ML 30" WOF Tunnel Build up and Cowl design

[Zach Davis]

JW,
Thank you for the compliment. I feel like every hull I build is a little straighter, and a little better. Maybe one day I can build them as good as JD! You do plumbing? I actually work in Civil Engineering as a Cadd designer. The pipe on this boat is a true Irwin. I received one of Jimmys pipes today actually..and it looks about the same. What are the differences. I have not been in this hobby long enough to know much about the Irwin pipes. I thought the Jimmy guy was the Irwin builder??? Let me know! Mike

I think the rear cone has a steeper taper on the Irwin and Jimmys is a little more gradual but the rest is the same.

I believe your right about Jimmy being the fabber all along, although I never really knew for sure cause I don't always pay

attention from 1300 miles away.

I do remember Jim Irwin talking about an arguement between him and someone un-named concerning the taper in

the baffle cone. One wanted it speeper than the other,, maybe Jimmy was the one that won the arguement in the end,,

don't know for sure whether was Him er not.

Wheres "moparbarn" when you need him anyway? He knows everything h34r:

J-dub

Funny you say that, I was wondering where Robin has been my self.

Zach

 

[Jerry Wyss]

You do some nice work there Michael, I've always wanted to say that. Now I have some time while I'm home(on a work day), doing taxes, renewing endless plumbing licenses and a bunch of other related misery of the same.

I see that O/B pipe on your gold engine, looks like a Irwin,, is that what it is? Or is it Jimmys pipe?

JW

The other reason I asked you about your pipe Michael is that it looks like a long pipe length. Have you ever

measured the length from the center of piston to the start of the reverse cone?

I'm not picking on you, I'druther you succeed in the running of your engine to its full potential. I'm not sure

of the exhaust timing of the 3.5 K&B SS but I would guess that its in the 176 to 178* area. I would believe

(if thats true) that the pipe length would have to be below 8.5 inches, maybe considerably below.

Most of the length can be lowered by fashioning a much shorter header,, alot of length accumulates there.

The other way is to get your exhaust port up,, sleeve shims are a possibility and cutting the exhaust port

roof is the other.

I'm intrested to hear what your actual length is now.

Just ready to help is all,,

JW

 

[Mike Luszcz]

That's cool, I have no problems with help! I will check out the length tommorow. I actually need to change the way I have it mounted because the header has a flange that ties the pipe a lot closer together than it is right now. The header and pipe came from someone that really knew there stuff. I will have to get pics to show you how they designed the header to pipe coupling. I will get pics tommorow. I plan on running sunday... Its gonna be 66 deg here!

 

[Jerry Wyss]

I took pics of some headers that show how they take some radius out of the 90* bend.

The manufacturers considerd it important thankfully, and so do I.

I know these headers are for the "exhaust nipple" type connection that the K&B doesn't have

but it shows what I was getting at in the other post.

I made one for the O.S.XM out of the aluminum tube that gets cut off these headers and a

aluminum plate that I fabbed. I cut, ground and fit the reduced radius 90 and J&B'd into

the flange. It held up fine but gave it to Steve Deryck,, the guy that was making a milling

machine to cut model boat props. Haven't heard from Steve in long time,, wonder how it

turned out?

 

[Mike Luszcz]

Well, I got out to the pond yesterday, ran all 3 of my boats. Awesome day here, 70 deg! Got the SS engine broken in, and tuned in some. You guys are right, they have no idle lol..I am not use to this since my 11cc will idle right down. This boat is fast! I need to do some engine adjustment, put a little down angle on it, as it is doing a little hopping, but when it levels out, I think the only thing in the water is the prop! I have a feeling its gonna be way faster than my 1/4 scale tunnel, and that one is doing 45-50mph right now on radar. These 3.5cc engines are so much quieter than the big ones! The boat seems to handle pretty well too. I added some stumble blocks when I got home to see how that affects it. I will get pics when I can get someone to go to the pond with me and take them while I drive.

Jerry, will J&B cold weld hold up to nitro fuel? I have a tuned pipe I cracked at the hanger mounting area, and no one will repair it..it now has a hole where the mount was, and I want to put an aluminum plate over the hole..but was not sure cold weld would hold up. Let me know.

 

[Jerry Wyss]

Well, I got out to the pond yesterday, ran all 3 of my boats. Awesome day here, 70 deg! Got the SS engine broken in, and tuned in some. You guys are right, they have no idle lol..I am not use to this since my 11cc will idle right down. This boat is fast! I need to do some engine adjustment, put a little down angle on it, as it is doing a little hopping, but when it levels out, I think the only thing in the water is the prop! I have a feeling its gonna be way faster than my 1/4 scale tunnel, and that one is doing 45-50mph right now on radar. These 3.5cc engines are so much quieter than the big ones! The boat seems to handle pretty well too. I added some stumble blocks when I got home to see how that affects it. I will get pics when I can get someone to go to the pond with me and take them while I drive.

Jerry, will J&B cold weld hold up to nitro fuel? I have a tuned pipe I cracked at the hanger mounting area, and no one will repair it..it now has a hole where the mount was, and I want to put an aluminum plate over the hole..but was not sure cold weld would hold up. Let me know.

Not sure about a crack but what would it hurt to try, 'bout impossible to TIG weld one of those things once they get

burned oil in them. Scuff the surface really well, make the patch fit nice an wail on it. Slow set J&B and give it a good

three days to cure before using,, I think it will work.

The header I J&B'd showed no signs of being bothered by anything. I also have a converted buggy engine to O/B use

and counterbored the crankpin to accept a 4-40 socket head screw to drive the TT PTO. I J&B'd that screw in there

and its still in there.

 

[Mike Luszcz]

Alright cool, I will give that a try this week. I really would like to repair the header and not just pitch it! Mike