Carbon Fibre Integrated Hovercraft....no, not really the answer!

added by russ on May 28, 2015 at 10:23

Unfortunately, the days of cross channel 300 ton monster hovercraft are behind us, killed off by many factors - unavailability of engine servicing, increased fuel costs and finally, the end of duty free.

Nowadays, the Russian Navy ZUBR, and the US Marine LCAC's operate the world's largest hovercraft. Here in the UK, the Hovertravel AP1-88 flies the flag for the largest craft in the UK.

Down at the ‘other end’ of the scale, our original single seat ‘Snapper’ of 1998 now has a larger sibling in the shape of the Coastal-Pro, a 3-4 seat commercial craft which has been selling well to people who need a practical, safe and effective hovercraft for such uses as transport on frozen rivers, through tidal estuaries and over mudflats.

The biggest difference between the Coastal-Pro and our earlier hovercraft (the Marlin, Snapper and Mark One Coastal-Pro) is that it uses a separate lift system, which is controlled independently from the thrust system. Our smaller hovercraft use just one engine to give both lift and thrust, a system which works really well on smaller hovercraft but is redundant by the time the craft gets to 3 seats/4m or so. The Coastal-Pro is the first of these twin-engined hovercraft from BHC, but larger ones will follow.

 

As a result the Coastal-Pro can lift over 300kgs from a dead-start on water, and carry considerably more on land or over water without needing to stop. The earlier craft without he separate lift engine displayed some shortcomings in this area, which is why the  new Coastal-Pro was born. Quite simply, larger hovercraft don’t work with a single engine and fan.

Interestingly, one company has recently released an integrated 5m hovercraft built from Carbon Fibre which they claim is capable of seating (variously!) seven to nine people or an astonishing half-tone payload – from a water start, this is a hovercraft’s biggest challenge. Of course, none of the videos actually show it doing so with 7 people on board (just big cardboard boxes in the back full of what I wonder? Air?) If you have a desire to never hear again, take a look at a video of it in action (WARNING : HEARING DAMAGE VERY LIKELY!) VIDEO

The whole design concept of a 7 seat integrated hovercraft is simply wrong. It’s a fundamental design flaw akin to building a 400bhp three wheel Ferrari or an aeroplane with one wing. This particular example is powered by a 120bhp turbocharged engine – huge complexity and noise levels fit to burst eardrums (this, from our analysis is around 96dbA at 25m, loud even for a racinghovercraft!) A carbon fibre hull is space rocket technology stuff, sure. But in hovercraft use, it’s brittle and shatters quite easily, a more useful design would be to back it up with Kevlar (something we and many others have learned from racing hovercraft over the years of competition) – on its own, it’s a poor choice.

The problems can be seen quite clearly on the promo videos, the integrated design means very poor hover height, the hovercraft never truly hovers which means the skirt is dragging and will wear out in no time. Worst case, poor hovering can mean it will catch the ground travelling sideways and stop dead or flip over…ouch!

You cannot simply ‘’scale up’ small hovercraft and expect them to work as well – there has to be limits, and this one’s been crossed - and here's the result.

Meanwhile...put your fingers in your ears, turn down the volume on your PC and and play THIS VIDEO!

Take a look at this photo - wow! No words needed!

 

 

The bottom line is that despite being a much smaller hovercraft, our Coastal-Pro (all 65bhp of it) will outperform this 5m, 120bhp offering. It’s around 1/3rd of the noise level, three times as economical, carries just as much payload, is easier to drive, more reliable (seriously – a turbocharger and extensive electronics in a saltwater environment???) – oh, and much prettier! :-)

All those years of R&D, racing, cruising, commercial work and using our own craft in every conceivable environment have given The british Hovercraft Company unmatched experience in the design and production of real, working hovercraft. No bull, no wild figures, no opinion – we’re proud to say our hovercraft perform exactly as promised in our literature and on this website

By all means, try out other hovercraft brands – then come along to us for a demo, we’ll be happy to see you and demonstrate the advantages of a clear design philosophy.

For demonstrations, please call us on 01304 619820

 

 

Hod Pod's 'Buyers Guide' - What a load of Nonsense!

added by russ on July 7, 2014 at 07:27

 

 

Buy a Hovercraft

An insinuating, somewhat snide 'buyers guide' clearly aimed at The British Hovercraft Company by UK manufacturer ‘HovPod!’ We were mailed the link by one of our customers who thought this thinly disguised ‘buyers guide’ was anything but impartial advice!

 

We don’t usually respond to the petty digs of other manufacturers but this one goes a bit far and contains many inaccuracies and half-truths so in the best spirit of the Tesco/Asda war, BHC would like to take the opportunity to state the other side of the argument. But seriously HovPod,  man up if you have something to say to us! We've offered time and again to put a craft up against the HovPod for a ‘back-to-back’ review. What a great read that would be…

 

The world's best-selling personal hovercraft.

-vs-

The worlds heaviest personal hovercraft.

 

But whenever we do, the HovPod marketing machine suddenly becomes a shrinking violet and goes all quiet and shy!

 

Oh well, read on and judge for yourself, and whether you agree (or even care!) or not, bear in mind that we at least have the minerals to answer our critics directly - rather than hide behind  statements like ‘Some manufactures…’

 

We have The bold statements below are from the HovPod buyers guide, the italics, our response to some wild, incorrect and sometimes, plain-silly statements.

 

Here we go then….

If you only ask 6 things, be sure to ask suppliers the questions below:

 

1/. Hovercraft Construction

Hovercraft are weight sensitive, so manufacturers reduce weight wherever possible – some glass fibre hovercraft are very lightweight, the construction is much thinner than boat GRP, so may not last many seasons if you intend to race hovercraft.

Cruising hovercraft tend to be more durable but heavier, so decide how you will use before you choose your hovercraft. HDPE is far stronger than glass fibre, and extremely buoyant.

Question – what is the hull made from, how durable is it, if I damage the hull, is it game over? How much will it cost to repair? How will it handle ice?

Answer - Well, at least we start with some agreement! I agree with the comment "Hovercraft are weight sensitive" – In fact better than agreeing with it, we actually apply this principle. The writer of this 'guide' conveniently misses the fact that HDPE (which the HovPod is made from) is almost unbelievable heavy. The Marlin III and HovPod are roughly the same size but the HovPod is 415kgs against the Marlin's 225kgs! That’s like having two fully grown men on board before you even start! This is simply way too heavy for a hovercraft of this size and as a consequence, performance is never going to be adequate. One HovPod model uses 120bhp – yet our 35bhp craft outperforms it! All HovPods need big power just to make a pretence of working - so in goes a raucous 2 stroke motor, loads of expensive fuel and reduced range! Physics apply to hovercraft too, they're not magic! HDPE isn’t stiff like a Marlin, it’s just a bit ‘droopy’ (see 1m10sec) which means the shafts cannot run straight and fans are likely to rub on the duct - this inevitably leads to a regular and embarrassing failure to perform (although we're sure this isn’t the case with the HovPod.) Aesthetically, HDPE has a horrible 'orange peel' finish, so it cannot ever be fully cleaned of mud, dust or sand - so HDPE will never look good again once it's been used, especially in mud or sand - no, HDPE is best used for public toilets – another popular application.

GRP works beautifully if  laid up by professionals with industry/hovercraft knowledge (which is why 99% of manufacturers use it!) Add in some strategically placed Kevlar (you know, bullet-proof vests!) and core material for buoyancy and stiffness - you have a strong, stiff hull structure which looks beautiful and cleans up like new.

 

2/. Hovercraft Engines

Some suppliers try to maintain that 2 stroke engines are louder than 4 stroke engines; actually most hovercraft noise emits from the fan blades tips and larger ducts are more air efficient than smaller duct sizes, less powerful engines need to rotate the blades faster to get more air throughput. Diesel engines are only found on larger hovercraft, they do not have the power to weight characteristics required for smaller hovercraft. Some suppliers invalidate engine warranty by modifying the engine to get maximum energy output, engine manufactures don’t like their products running on high stress all day, who does!

Question – is full engine manufacturer’s warranty offered with this hovercraft?

Answer - No engine manufacturer warrants engines for hovercraft use (salt-water you see…) so I can  help with this one. 'No!' The question is, does the hovercraft manufacturer offer one - after all, they should understand the installation and prepare the engine for marine operations.

Anyway, welcome to the world of fantasy. A world where 2 strokes are no louder than 4 strokes? Here’s a fact : 2 Strokes are louder than 4 strokes, due to the way the engines work. The reliability of microlight-derived two strokes in a marine environment is awful - any saltwater on a plug lead or air filter and you've pretty much guaranteed you're coming to standstill (been there, done that – we moved on from two-strokes 12 years ago and never looked back!) Less powerful engines do not mean a faster fan and more noise, it's strange that a manufacturer would spout such total nonsense! The variables are : Speed of rotation, size of fan (same on both craft), the pitch of, and number of blades but it would appear that the writer of this 'buyers guide' doesn’t know much about integrated hovercraft. The overweight HovPod needs 12 blades in order to lift which reduces 'push' - the Marlins use 6 and is on full lift at 2000rpm, the HovPod uses 12 and just lifts at 5000rpm! (See picture)

No, the only reason you'd use a 2-stroke is because the basic hovercraft is so damn heavy it needs big power from the lightest engine. But the downsides of 2-strokes are enormous which is why they are now largely defunct in any modern vehicle. Think about it - would you rather have….

A screaming, noisy, highly stressed and noisy two stroke drinking £30 in fuel every hour and needs refilling every 45 minutes (HCGB Magazine test) - or….

A quiet, low-revving reliable four-stroke sipping no more than £10/hour in fuel and running for 3 hours between refuels. An engine designed to run quietly all day, with no fuss.   

Reliability, limited range, noise and pollution - no wonder that two-strokes are banned in so many countries and haven’t been seen in cars, motorbikes or jetskis for many years.

The two-stroke is (sorry to get all ‘Sex-in-the-City’ here) "Sooo last century!"

Alternatively you can order your HDPE hovercraft with a 120bhp 4-Stroke, turbocharged Weber engine.  I’ll say that again… 120bhp! In a 3m hovercraft… why for God’s sake…why??? How can that possibly be necessary? A Marlin would be lethal with 120bhp, our 50bhp motor is fast enough for pretty much any petrol head!

3/. Hovercraft Safety

To get over this power inadequacies, some suppliers decide not to fit a rear fan guard to allow cleaner air-throughput for greater efficiency – you need to decide if a rear fan a sensible safety feature when kids are around, or not. Fans spin at 2000 rpm – kids might wish to learn play guitar as they get older. In rare cases, fingers have become detached, there was even one fatality recorded in New Zealand – self builder, no fan protection, front or rear.

Question – Is a rear fan guard fitted? Or just a warning sticker? Younger kids don’t read so well.

Answer- Oh dear! The Maritime & Coastguard Agency published a 'Hovercraft Code of Practice' in 2016 with no requirement for REAR guarding (but closely specified front guarding), plus The Hovercraft Club of Great Britain and Hoverclub UK all accept that a rear guard is not necessary provided other methods are used to reduce the potential risk posed by the fan assembly (including cone/duct/stators/rudders/safety stickers etc) Presumably the scaremongering writer of the buyers guide would also like to also enclose helicopter fan blades and the bottom of car engine bonnet compartments – you know, just in case our little guitar prodigy climbs underneath it and shoves a highly skilled hand into the fan belt.  Front guards are a different matter altogether and all HMA* manufacturers fit a protective guard of approved design. rear guards are not necessary, and they simply add to the cacophony of noise a 2-stroke motor makes.

4/. Hovercraft Plowing

Some hovercraft plow in on water – plowing refers to sudden deceleration which might cause the hovercraft to spill contents over the handlebars, passengers and all. Some suppliers reduce plowing tendencies through design, other suppliers say – “hovercraft plow, live with that”.

Question – Does the hovercraft have a design to reduce the risk of plowing?

Answer - Well, I can’t speak for everyone else, but I can tell you that BHC Hovercraft have been designed to run fast on water in all conditions with good handling characteristics. Have we 100% eliminated it? Nope, but then again - nor did they on the cross-channel SRN4's! A good skirt design is crucial as is a decent, non-peaky power delivery and easy handling (ie less weight allows the craft to recover from a partial plough-in.) It really isn’t the issue some would have you believe.

However, if you raise the skirt pressure high enough (for instance by making the hovercraft really, really heavy for its size…) and really, really slow, then the chances of  a plough-in are reduced.  'Nuff said?

5/. Hovercraft Hump

Particularly so in shallow water, hovercraft need maximum power to get airborne – to get over the pressure wave all hovercraft create. Hovercraft suppliers may fudge their specifications to mislead people, since it is not widely understood, that hovercraft can pick up 50% more weight when starting on land. We have seen some suppliers showing 4 or 5 people skimming over a puddle – this is misleading, since the issue only involves starting on water – if you stop and cannot get back on that air cushion, it could be a long swim home. You must drill down to ask this question -

Question – What weight can be lifted when starting from an on-water start?

Answer - This made us laugh here at BHC. The pithy little comments about "4 or 5 people skimming over a puddle" refers to THIS VIDEO in which our Coastal-Pro (the previous single engine design) is shown buzzing round with 6 adults on board (described as 'just for kicks' in the caption, we actually allow ourselves to have fun with our hovercraft and push them way beyond what we claim in our literature - to see what the limits are and drive development!) But keep watching, we clearly show it easily going over hump in our 'puddle' with three on board. Our actual claims for 'hump' performance made on our website and in our literature is 200kgs (Marlin) and 300kgs (Coastal Pro Rampage) or 350kgs (CP Toyota)

And… I'd say that people in glass houses etc…this is a HovPod attempting to get 'over hump' VIDEO (Turn your volume down before watching!) with one person on board! Yet HovPod claim something ridiculous for their already ‘battleship-heavy’ craft - 375kgs!

 

I'm so confident with the claims Flying Fish make that we recently introduced a Money Back Guarantee  if performance is not as claimed.

So that's that one 'drilled-down' then.

 

6/. Hovercraft Skirt Material

Hovercraft skirts can be designed as one bag, or many sections – multiple sections are better since if damage occurs, it is cheaper to replace one section than the whole bag skirt. Neoprene coated nylon will deteriorate when expose to UV (sunlight) Hypalon tears too easily, we recommend polyurethane coated anti-rip nylon weave.

Question - How long will the skirts last? What are the replacement costs? How much will shipping cost?

Answer - Not much to say here - other than we've been using neoprene coated nylon (to our own secret recipe - it’s a bit like the Colonels chicken, there’s a little something else in there we can’t tell you about!) and have found no other material lasts as well. Of course, if you had a particularly heavy hovercraft (which didn’t lift properly as a result) then you may find a heavyweight material made of what is basically a RIB tube material, may last a little longer. Skirt life and performance does rather depend on whether your hovercraft actually hovers! The HovPod uses 375gsm material, over twice as thick as that on the BHC hovercraft…and the Hovercraft Club of Great Britain review of it said “lt feels like driving a car with the handbrake on.”

Conclusion

The bottom line is that a personal hovercraft built out of HDPE plastic will never perform as well, or as reliably as a GRP one. It’s too heavy and floppy - and because of that, a hovercraft made of HDPE is compromised right from the outset. Two stroke engines suck for hovercraft/marine applications.

Here at BHC we prove our commitment to our deigns by racing them both inland and in a coastal-environment, by organising cruising events on behalf of the UK Hovercraft Club, by taking part in a dozen ‘Rhone Raid’ events (400 miles over 6 days) and even nipping home in them on sunny days!

So, here’s OUR ‘buyers guide’

1.    Try driving a HovPod

2.    Try driving a Marlin

3.    Decide for yourself.

We try to play nicely, but HovPod have a long history of telling the hovercraft community it’s doing it all wrong so, this seems like a good place to finally address it and take the opportunity to re-issue an old challenge.

“Let’s have it out once and for all. Instead of making up smarmy little ‘buyers guides’ which are anything but a buyer's guide, or making up nonsense for your 50+ websites (yes, honestly!), let’s get one of your craft and one of ours, a mutually agreeable magazine reviewer and see which one comes out best!”

Response provided by The British Hovercraft Company Ltd.

*Hovercraft Manufacturers Association

 

 


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