ML SX400 Nitro Build

I'm trying to get back into my boats.. Sold all the .21 engines and pipes, hung on to the sport and rigger hulls that I designed and built. And that leads me to what I really want and that is to get this wooden SP40 hull together. I don't know if anyone has ever built the SX400 into a SP40 boat.

A couple questions. The boat is further along than the pics show.

-The tanks have been modified and are now placed under the top decking in the position shown. I am going to run as large of diameter fuel like that I can to avoid some of the dual tanks issues people have had,.. going rich after one empties,... Which way should the fuel flow? On my SP21 boat I ran the tanks so that that the non TF side emptied last. This was to counter torque roll. I never had the left sponson lift but the TF side would get light toward the second half of the run. Should I empty the left, non TF side first? Or the empty the TF side first?

-Strut,.. currently I mounted the strut on the transom and I have a rounded bottom strut. It's a long afterplane this way.. any suggestions on how to optimize this arrangement?

There is a bulkhead in the hull that is right where I need to run the pipe. Can I cut that at the top to pass the pipe and maybe add some fiberglass around the rest of it in corners? This would make my build much easier.

Planning props are x448 - 450 - 452 maybe 648,.. any other suggestions? wonderi ng if I ll have problems keeping the prop hooked up as so me have mentioned with the transom mounted strut..

Engine is mounted with engine C/L about .25 rear of the sponson heel.

Front radio box design..

Thanks fro your input..

Running a fresh AA45, 65% nitro.. AA pipe.

I got the exact same gas tank setup you have Anthony. I have the right side emptying first to keep the weight on the left sponson.

I don't know if this helps but here's the right tank and the routing for the fuel lines. The left tank is of course on the other side.

What hull is that. Looks awesome. Wood? Wonder if I should place radio box like that

anthony_marquart said:

What hull is that. Looks awesome. Wood? Wonder if I should place radio box like that

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It's a Doug Shepard Hull. The radio box was in front of the motor. But it made everything difficult. So I made the radio box where it's at now. I added some weight to the nose to compensate the change in CG.
I've noticed since I changed the radio box location turning slight left makes the boat spin out a lot easier.

Any input on removing the top of the rearward bulkhead from the ML SX400?

What area Tony?

the first one in front of the transom

I cut it out. It was actually the second from the transom. Got the pipe mounted. Just need to do the radio setup and plumbing. Then tear down and seal it up.

Got the radio box cut down,.. pipe mounted,. I am going to run the pipe out the cowl. I saw one like that and liked it.

Looking for input on starting pipe length,. props,..

Right now it balances about 2 in aft sponson heal,.. thoughts on that?

I really like this this design,..

Rudder on the right.. I know most are left but I think that is left over from running TF w no curve..

Needle is a bit far from carb,.. think it's too far?

needle location.....

anthony_marquart said:

Got the radio box cut down,.. pipe mounted,. I am going to run the pipe out the cowl. I saw one like that and liked it.

Looking for input on starting pipe length,. props,..

Right now it balances about 2 in aft sponson heal,.. thoughts on that?

I really like this this design,..

Rudder on the right.. I know most are left but I think that is left over from running TF w no curve..

Needle is a bit far from carb,.. think it's too far?

Click to expand...

2" behind sponson heal should put you real close to the centerline of the turn fin so that should be good, don't go any farther back though. Definitely run a Tyndall turn fin! The ML boats work just fine with the rudder on the right. The needle will be ok that far back, have run many that way, it'll just take a second or two longer to see the change when you make a mixture trim.

Anthony. Are you hanging the strut off the back.

Samuel Hagan JR said:

Anthony. Are you hanging the strut off the back.

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The answer is in the first post.

Don Ferrette said:

Samuel Hagan JR said:

Anthony. Are you hanging the strut off the back.

Click to expand...

The answer is in the first post.

Click to expand...

It is isn't it.

When is the first test run.

Hope within a couple weeks. Strut off transom. Just need to do radio linkage and seal the boat.

Looks good Tony! Is having the pipe out of the cowl legal in sport 40? I honestly dont know the rule on that! haha, just wondering.

I wondered about that too.. I saw a pic of one running at Hobart.. so I think it is.. It's not Scale.. but if they don't let me play,.. Ok,.. I'll play somewhere else..

anthony_marquart said:

I wondered about that too.. I saw a pic of one running at Hobart.. so I think it is.. It's not Scale.. but if they don't let me play,.. Ok,.. I'll play somewhere else..

Click to expand...

It's legal in IMPBA, NAMBA requires the pipe to be covered.

Anthony,

You could turn the exhaust header over and run the pipe down into the hull and out the transom. I run all my sport 40's and sport 20's that way. Then you are legal for IMPBA and NAMBA.

Nice build. Keep up the good work.

Bert Dygert