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dave_s
6-Aug-09, 07:26 PM
Hi Everyone, this is my first post & I've joined the forum looking to get started in hovercrafting.

I live in Astley(M29) and I'm looking to get into hovercrafting. Is it possible to have a go at this without buying a craft by hiring one etc?

Is there anywhere in my area that offers this? & is it possible to get into the sport without owning one. The problem is not so much cost, but having somewhere to store it (I live in an apartment).

I've always been fascinated by these craft & would love to have the chance to fly one.

Cheers

Dave

daly5546
6-Aug-09, 08:34 PM
Dave,

You only live 5 miles from 3 hovercrafting families.

Send me a pm with your number and I'm sure we could arrange something.

crazykp55
9-Aug-09, 10:28 AM
Great, i'm not the only new member with no experience in hovercrafting. I also have always been facinated with the sport but never had the money to build one till now. I am really stoked to get this project underway but really have no plans and any clue on how to go about starting the project. Can NE one help me? I have searched the net for a good set of plans for a "real" hovercraft. Not one of those shitty home made things. All the links I have found have proved to give me the run around just to find that I need to call to order the plans. I'm not about doing all of that. Would appreciate any help. Thanks all. Best of luck to all in this great world of hovercrafting.
Keith

Jon Pert
9-Aug-09, 01:58 PM
Great, i'm not the only new member with no experience in hovercrafting. I also have always been facinated with the sport but never had the money to build one till now. I am really stoked to get this project underway but really have no plans and any clue on how to go about starting the project. Can NE one help me? I have searched the net for a good set of plans for a "real" hovercraft. Not one of those shitty home made things. All the links I have found have proved to give me the run around just to find that I need to call to order the plans. I'm not about doing all of that. Would appreciate any help. Thanks all. Best of luck to all in this great world of hovercrafting.
Keith

Hi and welcome,

Quick question to start with. Do you want to race or cruise your hovercraft?

gavinparson
10-Aug-09, 08:30 AM
I have searched the net for a good set of plans for a "real" hovercraft. Not one of those shitty home made things.

I Just did 600Km up the Rhone and Saone in one of those! Can't be that bad. Depends who builds it though eh?

crazykp55
10-Aug-09, 03:28 PM
Hi and welcome,

Quick question to start with. Do you want to race or cruise your hovercraft?
I have never flown a hovercraft before so I will be cruising to start out but eventually would like to get into racing.

Jon Pert
10-Aug-09, 04:17 PM
Crazy,

Where abouts are you based? We can point you in the direction of local branches etc that could help you out.

Ian Brooks
10-Aug-09, 08:15 PM
I have never flown a hovercraft before so I will be cruising to start out but eventually would like to get into racing.

Hi

Take a look at this:

http://www.hovercraft.org.uk/showthread.php?t=6

It should help you make an informed decision regarding the craft you buy ar build. You will see that racing and cruising craft are typically very different, and what you choose may close off your options so be careful.

Don't be too hasty to dismiss homebuilt hovercraft - some of the most capable and successful cruising craft are homebuilt - the key is obtaining good plans and sticking to them. There will be plenty of advice regarding which plans to choose should you go that way - but you will need to buy them! And without storage, I fear that a homebuild would not be feasible (although it has been done in an attic with a crane used to lift it down when it was finished!)

This is my homebuilt:

4003


Ian

fastflow
10-Aug-09, 08:56 PM
hello there
just say i am new to this site and great it is for information it has been
and how freindly u all are.
i recently refurbed a boat and sold on sat and looking for a new project
and have been looking at hovercrafts but i am a bit unsure if it would be suitable. i am big on sea fishing and saw on utube a bloke fishing out of one and can see alot of advantages to them.
the biggest i have space to build is 18" bye 8" what wave force could it take before it was unstable
it would also need to be able to
fish 2 people
carry 4 people
and have a small cab
and to take force 6
but some of the advantages so far are better than a boat
or should i just get a 18" boat
cheers

fastflow
10-Aug-09, 09:06 PM
and to say has anyone seen the donar on utube now that thing is mint

Ian Brooks
10-Aug-09, 09:39 PM
You would need something like this:

http://www.sevteckits.com/sevteckits/html/prospector.htm

Also check out:

http://www.hovercruiser.org.uk/building-a-hovercraft/prospector.html

However, not much that could be used in force 6. The Prospector will operate in force 4 - 5, but at force 6 it would be getting a bit hairy.

Ian

fastflow
10-Aug-09, 09:49 PM
sorry about that i ment force 5
and that dose look well nice and will buy a set of plans in morning
i have got sum ideas of my owen but need to do a cad drawing i will post them for u guys to look at when finshed to see what u think
are they stable when a float enough to fish of

Ian Brooks
10-Aug-09, 09:58 PM
Yes - you can fish off them, they are stable and float happily when "off cushion". If you surf the Sevtec site, there will be details there somewhere.

The design is customisable to some extent - everything below the upper skirt attachment line should be done strictly to plan, also the prop, lift fans and engine frame kept to plan. But the upper decks can be customised, provided that weight is kept under control. You could add a small, lightweight cabin if desired.

Cheers
Ian

fastflow
10-Aug-09, 09:59 PM
thank u for them just been reading and that sounds perfect for what i want what a nice hovercraft
could u devate from the plans and make it more curver or would it compemise strength

fastflow
10-Aug-09, 10:01 PM
sorry sent that after your reply

Ian Brooks
10-Aug-09, 10:04 PM
Hi

Curves are possible... it just takes time! There are limits to what can be achieved with the foam/fibreglass construction, if you look at the sevtec site theres a section on other builders craft,that should give an idea what is possible

http://www.sevteckits.com/sevteckits/html/builders.htm

Ian

fastflow
10-Aug-09, 10:04 PM
i take it u made one
how long did it take
and did it go over orginal costs very much

Ian Brooks
11-Aug-09, 05:53 PM
Hi

I built a surveyor - which I am very pleased with...

It took 14 months to build in it's original trim (it had another engine since then). You should budget anywhere between 3k and 5k, depending on what sort of a nose you have for a bargain.

Ian

crazykp55
17-Aug-09, 04:01 AM
I am based in Ft Polk Louisianna in the US. I am currently looking into finding plans for a racing hovercraft. I bought some plans for a cruiser but dont much care for the design. Woundering if you could help me find some plans for a racer. Thanks for the help.



Crazy,

Where abouts are you based? We can point you in the direction of local branches etc that could help you out.

Ian Brooks
17-Aug-09, 07:37 PM
Hi

Have you seen the Hoverclub of America site?

http://www.hoverclubofamerica.org/

Ian

fastflow
18-Aug-09, 09:19 PM
hi ian
after your advise i am going for the sevtec explorer and after watching the north to alaska vid that just about conviced me there and then.
there are a couple off things bugging me about it
the engine they use aint very good there are plenty of tds with more bhp to weight.do i have to stick with theres ?
and the lift fan placement to the thrust fan they must counteract with each other (looking at the donar hovercraft for ideas ) prob a bit over my head but we can all dream.
the other thing is i have been trying to download the lift cal and other things like pics but wont let me it keeps coming up as v buliten
cheers
jon

webadmin
18-Aug-09, 09:53 PM
the engine they use aint very good there are plenty of tds with more bhp to weight.do i have to stick with theres ?
and the lift fan placement to the thrust fan they must counteract with each other (looking at the donar hovercraft for ideas ) prob a bit over my head but we can all dream.
The Explorer has plenty of space in the engine bay - you could fit almost any engine in there if you keep it reasonably light (the plans give max weights). The video craft was built 12 years ago and had a puny engine - although the performance is pretty impressive from only 68HP! Personally I would go for at least 100hp to give better bad weather performance.

Don't worry about the lift fan placement - it doesn't affect the performance to any degree at all. The craft works - don't change anything unless you know exactly what effect the change will have.


the other thing is i have been trying to download the lift cal and other things like pics but wont let me it keeps coming up as v bulitenIf you PM or email me a screen shot of the error message and I'll take a look at your problem

Ian Brooks
18-Aug-09, 09:58 PM
The subaru is light, cheap and reliable... it works and I would be inclined to build to plan. John Robertson's Prospector uses one and has impressive performance.

Likewise the lift fans - they work... It turns out that air can get around surprisingly tight bends!

Cheers
Ian

atters
19-Aug-09, 06:30 AM
I have also always thought that the setup was daft but "If it ain't broke!!"

Thinking about it, there are advantages, like noise, caps and things being sucked in, waves being sucked in, makes a great place to mount the roof.

See, Lots of better reasons that just OH I GOT GREAT AIRFLOW...:p

fastflow
19-Aug-09, 10:45 AM
if it aint broke is one of the best qotes going and if i am honest i wont change a thing but if we didnt change anything we wouldnt have put a man on the moon and there wont be such a thing as a hover craft?
but at 2.5 gallons per hour =16mpg in a nut shell that is a bit naff.
and as fuel and noise are an issue to me.
as i cant find any stats on subaru lump would anyone be able to tell me
what revs dose the subaru lump kick out when at 40 mph
what the torque is
bhp and weight it is
so i could compare with sim size tds
and looking at it 2 engines are look that they could be better for the job.

air movment.
u are right in that i dose go in any gap but airflow is affected in a simular way to water and therefore any resistance = more power to move and noise from friction and engine and this in turn will use more fuel there is also an inbalance on the prop because free flowing air on the top half and restricted air flow on the bottem half which in turn causes friction and ware on breaings etc.

i am not pulling this craft to peices i really love it but there is always room to improve and if i where going to do it now would be the time to look in to it and i do appercate all the advice

ps dose anyone live near to bournemouth area
cheers

Jon Pert
19-Aug-09, 11:22 AM
It's very difficult to get a true mpg figure as there are to many variables. If you are doing a constant cruise then you may only be on half throttle once you are up to speed for example. If you have a good tailwind then you will be on considerably less throttle. If you have a strong headwind then you may well be on full throttle all the time. This is where you have to calculate the fuel reserve you will need to get you back safely in ANY condition, weather changes very quickly at times!!!

If you can find a diesel engine that is light enough then you have found the holy grail, do tell more!

John Robertson
19-Aug-09, 11:56 AM
.. but at 2.5 gallons per hour =16mpg in a nut shell that is a bit naff.
I don't think you will find any other water craft that can operate at that kind of speed (40mph) and return that kind of consumption. Reduce the speed and the consumption falls - just as it does with any other vehicle. In my experience, hovercraft are around 30-50% more efficient than similar size boats (at the same size/payload/speed). The reason is mainly reduced drag (less energy used to overcome drag versus energy used in the lift system - the faster you go, the more efficient they become)

The amount of energy you get from a litre of fuel is the same no matter what 4 stroke engine you burn it in (two strokes ARE less efficient, diesels appear more efficient but diesel fuel has a 20% higher energy density than petrol). If you need 40kW to operate a hovercraft it makes almost no difference to fuel consumption what engine you choose to burn your fuel in (you will actually need to consume more than 100kW of "fuel energy" to get 40kW from an internal combustion engine :eek:).


air movment.
u are right in that i dose go in any gap but airflow is affected in a simular way to water ...... there is also an inbalance on the prop because free flowing air on the top half and restricted air flow on the bottem half which in turn causes friction and ware on breaings etc.

The intake airflow pattern is a 3D cone shape (the prop inflow shape extends far out the the side and above the craft). The prop pulls in several hundred times more air than the lift fan does (the lift fan only has to replace cushion air lost though the skirt gap - the prop has to throw vast quantities of air backward to generate thrust). The lift fans are "stealing" a very small amount of the air being pulled in by the prop making any efficiency loss almost insignificant (do the calcs and you will see what I mean - or do the fluff-on-the-end-of-a-stick test on a real craft.

You may have noticed that there are all kinds of lift fan locations and orientations out there - everything from horizontal to vertical. They all have different advantages and disadvantages.

It is very important from the noise point of view to reduce intake turbulence but, as with all designs, there are other factors involved and compromises always have to be made.

atters
19-Aug-09, 12:04 PM
resistance = more power

That is Y I chose the Surveyor, and I have not the budget to build the bigger craft, plus, what would I ever do with it?

Sevtec have a great design and its that way for a reason. I have tried to improve on craft before and it was just like throwing money away.

Like all of the guys say. Do what you like to the decks but fundamentals like drive and hull leave alone.

OR DO IT YOUR WAY, YOU WILL ANYWAY, us guys never think someone knows better.

John Robertson
19-Aug-09, 12:48 PM
Sevtec have a great design and its that way for a reason. I have tried to improve on craft before and it was just like throwing money away.

Something else to consider is that, if you change something, how will ever you know whether the change is an improvement over the original design if you don't know how the original design would have worked because you didn't build it and test it?

I'm the same as everyone else in thinking I can do it better - the fact is I've learned the hard way that 9 times out of ten I can't :blush:. The reason isn't always down to expertise or qualification - it comes down to being in possession of all of the design criteria and performance parameters (and a big lump of real-world experience of hovercraft) and then being able to make the best compromise decision (EVERY design decision is a compromise).

firth5731
19-Aug-09, 05:45 PM
i am adding things like flow straighteners cos they work,
my craft did`nt have them, so now it does , can`t do any harm but i wouldn`t dream of changing something major as i hav`nt got a clue.

fastflow
19-Aug-09, 10:49 PM
i wouldnt dream of ever saying i know more than anyone else as u guys have dun this for how long and i havent evan been in one
all i am doing is reserching and saying at what appers at first glance a flaw
and as said before i would never dream of changing anything that i am investing this much money in to unless i was 100% sure it would work.

and i was hoping that if and thats a big if i were to change anything i would hope i could compare to one of yours cos if it worked wouldnt u want to know y it worked how it did and how to fit it to yours
and yes i would give anyone who asked a cad drawing and any info they wanted

i am sorry if i pissed anyone off

shame about not changing engines i can get loads of free bandit 600/1200 as long as i dont want to use 1/2 gear
going to try to speak to the desginer of the donar as they seem to have cracked it
and cheers for the info i have taken all of it on board

Jon Pert
20-Aug-09, 07:04 AM
Hi Fastflow,

What horse power are the bandit engines? Quite a few club members use motorbike engines for both racing and cruising. For cruising the BMW K75 and K100 are currently the engine of choice as it offers good power to weight. I wonder if a bandit engine could be used in the Sev? I'm sure a Sevvy will be along to say yay or nay shortly!

The guys who have built Sevtecs have indeed made improvements to them but they all started off with a standard build in order to have a datum to gauge the success of the mod. As Atters says, joining the club has given him a lot of info that otherwise he would have struggled to find.

The DONAR is indeed an impressive piece of kit, amazing what can be done with a limitless budget. I think it was developed as a one off to test technology for their much larger military craft. The room to place the lift fan on the roof was provided by having 2 ducts so the engine could be sat well back inbetween them, it uses skirt shift to keep the craft balanced. Using a single duct like all recreational craft means that the engine has to be located further forward, which is ideal for balancing the craft but obviously eats into the space for an unobstructed lift fan (if it is to be situated at the rear). The DONAR has a few shortcomings, the low overhanging nose would get severley damaged on some of the banks and slips we have in the UK but it is afterall a one-off technology showpiece so functionality is not at the top of the list.

What sort of budget have you got? This will instantly let you know what is possible.

Let us know if you manage to talk to someone about the DONAR and what info you get about it, would make interesting reading. :)

P.S. Don't worry, I don't think you have p****d anyone off it's just that many, many people that ask about building a craft seems to think that they can modify it to make it better (before they have even bought a fan blade!). It's almost like ordering a car at your local dealership but then putting a completely different suspension system in and converting it from front to rear wheel drive before you have even driven it! I would personally build to plan, learn how to operate it, learn the principals and then modify one thing at a time if you feel the urge. You never know you may come across something that has been overlooked in the past and improve craft for all of us, god knows I'm trying to find that!! http://www.jonrb.com/emoticons/thumbup.gif

John Robertson
20-Aug-09, 09:15 AM
I don't think you've p***ed anyone off either Fastflow

My responses may be a bit long but that's only because I try to explain the why's rather than just saying something is good or bad.

Don't let me put you off using a diesel engine - just make sure you know all the details first (another one - diesel fuel is 15% heavier than petrol :) - less volume of diesel fuel is needed than petrol but it weighs more - weight is everything for a hovercraft). The only two advantages I can see of a diesel are the lack of an HT system and their low-revving nature (and the fact that diesel is cheaper than petrol per unit of energy) . I'm not at all sure that there are any others but feel free to convince me otherwise?

Hovercraft are almost unique in that almost every part of the craft has an effect on every other part. It is very easy to end up in a spiral of "enhancing" that results in something that doesn't work well (or even not at all!). The Donar craft certainly looks really nice but I have to ask the obvious question - [cynical mode ON] if it works so well why are there not hundreds of them out there?? [cynical mode off] In my view, the part of a hovercraft that could do with further development is the skirt system - it affects drag, hump performance, stability and efficiency - almost everything!

Bike engines can be a good choice but you need to look at where they develop their power. For a cruisng craft you really want peak power as low down the rev range as possible - this will help reduce noise and make the transmission system simpler (it's a bit difficult to get a belt reduction drive to operate at 200000rpm for any length of time :)). The BMW engines are a good choice as they are relatively low revving units. For cruising, reliabilty has to be top of the list when choosing an engine - you need one that will happily run day after day, ALL day at 2/3rds power. As Jon says, the craft must cruise at 1/2 power under ideal conditions - the other half is needed when things get hairy!

The chances of picking up an old Subaru engine must be almost nil nowadays. There are, however, tons of suitable small aluminium car engines out there. Almost anything will do (it's hard to find much under 100HP nowadays), but look at the peak torque RPM and the max power RPM that will give you some idea of it's most efficient operating speed - the lower the better.

If you are really serious about this stuff then I would recommend joining the club - there is a wealth of information available on this site to members, including a 40 year magazine archive that has technical articles and examples of almost every type of hovercraft design ever made.

fastflow
20-Aug-09, 11:51 AM
i have got about 5k to cuck at this and 10k if i sell my defender (if any one is looking to buy one)
the bandit engines i got told are between 70 and 85 bhp
but u cant use 1/2 gear thou and i have been told i can get 1/2 a month
i cant seem to find any stats on engines only on the cars so cant get weight info
cheers

fastflow
20-Aug-09, 01:54 PM
the other thing i have always wondered is way auto gear boxes arnt use on boats and hovercrafts????

John Robertson
20-Aug-09, 02:18 PM
5K should build you a nice craft with care.

Check the max power RPM for the engines (there are many different Bandit engines up to 12500rpm). Also check the weight with the gearbox - some bike engines are surprisingly heavy! If the rpm is high you could leave it stuck in 3rd or 4th and use the gearbox as part of the reduction drive. I have to ask the obvious question - how come these engines are so easily available as there appears to be a reasonable s/hand market for them?

It is hard to get engine weights - the only real way is a visit to your local scrapyard - if you can't get it off the ground then it's too heavy :D


the other thing i have always wondered is way auto gear boxes arnt use on boats and hovercrafts????
Because you don't need a gearbox at all (although outboards have a fixed reduction/reverse gearbox). In general, the load curve more or less matches the power curve of the engine because you are driving a fan or prop - unlike when you try to start off up a 25 degree hill with your car.

fastflow
20-Aug-09, 07:47 PM
my mate runs a stunt school and and they hammer first gear it works in first but noisey and apprently it cost more to fix than to get a second hand lump he said he throu out around 30 last year but this he is not doing so well.
they are really light i carried 1 round to the back of my place without to much sweat
do u think two would do for mine hovercraft
and sorry for asking so many qustions but y do u use belts insead of chain for drive appart from noise

atters
21-Aug-09, 06:26 AM
y do u use belts insead of chain for drive

this is Y.....

fastflow
21-Aug-09, 06:52 PM
not sure what u ment ????
i am still no wiser

Ian Brooks
21-Aug-09, 08:22 PM
If the chain comes off, you have a bad day. If a belt comes off, you stop, put another on, and go home!

Atters will fill in the details!!!!!

Ian

Ian Brooks
21-Aug-09, 08:33 PM
Hi

No-ones fed up with you for asking questions - keep asking!

Modifying hovercraft to get better performance is really, really hard. The designer of the Sevtec, Barry Palmer took 30 years to perfect the Sevtec designs, and from a skeptical beginning, I've learned the hard way he is almost always right! I lead a design and development team - so improving designs is my job - but it took me 3 attempts and hundreds of hours to make my "improved" Surveyor equal to the standard design!

When I looked at bike engines, I found that most rev'd too high and were surprisingly heavy. The exceptions are the BM's. The truth is there are no ideal hovercraft engines out there - although for many people, the larger Briggs V twins are as near idal as you can get - I use the populer 35hp Briggs. Diesel in considered by many to be a good idea, mostly for reliability reasons, but up to now weight has been a major problem (and I would not put a turbo onto a hovercraft) as there are still (to my knowledge) any truly lightweight diesels available. Maybe that will change, but for now you would in my view need a large craft to carry a diesel.

Cheers
Ian

atters
22-Aug-09, 07:49 AM
I cant seem to upload the pics for some reason.

atters
24-Aug-09, 06:48 AM
Yay, now we can see Y not to use a chain....

hector46
24-Aug-09, 08:12 AM
Hi,

I too looked at bike engines, I currently have 750 Suzuki with the 4 cyl 16v engine. They are reliable but I wouldn't use one for cruising as they are relatively heavy and produce their power top far up the rev range for a cruising craft. There are increasing numbers of all aluminum engines out there that would work well, get the electrics right and you should have no problems.
As for diesels, they will be used in the larger cruising craft more often but are still heavy and have almost as much electrical components to fail. The only one I would consider just now is the three cyl VW 1.4ltr. It was fitted to the Polo or Fox. You would be best to get the whole car so as to get all the little important bits and you could use some of the other parts off your car for the hovercraft too.

Steve

fastflow
29-Aug-09, 01:32 PM
yep that def answerd y u dont use chains
and i will look in to vw engine
cheers for that