TCHedOff

Ron: What's a good way to find out where material on the header needs to be removed (for improving flow)? This is something I'd like to do this winter.

MX.2191: If you use a jigsaw, make sure to use a fine toothed blade. You're gonna find that the up/down motion likes to grab the wood (on thin material like 1/16) and flex it up and down and you'll get tear out on the wood. I usually use a sharp exacto knife on the thin stuff. But 1/8" think and thicker the jigsaw will be fine. One way to stop the up/dwon fexling & tear out on thin stuff is to sandwich it between scrap wood. Oh yeah, when I use an exacto knife, I like to have something with an edge for the eaxcto blade to ride along when cutting.... for straight lines I have a metal ruler (many other things would work fine); for curves and custom cutting, I'll often cut a piece of scrap wood the same as the part I want to make and just follow around the outside edges. I do this because it keeps the exacto from doing a "OOPS" across the part you are making and leaving a nice scratch.

Ron Olson

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Todd, the gasket will give you a good idea as to what needs to be removed. Alternative two would be to just use a piece of masking tape and stick it down to the exhaust pot on the engine then transfer it to the tape then stick the tape onto the header flange. The cut-off wheels work great as they allow you to get the angle that you need to flow into the header's pipe. Use all new cut-off wheels to make sure they're all the same diameter. I usually don't use them as they're flimsy by themselves but in the stack they're also great for making a flat on your flex cable for the drive dog's set screw.
If you look at the link that I gave on the last page you can see how badly it's choking the exhaust. This is also a great little cheap mod for the Pro Boat TC 31 and Shockwave nitro boats but on those you really have to watch carefully so that you don't grind through the header pipe.

I really need to do a thread on this. All I need is another header to do it to.

mx.2191

I thought I'd do a quick update on the build. The header arrived. It almost matched the exhaust port of the engine. I think it's a mm larger on each side which I haven't really done anything. The header takes a couple of 3mm screws but the engine takes 2.5mm so I think i'll just have to bore the holes 0.5mm larger to make it fit� The header is a funny shape and I had to bend it slightly so it's not pointing to the bottom of the boat. I think it will do for now. I'll post a couple of pics once i get the camera working again. I'm a bit gutted with the stringers though. After I cut them out I realised they warped a bit. so they'are sitting there with lots of clips and a steel bar trying to get them straight again!!! But I think i might have to redo them again. I'm thinking, will be it even better to use thinner ply/balsa and carbon fibre the whole thing? It will be stronger but does it add unnecessary weight to the boat? Has anyone done anything like this before?

TEHedOff: thanks for the advice, yes, jigsaw worked good. I went with the finest saw bit i could find. And the lite plys were very easy to cut with a excel knife! So no drama here.

Ron: I agree, a thread would be great........a free way to get more power out of an engine is definately going to be sought after!

Macleod

Justin,

I used thick ply for my stringers.

Used epoxy and cabosil to set them in place then epoxied them in with glass cross weave cloth after the epoxy bog had set.

mx.2191

can't believe it's been more than 2 weeks since my last update....it's been a slow build and finally the hardware and tuned pipe arrived....

Ron, here is a photo of the header port. The gasket matches exactly to the exhaust port on the engine. i guess i might just leave it and see how it goes.

i've roughly placely the engine in the boat just to see where i should be drilling the mounting holes on the stringer. 30%? one photo shows at 30% and it looks like its too far to the tronsom. with all the hardware will the boat be too heavy to the back? and is the tuned pipe too long? the 2nd photo shows the engine sitting at around 35%. is it very very critical to place the engine at a precious location? i just can't decide!

Ron Olson

My Feedback: (1)

You're going to find once you install all of the hardware and radio gear that it's going to add a lot of weight to the rear. Once you add some floatation in the front under the deck and the fuel tank, the CG is going to move around. Expect to whack some length off that pipe, start with 8-1/2" from the glow plug following the path of the exhaust to the widest part of the pipe.
The trim tabs may or may not be needed. I had some on mine but removed them.
Oh yeah, throuw that streamlined prop nut away unless you like buying lots of new props! If you want to keep it, add a nut between that and the prop or a slice of fuel tubing.
The header looks good.

mx.2191

thanks Ron. I ended up mounting the engine at around 35% of the boat length from transom to glow plug. i'm going to glue everything together if i get some free time tonight. would you cut the pipe from the front end or the rear? I think i will end up with something similar to unclecrash's boat with the pipe sitting on the radio bulkhead..... i quite like that set up anyway.

Ron Olson

My Feedback: (1)

The rear is called the stinger, don't cut that end off. If you have a pipe cutter, even a cheap one, it makes a nice clean cut. I gave up on using hacksaws and a Dremel a long time ago. Yeah, I'm a cheap SO*!

You're going to find that you're not gonna have a whole lot of room in that radio box so go small. Get a radio system with a tiny RX and mini-servos. I use 4-cell flight packs rewired from backyard flyers to power the RX.

mx.2191

cool.....a pipe cutter? a new tool to my collection!!!  yeah, i realised the size of the radio box. I got some cheap mini servos but unsure about the torgue required for the rudder. as for throttle that's plenty (i think). thanks for the battery tip. I did wonder about the size and weight of 4 AAs....

Ron Olson

My Feedback: (1)

I'm using Hitec HS-81 MG's in mine but I'd step up to the 82MG's or 225 MG's.
Note on mine that Grimmie built that there is a cut out area for the pipe. That's what makes mine tight for the radio gear. It also helped as I mounted the servos to the side of that using carbon fiber angle just for the cool factor plus I had it handy, the same with the carbon fiber radio box cover.
Four AA's are also a lot of weight and the less weight anywhere on boats this size the better.

mx.2191

Thanks Ron for that. The servos I've got is called Hextronic HXT900. Speed : 0.12 sec/60(4.8V) Torque : 1.6 kg-cm. I guess it's not powerful enough? [] I'll see if i can get some other ones for cheap!

I picked up a new fiberglass hull for really cheap! It's 1050mm x 350mm for which I'm thinking a .46 or a 26cc? I found an new OS MAX-4VR marine for a very reasonable price as it's been sitting in the cupboard for years. Do you by any chance have any experience with this engine? The new version is like 3x the price. This seems to be a really good buy, and may suit nicely to the hull. Just another project........

Ron Olson

My Feedback: (1)

Ya got me, I don't know the metric system that well. I do know that a .46 is 7.5cc. I really need a conversion table..........

mx.2191

You are the same as me with imperial! The hull is roughly around 41" x 14". As for the engine I should've made it clearer. I'm tossing between .46 nitro or 26cc gas, but not sure which one is a better/cheaper/faster option....

As for the "little" boat......it's sittin there waiting for the epoxy to cure......seems like forever......

Ron Olson

My Feedback: (1)

At 41" it may be a little on the small side for a gas engine but right in the neighborhood for a .45-.67 nitro.

mx.2191

cool. thanks Ron, I guess that OS MAX-46VR should be ok to start with? Would you be able to guess what RPM this will put out?

Macleod

Your wish is my command...Ron.

Click on the expand icon at the bottom right of the image once it pops up.

Ron Olson

My Feedback: (1)

Thanks Ross, I needed that!
I just checked the OS Engine site: http://www.osengines.com/index.html and they don't give any spec's on your version so just as a guess, I'd say around 25,000 or more RPM.

mx.2191

Thank Ross for that table. Very helpful indeed! This will help people heaps as I'm about to ask another question that involves a bit of conversion.... While the hull is gluing I'm thinking about the prop I'm going to use and run into another problem. The driveshaft I have is a 4mm (.157) and the prop I was going to use X637 is a .125 so I'm like .9mm too small. I guess my question is would it be possible at all to put through a 4mm drill bit to make it fit? Or is there another prop that would suit better? []

Ron Olson

My Feedback: (1)

Ross, I was messing around with my new cell phone tonight at work and found a calculator in it that does metric conversions! No excuses now!

Macleod

Ron, does the phone still work ?????

I know what you are like with technology....Hmmmm..???????

mx.2191

Wake up people......

Yes, i'm still around. thought i'd update on the build..... NOTMUCH! Well, just been super busy and just slowly moving along with the build. Since my last update, I've

got all hardware I need
glass renforced the hull,
made a set of engine mounts
put in the stuffing tube
fitted the hardware to see what it would look like
cut the flexi cable to length (oh, and I suspect the cable i have is a right-lay!!!! it doesn't look like the ones in some of the photos here. I bought it on ebay and the guy insisted it was left-lay. When i cut the cable it has another layer inside with opposite lay. Not sure if it will work but it's too late. the whole setup is in metrics. the cable has a squre end that goes into the shaft.)

a new header is on order - the current one looks terrible from all the bending to make it fit. I order the same one you have Ron. It looks like i'll have to port match it once i get it.

Just working on the radio box and the waiting for more wood to finish the side and deck. I'm aiming to get it finished by mid-april!!!

Pics are coming.....

Macleod

zzzzzzzzZZZZZZZZZ !!!!!! huh WHAT?........lol

fastpepper

anyone know a good pipe for a http://www.tiger.com.tw/product/9554.html
engine?
thanks guys....

mx.2191

fastpepper, i think there is a link at the bottom of that TT page for a pipe. have you tried that?

mx.2191

haha......funny, Ross.