Building with Craft Foamboard

[ashley needhamParticipant @ashleyneedham69188]

Paul. Nice job. Shame about the yellow paint.

Ashley

[ashley needhamParticipant @ashleyneedham69188]

Paul. Nice job. Shame about the yellow paint.

Ashley

[ashley needhamParticipant @ashleyneedham69188]

Paul. Nice job. Shame about the yellow paint.

Ashley

[Paul TParticipant @pault84577]

Ashley

I was very pleased with the flag effect artwork but the yellow paint has ruined the entire effect.

Paul

[Paul TParticipant @pault84577]

Ashley

I was very pleased with the flag effect artwork but the yellow paint has ruined the entire effect.

Paul

[Paul TParticipant @pault84577]

Ashley

I was very pleased with the flag effect artwork but the yellow paint has ruined the entire effect.

Paul

[LARRY WHETTONParticipant @larrywhetton68737]

Hi Paul,

Very nice , it would make a nice free plan feature, get Colin on board,

it would make nice change , from grey boats ,

if there…

is a plan i am keen , a good young modler build……….for school prodject .

by the way i hope you are better…. cheers Larrry

[LARRY WHETTONParticipant @larrywhetton68737]

Hi Paul,

Very nice , it would make a nice free plan feature, get Colin on board,

it would make nice change , from grey boats ,

if there…

is a plan i am keen , a good young modler build……….for school prodject .

by the way i hope you are better…. cheers Larrry

[Paul TParticipant @pault84577]

Hello Larry

I am feeling much better especially now that the dressings have come off my foot and thank you for asking.

I haven't produced plans for my hovercraft as my model is close to Mark Porters Griffon design, I simply knocked up the craft as a test bed for building with foamboard.

Paul

[Paul TParticipant @pault84577]

Hello Larry

I am feeling much better especially now that the dressings have come off my foot and thank you for asking.

I haven't produced plans for my hovercraft as my model is close to Mark Porters Griffon design, I simply knocked up the craft as a test bed for building with foamboard.

Paul

[LARRY WHETTONParticipant @larrywhetton68737]

Hi Paul,

Thank you for reply, and info , where do you bye board..?.. Larry…

[Paul TParticipant @pault84577]

Hi Larry

At the moment ebay is the cheapest

**LINK**

[Ian GardnerParticipant @iangardner62867]

Paul, the hovercraft looks great and I bet we're all on tenterhooks to hear how she performs. Having returned this morning from our new water without having wetted a boat's bottom because of weed, I may have to think again about a hovercraft!

Anybody know how to get rid of weed!?

Ian

[Paul TParticipant @pault84577]

Ian

The hovercraft performs quite well but needs more lift power so now I am playing around with different lifting fans to see which works best. I realise that in many ways I am 'reinventing the wheel' but I do enjoy this kind of research.

The only eco safe way to remove weed is to rake it out….hard work!

Paul

Edited By Paul T on 13/05/2013 07:07:36

[Paul TParticipant @pault84577]

One unexpected problem is that the hovercraft is rear heavy and even when I balance up the model without the thrust motor in it still sits heavy at the stern.

I am confused as to why this is as the entire superstructure is equally balanced around the lift motor and there are no gaps or rips in the skirt.

I need one of Bobs eureka moments.

Paul

Larry I have sent you a pm about this model.

Edited By Paul T on 16/05/2013 16:00:46

[Colin BishopModerator @colinbishop34627]

Is the airflow from the fan balanced under the skirt or could you be getting some sort of directional eddy which affects the balance?

Colin

[Paul TParticipant @pault84577]

Good point Colin

The computer tells me that the airflow is rate is balanced but I'm still playing with different fans so I might be getting lumps in the airflow.

Perhaps some alterations to the sub chassis might be required.

Paul

[Amy jane SeptemberParticipant @amyjaneseptember49770]

Hello Paul

Just a thought on your fan experiments. Have you considered making a fan that blows the air side ways, centrifially off it's perimeter, and deflecting it down wards around the skirt, (this is the way a flymo mower works) rather than blowing it directly downwards. It is the pressure difference between the underside of the hover craft and the atomosphere than keeps it afloat, (you know this already of course!) It doesnt take much pressure diference, but requires a lot of air volume to maintain. I say this on the basis of my husband having converted two stroke flymo lawn mowers to four stroke, and by making a fan that shifts a larger volume of air the heavier and slower turning four stroke could be made to lift very well indeed. Just a thought.

[Paul TParticipant @pault84577]

Hi Amy

That might just be the answer I will design a plenum chamber and give it a go.

Thank you for the very welcome input.

All the best

Paul

[ashley needhamParticipant @ashleyneedham69188]

I hate to say it, but perhaps some ballast at the front migh help?? I know this is counter to keeping the weight down, but is an option.

A grid or shutter arrangement under the lift fan might be able to diffuse the air to parts that normal air cannot reach.

very intersting this and I am paying close attention.

My srn4 prototype was nose down when moving forward, and the lift fans were at the front. the skirt was solid so???

The rear fan could have a small deflector/flap/wing to provide lift at the back?

is this back down attitude at speed, stationary, or over land or water?

Ashley

[Colin BishopModerator @colinbishop34627]

Paul,

I think Amy Jane is right. I did a bit of googling last night and it does seem that the design of the plenum chamber and air distribution has a significant effect upon the balance of the craft. To use an upside down analogy, think of a shallow rectangular baking tray with water in it – the whole thing is very unstable and the water slops about with the slightest movement ,completely altering the balance of the tray.

Colin

[ashley needhamParticipant @ashleyneedham69188]

Do Griffons have a plenum chamber or does the air just get dumped onto the ground surface… ? Never looked..not thought much about it before.

Paul, photo of your bottom please so we can see the underneath layout for my education, thanks.

Ashley

[Paul TParticipant @pault84577]

Oh Ashley be careful what you ask for…

Colin put your editing hat on standby.

[TelstarParticipant @telstar]

Hi Paul Just a thought, If you fitted a plenum chamber directly under the fan, "sealed" then ducts from the plemun out towards each corner, by putting adjustable dampers in the ducts you could perhaps balance the "thrust". Alternately perhaps series of baffles to split up the underside to prevent the "sloshing" about (see Colin's post)

Cheers Tom

[Paul TParticipant @pault84577]

Hi Tom

Thanks for the idea it has given me more food for thought.

Cheers

Paul

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