "lifting" prop? The X series props have alot less lift than a 1400 series.

I think your missing the obvious.

Even full scale unlimiteds run negative angle as it helps to get the rear of the boat off the water resulting in more speed.

I'll disagree here. I've run many scales over the years with zero strut angle BUT spent plenty of time on overall set up. The only riggers I ever ran that needed negative on the strut were Eagle SGs. All my current riggers run flat (zero angle) struts. I would look real hard at strut depth first...........

I guess I should clarify, How many guys run SPORT boats with flat angle struts?

Yes, after balancing, prop changes, struts at the proper depth on a SPORT boat. Then it will run correct. My 69 pay n pak runs a flat strut but thats a different animal.

Alot of us who have been in this hobby for 40 years can take a hull and bench trim on a sheet of glass and wind up with a hull that usually runs not too bad right off the bench, first time out. But, there is always room for improvement. Lots of testing, racing time is required to get it working properly. I do alot of my tweaking during races, its a never ending deal.

As Don says, drop the strut, see what happens. Some of this stuff is just common knowledge that we all learn over the years. Who knows, if a strut change and as much weight forward, a lifting prop, does not correct the problem, then air trap and sponson mods may be required.

You might also check the running surfaces on the sponsons to be sure they are flat with sharp edges.

 

[SayMikey]

How many guys run struts with no angle? Yes, if you can design the perfect hull to carry the weight, have the fuel on the center of gravity, figure out the density of air under the boat for different temperatures and altitudes, then you might be able to run the strut with zero angle. This will give you the ultimate speed. Even riggers need downforce and run 1-2 degree's of negative angle. I would try this before glueing and sheeting the bottom of the hull.

Have you tried to put negative angle in the strut? Have you tried a "lifting" prop? The X series props have alot less lift than a 1400 series.

I think your missing the obvious.

Even full scale unlimiteds run negative angle as it helps to get the rear of the boat off the water resulting in more speed.

My PT8255 has a straight driveline no to 1 degree of angle.

 

[Mike Betke]

Mike L. ML Boat Works PLEASE DO NOT TAKE THIS THE WRONG WAY, I think you have done exceptional work for our RC boating community and offer some awesome kits.

Rob,

I'm sure you have run against Rob Betke from you neck of the woods,

I ran with him in Evansville a few years back and was amazed at how his boat ran, when I found out it was an ML kit boat.

He then showed me the bottom of his boat.

Yup, just as I have explained above. The ram wing had been filled in forward and the boat was perfect ALL WEEKEND long

Here's the pic of the bottom of Rob's boat. We had to do this to keep it from blowing off the water. Of course we tried adjusting the strut first and it did not help that much. For me, adjusting the strut is always the first move as it is the easiest thing to do. Note that this boat is set up for Nitro, which is a huge difference when it comes to weight and C/G. We also have about 2 degree of angle in the strut. I would try this first with an and electric set up. We also ran a Prather 250 prop.

Another thing to note is that I put the strut on center with the boat even though the cowl is offset. You can see the driveline in the pic. I initially set it up this way so I can't tell you if there is a difference if you offset it. We ran the rudder on the right, but if I had to do it over again, I would have put it on the left. I think it helps keep the left side sponson down a little. The boat would like to lift the left sponson going down the straight sometimes.

With the Nitro set up like this, the boat has won almost every major race over the last 3 years in IMPBA.

 

[TREVOR JENSEN]

Thanks for the continuous information guys, have lots of testing to do now over the next few weeks.

Thanks Mike Betke for the pic of the filled in front bottom.

Thanks

Trev

 

[FloridaScaleBoater]

Mike L. ML Boat Works PLEASE DO NOT TAKE THIS THE WRONG WAY, I think you have done exceptional work for our RC boating community and offer some awesome kits.

Rob,

I'm sure you have run against Rob Betke from you neck of the woods,

I ran with him in Evansville a few years back and was amazed at how his boat ran, when I found out it was an ML kit boat.

He then showed me the bottom of his boat.

Yup, just as I have explained above. The ram wing had been filled in forward and the boat was perfect ALL WEEKEND long

Here's the pic of the bottom of Rob's boat. We had to do this to keep it from blowing off the water. Of course we tried adjusting the strut first and it did not help that much. For me, adjusting the strut is always the first move as it is the easiest thing to do. Note that this boat is set up for Nitro, which is a huge difference when it comes to weight and C/G. We also have about 2 degree of angle in the strut. I would try this first with an and electric set up. We also ran a Prather 250 prop.

Another thing to note is that I put the strut on center with the boat even though the cowl is offset. You can see the driveline in the pic. I initially set it up this way so I can't tell you if there is a difference if you offset it. We ran the rudder on the right, but if I had to do it over again, I would have put it on the left. I think it helps keep the left side sponson down a little. The boat would like to lift the left sponson going down the straight sometimes.

With the Nitro set up like this, the boat has won almost every major race over the last 3 years in IMPBA.

Oberto Bottom.JPG

Trevor,

This is exactly what I was talking about!

I have seen this boat run,,,, it is ROCK solid.