Where is the flotation??
KIRK JENKINS
completely..Pulling everything off to restore it... from cutting out the
old rusted motormount from the bottom of the haul right on up to
rebuilding the motor...
"Where's the FLOTATION in this boat???
Cutting a good size hole in the back for the motormount i thought for
SURE I would see some foam...But no sign of it yet ...Can someone tell
me if this has any, and does it need it??
Kirk Jenkins
Challenger Pad Systems Inc.
Barry Palmer
and outer hulls, and just below the cushion feed holes. This was brought to my
attention when a Scat lifted off, leaving its entire ABS outer hull bottom on
the ground, broken off at the air holes that feed the fingers. I do not know
whether or not the ABS problem and cold water has been solved.
Very possibly someone may have dug the flotation foam out as it tends to become
soggy, bad idea since there is so little hull on a Scat, it is very close to
tipping over backwards when floating if no one is aboard.
>Subject: Where is the flotation??
>From: KIR...@webtv.net (KIRK JENKINS)
>Date: 7/7/03 6:59 AM Pacific Daylight Time
>Message-id: <18927-3F0...@storefull-2274.public.lawson.webtv.net>
Barry Palmer, for <A
HREF="http://members.aol.com/sevtec/sev/skmr.html">Sevtec</A>
hoverflyte
liner in the plenum. It leaves a lot to be desired for sure . You can add
floatation real easy , check my word.doc at http://www.hoverflyte.com click
Scat upgrade page and check out the list of "how to's" .
DBP
"KIRK JENKINS" <KIR...@webtv.net> wrote in message
news:18927-3F0...@storefull-2274.public.lawson.webtv.net...
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KIRK JENKINS
with the Scat ...
Do I need to lower my opening for the intake to make it closer to the
fan to fill the plenum...I am not sure what that platform is called yet
hoverflyte
duct's total airflow and sends part to the plenum (and then under the craft)
, the rest goes out the rear of the craft for thrust.
I know of people who prefer to just run them "as is" rather than go
through the trouble but:
If you decide to extend the splitter plate so it is close to the fan ,
be advised there is a good chance you will end up with too much lift air
volume . You don't really GAIN lift air , rather you reduce the amount of
lift air volume that "sneaks" back up between the splitter plate and the
fan. Since the loss is reduced (one can also say the efficiency is
increased) , you end up with too much lift air volume and will have troubles
with "blowing a hole in the water".
The purpose of lowering the splitter plate is to reduce the amount
of air shoved into the lift duct . This both reduces the tendancy to blow a
hole in the water AND increases the area of the duct used for thrust and
therefore makes the craft have more thrust volume , which often can mean
being faster.
So to simply answer your question , no you don't HAVE to lower the
splitter plate . But as time goes on you will want to make improvements to
make the lift and or thrust better.
There is a Yahoo group specifically targeting Scat hovercraft so
join us if you wish , here's a link:
http://groups.yahoo.com/group/scathovercraft/ .
DBP
"KIRK JENKINS" <KIR...@webtv.net> wrote in message
news:24160-3F0...@storefull-2273.public.lawson.webtv.net...
Barry Palmer
and base area of the craft, not the quantity of cushion airflow, and raising
the splitter merely splits off thrust for more cushion air, and that makes it
more difficult to get the craft out of the hole. Larger cushion flow volume
may generate more spray, however, and one will think the hole has gotten
bigger.
>Subject: Re: Where is the flotation??
>From: "hoverflyte" hover...@comcast.net
>Date: 7/8/03 2:48 AM Pacific Daylight Time
>Message-id: <2swOa.4550$GL4.2037@rwcrnsc53>
>
> I think what you refer to is the "Splitter Plate" . This divides the
>duct's total airflow and sends part to the plenum (and then under the craft)
>, the rest goes out the rear of the craft for thrust.
> I know of people who prefer to just run them "as is" rather than go
>through the trouble but:
> If you decide to extend the splitter plate so it is close to the fan ,
>be advised there is a good chance you will end up with too much lift air
>volume . You don't really GAIN lift air , rather you reduce the amount of
>lift air volume that "sneaks" back up between the splitter plate and the
>fan. Since the loss is reduced (one can also say the efficiency is
>increased) , you end up with too much lift air volume and will have troubles
>with "blowing a hole in the water".
> The purpose of lowering the splitter plate is to reduce the amount
>of air shoved into the lift duct . This both reduces the tendancy to blow a
>hole in the water AND increases the area of the duct used for thrust and
>therefore makes the craft have more thrust volume , which often can mean
>being faster.
> So to simply answer your question , no you don't HAVE to lower the
>splitter plate . But as time goes on you will want to make improvements to
>make the lift and or thrust better.
> There is a Yahoo group specifically targeting Scat hovercraft so
>join us if you wish , here's a link:
>http://groups.yahoo.com/group/scathovercraft/ .
>
>DBP
>
hoverflyte
hole in the water" I mean just that. The depression that is generated was at
times deep enough the gunwales of the Scat were visually at or very nearly
level with the "mean" level of the rest of the lake's surface, and you are
correct that it was primarily generated more by the spray than anything
else. The depth of the hole in the water is not neccessarily relative to the
weight of the craft though , the volume of lift air creating the spray can
have an extremely profound effect. You seem to be wanting to make a point ,
but I soppose I'm a bit daft as I still fail to see any point that I didn't
make , or at least I thought I made ; perhaps except that you didn't
accurately read and process the data I offered.
I did not raise the splitter plate :
#1. I moved (read extended the leading edge) it very close (less than 1/4"
from it's origonal 3.5" to 4" gap) to the back of the fan . This did not
alter the volume into the plenum ; except that it did alter (read reduce by
a huge margin) the "backwash" of air that was forcing it's way back up
between the fan and the splitter (which also acts as a plenum pressure
regulator but that's a side note).
#2. I then lowered the splitter plate (it goes from one duct wall to the
other , at the bottom of the duct in a Scat) . This (by virtue of the fact
there are a set number of square inches of area within the duct in the plane
of the fan) reduced the area of the duct for use by the lift system and
therefore the volume of air forced into the plenum was also reduced. At the
same time ; by decreasing the area of the duct used by the lift system ,
inherently increases the area for use by the thrust system.
There are some other points that could be made
regarding what it (extending and lowering the splitter plate) did and did
not do but I honestly don't think you wish to discuss the attributes of a
Scat and the effects of making modifications or improvements on them .
DBP
"Barry Palmer" <sev...@aol.com> wrote in message
news:20030708113730...@mb-m07.aol.com...
John Lloyd
weight is exactly the same as the weight of the hovercraft making the
'hole', in exactly the same way that a boat displaces its own weight of
water. As speed increases the 'hole' moves rearward until, at the so-called
"hump speed", the 'hole' is left behind. This is equivalent to the planing
velocity of a speedboat. Hump speed is determined by nothing more than craft
length, the calculation being: 1.9X where X is the square root of the craft
length in feet.
"Barry Palmer" <sev...@aol.com> wrote in message
news:20030708113730...@mb-m07.aol.com...
> I do believe the "hole in the water" is determined by the craft all up
weight
> and base area of the craft, not the quantity of cushion airflow ... SNIP
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hoverflyte
stagnant and not blowing a huge amount of spray ............therein is where
"the numbers" go right out the window.
A (ex:) 500 lb craft putting out no air will displace as you have
stated but have that craft's lift system blowing 5000 cfm of air and it's a
different situation. The 500 lb craft will now (along with the excessive
lift air) actually displace more than it's own weight ...... because of the
spray.
DBP
"John Lloyd" <ho...@waitrose.com> wrote in message
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Barry Palmer
compared to the craft weight. The vertical component of the air leaving the
craft would be maybe 40 feet per second, entrained water perhaps the flow of
the typical garden hose, (since I do not know the base area of the 500#
machine in the below post) that would be 5000/60*.00238*40= 8# plus garden hose
flow, .5#? , which may be the same as the momentum of accelerating the air
downwards into the lift fan, also about 8# with a reasonable sized lift fan, so
modulation of the flow due to high flow velocity would tend to reduce craft
weight. The hole may be deeper in places, but is still somewhat the same
volume.
Make the lift fan larger, and the cushion flow extremely high the hovering
craft would fly free, and the hole would become larger in diameter and
shallower as surounding air is entrained but still the displacement volume of
the hole would be the same. As the craft gets fairly high, the hole would
still be there, but so large one could not perceive any depth.
>Subject: Re: Where is the flotation??
>From: "hoverflyte" hover...@comcast.net
>Date: 7/15/03 12:02 AM Pacific Daylight Time
>Message-id: <JFNQa.66229$H17.20586@sccrnsc02>
>
> While these figures are very well , it is based on the craft being
>stagnant and not blowing a huge amount of spray ............therein is where
>"the numbers" go right out the window.
> A (ex:) 500 lb craft putting out no air will displace as you have
>stated but have that craft's lift system blowing 5000 cfm of air and it's a
>different situation. The 500 lb craft will now (along with the excessive
>lift air) actually displace more than it's own weight ...... because of the
>spray.
>
>DBP
>
>