Home-made twin .21 catamaran

[gratte-tout]

Oops, the today's video..

http://www.dailymotion.com/Gratte-tout/video/8235997

As you will see, I also ran my other boat, with an OS 61 VR-M, capable of 90km/h, but it was too windy today..

 

[misshydro]

pretty good run! But you may have to put weight in the sposons area to keep the nose down= no blow overs or harder to blow over at higher speed . I say we would love to see that cat running at high speeds to see how she'll go!

 

[gratte-tout]

The white one is not the same as the twin..!

The white, at the beginning of the video, is the first I made. The today's twin is the same hull, a little more short.

The white one is very safe when there's no wind, but today it was hot because a lot of wind (80 km/h sometimes). That's the first blow over i made since I finished it (more than one year..)

More video on my first cat :

http://www.dailymotion.com/Gratte-tout/vid...-211007_extreme

http://www.dailymotion.com/Gratte-tout/vid...in-2007_extreme

 

[dannyual767]

Fabrice, it looks like your older, OS .61 cat really runs well. I think that you've got your hull designed pretty well and once you get your twin .21 pipes a good bit shorter, I'm sure that smaller boat will perform better as well.

 

[gratte-tout]

Thanks. The videos I show you are pretty old, it was the beginning of the settings of this hull, now it's running very stable, I found the good prop and the good engine setting. Yesterday it was to windy to use it, I may have solve the blow over problem by setting another angle to the drive, but I didn't want to unset it for one sindy day.

I know the hull is very stable at high speed (I'm actually at 56-57 mph with 16% nitro), and I would like to set the twin one to ear this hull with 2 .21 screaming!

I think I'm going to buy two 1328 tuned pipes (Macs).

If you have others to advice me, let me know

Thanks.

 

[gratte-tout]

Last runs : I've changed the plane pipes I bought (!) by two muffled marine ones, and reduce the lenght from the plug to the end of the first tap of the pipe. I'm now at something like 24cm, it's difficult to make more.

Sorry for the video with the camera on the floor, I was alone this morning at the pond.

http://www.dailymotion.com/Gratte-tout/vid...du-130408_sport

It's far more fast from the first tests I made.

Just have to re-set the engines.

 

[dannyual767]

Fabrice, it looks like your boat really likes those shorter marine pipes! Its running real good and I'm very impressed with your build and the performance that you're getting now. Very nice job.

 

[gratte-tout]

Thanks.

I'm actually looking to set the engines as perfect as possible, as you may see on the vid, they still pretty rich, and not really at the same rpms.

The left engine is rewing too much than the right one, and at full throttle, I can't go straight, and I can't go to left if I don't down the throttle.

This run was short, we had rain for 4-5 days here, the pond (feed by a bigger one - and a river on its start) was 2-3 metters upper than usual, I had trees in the water, I was not a real nice days to set records.

But I'm still working on it.

 

[MEAN GREEN]

Thanks.I'm actually looking to set the engines as perfect as possible, as you may see on the vid, they still pretty rich, and not really at the same rpms.

The left engine is rewing too much than the right one, and at full throttle, I can't go straight, and I can't go to left if I don't down the throttle.

This run was short, we had rain for 4-5 days here, the pond (feed by a bigger one - and a river on its start) was 2-3 metters upper than usual, I had trees in the water, I was not a real nice days to set records.

But I'm still working on it.

looking good Fabrice you are right the motors are not in synic aka matched Do you have a cowl for the boat yet

Gavin

 

[gratte-tout]

For this time, no cowl, I have to do it in fiberglass and I'm not really skillfull with it.

I have to build the mold to built it, and it's taking time.

I think I will let it open for this summer, and will try to make a cowl this winter. It's better when you're setting a boat, almost with two disturbed engines :lol:

In fact, even if I had one, I think I will not use it as long as the engines are not perfectly setted, I also have to find the better prop for this hull with twin engines.

I'm setting this one while mounting my other boat, the HTB 360 with a 13cc K&B, this one is also going to have its rc trim system

 

[Dr Hydro]

Hey Fabrice...the boat looks great!! Have you ever thought of making the outdrives steerable? You could do away with the rudder and gain more speed. Just a thought. I also did not have a lot of experience with fiberglass but a friend told me how to make a cowl. You do not need to make a mold which is a lot of work if you do not plan on making a lot of the same boats. We have blue foam used in home building that is about 1/2 inch thick.I hope you can find some also. Another foam to use is the green kind that florists use to hold flowers in place. What you would do is glue as many pieces together as you need and, using sandpaper, shape the foam into the shape you like. Take your time and be careful when sanding because I do not know of any putty you can use to repair any spots where you may have sanded too much foam away. Then you would coat the cowl with epoxy and watch it closely as it dries. When it dries to the point where it is not wet but is really sticky or tacky, lay your fiberglass cloth on the cowl and press it into place. It must be placed on the cowl with the fibers at a 45 degree angle to the centerline of the cowl. This will allow it to wrap around the different bends without wrinkling. After the epoxy dries totally, mix some more epoxy and paint a thin coat on the cowl. Use an old credit card or a playing card and scrape off as much epoxy as you can. It may still be a little rough but you can smooth it out with some automotive putty. Sand it smooth and paint it. Then, sand the inside to make croom for your engines. To attach the cowl to the boat I would use 4 of those rare earth magnets on each corner of the cowl and 4 on each corner of the boat. Those are the really small magnets that are very strong. I hope you will give it a try. I did not think I could do a good job either, but it came out looking great. It is also alot cheaper than using the mold making process. Good luck and keep up the good work. Jim

 

[gratte-tout]

In fact, I already built such a cowl, with the method you are talking about.

I designed the cowl as I wanted to be, and I designed a wood frame to have some references for the foam. The wood parts were designed to make possible to fill the holes with many thick of foam, the same as you told me.

Then, I put the foam, sanded it to get the shape I wanted.

After this, I used polyuréthane resin with fiberglass.

I would like to make a mold because my first method is very long, after the resin is completly dry, you have to sand it many times, putty, sand etc.. And the shape is never really perfect.

My first cats cowl is done like this, I would like to try another method.

For the steering, the drives are not designed to be driven on left or right. The first I made were fully "steerable", but it was too complicated to control them on depth and on side.

 

[jtd]

My name is jason or jtd. ive been designing my own boats for years & scatch building them .

and in the last few weeks have been gathering information about the 50' mystic twin turbine hull , for a build just like this , I mean identical to this . your boat is amazing along with your talent.

I was thinking of useing twin .67's but I dont have a length or beam measurment decided on. & dont have cad. any nfomation you mite be willing to share would be greatly aprecated. I know you have worked very hard and long on this . Idont expect that you would share all your secrets but i have to ask. It would be for my own personal pleasure . you can e-mail me at ([email protected]) I live in the states. thanks jtd

heres my latest build.

 

[dannyual767]

Fabrice, like Jason, I'd like to build a boat like yours as well. I'd rather use a single inboard since I have both a K&B .67 and OPS .65 and .67 sitting around doing nothing. I'd like to put at least one of them in a scratch-built, wood cat. Can you share plans with us?

 

[gratte-tout]

Guys, I have to check some details for the hull plans. In fact, I've sold them to a french magazine, and I don't know how I can "use" them now.

I'm actually thinking about mounting another twin, I have an OS 81 VRM, I'm looking for another one to built it, next winter perhaps, but in the pads it's dufficult to put this big engines, in the spanson it could be easier.

However, I may start with giving as much advices as you need now, then why not sharing my plans.

Good day to talk about it, this is the video of the taday's runs.

http://www.dailymotion.com/Gratte-tout/video/8777556

I still looking for more rpm (i'm near 26.000 here), and almost trying to run it straight, because I can't turn on left, I don't know if it's because the left engine is turning faster than the right one (sill invert them to check), or due to the prop's torque. As I'm always turning on left on the video, and this eat some precious km/h..

If you have any ideas about it..

Thanks.

 

[gratte-tout]

Hi huys,

Last news, I reduced the lenght of the pipe for 1.5 cm, to have more and more rpm

With props with little prop alk such as X448, I can better go straight than with props like 1742/3.

Speed increases with every new runs, I'm actually @ 68km/h, it's not bad, but I'm waiting for even more.

I'm actually waiting for videos from a friend, mine is long, and with other boats from friends.

http://www.dailymotion.com/Gratte-tout/video/8916050

You can see my two cats at the end on the video, the .61 red one (with the inboard video) and the yellow twin at the end.

Enjoy

 

[gratte-tout]

Thanks to a friend for his PERFECT pictures of my two boats

My .61 cat

My twin :

 

[Dr Hydro]

Great videos Fabrice. Those electric boats really fly!

 

[gratte-tout]

Last video guys, I'm quite happy as you may see, it starts to be fast!

http://www.dailymotion.com/video/x5cofa_tw...au-040508_sport

 

[Bruiser7000]

SO! very! SWEET!!

Thanks for posting pics