Turbo Fan Jets

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Turbo Fan Jets

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20 August 2015 at 20:46 #7030
mike farrell
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@mikefarrell21522
Turbo fan jets
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20 August 2015 at 20:46 #59804
mike farrell
Participant
@mikefarrell21522
Hi All I am currently designing and building a Catamaran (based on Paul Ts River Catamaran) .I have decided to supplement the drive trains with 2 x70mm Turbo Fan Jets to help speed up the drive .

What I failed to consider was how many air changes I will need to insure the best use of the Fan Jets

Do I need to have openings to allow air changes ?

I am using 4 brushless motors so have some concerns about cooling?

Any thoughts before I continue the buildMichael
21 August 2015 at 12:17 #59815
Dave Milbourn
Participant
@davemilbourn48782
Mike

Can you explain what you understand by "air changes", please?

As far as I known, a ducted fan needs unrestricted airflow at both ends, like a jet engine. If you don't have any openings to allow air to get into it then it has nothing to compress and blow out of the back. Similarly if you block off the exit of the air then you'll quickly even out the pressure between the outside air and the fan enclosure and it won't suck in any more air. Or have I missed something? Ref cooling, the fan motors will be cooled by the flow of air through the DF units. You may need supplementary water cooling for the speed controllers and the main drive motors.

Dave M
21 August 2015 at 16:33 #59816
mike farrell
Participant
@mikefarrell21522
Hi Dave ,I did not make it clear why I asked the question so an explanation .

I am building a model of the American Navy X Craft now called the Sea Fighter. It is a fully enclosed Catamaran .It was designed as a rapid craft with a speed of 58 nautical miles per hour. It was used for a short period in the West Indies but sold off very quickly. To get any near the speeds I had to consider how to get it go faster I decided to attempt to use 2 Ducted Fan Jets to supplement the props ,

To date the prop train are water cooled and I am using cheap plastic props until I can establish what size props I will eventually use .

I have not totally enclosed the Cat so can cut a air supply to the DFJs .

Hope I have made clearer as to what I am targeting Thanks Michael
21 August 2015 at 18:31 #59818
Dave Milbourn
Participant
@davemilbourn48782
Not really, but go for it anyway. Ashley is silently envious………………….

Dave M
21 August 2015 at 20:12 #59819
Paul T
Participant
@pault84577
Hi Michael

The ducted fans need a large volume of air to operate so any openings in the hull need to have the same overall surface area as the ducted fans main inlet, although not necessarily the same shape, any connecting ducts between the inlet and fan must also maintain the same overall size without any tight corners or pinch points.

I can help further if you email me some 'work in progress' photos.

All the best and hope to see you at Haydock ( bring the Sea Fighter and we can discuss it there)

Paul

btw would you be interested in having my prototype Thor?
21 August 2015 at 21:20 #59822
mike farrell
Participant
@mikefarrell21522
Hi Paul I will bring some photos over next Friday to Haydock. .

Taken your advice and ordered some ally grills and will now steal my daughters cloths dryer trunking and set up a direct line of air intake to both DFJs

I will email you later to let you know my current issues

Have not fitted water intakes as yet but will pick some up from the show .

Bench tested Port drive train and DFJ and Starboard drive trains ,all clear and tested the steering system and all clear again .

Painting is slowing me down as it takes 3 coats of undercoat rubbed down between ,not getting it up to what I want and cannot get it ready for Haydock. Michael
22 August 2015 at 10:40 #59826
ashley needham
Participant
@ashleyneedham69188
Mike, Likely not worth the effort. Need massive clear air intakes preferably rounded or the units will add very little frust. They are also likely to push the nose down. Use more powerful main drives.

Ashley (from a man who has seen)
22 August 2015 at 12:56 #59830
mike farrell
Participant
@mikefarrell21522
Thanks for your thoughts Ashley ,if I do,nt try something different I,ll never know for sure . To increase the motors in Brushless will come with a massive increase in cost and the ESC added .

If it do not work I can build a flying boat .

I,ll have fun tryingMichael
22 August 2015 at 15:46 #59832
Paul T
Participant
@pault84577
Oh Dear

Despite Ashleys obvious 'frust'ation with DFJs the ductways that you want to build (which are called Plenums) are relatively easy to construct providing the external intakes are not to far away from the DFJs.

Ash you will really have to come up t'north and learn some proper engineering that doesn't involve hardboard or duct tape!

Paul

Edited By Paul T on 22/08/2015 15:48:14
24 August 2015 at 16:44 #59870
ashley needham
Participant
@ashleyneedham69188
Mike.

Not sure that the cost for brushless will be massive. Obviously the EDF will work and provide extra frust, just not in proportion to the ampage consumed that could go on better/more powerful main otors.

As you say, worth a punt.

Paul. Next year son, I will be there and you will see the magnificence of my creations. No duct tape (not promising on the other)

Ashley
24 August 2015 at 19:03 #59877
Paul T
Participant
@pault84577
Hi Ashley

I will have the cobbles swept and the red rug laid out.

Paul
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