Home-made twin .21 catamaran

Hi all,

To introduce me fast : I'm fabrice, 26 yo, living in Lyon in France. I'm CAD designer, on catia V5.

I can't speak perfect english, so excuse me for mistakes I may do.

My hobbies are designing catamarn's hulls on my CAD software. I made a first one, all in plywood, mounted with an OS .61 VR-M engine. It runs well for a first shot, for the first year of test I made something like 55mph with a 1455 prop. I bought fex days ago new props, I may do better.

This is the CAD screenshots



And this is the hull i made





My pleasure is to do as much as I can all parts I put on my boats. As I bought few months ago a milling machine, and using a mini lathe, I try to manafacture myself parts, like rudders, engine mounts ...

My project today is to built a hull such as the first one, but with twin nitro .21 engines.

I bought two STS D21T MKII engines, I saw manys vids on the web, they were in truggy or similar and I choose them because they seems to love high rpms..

The hull is similar to the first one, but modded to mount the two engines. I decided with friends on another forum board to install rc trims on the drives, to pilot them on water with my radio.

Here are the screenshots of the work I made on the CAD software : 180 parts designed.

The engines I bought :



Then after "marinising" them and machine their mounts :







As you may see, I use squarred flex, so I had to machine square drives adaptators, I just have to bought a special tap (1-4" - 28), and hop!



The female squarre is made with a fil. (not sure of the word)

I also machine a special rudder, with dual water pickup, one per side of the rudder. It's quite large (5mm thick), but I will see if it's too much. I think it will be efficient!

So picts about it's machining

















Completed with its mounts and arms :

To finish machnining, the drives I also designed & machined. They are designed to be rc piloted..

To finish, some picts about the hull construction, they talk for me :

Just after having cut the 3mm thick (or 6 where it'snecessary) plywood :



On gluying bench :



Where the engines will be..









I'm here today, I may keep you informated if necessary.. All about finishing the construction of the hull, first test etc..

I will also put a system like the Eagle tree data recording, to inform myself about the rpms and the t° of the engines, It will be interesting to perform the hull settings.

Regards.

that is some very nice work. i cant wait to see more. it would be really cool to see the finished product on the water running

No problem.

I will update this topic as soon as I make nex things.

Great work so far Fabrice. A twin .21 cat should be lots of fun. I might suggest you look into rotary cars insead of the slide carbs used for cars if they make actuation simpler for you. The OZ VZ-M motor has a very nice 10mm carb which may fit your STS engines with a little machining to match the diameters. Keep us posted.

Tyler

Too lattle ^_^



I've alrady bought them last summer, to prepare this project.

You're just wrong on the carb neck, they didn't need any machninig, I choose them because they fit the STS engine without any mod. Sts crack bore is also 10mm.

I hope this booat will be fun, certainly difficult to set, but when setted.... lots of couple of rpm!

Fabrice, you'll like those carbs a lot. Easy to tune and OS reliability!

Tyler

RaceMechaniX said:

Fabrice, you'll like those carbs a lot. Easy to tune and OS reliability!
Tyler

Click to expand...

I've got 3 OS engines, as you I think they are easy to tune and reliable. The 9A carb on my 61 VR-M is the best example! On set, never touch again!

A friend was just sceptical about the big bore of the venturi, he thinks as big as it is as difficult is the engine to set, I don't think so.

Nice work !!! You definitely have more time on your hands than any of us over here ! rudders look way thick , one inlet woud be sufficient for those motors . Keep up the good work !

Another real craftsman for sure!! Love the idea and those outdrives are to die for. This will be a great project to watch.

Regards Curt

That's beautiful!! I love that machine work....I wish I had the knowledge/tools to build hardware!!

Hey Fabrice....cool looking equipment. I can not wait to see how it runs. Good luck!

Tom, I would be hapy to show it you, if someone tell me to go to florida or else to have a nice trip and have a run with you!

You're right, the rudder is quite thick, I wanted to be sure of the cooling of the engines, two bores for two engines.

I see marine specialtie in your profile, are you the owner of the shop? If yes, i had bought many times at your store.

It's time to do such thinks, it's true, machining almost is very long, but wood and aircraft aluminium are two great material to machine.

What is a craftman? :huh:

Thanks all for your messages.

Love the work you have done mate, Any chance you would sell a set of your cat struts?? also you might want to put some sleeve shims in your motors to raise the timing up a little, Car motors are not timed to run in the 25k rpm range like boat motors run.

being called a craftsman is a complement, Were admiring your work.

Travail excellent!

BB Mods said:

Love the work you have done mate, Any chance you would sell a set of your cat struts?? also you might want to put some sleeve shims in your motors to raise the timing up a little, Car motors are not timed to run in the 25k rpm range like boat motors run.
being called a craftsman is a complement, Were admiring your work.

Travail excellent!

Click to expand...

Thanks!

It would not be worth to sell the strut, if I counted the time to do one, it will mean my work will be paid something like 5€ the hours, knowing I need 8-9 hours to do one... I almost I will have no more time to finish this hull!

Aluminium is an aircraft one, called here Fortal. It's actually used to make some some injection molds for the plastic industry. It's very hard, but great to machine, it's nt gluying like the standard aluminium Au4g

If I had some time in the future, why not doing two, but not in the two months arriving.

I can't understand what means "to put a sleem shims in my engines to raise the timing up"?

May you explain it please?

Ok, On the motors you have the intake/exhaust/transfer port "timing" aka when the ports open and close, is set at a lower number because the motors were made to run in cars/trucks and spin high 35k+ rpms, in a boat we cant use that many rpm's so we raise the timing up to higher values to make the motor match the rpm range we can use, being 23k~28k RPM's. If you put lets say .010" worth of sleeve shims (like head shims but these go under the sleeve between the crankcase and the bottom of the sleeve) The port timing will be raised thus turning a car motor into a boat motor, I don't know the motors you have, so don't quote me on the shim thickness, Sone one else here might have used the motors you have, and might know how thick of a shim you need. I would contact Jerry Wyss here on the forum and ask him some questions!

So if I understand weel, you don't talk about these shims :



This is head shims.

Where go the shims you talk about? Under the neck of the sleeve? If I understand well, if I use a 0.2mm thick shims, the sleeve will be raised of 0.2mm, is that you said? The ports will also be 0.2mm higher than before. What aboute the piston, the compression will not change, as it's conical?