Blazer Slingshot with SG rear exhaust

[rhomodel]

Several builds have been presented already on the Blazer Slingshot and by no means can I do better. However this one is with a rear exhaust, reed engine and that poses a few small challenges. Firstly th ekit is great and would have everything needed for a normal build. However my choosen engine is a bit different: a reed inlet, rear exhaust engine...
As the tub inside width is only 4,5 inch it poses an isue with normal mounts, also with the SG provided ones as they are 4 inch wide without the rubbers.
Secondly due to the ignition system the engine can't be placed low and needs to be about 1/2 inch higher than the pre-lazered holes.
Here some pictures

 

[Mike Hughes]

Who builds that motor?
Mike.

 

[rhomodel]

Mike, SG racing builds the engine. They have no website and you need to have an Italian connection in order to be able to get a hold of them: They only speak Italian.. and don't seem to do any form of electornic communication. I did meet with Sassi the last race I had in Italy. The concept is very interesting as you can see: would also be a great engine for the offshore or marathon class..

 

[Mike Hughes]

It looks very similar to a BZM. Too bad it is hard to get them. Would be interesting with an inline setup. I really like my BZM. It is a tork monster.
Mike

 

[Don Ferrette]

Have you considered adding a belly pan to the bottom sheeting directly under the motor? Just make it large enough and deep enough to accommodate the lowest (deepest) part of the motor. We've been doing that in some of the 1/8th scale hulls for years.

 

[rhomodel]

I did not Don.. actually it is a very good suggestion as it would have saved me a lot of trouble: just spend a whole day in the shop making a set of CF mounts so all fits.. As the tub is ready now I will see how it will drive: if not ok I can always redo teh tub with a belly pan....
And about availability of the SG: While BZM is a commercial company I have the impression SG is not. Though their concept is good: for example the exhaust post has 2 booster ports, something BZM will only release end of this year ( I also met Pietro of BZM in Italy).. Wil post some more picture later of progress.

 

[rhomodel]

Some more progress to report: fixed the rear shoes to the boat: normally no big deal, but always a bit tricky to get it to harden in teh right place. So drilled 2 mm holes and inserted toothpicks for guidance: appplied thick coat of epoxy and clamped things in place.

A tip for claping: as the surfaces are not at straight edges, the clapms tend to slide away, for you only to discover the next day after curing things are not in place as they should be. So bought a roll of anti slip tape ( zelf adhesive course sandpaper also works, stick that to the sloped surfces and no more slipping of clamps while the eposy is setting..

 

[rhomodel]

Other challenge is the motor mounts: The provided aluminium ones are 4 mm thick: 2 mm too thick each to fit inside tube.
So laminated an L shaped carbon profile ( Simply us clingfoil and 2 alu L profiles, nice weaved carbon for the outsides and all kind of leftover carbon and glass cloth to create the needed 2 mm thickness).
Then the nice work of shaping things in shape and after lots of carbon dust a perfect sitting engine...

Then temp mont everything and suddenly it starts to look like a rigger.... However still heaps of things to do befor being able to run it...

 

[rhomodel]

Now is the time I put a lot of effort and time in things, but you don't see so much result. anyhow want to share a trick on how to curve washers to fix the booms. And although I had never had any issues with fixing booms to the tub without a curved washer here's how I make a curved washer, that is reducing high stress area's..
So I turned a small pieces of aluminium to teh same diameter as the booms, then drilled and tapped a hole to match the size bolt that will hold the boom ( in my case M4), take a washer, fix it over the boom with the screw and clamp it in the 3 claw jug of my lathe. Then turn close the 3 claw and the washer will curve to the alu rod, hence the boom..

 

[rhomodel]

And work for a new cowl.. Hard to replicate the nice lines of the slingshot cowl.. but then these are one of a kind so anything goes.. I sanded a block of 2k Foam and glued it to a plate of triplex, matching the curve of the tub... Initial form was't ok at all as you can see in first picture so shaved off more, but I had to match the contours of the engine and ensure everything is enclose..... This as the carb is sitting so high the original cowl has to be moved very far forward, plus of course no carb or exhaust protruing to the sides...

 

[rhomodel]

Started on the tedious filling, sanding filling process... All for a smooth plug... Rest of teh boat taking shape...

 

[rhomodel]

slowly booking some progress, after a few rounds of filling and sanding I could apply the black mold stuff and lay up some glassfiber woven mat

 

[rhomodel]

Suffering a bit of a mishap with the first cowl laminating attempt: wanting to do a nice and even white gelcoat I applied the epoxy too quick or did not add enough hardener and almost ruined the mold. Aceton came to the restcue cleaning the mess and attempt #2 underway. I did notice that the not-set gelcoat did discolor the inside of the mold to a strange glow..

 

[rhomodel]

Been working slowly, but steadily: Exhaust brace made of CF: took a pipe with the right diameter and made 2 flanges to act as a mold. And finally some semi-finished pictures: it's starting to look like something that will be able to run. Though I need to think about a paintscheme if the rest of the boat..

 

[rhomodel]

Work on the sponsons.. because of the sloped side wall it cries out for some decals... Well I I think reverse decals are also nices: just to be able to show the original wood grain. Wood is good.

 

[Rene Berndt]

Great project Julius. The colour looks naerly like my Slingshot.

 

[rhomodel]

Yeah I know: yours is more the circus circus scheme isn't it? Have you already driven it Rene?

I wanted to have a boat that you can clearly see during a race, so hope this pink will do the trick. But got carried away and did some extr astuff as you could see.
The boat is almost finished so I can post the final pictures of the build process soon.

 

[Rene Berndt]

Yes it is. It need some tuning and time.

 

[rhomodel]

Boat is finished. Only when all was installed did I realize the the hood is a bit of a tight fit. So had to do some tricks make it fit: Cut the carby needles so they are not too wide, ignition wire tied to the cilinder and then the throttle control. In the end decided to use bicylcle spokes and bend them to fit the contour of the engine. Anyhow all fits now and I'll have a shakedown run next week...

 

[Buckshot]

Excellent! Can’t wait to here how it goes, good luck.