Scratch building a slingshot for cmb 27

[doug long]

Bruce,
Mcmaster carr sells small velcro straps that you wrap around your sponsons tubes and then stap it in. No holes in the bottom of the boat.
Doug

 

[Roxyflash]

Wife’s ended up in hospital Monday nite to Friday so put the build on hold.Got back to it Saturday received a cowl from Dan that fits his outrigger.Its very narrow so I used a plate of g10 1/16 thick cut to fit inside of opening.I used some scrap pieces of wood to get it to sit level.I trimmed the long tongue piece off of cowl and sanded the sides and bottom to fit the g10.I glued it on the g10.After looking at it I should have rounded the tongue piece but still looks ok to me.I also drilled the transom for strut and rudder and fabled the linkage out of 3/16 stainless tig rod Mounted the pushrod rod boot.After the cowl was glued on the plate I cut the inside opening and fitted it over the engine.

 

[Rich Jones]

Looks like a nice custom cowl Bruce. Good job! Hope the wifey is feeling better!

 

[Roxyflash]

She’s doing better thanks i have been sealing the boat need to get the cowl lock figured out next I’m hoping to clear the boat Sunday if all goes well

 

[Roxyflash]

Used the zipkitts magnet hold down for cowl they worked like a dream I made a hardwood mount in the tub I made them long for more glue area.Sunday I cleared the tub and sponsons.Painted the cowl and lids.Was almost 50 here so I cleared first then took those pieces inside the garage then painted the cowl and lids took them inside.I have to paint outside the garage is attach to the house and the fumes get into the house and wife can’t take the smell.I used a space heater to heat the garage till the paint dried then took it in the basement for the final cure.I had a few sand tru on the area on the top of front sponsons and the back top of rear sponson.I didn’t want to paint the whole boat as it takes more steps and adds a tiny bit more weight.

 

[Rich Jones]

Used the zipkitts magnet hold down for cowl they worked like a dream I made a hardwood mount in the tub I made them long for more glue area.Sunday I cleared the tub and sponsons.Painted the cowl and lids.Was almost 50 here so I cleared first then took those pieces inside the garage then painted the cowl and lids took them inside.I have to paint outside the garage is attach to the house and the fumes get into the house and wife can’t take the smell.I used a space heater to heat the garage till the paint dried then took it in the basement for the final cure.I had a few sand tru on the area on the top of front sponsons and the back top of rear sponson.I didn’t want to paint the whole boat as it takes more steps and adds a tiny bit more weight.

Looks great. Really nice project. It looks like you are maxing out the angle on the sponsons by the look of the front boom and its location in the slots. I will be interested in knowing how the boat runs and handles with the sponsons at that angle. Thinking it’s at least 5 degrees or more. I was told around 4.2 and 4.0 right and left. I was running with them bottomed out to start. It was hard to launch at that position. I shimmed to what I thought was 4.2 and 4.0 but it but it was more like 5 and 4.8 and I thought the boat handled fine. I did reduce to 4.4 and 4.2 and honestly I didn’t feel it was as good. I wound up adding one more washer on each side (sort of meeting in the middle) and that’s where I’m at now.

 

[Roxyflash]

There not bolt down yet but may have my front blocks a little high need to figure out the coil mount everything else is done other then cutting the flex shaft.The coil has a short plug wire and doesn’t give you much option to mount it I may see if I can remove plug wire not sure how it’s mounted in the coil I know like the Rcmk there replaceable not sure on this coil there made for a Ktm 50 ignition there cheap like 20 bucks shipped tru eBay.

 

[Roxyflash]

Took a chance on the coil grabbed the plug wire and twisted it out it’s a replaceable type good thing is it’s 7 mm wire so was able to use a solid core automotive plug wire.Only place it would fit was under the carb so I made a wood mount .Started rigging the parts on mill the strut bracket so the rudder bracket is flush on side of tub and cut the rudder blade.Need to get some 440 screws for the tank x brace so they can set flush.Mounted the antenna tube switch servos linkage boots and oiler.Tomorrow will cut the flex shaft mount drive dog and screws for boom tubes.

 

[Roxyflash]

Finished the build reinforced the boom tubes with 1/2 inch tubing in the middle to help support the extra weight of the CMB engine.I used some plumbing washers to seal the side of tub To tubing.Set the radio up installed the receiver and antenna.Bought some flat head screws for the x brace added some foam to hold tank in place.Next thing is to test fire the engine.

 

[Roxyflash]

Adam came over to pick it up we test fired the engine pulled the plug choked the carb till fuel was coming out the plug hole insert the plug thing fired right up.Checked to see if if radio would shut it off it did.Refired it up set the low speed Adam was happy.Now time to build the kit slingshot.

 

[Lay26]

I feel, and this is my opinion, that the boat already has some weight up front, especially with a full gas bag. If anything, I might be tempted to move the motor back a little, but then you run into clearance issues with the collet and the stuffing tube. With my zenoah mounted in the place the kit calls for, it’s a little tight. I guess you could shorten that stiffener box that the stuffing tube runs into if you wanted to try it. If not, I would just leave it where it is. While it’s heavier, it is right around the cg already so it shouldn’t make that much difference.

I just did that very thing with Test Run......my wood X version has the motor moved back and the smaller radio box that allows everything to work....cant wait to run it...

 

[Rich Jones]

I just did that very thing with Test Run......my wood X version has the motor moved back and the smaller radio box that allows everything to work....cant wait to run it...

Anxious to hear how it goes!

 

[Roxyflash]

I’m curious also weather has changed all the 2 foot of snow is mostly gone.Im hoping to paint the kit slingshot Saturday.

 

[Rich Jones]

I’m curious also weather has changed all the 2 foot of snow is mostly gone.Im hoping to paint the kit slingshot Saturday.

What kind of temps are we talking about painting in? Just out of curiosity. I’d like to get some primer on the Lauterbach but highest temps in the near future will be upper 40’s or low 50’s. What’s your rule of thumb for primer, base clear, etc…?

 

[Roxyflash]

I heat the garage then I paint it out side as soon as it’s painted I bring it in where’s it’s warm I like 50 or more degrees

 

[Rich Jones]

I heat the garage then I paint it out side as soon as it’s painted I bring it in where’s it’s warm I like 50 or more degrees

Cool thanks for sharing. Good luck with the paint job!

 

[Bill Eilers]

If you want a spare eng I have a late model 26. Let me know. Gota post it before you buy it. Gota stay inside the rules. It comes with spare parts, o rings, piston rings, maybe even a piston. And sleeve, has the cmb motor mounts. Pm if you're interested. It's been sitting. Needs bngs. Comes with a piston stop, setting timing.

 

[dave roach]

RoxyFlash
Looks like you are all set.All you need is a nice set of Delron boom collars for that.

Dave

 

[Rich Jones]

RoxyFlash
Looks like you are all set.All you need is a nice set of Delron boom collars for that.

Dave

Here’s a pic of mine with Dave’s collars on.

 

[Roxyflash]

Those are nice a thin where did you get them?I didn’t realize the blue on you slingshot is almost the same color as mine.