View Full Version : Air flow

lazza - n/a
26-Jan-06, 06:19 AM

I'm just in the process of thinking up a idea to modify the way my radiator recieves its air flow (currently its not quite enough and the craft runs at about 98degrees C ) . My question is.. If i was to drill two holes into the plenum chamber through either side of my cockpit and then run a couple of pipes (or similar) to the front of my radiator would that make much difference to the lift/ cushion pressure ? obviously the larger the hole is the more it would effect it but i'm wondering as long as they are smaller than the holes to the skirt would that be ok ?

It's only one of a couple of ideas going through my head so im not committed to it , was more curious if its a fesible option.

jon_curtis - n/a
26-Jan-06, 08:22 AM
i did see a craft where, someone took the cooling fan off their rotax 503, and had a bit of flexy pip from the plenum to a cover over where the fan was, so yeh it can be done!

srn4 - n/a
26-Jan-06, 12:11 PM
Hey lazza.

Can you not put some kind of scoop on the top of the engine cover, kinda like a turbo intake. If its high enough it might draw in more air than the scoops in the footwell http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif

Alternativley can you not get an electric fan to cool the radiator continuously???

The only think that worries me about sticking holes in the plenum walls is that you are going to be inviting a lot more water into the engine bay... http://hovercraft.org.uk/images/icons/smiley_icons/icon_confused.gif


dazling - n/a
26-Jan-06, 03:32 PM
hi ya lazza

i've been giving your problem some thought and also looked at a few of the constuction pic's

i was wondering if the engine ran at a diff temp with out a passenger ( who may be obstucting the intakes )?

secondly , and i know this would mean modifying the bulkhead but have you thought about using 2xsmall rad's ( like an F1 car )mounted at the top of the bulkhead at either side of the craft ( forward facing )

lastly , do you have enough extract for the engine bay ,maybe towards the rear of the engine bay so the fan could assist in pulling the air through

just a few thoughts

DAZ http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif

jon_curtis - n/a
26-Jan-06, 03:59 PM
It dont look like much airflow at all is going to get to your rad tucked away in there!

i can see why you want to get air from the plenum in there!

how about trying duncans suggestion of fitting a elecy fan like there would be in the car setup, it looks like you have room!

lazza - n/a
26-Jan-06, 04:35 PM
Thanks for the replies, i already have a electrice fan mounted on my radiator which is why i can still use the craft. I have tested it without a passenger and the craft still gets just as hot. If i hold a piece of paper up to the vents for the radiator the paper gets sucked agaisnt the vents even when the craft is not moving so the multiwing fan is to a certain degree drawing air through the radiator on its own.

Running a scoop is another thought i've had which is more likely the first option i was going to try but was just curious if stealing air from the plenum was a option worth thinking about. Sucking in water is good point, so i'll keep thinking for now.

Preferably if i can stick to using the one radiator where i have it then i will, rather than mounting 2 radiators side by side.

26-Jan-06, 08:21 PM
...currently its not quite enough and the craft runs at about 98degrees C ...

...It's only one of a couple of ideas going through my head...

This may sound like a stupid question, but are you sure the timing is set correctly? If it is set to far in advanced, it might seem it's running right, but as a result it can run hot. Just a thought? An other idea I've had great success with in 2 cylinder fan cooled engines that used dual carbs, is to run a slightly larger jet in the back, as well as using different heat range spark plugs, (i.e NGK 8 and 9) between the front and the back cylinder.

Michel - n/a
3-Mar-06, 06:02 AM
Hello Larry,

have you tried to displace the radiator itself and put it out of all covers ?

Beware in that case, a too high position increases pressure in ducts and gaskets.

Or simply add a secondary small radiator.

You know , on a car , when electric radiator fails or if hot temp is reached, put inside cockpit heater to max hot and a very small radiator is able to cool down a big car engine.

Add 2 lines and settle a small radiator inside, or behind, or on the side of your duct.

Easy, cheap and safe.


nickyd - n/a
3-Mar-06, 11:51 AM
hi lazza,

never tried it myself but i have seen a rad mounted behind the fan but underneath the splitter. So effectively attached to the rear planing surface. I should think it would get a fair bit of cold air in here, plus it won't be restricting any airflow.....


lazza - n/a
3-Mar-06, 08:03 PM
Thanks for the replies. I have in fact cured my "suspected overheating" issue. In the end my wife and i went to work and tested the brand new temperature gauge i had in it and it read correctly up until 80 degrees C from that point on it started to lose accuracy, so when that gauge was reading what looked like 98 degrees it was in fact running at 94 degrees. I now threw that gauge away and fitted a digital temp guage and also fitted the 'dual' fans that the nissan radiator originally come out with and now the craft runs at around 88 degrees on average and the max i've seen it at was 94 degrees when the vents were all blocked with leaves and stuff.

I'm a happy man again now because that means i didn't have to drill or cut into my hull or do any major modifying. It is also interesting to know that even though the air vent design that my craft has for cooling the radiator doesn't look like it would be enough to cool a car engine, it actually is sufficent even though it meant adding a extra 1.4kg of electric fan.

Sean Atterbury - n/a
4-Mar-06, 09:08 AM
Does this mean we can expect some new video's of the craft in action? http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

lazza - n/a
4-Mar-06, 10:37 AM
sure can , when the weather decides to improve. I think we officially had the last day of summer last week *sigh*

Sean Atterbury - n/a
6-Mar-06, 04:04 AM
Same c**ppy weather here, could not get out this weekend either. http://hovercraft.org.uk/images/icons/smiley_icons/icon_mad.gif

Stupid rain and cold. http://hovercraft.org.uk/images/icons/smiley_icons/icon_sad.gif