Topic: Omra Makara D Class (Read 159028 times)

2772e · « **on:** March 23, 2007, 07:47:47 pm »

Received this week my first attempt at a deep V petrol powered offshore mono.

Subject to the build success and the tuning, handling i intend racing her in Omra D series later this year.

Thanks so far to Martin and Danny for their advise, i hope theres plenty more where that came for, and the rest of you!

So far i have flatted back most of the hull and started painting her in a dark blue silver fleck, drilled out the rear engine hatch and prop tube.

Met with my vinyl sticker man today and agreed on the sponsors etc. But thats a secret until the next installment.

Tomorrow the engine bracketery etc.

Regards

Simon

omra85 · « **Reply #1 on:** March 23, 2007, 08:37:09 pm »

Ooooh, I like, I like

Hope your graphics are nice and bright, blue metalflake I can see on the bank, but at 100 yds ??? (even though it won't be me "challenging" you)

Still you're not going to stop, are you

Are you side mounting the engine? Its a good way to get the pipe central, just don't forget the balance side-to-side as well. Wish I had that amount of room in mine!

Good luck, and we're always here for advice (some of it may even be worth listening to)

Danny

2772e · « **Reply #2 on:** March 25, 2007, 08:17:01 pm »

Did not get a chance to do any work on the Makara yesterday as it was wifeys birthday! :'(

Back on to her today with avengance.

Engine glassed in and mounted, prop tube bent and installed, skeg and rudder bolted on and top sides painted.

Oh and the electrics box mounted.

A pretty good day i think!

Any ideas on how the throttle linkage set up works, is it a bar thing or one of those bike brake thingy's. ???

Regards

Simon

omra85 · « **Reply #3 on:** March 25, 2007, 08:41:47 pm »

Simon
Your engine mounts look fine, but you have too much unsupported flexi showing. As the engine moves around whilst running, it will set up oscillation in the flexi which will increase to a point where it will snap or twist up the inner. You need no more than 15mm MAX between the end of the outer and the engine collet. Have you the rest of the outer you cut? If you have, find a short piece (25mm) of tube that will fit snugly over the outer then JB weld or solder it together to extend the tube. The PTFE liner will need to be replaced with a full length piece for the new length.
Sorry, mate - but better to tell you now, than you have a broken flexi trash the inside of your boat!

For the throttle, is the carb lever a front to back motion or is it at an angle. If it's straight, I would use either 1.5mm brazing rod or 2mm bike spokes (stainless). If it's straight but at 90 deg, you can use a bell-crank (like in your other). I know a few with sparkies who use 'bowden' (brake) cable but there is usually some slack in the set up which can cause throttle inconsistency. Also the type I once used (never again) rusted up and kept jamming. You also need a spring to pull the throttle lever back (bowden is great for pulling, but useless for pushing) which means that there is a constant load on your throttle servo.

Who said it was going to be easy - the best things never are

Danny

2772e · « **Reply #4 on:** March 26, 2007, 09:25:18 am »

Danny,

Thanks for the post, i would prefer to know now, rather than later. I have still got the tube so i will refit it, ta.

As far as the ptfe liner, i havn't got one. Its a bit like a pxxxk in a bucket. I will get onto Prestwich and see if they can send me one today.

Would you suggest strapping/mounting the top end of the prop tube to save any movement as well, i have glassed it in at the other end?

Regards

Simon

w3bby · « **Reply #5 on:** March 26, 2007, 12:04:53 pm »

You don't need the PTFE, some people run with it and some without. As long as the shaft is lubricated you will be ok.
You will need to fasten the tube at the motor end as well. Make a bracket from som ply.

Looking good otherwise

omra85 · « **Reply #6 on:** March 26, 2007, 01:42:17 pm »

I suppose the shaft liner depends on who's shaft you buy. I've never trusted steel rubbing against brass (even with lubrication) so I buy Aeromarine ones which have a liner (mine look and feel more like polythene than PTFE though).

Ian's idea of a ply bracket is good. Anything to stop movement of the outer. I normally just use P40 but my shafts are a lot lower than yours (smaller engines) so yours would need a great blob of P40

Double linkage to rudder, eh. No excuse for poor steering there then

Love the SHINE on that rudder

, bet it doesn't stay like that

Danny

w3bby · « **Reply #7 on:** March 26, 2007, 03:30:30 pm »

Here's a stuffing tube holder and a throttle setup using pushrods. Do NOT use heavy pushrod for the throttle as it can cause fatigue in the carb if it doesn't have some give in it.

2772e · « **Reply #8 on:** March 26, 2007, 09:42:00 pm »

Ian,

I dont suppose you have got a close up of throttle linkage of the Zen on the bench.

That set up looks perfect. Is it commercvially available?

Regards

Simon

w3bby · « **Reply #9 on:** March 27, 2007, 12:17:56 am »

It's a simple bellcrank fastened to a bit of aluminium bolted to the front mount, a couple of ball joints and a pushrod. There are systems like this available but it is just as cheap to buy the bits and make your own.
I felt the bellcrank was a little weak so I drilled out and bushed the circular servo disc you see in the first picture. Altogether a more robust setup. I use the shrink tube to hide the rust on the pushrod as we boat in salt water

2772e · « **Reply #10 on:** March 29, 2007, 01:31:03 pm »

Sad news i am afraid, just spoken to my sticker man and they are not going to be ready untill next Wednesday, gutted! :'(

Just have to wait a bit longer.

Steering and throttle cables turned up today from Prestwich so in the garage tonight!

Danny, just saw a picture of your boat with twin fuel tanks, are they ajoined and if so are they commercially available? I have been looking at my big yellow 1 litre tank and its mounting. To clear the prop tube i have to mount it over the top! Not good me thinks, centre of gravity and all that fuel sloshing around.

Regards

Simon

omra85 · « **Reply #11 on:** March 29, 2007, 07:07:02 pm »

Hi Simon
My tanks are all Prestwich. They are 1 piece with a groove in the top for the tuned pipe. Have a look at Dave's website, tanks are on the middle of the opening page.
I use the PT3A but I must admit - the NEWEST is 15 years old

(They still bear prop grooves from when I did multi racing).
They are expensive but dead easy to mount and last forever.
They are not used much in D class as the petrol boats don't use anywhere near as much juice as the glows. My 'A' class uses 1.5 litres in 33 mins (good job the races only last 30 mins)

Most of the D's use the smallish aircraft type tanks, or a few make their own from tin which is soft solder joined . I would have thought your 1 litre would last at least 30 mins.
There was some talk of using IV (blood) bags. Quite a few of the World Champ competitors use them. Very low, and apparently OK for petrol (not methanol, though) :(
For information, here's my 7.5cc one

Good luck
Danny

2772e · « **Reply #12 on:** April 04, 2007, 08:01:55 pm »

Guess who turned up today? ???

Sweet! :-* :-*

Engine ready to go, electrics ready to go, fuel tank to be done, exhaust on order.

Ready for the water in two weeks.

omra85 · « **Reply #13 on:** April 04, 2007, 08:14:13 pm »

Very smart, Simon! Now, as long as you don't drive like David Coultard............

Danny
PS Off to Torquay this Sunday, so if you see on the news that a model boat is attacking France, you know I've gone off course

BJ · « **Reply #14 on:** April 17, 2007, 11:07:29 am »

Nimrif's Makara looks amazingly similar to the AeroMarine Challenger series of hulls. Wonder what would be the result of a head to head between two equally matched boats?

glennb2006 · « **Reply #15 on:** April 17, 2007, 02:59:03 pm »

Hi there 2772e, with luck there will be some photo's here both of the throttle linkage, which uses a straight pushrod from the servo onto the bellcrank, nice and simple, also an IV bag fuel tank.

So far so good.

Sorry they are blurred.

Glenn

2772e · « **Reply #16 on:** April 17, 2007, 05:56:55 pm »

Cheers Glenn,

In the end i went with a cable and a plastic 1 litre fuel tank in between the servo box and the motor.

Should be on the water this weekend with any luck so will see how we get on.

Thanks for the pics.

Simon

glennb2006 · « **Reply #17 on:** April 18, 2007, 12:57:59 am »

no problem Simon,

good luck with it this wekend. Mines ready to go now, if I ever manage to tear myself out of the house I may get round to getting some retesting done on it. Hoping to run mine at Windermere for a one off this year.

Glenn

2772e · « **Reply #18 on:** April 22, 2007, 08:25:46 pm »

Maiden voyage over yesterday, and a success even if i say so myself.

No rudder adjustment, runs straight.

No leg adjustment, gets up and planes just right

Just need a bigger lake and some buoys to get my eye in and we will see how she goes.

Another 1 litre of rich mix and then we can start the tuning and fun bits.

Offshore i think she will need some more weight.

Only problem was the batteries went flat, so could not try her with the top on. One more weekend before my fist race at Stevenage, no pressure.

http://www.youtube.com/watch?v=I4g-RbHRSCA

Cheers

Simon

Thanks for all the help during the build.

Regards

w3bby · « **Reply #19 on:** April 23, 2007, 11:28:36 pm »

Nice maiden, looks comfortable on the water

2772e · « **Reply #20 on:** May 04, 2007, 10:12:06 pm »

After a week of tightning down and finding a lake i could run a petrol on, big enough and local enough.

2nd trip out to Brentwood Model Boat Lake last weekend.

Engine running in and engine tuning.

a few final tweeks and screw her bacjk together and we should be raedy for the fist race this weekend.

At least i know now she flies as well as she floats.

http://www.youtube.com/watch?v=7vYkQCghGZY

omra85 · « **Reply #21 on:** May 07, 2007, 12:47:17 pm »

Now that I've eventually met him, Simon does not seem the type to blow his own trumpet, so I will blow it for him!
His Makara took part in it's first race at Stevenage yesterday and he had a quite eventful day. The race he was in had quite a few very experienced drivers, he drove safely and his boat performed extremely well. The handling was stable and the speed was more than acceptable - it was bl**dy fast

He would have probably been in with a placing but for a slight problem with the radio (box mounting re-design, I think).

Anyway, the purpose of this post is to inform you all - Simon included (he had to leave early, so I don't think even HE is aware yet) - that his boat won the Concours de Elegance trophy for the BEST turned out boat of the day.

Having read back through this thread I think that Simon's is a remarkable achievement, given it's his first OMRA boat and his first outing.
So - well done Simon!

Danny

DickyD · « **Reply #22 on:** May 07, 2007, 01:15:56 pm »

Very impressive boat. Nicely turned out.

She does fly well !

Richard

2772e · « **Reply #23 on:** May 07, 2007, 09:04:32 pm »

A big thank you to everybody for their advice on building the boat and setting her up, without it i would never have made the first race.

It was nearly a success yesterday, turns out the two bolts that hold one side of the electrics box had shaken loose and i lost steering on a buoy, she spun stalled and started to disintegrate. (should have used lock washers!) Thankfully the lid floated (glad i put that polystyrene in at the last minute) and all the pipe lagging distributed all over the lake! Sorry chaps!

Glad she did stop though, on closer inspection the petrol tank must have touched the exhaust and petrol was squirting out. Ideal ingredients for an accident! Thats irony!

Back to the garage this week for the rebuild, a bit more testing on Saturday and hope to see you all the following week at Kingsbury!

Regards

Simon

martno1fan · « **Reply #24 on:** May 09, 2007, 03:37:31 pm »

well done on your first race simon she goes real nice mate,looks great too.as for the pipe lagging zip ties work well to hold things together and in the right place

.mine are that tightly fitted between the bulkheads they dont move.its a good idea to fasten them to the engine somehow in case your boat disintegrates in a crash also ,that way the engine will be suspended by the foam and wont sink.

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Author Topic: Omra Makara D Class (Read 159028 times)

omra85

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omra85

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BJ

omra85