[Alberg30] Re: Plastic Boat Sheds
Henry Hilliard
island_light at lycos.com
Thu Dec 4 09:37:50 PST 2003
Don,
Thank you for the comprehensive advice concerning plastic boat sheds, clearly you have the experience to back it up. If I have any further questions after I absorb the attached I"ll contact you directly.
much obliged,
Henry Hilliard
"Celeste" #394
---
From:
Don Campbell <dk.campbell at sympatico.ca> [add to address book] [protect or block sender]
Subject:
Re: [Alberg30] plastic boat sheds & Don Cambell's comments
To:
island_light at lycos.com, Alberg 30 public list <public-list at alberg30.org>
Reply To:
dk.campbell at sympatico.ca, Alberg 30 public list<public-list at alberg30.org>
Henry;
There are two things necessary with the greenhouse. The first
is to have it really secure to the earth. I have 3 on the farm that
are really greenhouses and have lost one when one end opened in
a gale and lifted 48 - 36" pegs out of the ground. Just a few sandbags
won't do if you need to close the ends. If you are on pavement,
get out the Hilti and use extra long nails. It may be easier and
cheaper but cooler to add 12 or 16 feet to each end of the length
so rain won't blow in and not bother closing the ends. The only
thing you need worry about then is the lift off the plastic similar
to lift off a sail with wind. I have used this set up for rain shelters
on my wheat research and it worked well with all ground stakes 36"
into soil. It is possible to use hurricane ties to eyes in
the soil to help hold the frame.
The second thing that needs to be done is really good attachment
of the plastic to the walls of the frame. If you are using horticultural
plastic, 6 mil is quite stiff and normally UV stable. I would have
thought 4 mil sufficient for a temporary structure. Don't count
on reusing the plastic, even the 6 mil material. You can reuse the
structure if it is left intact, but the plastic will not
move if you relocate the frame. You can see how much they want for
the normal poly lock system they sell. It is ususally expensive
so you might want to use 2 x 4 and then first strap the poly over
the 2 x 4 and then restrap it on the top edge with a second strap.They
will show you how to use srapping to attach plastic. they have done
it themselves before poly lock was invented. Avoid sags in the
plastic like the plague. Also keep the number of perlines to 3
if possible.You will find that every drip of condensation will fall
from the lowest point of the sag or where the plastic hits a perline.
Once it starts, the surface tension is broken and yu get a small
rivulet that will flow for seconds.
Any loose attachment of the plastic sheet will allow for flapping
in the wind and wear over the frame so holes will form. Most greenhouses
are double poly and a fan blows air into the envelope to maintain
pressure on the films so flapping is minimized..
Plastic needs to be applied on a really calm day, usually first
thing in the am or last thing at night. A quick attach system really
helps and uneven or local pulling of the plastic will stretch it
and cause bunching and sags where you don't want them. I like to
have 4 or 5 people for a sheet of plastic that is 100' x 28'. Pull
it down the centre top and let it fall free to both sides. Don't
try to lift the sheet over from one side. It will stretch out of shape.
As for ventilation, the louvers you suggest will do fine for
air flow for condensation reduction but not elimination, and pressure
equalization, but for painting, use a fan. This means that the air
inlet (Doors) at one end need to be of sufficient cross-sectional
area to allow enough air in to keep the fan at its optimum air volume.
You will will want to change the air once every 3 or 4
minutes at least. With plants in the greenhouse, we change air about
every 1-2 minutes since temperature will rise 10 degrees for every
100 feet of length with sun on the house in 2 minutes. That is where
no ends may work well - no restriction, and no fan needed. You need
to look at the height the fan needs to be in the end to clear the
painting area of fumes. My decks on boats in the shed are
about 8 - 10 feet off the floor, depending on whether it is on the
trailer or on a cradle. There is laminar flow in a greenhouse so
put the fan at painting level. A 2 speed fan motor is nice for warm days and extra air flow.
Don't paint if there is a possibility of condensation forming on new paint. Good fortune.
Don
Henry Hilliard wrote:
> I read Don Cambell's comments on plastic tenting (Vol 169, Issue
14) with interest as I am in the process of building a "greenhouse"
boat shed and I plan on using a 6 mil material from a greenhouse
supplier. Others in my area (Maine) have used this material with
success yet cautioned me to install adequate venting - in their
cases old house shutters up high at the ends to assure a flow of air.
>
> I intend to prep the deck and top sides over the winter and paint
in the spring. Any advice or info from you Don others would be much appreciated.
>
> Henry Hilliard
> "Celeste" #394
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