Brutus

[Bob Abell 2Participant @bobabell2]

Ashley

Paul has sent me a PM………He is not adamant at all

His Dr No act is only part of his banter etc

I just go along with it

I have no problem with the thread banter….It's just a bit of fun

Haven't looked at the ESC's yet but I'm sure there are no cooling pipes on it?

The prop shafts look very puny for 950watts!

Paul is looking into the cooling side of things

Bob

Bob

[Bob Abell 2Participant @bobabell2]

Ashley

This is going to be fun?

Had a look at the ESC`s and there is no cooling feature?

It says in the one page manual, that when the ESC reaches 100 c, the controller will switch off and come on again as it cools down

Is this normal?……..Come in, D.M.

Bob

[ashley needhamParticipant @ashleyneedham69188]

Bob. Looks like to me there is a little cooling fan built on to the top of the ESC, and so it is air cooled and not water cooled. Lucky lad. Still, will need some air circulation around the boat interior.

Ashley

[Paul TParticipant @pault84577]

Bob

I'm looking at introducing some cooling vents into the cabin roof, should have a rough sketch by tonight.

Paul

[Paul TParticipant @pault84577]

Bob

Re the cabin roof…please check the distance from F3 to the front of the cabin it should be 33mm and the cabin roof is parallel with the foredeck try relating drg 15 to the plan drawing 19

Re the 230mm tubes….they are really to short for Brutus as the design calls for 400mm (and the Ellie is designed for 500mm)

Paul

[Bob Abell 2Participant @bobabell2]

Shop floor to Drawing Dept

Further to the cabin wall mystery. My plywood cabin wall starts at the window corner and ends at the stern

The wall rests on the corner and rests at the stern….on the hull deck

There is a gap of about 10mm in the middle at Former 5, higher than your side view drawing shows

10mm is quite an error!

The hull is made from assembling the formers and joining them with the stringers, so the hull is Bob on

The cabin wall was cut to suit my hull and the top shape was taken from your side view

I can correct the cabin roof to make it parallel to the deck, by cutting the roof

Sorry about the long winded explanation

Don't think much of your ventilation proposal, it's not dramatic enough!….I would like to see something more like a vent opening…. We also need to get rid of the warm air too

Let's invent the vent later, when the cabin is in place?

That's enough of hot air for today

Bob

[Bob Abell 2Participant @bobabell2]

Shop floor to Drawing Office

Assuming the overall length of the Brushless motor is 60mm and quite light, What length of pro shaft do we need?

Don't fancy the belt drive, btw

We're on the home run now, Paul!

Bob

[ashley needhamParticipant @ashleyneedham69188]

What you want is something hi-tech, and the way forward for an air scoop is the NACA duct (look it up) , with perhaps some vortex generators ahead of this to assist in keeping the air low on the deck. very snazzy, in an understated way. Would look simply top-hole!

Your motor doesnt need belt drive if results for similar sized motors at our pond are anything to go by. Very torqy these motors.

Ashley

[ashley needhamParticipant @ashleyneedham69188]

The NACA ducts are the sunken ones

[Bob Abell 2Participant @bobabell2]

Thank you Ashley

That`s nice to hear about the talkie motors, but I just can`t believe how small they are!

I like the air vents!……..Very snazzy indeed and hi tech too

I notice they look very much like a VENTURI shape…….Which way is the air flow?……..I`ll make a card model of the raised type, for Dr No`s approval

The rear cabin wall is ideal for a few louvres too

Cabin problem sorted now

Bob

[ashley needhamParticipant @ashleyneedham69188]

Bob, quote " This design is believed to work because the combination of the gentle ramp angle and the curvature profile of the walls creates counter-rotating vortices which deflect the boundary layer away from the inlet and draws in the faster moving air, while avoiding the form drag and flow separation that can occur with protruding scoop designs" so there we are, and now you know….

Air flow is right to left in the above photo.

Ashley

[Paul TParticipant @pault84577]

Bob

Re the cabin roof …from your description it sounds as though the cabin you have cut out is to large, the following is a drawing showing a couple of check dimensions and location positions so that you can check your cabin.

Please check these dimensions and let me know what you find.

Re the air vents……..

Ashleys vortex vents rely on speed to be efficient and it is doubtful that the model will ever achieve the kind of speeds required to induce airflow, however these vents will let in lots of water and so they are not suitable.

The ventilation drawing that I have sent whilst not dramatic but should be sufficient for the purposes as it allows plenty of air into the model whilst being high enough to prevent water ingress but to design a better system I will need the manufacturers heating and airflow requirements.

Re the propshafts…….

To recalculate the length of the shafts I will need the exact sizes of the motor and its mounts. The design problem that forced the need for drive belts is the requirement for the shafts to be fitted at a shallow angle and getting the motors as low as possible in the hull.

Paul

[Bob Abell 2Participant @bobabell2]

Hello Paul

My dimension is 590mm but is easily changed

Take a look at these WIP pictures…..

General view of your magnificent Sea Axe Launch!

You`ve done an excellent job, designing Brutus!……Very well done, Paul

Nice shot of the build

Do we want the roof to overhang at the sides?

I think the cabin is sorted

I think the windscreen may look OK if we glue it on the outside of the cabin?

A window edge may look out of date!

Rudders installed, by Gorp of the week!

Why Gorp of the week?…… you ask

Because I hadn`t realised….They were different sizes!

[Paul TParticipant @pault84577]

Bob

Very nice progress photos and thank you for taking the time to post them.

To answer your questions:

1/ The roof finishes flush with the cabin sides so there is no overhang.

2/ The windscreen was intended to be flush with the cabin wall and could have been painted on but with your heating problem I redesigned to create the recess and allow some air into the boat. On this subject I have drawn up some small hot air exit vents to go into the rear deck above the roller door but I need the motor manufacturers recommended air flow / cooling data to get the sizes right.

Its difficult to tell from the photos but is the foredeck recessed or flat?

What size rudders have you fitted?

Paul

 

Edited By Paul T on 09/02/2014 14:01:16

[Bob Abell 2Participant @bobabell2]

Paul

You could have enthused a little!

The fore deck is flush with the main deck, the height is not set yet

The rudders are 2"deep x 11/2" wide and 13/4 deep x 11/4" wide….Which size would you like?

Motor dims……..

Ref ….TURNIGY D3536/6…….1250kv

O/A length……105mm

Bracket……35mm

Motor……….40mm x 35mm dia…….Shaft 4mm dia

coupling……30mm

No info figures regarding motor cooling, it says….."put a whole in model cover"

One ESC per motor

 

Bob

 

Edited By Bob Abell on 09/02/2014 14:27:38

[Paul TParticipant @pault84577]

I am enthused

[Bob Abell 2Participant @bobabell2]

Thanks Paul

I like it too……It will be a great attraction at Ellesmere Port?

I'm thinking about the surface finish now

I could cover the entire model in stiff card and then spray it with Halfords spray cans

We could get a high gloss car type finish, without having to fill and rub down!

Bob

[Paul TParticipant @pault84577]

Covering with card and spray painting sounds like a good idea all you need are some very large sheets of card.

[ashley needhamParticipant @ashleyneedham69188]

Bob, not keen on covering with card MYSELF, you have a perfectly decent flat bit of ply there, a few coats of Eze-cote with rubbing down and then spray primer/topcoat should see a wonderful smooth shin finish surely??

Ashley

[Bob Abell 2Participant @bobabell2]

Ashley

You are probably right, I've not used Ezekote myself

How do I apply it?….

How long does it take to dry etc

If you reckon it's a better option, I give it a try

Bob

[Colin BishopModerator @colinbishop34627]

With EzeCote, you just brush it on and it should be pretty much dry in 20 minutes at room temperature. Water clean up too so what's not to like?

Colin

[Bob Abell 2Participant @bobabell2]

Many thanks, Colin

Has Ezecote got some sort of grain filler mixed in with it?

Bob

[Colin BishopModerator @colinbishop34627]

No Bob, it is just a creamy liquid but don't put it in your tea! It will fill the grain OK.

Colin

[Bob Abell 2Participant @bobabell2]

Thank you, Colin

I'll get some in

Bob

Edited By Bob Abell on 10/02/2014 05:32:55

[ashley needhamParticipant @ashleyneedham69188]

Bob. It is a bit like a thick Acrylic varnish, In the bottle and when applied is as as Colin says, a creamy white, but dries to a satin finish. It will seal your grain as it is reasonably thick. When dry it will sand to a great smooth finish, and also as stated it is water brush clean.

Although in a warm room it will dry in 20 mins I would give it an hour or so to harden a bit before sanding.

If you use this stuff in conjunction with that very fine almost silk like fibreglass cloth the aircraft boys use it really will provide a silk surface over your model. It conforms to curves very easily and also comes in very large sizes, so you could cover each side with one piece and also the bottom in one go, perhaps with a single cut to get over the extreme knife edge.

It takes any sort of paint finish.. cans,, oils whatever. Great stuff. Buy some, because you are worth it.

Ashley

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