[Rhodes22-list] Help re Dinghy

[Roger Pihlaja]

Doug,

There are basically 3 types of inflatables: soft-stern, sport boat or
hard-stern, and rigid inflatable boat (RIB).

The cheapest and lowest perfomance catagory is the soft-stern type.  The
soft-stern type usually has no keel & a soft floor, although some higher
priced models from Zodiac & Avon do have flooorboards.  They are usually
rowed.  A small outboard or electric trolling motor can be mounted thru the
use of an optional motor mount.  Usually the horsepower rating is low, < 5
hp, which limits the soft-stern inflatable to nonplaning displacement hull
speeds of 3-4 knots.  These boats are usually the cheapest, lightest, easist
to stow, easiest to assemble & setup.  With no keel, these boats have the
poorest rowing performance.  If you don't have too far to row in protected
water, these soft-stern inflatables will get you there & back with no frills
& many have been in service for decades.  If this is all you expect from
your dingy; then, the soft-stern inflatable will fill the bill.

Currently, the most popular type of inflatable in terms of sales/year is the
sport boat or hard-stern boat.  As the name implies, these inflatables have
a rigid transom made of marine plywood or FRP.  Most will also have
floorboards and some sort of an inflatable keel.  The combination of the
floorboards and keel give the hard-stern inflatable a shallow draft V-hull &
sufficient rigidity to reach planning speeds.  The hard stern permits the
use of larger horsepower outboards.  We have a 10 foot long inflatable sport
boat with a Honda 9.9 hp outboard.  With one adult on board, our inflatable
can fly along at 20+ knots.  It can still plane with two adults; but, top
speed drops down to around 12 knots.  With the greater hull rigidity and
keel, the hard-stern inflatable also tracks better & is blown about less by
crosswinds when rowing vs. a similar sized soft-stern inflatable.  Load
carrying capacity is quite similar.  Hard-stern inflatables are somewhat
heavier, require somewhat more assembly & setup time, and are somewhat more
expensive than soft-stern inflatables.

Finally, the RIB type has a rigid aluminum or FRP "tub" surrounded by an
inflatable bladder.  The central tub has seats for the passengers, a shallow
draft V-hull keel, and a rigid transom.  The inflatable bladder simply
provides floatation.  RIB's are probably the ultimate in inflatable boat
performance & safety.  The US Coast Guard uses them as search & rescue
craft.  RIB's can be as big as 30 feet long with twin 200 hp outboards!
They row the best and perform the best under power.  However, they are also
the most expensive & heaviest of the inflatables.  They are not usually
deflated when not in use.  Instead, they are usually towed behind the mother
ship or stowed on davits.  Unless you are willing to tow your inflatable,
the RIB is probably not a good choice for an inflatable tender for your
Rhodes 22.

Having choosen the basic type of inflatable, you still need to choose the
material of construction (MOC).  The two most common MOC's are polyvinyl
chloride (PVC) and fiber reinforced neoprene rubber (Hypalon).  In general,
Hypalon has better UV resistance and abrasion resistance than PVC.  Hypalon
boats must be glued together whereas PVC boats usually have welded seams.
PVC boats are usually less expensive.  Both MOC's can be repaired similarly
well.  But, you must use the correct repair kit, i.e. a Hypalon patch kit
will not work on a PVC boat & vice-versa.  Quality inflatables can be made
in either MOC.  At the moment, high end inflatables are usually made with
Hypalon.  Our inflatable is made from Hypalon.

We keep our inflatable on our beach on top of a self-launching & storage
rack of my own design.  To extend the life of our inflatable, we cover it
with a fitted boat cover in between uses.  UV fabric degradation is a
cumulative exposure type of phenomena & any inflatable will last longer if
you keep it covered up when you are not using it.

With the hard-transom inflatables, you also need to choose the style of
floor: high pressure inflatable, roll-up, or sectioned.  I don't have any
experience with the high pressure inflatable style floor.  The venders claim
that by inflating the specially designed bladders in the floor of these
boats to 10-15 psi, they can achieve floor rigidity comparable to sectioned
floors.  I've stood in these inflatables at boat shows & the floor seems
impressively rigid.  But, I've never seen a review in any of the boating
magazines and I've never tried one myself on the water.  The advantage is
reduced weight & setup time compared to sectioned floors.  The oldest
technology is the sectioned floor.  Here, the floor is a series of  3 to 5
plywood pieces that interlock together while the boat is deflated.  Then,
the tubes are inflated around the floor sections, which locks them together
& gives the floor & keel a lot of rigidity.  The disadvantages are weight &
lengthy setup time.  Our inflatable's floor is the roll-up type.  Here the
floor is a series of aluminum or plastic slats that are hinged to each other
as well as the rigid transom.  You simply unroll the floor, check to make
certain all the edges of the slats are lined up with each other & inflate
the tubes around the slats.  It's pretty fast & idiot proof.  The weight is
slightly higher & rigidity slightly lower than the sectioned floor type;
but, not much.  In addition, the aluminum or plastic floor slats are much
more maintenance free than the plywood floor sections, which must be
periodically sanded and varnished.  Our roll-up inflatable floor has had
zero maintenance & has been totally bulletproof since it was new in 1996.
We simply stand up the inflatable & hose out the interior with a hose.  The
plywood floor sections in inflatables I've used can be very slippery when
wet.  The roll-up slats have a molded in nonskid pattern which prevents them
from becoming slippery.  Note, some roll-up slats don't have this molded in
nonskid pattern & it's something to check for when shopping for an
inflatable.

What size inflatable do you need?  If you want to be able to get up on plane
& zip around the harbor; then, 10 feet LOA & a 6 hp outboard is about the
minimum.  Sizes shorter than 10 feet LOA will be lighter & easier to stow;
but, will handle rough water & boat wakes dramatically less well than a 10
foot inflatable.  You can get up to 4 people + a reasonable amount of gear
into a 10 foot inflatable, although you will need to take it easy on the
throttle when the boat is loaded up that much.  In terms of safety, a 10
foot inflatable will be rated for up to a 10 hp outboard & about 1000 lbs of
load.  Usually, there will be 4 separate air chambers in a hard-transom
inflatable in this size range: the two side chambers, the bow, and the keel.
Each of the air chambers is rated with sufficient floatation to support the
entire rated load.  I'm a big guy, about 240 lbs.  I can stand up & walk
around in our inflatable.  I can even stand on top of the gunnel on one side
with no one counterbalancing the boat without flipping it!  We've had our
inflatable filled to the gunnels with water (kids - don't ask!), pulled the
drain plug, & watched the boat rise as the water drained out.  If all you
want to be able to do is row for short distances in protected water; then,
you can get away with a smaller soft-stern or hard-stern inflatable.  Our
inflatable is a great fishing platform.  We use a Minn-Kota 30 lb thrust
trolling motor for fishing & when cruising.  The Group 24 gel cell deep
cycle battery goes in a hard plastic battery box & is secured by the same
tie-down strap usually used for the 3 gal gas tank when the Honda 10 hp
outboard is mounted.

Although we can deflate our boat & it will store in the lazarette
compartment, we usually just tow it behind Dynamic Equilibrium.  The effect
upon sailing performance is negligible.  The below picture link will show
you a picture of Dynamic Equilibrium sailing several miles offshore in Lake
Michigan.  If you look about 50 feet astern, you will the see the gray
inflatable in tow.

http://www.rhodes22.org/rhodes/pics/RogerPihlaja1.jpg

This second picture shows me sitting on a dock purifying fresh drinking
water on an uninhabited island about 30 nm offshore in northern Lake
Michigan.  You can see Dynamic Equilibrium lying at anchor in the
background.  My younger son, Gary, is standing in the inflatable behind me.

http://www.rhodes22.org/rhodes/pics/Garden_Island1.jpg

Our inflatable is a Grizzley model made by Bear Boats in Ontario, CA.  I
think Bear Boats has gone out of business since 1996.  Our purchase price
was about $1000 in 1996.  If I were replacing the inflatable today, I'd be
looking at comparable Hypalon roll-up hard-transom models from Zodiac &
Avon.  Whatever model you buy, make certain there is a grab rope all the way
around the perimeter and make certain the towing loops & other hardware is
HD & strongly attached.  These are areas where lower priced inflatables tend
to cheap out.

If you have some specific questions regarding inflatables, just ask away &
I'll try to help.

Roger Pihlaja
S/V Dynamic Equilibrium



----- Original Message -----
From: "Doug Mistler" <mistler at mindspring.com>
To: "'The Rhodes 22 mail list'" <rhodes22-list at rhodes22.org>
Sent: Sunday, November 28, 2004 12:33 PM
Subject: [Rhodes22-list] Help re Dinghy


> Hi, Rhodies,
>
> Your advice would be appreciated re an inflatable dinghy for the
> Rhodes 22.  What you have you found to work reasonably well? I
> have searched the recent archives without success.
>
> What fits and where do you store it?  What would you avoid?
>
> A Mercury 6'7" inflatable with slatted rollup floor I have
> looked at weighs 35 lbs and deflates to 3' 3" X 1' 10" X 15".
> How is that for storage?  Do I need to look at "light duty"
> dinghys without the slats?
>
> The dinghy will be used mostly on the Eastern shore of the
> Chesapeake bay while gunkholing.  Most of the time I shall be
> singlehanding, but may have the occasional company of my wife or
> son.
>
> Fair winds!
> --Doug
> "Red Rover"
> Deale, MD
>
>
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