Traxxas M41 - Real Speed & Porpoise????

Greetings... I acquired an M41 for a great deal to give to my brother who is not a super experienced modeler... but knows enough to make this run ok...

So, I replaced the trim tabs, put in dual cooling, new motor jacket, and a set of nice 60C 5000 3S batteries...

Issue is no matter the battery placement, the boat seems to want to porpoise, but onto to its right side (almost like a torque roll)... I moved the left battery further forward thinking staggered batteries may work, but no joy... I have not tried dropping the left trim tab down yet (both are set in line with hull)...

And I am also topping out at just 38 MPH on the boat... while the porpoising may kill some, I saw on the box it was supposed to be 50MPH?

Would love any thoughts and help... this one has me a bit stumped...

Thanks!!!

Sounds like you didn't adjust the only thing that needed to be adjusted. It's that thingy that holds the thingy that actually pushes the boat. :)

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Originally Posted by bonefisher

And I am also topping out at just 38 MPH on the boat... while the porpoising may kill some, I saw on the box it was supposed to be 50MPH?

Would love any thoughts and help... this one has me a bit stumped...

Thanks!!!

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Ahh Traxxas and their advertising gets another one!

The 50 Mph claim is probably with the boat properly set up by someone who knows what they are doing (no offense meant) and with an appropriate (non stock) prop in just the right conditions (whatever those may be).

Like boredom said, the height of the prop can also affect the angle of the boat in the water as it runs.

How much adjustment is there for prop height?

What prop do you have on?

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Originally Posted by Doby

The 50 Mph claim is probably with the boat properly set up by someone who knows what they are doing (no offense meant) and with an appropriate (non stock) prop in just the right conditions (whatever those may be).

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Yep Doby has a great point. Your probably not going to pull the boat out of the box, toss in some 3s packs and do 50mph Lol. It doesn't matter if Traxxas did 200 runs with the boat and only hit 50mph once, the fact of the matter is they got the boat to do 50mph therefore they can put that on the box :wink:

Thanks all... def figured there was some overzealous advertising... just seems far off...

Will try to drop the left tab a bit to see if i can get her more in the water...

Would love any other ideas...

Chris

You completely missed the part where we told you what to do to fix your issue...

A video of it running would help too. Try adjusting the strut, trim tabs and moving your batteries. The manual should have illustrations on adjusting the strut and tabs. Dropping the trim tab is going to put more hull in the water. If you want to go faster, you need to get less hull in the water

If I missed it, then my bad... but I did not think "Sounds like you didn't adjust the only thing that needed to be adjusted. It's that thingy that holds the thingy that actually pushes the boat" was clear enough to action upon...

That could be the strut itself, the strut angle, the strut depth, the shaft, the drive dog space, etc... I certainly appreciate the help but did not feel I had enough to work with from that comment...

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Originally Posted by bonefisher

If I missed it, then my bad... but I did not think "Sounds like you didn't adjust the only thing that needed to be adjusted. It's that thingy that holds the thingy that actually pushes the boat" was clear enough to action upon...

That could be the strut itself, the strut angle, the strut depth, the shaft, the drive dog space, etc... I certainly appreciate the help but did not feel I had enough to work with from that comment...

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Like I said, read through the manual and it should have a section on adjusting the trim tabs/strut, and how it affects the ride attitude of the boat

Unfortunately manual is VERY light on this... one page... two paragraphs...

No big deal... just seemed odd to be so far off (25%) from speed... will continue to tinker... will try the tabs first...

angle the strut down, the bow will ride lower, more hull in the water, less speed, potentially more stable. Angle the strut up, the bow will ride higher, less hull in the water, more speed, potentially less stable. I'm not familiar with the M41 strut, so I don't know if its mounting hole is slotted to allow you to maintain a constant trim angle and simply adjust the height of the strut/prop. My 29" Blackjack likes the strut angle level with the bottom of the sponsons and roughly 1/8" higher than even with the sponson bottoms. Raise it too high, speed falls off. Set it too low, speed falls off, electronics get hot too.

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Originally Posted by Mxkid261

Yep Doby has a great point. Your probably not going to pull the boat out of the box, toss in some 3s packs and do 50mph Lol. It doesn't matter if Traxxas did 200 runs with the boat and only hit 50mph once, the fact of the matter is they got the boat to do 50mph therefore they can put that on the box :wink:

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I just got 52 out of mine!

Stock....

I am having issue with boat bouncing. I swear the overall weight is the reason. So light!

I moved 3s batteries more toward front, not sure if that helped.

New to boats, so any suggestions welcome.

Water is like glass and low wind.

If all suggested adjustments still leave the bounce in her step, I’d look at the ride pads and make sure the are flat (no concave spots) - if the are not, then fill with bondo and sand until flat. Also that all the angles are sharp.

If the sponsons are flat and you have pulled all your hair out, you could try a tunnel flap. I have had success with making an adjustable trim tab like flap that works with the air flowing under the tunnel. Possibly an air dam in the tunnel would be something else to try.

The boat is plastic, I do not see any flaws on the bottom. Every “pad” seems perfectly flat. Boat has no wopple on flat surface.

The prop had a slight crack in one blade, if that is the cause then Traxxas makes on hell of a prop. I have a racing prop from “Dasboata” I will try next outing.

Is the goal to have all 3 “pads” on the water? 3 per side that is. Boat should be horizontal to water surface?

You won't see the imperfections by just looking at the ride pads, unless they're REALLY bad. Take a straight edge and lay it across the width and length of each ride pad to look for low or high spots.

No, you wouldn't want all three ride pads in the water when running. That would be considered running "wet" and with that much hull in the water, will result in slow speeds and potentially higher temps on the electronics. Ideally, a cat will be riding on just the last ride pad as air is packed into the tunnel and pushes the hull up. This can be achieved with a combination of center of gravity adjustments (moving batteries forward or backwards), strut adjustments (angle of prop), height of the strut, and numerous other smaller tweaks.

Thanks.

I used a straight edge and actually was amazed at how true it is. Traxxas did a good job with this Hull it seems. I expected it to be off and moveable with pressure. Neither seemed to be the case.

M41 strut is adjustable hight and angle. Need 4 hands to hold everything however....

[emoji23][emoji23][emoji1787][emoji1787][emoji23][emoji23][emoji1787]


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I would set your strut at a neutral angle to start and make your center of gravity adjustments with the batteries to see about getting the bow to ride higher and free up the hull a little. Typically, CoG is set around the 30% mark when you measure the hull from the bow to the rear of the last ride pad. Don't include the length of any hull overhang at the back or the rudder. Measure forwards to find your 30% CoG, place a dowel rod or some type of balance point under the boat at that spot, and move the batteries around inside the hull until the boat balances front to back. On the following test run, if the boat rides to dry and wants to flip easily, you can move the packs forward a little on the next run and try again.

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Originally Posted by fweasel

I would set your strut at a neutral angle to start and make your center of gravity adjustments with the batteries to see about getting the bow to ride higher and free up the hull a little. Typically, CoG is set around the 30% mark when you measure the hull from the bow to the rear of the last ride pad. Don't include the length of and hull overhang at the back or the rudder. Measure forwards to find your 30% CoG, place a dowel rod or some type of balance point under the boat at that spot, and move the batteries around inside the hull until the boat balances front to back. On the following test run, if the boat rides to dry and wants to flip easily, you can move the packs forward a little on the next run and try again.

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I will do the strut as you suggest.

Today I got 40 mph out of 4s! Dasboata prop. Boat seems to be close to correct, bit of bouncing on right side....torque twist? I have a cataract so my vision sucks right now, can not quite see enough! Can’t wait to get that fixed!

Right side may need weight? Or trim tab adjustment. Maybe water inlet to create drag.

Boat had good flat running here and there and some bouncing. Tad windy and my own wake made for some odd choppy water.


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Catamaran hulls typically do not have or use trim tabs. At a minimum, I would run them flat even with the ride pads, but more than likely, trim them up a little to reduce the drag they're probably causing.

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Originally Posted by fweasel

Catamaran hulls typically do not have or use trim tabs. At a minimum, I would run them flat even with the ride pads, but more than likely, trim them up a little to reduce the drag they're probably causing.

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I wondered about that, thanks. A cat is a cat.......

Took off trim tabs, boat became a kite! [emoji1787][emoji23][emoji1787][emoji23][emoji1787]


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Then your boat is set up too loose. Move the packs all the way forward and set your strut with a little bit of down in it. It sounds like your strut has some up to it if it's blowing off that easy.

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Originally Posted by MarkF

Then your boat is set up too loose. Move the packs all the way forward and set your strut with a little bit of down in it. It sounds like your strut has some up to it if it's blowing off that easy.

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Do you have experience with M41? I am getting the impression it is different than most cats. I think it is too light, I compared it to Proboat about the same size. It weighs 40% less.

Today’s testing tells me the trim tabs really have a big effect on this boat. They are just bent stainless, next to impossible to adjust with any real precision. I will get some Hot Racing trim Tabs.

Also I did adjust strut down in the rear, I also think some weight in the front would help. Get some balance without having to have trim tabs do all the work, seems like this is using power vs balance to a point.

I did a test with tabs bent a tiny bit down, boat ran flat as can be, slow as hell!


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Originally Posted by MarkF

Then your boat is set up too loose. Move the packs all the way forward and set your strut with a little bit of down in it. It sounds like your strut has some up to it if it's blowing off that easy.

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Strut was set flat the day it went airborne.

Got 42mph out of 4s 90c packs today! Had packs way towards front 2 degree down angle on strut. Bouncing was not as bad, but still not trimming up and holding in the rear. Port side was breaking contact with water going straight. Any turning made boat settle down...

Tells me it was close.

In 6 weeks I get my cataracts fixed, part of my issue is I can not see *!***!***!***!**!


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Yes it does. When you been doing this as long as I have, I notice I like the challenge of setting up the boat more now. It doesn't matter what someone else does to their boat. There are so many factors that you just have to go and test and fix whatever the boat is doing.

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Originally Posted by MarkF

Yes it does. When you been doing this as long as I have, I notice I like the challenge of setting up the boat more now. It doesn't matter what someone else does to their boat. There are so many factors that you just have to go and test and fix whatever the boat is doing.

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It is amazing how every little thing matters so much, like a damn helicopter.


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Got 57mph out of M41 today! Wants to fly constantly at this speed. Experimenting with adding weight. I honestly think this boat is designed too light weight. Trimming does not seem to stop bouncing without killing speed. Serious balancing next!