Several Newbie Questions - Could Really Use Your Help!

[CatBuilder]

Hello, Everyone.

So far, I have asked a few questions on this forum and got some very helpful answers. However, the answers opened up a whole new set of questions! :D

If anyone could take the time to answer these newbie composite boat building questions, it would be greatly appreciated.

Background: I am building a 45' catamaran in the States. I have a choice of building in a warehouse/shop close to Canada. I have another choice of building in a fabric building in a low-hurricane potential area in Northern Florida. Here is what a fabric building looks like:

http://www.teksupply.com/wcsstore/EngineeringServices/allbizunits/prodimages/full/106645a.jpg

The boat is constructed using a whole slew of materials to keep it light weight, but it is primarily a plywood/epoxy composite boat. There is a small mold to build to do each half of the hulls in one shot before a stitch and glue to pull the hull halves together.

I can build this boat up where it snows from November to April or where it is in the high 90's from May to September. Both areas likely have high humidity as FL has humidity ranging around 90%+ in the summer and being on the water near the Labrador Current makes for thick fog most of the time up by Canada.

If I heat the warehouse up north to 50 degrees+ so I can work with West System and taking into account all of the other factors, it will cost me $10,000 more to build up north than to build in FL if I build for 12 months. More likely, it will take 24 months. In that case, it will cost me $20,000 more to build up north than in FL.

$20,000 or even $10,000 buys a lot of boat equipment. It's also unearned money my wife would have to come up with during the build. She's not a fan of that.

Questions:


Humidity: Both locations have high humidity. One location has high humidity and high 90+ temperatures much of the time. The other locaiton has high humidity and "freezing fog" which is like freezing rain, except it's from fog and cold. This means I can have 100% humidity right down to the freezing point. How should I deal with either extreme? Is there an appropriate epoxy I can trust my life and my entire net worth to? We live aboard and cross oceans... I want the best boat I can get.
Humidity Revisited: West System suggests between 8% and 12% humidity in wood when wetting it out. What will happen to my wood in 100% or 90% humidity? Will it expand and make my cuts off if it dries? Will it be insufficient for epoxy work? How do people work in high humidity with wood and epoxy?
Large Temerature Changes: In one location, the temeratures (low in the winter and high in the summer) will range from -10F to 90F. I'll be indoors, so I have control of the temperatures at great expense. Are there epoxies I could use that would make this easire so I didn't have to pay as much for climate control? In the other area (Florida), I'll have lows of 30F in the winter and highs of near 100F in the summer. Again, a large temperate variance, but mostly, it's hot. Are there epoxies that would make this work go more smoothly?
Peel Ply: Herman suggested using peel ply. I like the idea, but I wonder if it's affordable on a 45' catamaran? Do you have to put a new piece of peel ply on for each layer of epoxy you do, or is peel ply reusable? I'm looking at (IIRC) 6 layers outside the hull and 3 layers inside on a boat that's 45' x 25'. That's a LOT of surface area. I sure hate sanding, but has anyone successfully (and economically) used peel ply on larger boats?
Sanding Between Coats: Are there any trustworthy epoxies out there that don't need sanding and/or washing and/or scotch brite scrubbing at all between coats? As in... is there one that you can put a coat on, let it cure, come back to it in a few weeks and put a new coat on without any surface prep? Could be the pipe dream of all amateur builders, but I thought I'd ask! ha ha


Thank you in advance for any help you can offer answering these newbie questions. Epoxy has become a new variable in my build location choice. If there is an epoxy that can save me from having to control the temperature and humidity, it could save a lot of money. If there is an epoxy that could help me not have to sand/prep between coats, it could save a fortune in rent.

I want to build in the northern location, but heating the space and paying rent for extra sanding months is very expensive. Ideas?:confused:

[apex1]

Hello, Everyone.

So far, I have asked a few questions on this forum and got some very helpful answers. However, the answers opened up a whole new set of questions! :D

If anyone could take the time to answer these newbie composite boat building questions, it would be greatly appreciated.


To make it short:

go for FL!

It is much, much cheaper to control the resin properties from case to case than heating a shed all winter long (and probably half of the summer).

Forget about West resins as we stated already on your other post!
There are other formulations on the market without blush and at substantially lower rates.

No, you cannot use peelply twice!
No, you cannot skimp on sanding between layups, when you dont use peelply.

Even with peelply the bond between layers is only a mechanical one, it would be better to make the entire structure in one go! You then have a chemical bond between the layers, which is much, much stronger! Yes, that means probably paying some helpers for a day or two (depending on the size of the structure). When using slow hardener, very slow in FL, you have a larger time window to apply the next layer on the still uncured predecessor. That CAN make it possible to achieve a "one go" layup with one helper only.
You would not have to sand between layers when the method allows it, and the job is done very accurate! That can save weeks of sanding and / or, kilometers of peelply!
You have to postcure ALL slow hardener mixes after finishing the part! That is a MUST ! ! !


Regards
Richard

[Herman]

OK, I will throw in my 2 ct:

Go for FL. Although I like Canadian girls better I... Oh well, other chapter.

Still go for FL. Epoxy is a substance that really likes a bit of heat. All other problems can be addressed. There are epoxies that have a really large open time, so plenty of time while doing large layups. Also, there are blush-free alternatives and there are even epoxy resins that give a good bond on wet substrates, like wood.

Controling humidity levels can be done alternatively as well: Make a sort of warehouse area where you can lower humidity levels. Not only your wood will suffer, but also your glass.

About peelply: get yourself a good, cheap source. The Chinese stuff does not cost too much, I recon about 150% of the cost of sandpaper for the same area. Minus the labour...

Again about peelply: Do I understand that you want to apply one single layer, then cure, then sand, then do the next layer?
I suggest 2 things: Get yourself some nice and heavy non crimp fabrics (vectorply or similar, up to 600 grams / m2 is very easy to laminate by hand, more experienced people might use slightly heavier.)
Also do as many layers in one go. With the slow epoxy, don;t be afraid about exotherm ,as this will be very limited. I suggest starting at the bow, do a staggered layup which will give you full thickness asap, and slowly work your way back. That way you save a ton on peelply. Also I must say that peelplied laminates usually look more smooth and blend in the rest of the laminate better.

Slow epoxy will cure, but will stop at perhaps 80% of potential cross linking. Which means some 20% is still available to bond chemically. And after you have done all your epoxy work, you can do a postcure, and have that 20% crosslink as well, giving a tougher laminate with higher heat resistance.

Oh, one other thing: Try and find a supplier which can cut rolls into tapes. I usually cut rolls in half for diy builders, for much easier handling of the rolls, making for a faster and better quality laminate.

Also not having to cut tapes for tabbing is a huge time saver.

And even another thing: I have seen a carbon racer being built in Slovenia, in exactly a tent like the one you are showing. It can be done!

[apex1]

what I say................

[rasorinc]

Raka epoxy does not have blush.
http://www.raka.com/

[hoytedow]

Have you considered using a dehumidifier or making one?

http://www.consumerreports.org/cro/appliances/heating-cooling-and-air/dehumidifiers/index.htm?EXTKEY=SG72A00&CMP=KNC-CROAPPG&HBX_OU=50&HBX_PK=dehumidifiers+_ratings

http://assortedtips.blogspot.com/2008/01/inexpensive-natural-dehumidifier.html

[troy2000]

OK, I will throw in my 2 ct:

Go for FL. Although I like Canadian girls better I... !

Total sidetrack here: long, long ago in a galaxy far, far away called 'Youth,' I was headed for Quebec to hook up with a French-Canadian girl I had met during the summer in Wildwood Crest, south New Jersey.

When the gentleman at the border asked the purpose of my visit and I explained, he leaned back, gave me an incredulous look, and exclaimed in a heavy French accent: "you are from California, and you must come to Canada to find a woman?!?"

I had to explain that she was very beautiful, very special -- and very French. I'm not sure he bought the first two reasons, but the last one satisfied him....:p

[tunnels]

Humidity is something not to may people take a lot of notice of and they wonder why they have problems ! Wood needs to be dry as possible ,end of story !! working humidity needs to be below 70% all the time 24/7/365.
Temprature you need to work at 20c all the time . with 70% HUMIDITY AND 20c you can use any types of resins and glues !! Just remember humidity is moisture un the air and the dampness comes from every where so you need to be able to work inside a tent inside of a cocoon that is insulated and sealed apart from the door where you go in and out . The foor is a place where moisture is drawn up in great quantity so need to be sealed 110% air leaks and draughts so lots of rolled overlaps and taped inside and out .

I have worked and built boats at both ends of the scale, Minus -20c and 5% humidity in the south Korean winter in 2007 /2008 making plugs, moulds and 8 fibreglass racing yachts .
Also making fishing boats in Tahiti back in 1985 with +40c in the summer and 100% humidity with 3 dehumidifyers going flat out all day long and water running out of them contunuously . We had to have a tent over the place were working inside of .
:confused:
Its important that once you have your enviroment aclimatized to where its at the proper working temprtaure and humidity that you maintain it continuosly 24 /7 and if all is working 99% its easy to maintain with very little imput and work Plus all you materils need to be in there with you, like i mean everything all on old pallets up off the cold and damp floor etc etc . The tent is best made from a multi layered plastic with bubbles between to slow the escape of heat . a couple of good sized fans to draw the hot air from the top back down to the lower levels and keep the air moving slowly !!
Nothing is impossible !!!just need a little thought ! :P :D

[hoytedow]

On top of that you need to not be overcome by fumes, so a proper respirator is a must.

[apex1]

Humidity is something not to may people take a lot of notice of and they wonder why they have problems ! Wood needs to be dry as possible ,end of story !! working humidity needs to be below 70% all the time 24/7/365.
Temprature you need to work at 20c all the time .

Not necessary, really! There are more than enough professional boatbuilders in FL to prove these statements wrong! Or at least exaggerated.

It was all said already above!

[tunnels]

Not necessary, really! There are more than enough professional boatbuilders in FL to prove these statements wrong! Or at least exaggerated.

It was all said already above!

All the work i do is to survey standards reguardless of the size of the job and moisture in any shape or form kills resin and you can end up with undercured laminates that never reach there potentual hardness no matter how much you try to cook it !! take the moisture away and add i a little heat any resin will go hard be it epoxy, Vinylester or even polyester .

Simply do the job properly from day one and sleep soundly with no worries

:P

[CatBuilder]

Ha ha ha! As on all forums, there are disagreements and different ways to do things.

One factor that just changed was my wife. She decided it is worth 2 masts ($20K) to have me stay up North and work nearby. So, I will be staying up North and will have to heat a space rather than air condition it.

When you are building a boat and the wife is still working to make money during the build, you have to answer to the boss!!:D

Well, we'll try for this. If is is really much cheaper anywhere down South, I'll take it, but it has to be in a building that can be temp and humidity controlled.

Back to the other items:

I guess I have a lot of freedom here. I'm at the very beginning of a build. I have plans in hand, materials on order and I'm selecting the location.

Being a very anal person who prefers not to make too many mistakes, I am trying to envision the entire building process from start to finish. Because I haven't started yet, I can take a couple of weeks to devise "smart" ways of building.

I really like the idea Richard had (and also Herman had) of trying to do as many layers of epoxy in one go as possible. Considering rent will be about $1000/mo min and heat will run just a little less than that, I could save a lot of money *and* sanding by hiring a couple people to help me wet the boat out 24/7, right??

I figure I can hire a couple people to work with me wetting the hulls out 24 hours a day in small stretches. Labor is $10/hr here for this type of help. Plus, no sanding is good sanding! :D

Do professional shops do it this way? Wet out the entire hull(s) in one shot to keep the epoxy tacky and thus, prevent the need of washing off blush or sanding between coats?

I also like one thing Richard says about this technique: "It is a chemical bond rather than just a mechanical bond" really speaks to me. Plus, did I mention I don't much like sanding? ha ha ha Any elimination of some sanding along the build process would be helpful.

Great advice, also about having some of the glass rolls pre-cut. That's another thing a newbie wouldn't know right off.

Lastly, I was really thinking about doing as Tunnels said after re-reading some of the "Gougeon Brothers on Boatbuilding" book. They repeatedly discuss moisture and suggest an 8-12% moisture level in wood, no condensation, no blushing if it's dry and warm enough, etc...

It sounds like it might be easier (and possibly cheaper) to just use the best building space I can that is 20C (70F), 50% humidity, concrete floor, ventilation, etc... Two of them I have been looking at even have built in cranes on the ceiling. Maybe the building will go much more quickly and more smoothly, so I have fewer mistakes, fewer accidents and fewer months of rent to pay. According to the Gougeon Bros book, they did this in Michingan, which I know is very cold and very damp as well as being right next to Canada.

I plan to finish out the interior afloat.

Feel free to comment, anyone. I'm still learning, but those are my responses to what has been said, as a new builder.

[hoytedow]

I think you made the right choice for all the reasons you mentioned. Good luck with the build.

[apex1]

I really like the idea Richard had (and also Herman had) of trying to do as many layers of epoxy in one go as possible.

Do professional shops do it this way? Wet out the entire hull(s) in one shot to keep the epoxy tacky and thus, prevent the need of washing off blush or sanding between coats?

I also like one thing Richard says about this technique: "It is a chemical bond rather than just a mechanical bond" really speaks to me.


Doing the layup in one go is what we do in industrial boatbuilding (whenever possible).
The epoxy resin forms into one single molecule, when it is done this way. Otherwise it is just a couple of layers of your matrix, like a onion, and not as strong.

The humidity within the wood (usually about 12%) will not change much when you work in a humid place! It takes a long time before the wood absorbs water out of the air. In cold climate it cannot absorb it. There is (relative) more water in the wood than in the air.
Temperature changes during the actual layup and the related possibility of condensate are to avoid though!

Regards
Richard

[tunnels]

The humidity within the wood (usually about 12%) will not change much when you work in a humid place! It takes a long time before the wood absorbs water out of the air. In cold climate it cannot absorb it. There is (relative) more water in the wood than in the air.

You should try tell that to a wood floor layer that it doesnt change much . Have seen a 6 meter wide solid wood floor grow 6 mm over night and a total of 10mm in a a couple of days once it settled down :confused:
A basket ball court we left .4 mm between each 22mm thick X 200mm wide plank over the total width of the floor and even then the gaps would be completely closed in a day . With damp wood its the opposite and will shrink that much !:P

[apex1]

You should try tell that to a wood floor layer that it doesnt change much .

No tunnels, I should NOT! Not to a butcher either.

Did you ever bother to have a look at my Gallery? You would notice I have seen some wood before I posted the first word here..............................

[Herman]

Some practical stuff:

Your rent is slightly cheaper than here. Heating however, sounds expensive to me. Do you guys insulate buildings?

Here R=3 is the norm, but preferably better. You could opt for a bunch of bubble wrap film, and create a tent. No idea of the size of what you will be able to rent.

Problems with shrinking wood are also depending on building method used. Large chunks of wood tend to go everywhere, small and thin pieces, burried in epoxy tend to be quite stable.

Oh, and about the girls: I was talking about FL girls, not CA girls.

With California girls I think: "and where do YOU have a piercing?"
With Florida girls I just think of the "Golden Girls"... (I probably have been in the wrong place... Is Ft Lauderdale the wrong place?)

[CatBuilder]

Great post, Herman. Both educational *and* entertaining! :D

We do insulate buildings, but those are new buildings. The rent on those is much more expensive. I am looking at buildings from the 1940's, 1970's, etc... Many are metal buildings without much insulation.

The type of construction is not cold molded or anything with little pieces of wood. It large, scarfed pieces of thin plywood the size of half a hull which are then vacuum bagged, stitch and glued at the keel, bent into shape using a deck jig and so on. Deckhouse and decks are normal cored construction. Mostly, there is a lot of plywood and a lot of coating plywood with epoxy. There is also fiberglass on the outside of the hulls.

Herman, I'm afraid it may have been some years since your trip to the States. Now, ALL the girls have too many tattoos and piercings. Half the female population looks and acts like Amy Winehouse! They are good for a quick bit of fun, but you wouldn't want to spend any great length of time with them. Thankfully, I'm already married. ha ha ha :D

All in all, it sounds like as an amateur, I might be better of with more climate control. Maybe this will help me focus on some of the other problems at hand without other worries?



Some practical stuff:

Your rent is slightly cheaper than here. Heating however, sounds expensive to me. Do you guys insulate buildings?

Here R=3 is the norm, but preferably better. You could opt for a bunch of bubble wrap film, and create a tent. No idea of the size of what you will be able to rent.

Problems with shrinking wood are also depending on building method used. Large chunks of wood tend to go everywhere, small and thin pieces, burried in epoxy tend to be quite stable.

Oh, and about the girls: I was talking about FL girls, not CA girls.

With California girls I think: "and where do YOU have a piercing?"
With Florida girls I just think of the "Golden Girls"... (I probably have been in the wrong place... Is Ft Lauderdale the wrong place?)

[Herman]

Then try and build a tent in the old building. One of my clients bought a pile of scaffolding, the stuff where warehouses park their pallets in. He set them up around the place where the boat will be erected, with some wood and EPS foam insulated the back, and with large width sheet (agricultural) covering the whole lot, creating a tent. With a water heating system (radiators) he could reach 50 degrees C (some 125 F ??) easily. On top of that, you can create working space easily (some horizontals on working height) and you have space for your stock. Over here there are several companies doing second hand material like that, for very little cost (I buy with them regularly).

[hoytedow]

Nowadays they(the girls) remind me of shower curtains, they have so many "grommets" or other apertures.

[CatBuilder]

Digging this thread back up...

My building options (renting a building) have started to fall through up north. :(

One building had a neighbor or co-tenant. This person stores wood in the warehouse next to where I was going to build. They would not allow the building owner to locate a boat building project next to their precious wood piles. So.. that is out.

Next, I have a space that is 27' x 60' to build a 25' x 45' catamaran in. Very tight, but doable. However, one entire side of the building needs to be torn down to remove the catamaran. Also, when pulling the catamaran out of this open wall, there isn't enough space between the building and a fence. The fence (which belongs to another property owner) will have to come down and some bushes need to be cut down as well. For this project, there are electricians to hire, building fabricators to hire, fence company and then to move the boat over to the water by hydraulic trailer, then hire a crane to put it in. Rent? $1000-$1200/mo.

In FL? Build in a tent right at the water's edge with a travelift of the appropriate size right there in the yard with me. Rent? $0/mo

It almost seems that it would be cheaper to buy and run air conditioners in FL. I'd have to pay for $5000/yr in heat up north anyway on top of all that other stuff.

So FL guys... what does it cost to cool a 30' x 60' fabric building down there? How much a month? Also, what size air conditioner would you need? I'm thinking if I just run a big AC unit in the tent, I can take care of humidity AND temperature issues at the same time. Is that doable?

I will wait to see what the cost is for all those complexities with my last building up north before I start to seriously consider FL at the end of the week. Any tips on FL building in a tent with AC would be very helpful. I guess that goes into my other thread, but these two threads seem to have crossed a bit.

[apex1]

I guess that goes into my other thread, but these two threads seem to have crossed a bit.

Unfortunately that is tooo true. (and really annoying)


I say it again, no matter how many members may contradict, there are more than enough builders in FL doing exactly what you are planning. And they earn a living with it. Many of them do not run a AC unit in their shops.
Ask there how they handle the moisture issue, it is NOT that big problem!

Regards
Richard

[hoytedow]

Lack of insulation means ac works harder and longer. 20' x 50' insulated cinder block home in central Florida cools for about $100 to $120 per month during the hottest months. Probably double that for tent. Bear in mind, you only need A/C just days before, during and after laying on resin.

[CatBuilder]

Unfortunately that is tooo true. (and really annoying)


I say it again, no matter how many members may contradict, there are more than enough builders in FL doing exactly what you are planning. And they earn a living with it. Many of them do not run a AC unit in their shops.
Ask there how they handle the moisture issue, it is NOT that big problem!

Regards
Richard


It sure would save us a fortune to build there. It would be like getting free rigging or free engines!

I agree, it is a problem that can be overcome, just like building in sub zero temperatures in the north.

Only problem is I will be away from the wife since she is confined to working up north during the build. This is one of the major issues, but it may be necessary to build in FL because it is so much less expensive.

Sorry about the annoying thread crossing. I have a small forum also and it is very difficult to keep it from happening sometimes... but I feel the pain.

[hoytedow]

Many boatbuilders just work in big warehouse type buildings with good ventilation. Humidity has less effect during hottest time of day in sunny weather.

[CatBuilder]

Lack of insulation means ac works harder and longer. 20' x 50' insulated cinder block home in central Florida cools for about $100 to $120 per month during the hottest months. Probably double that for tent. Bear in mind, you only need A/C just days before, during and after laying on resin.

Wow! That's nothing compared to the cost of heat up north! I was estimating a similar cost, but I thought my understanding of air conditioning expenses was somehow off. I used BTUs and cost of electricity in FL.

I will glady pay for double that price to have a comfortable and dry working environment all year round, allowing me to be more productive as well. Thank you for the real figures here!

Now are you talking about temperatures and humidity in northern FL or down south, where paradoxically it is cooler in the summer (but where there are more hurricanes)?

[hoytedow]

I am talking about 25 miles northeast of Tampa in central Florida, home to many snow birds between October and April. December through February are our driest months when humidity is lower and fire danger is higher. Google Florida climate map.

[hoytedow]

In 2004 the eyes of 3 hurricanes came within 70 miles of my house. Check the trails.

[CatBuilder]

Thanks, Hoyt. My spot is a little further north (and east) of your area, though I did look a lot in Tarpon Springs. I have a spot up the river from Jacksonville. Fairly similar climate, I'm sure.

Thank you very much for all of this information. If I can make it through the hurricanes in a tent, it sounds like it might be a good place to build when looking at the alternatives up here.

[hoytedow]

We usually only get hurricanes between June and December.:P :D :rolleyes: :eek:

[CatBuilder]

I'm terrified of losing my boat to those things! ha ha ha

I guess maybe some build insurance might be the recipe to help ease those fears some.

[Charly]

Cat Builder,
When do you plan to start? If you are like me, shoot for the beginning of Hot humid weather (about now), that way, when you actually do get started, it will be cool and dry:)

I live about an hour north of Jax. In May, it gets STANKIN hot with drenching humidity, and continues until mid October. then it is real nice for the rest of the time.

Pesonally, I like the great oudoors. Fumes and dust will kill you in an enclosed space. Keep your stuff in hot boxes till you are ready to use it. build some air-tight containers out of osb, and put a light bulb inside. The heat from the bulb will run the humidity out, kind of like a "crisper" in a galley cabinet.

I may try a variation of that with the cylinder mould... by going ahead and placing the ply on the forms, so it will get "used to the shape", and maybe running some christmas lights or something underneath... until I get ready to wet it all out and bag it.

I am doing all this under my house, in my enongated garage. IT IS tight, but heck, its free, and it is an easy commute:)

[WestVanHan]

I used to be in the greenhouse business.

Build a hoop house:
-drive in pipes/spikes on measured intervals,install poly piping by fitting over opposing spikes to make large spans.Tie these together at the peak and maybe once down each side,and base, with 1x4's and U shaped piping brackets.
-install double layered poly,inflated to a 6-8" depth between layers, with a fractional hp blower.
-air layer acts as insulation,with small built in venting to get some air exchange,heat gain is carried out.A white tarp over the top will reflect most of the light as well.

Don't know prices of stuff,but a building the size you need was quite cheap in the day.Basically a bunch of poly pipe,and plastic.

When you're done,sell the "greenhouse"

[WestVanHan]

Quick figure:

40 x 60 with half cylindrical structure-20' peak:

-hoops would be 62',so 3 x 20' (close enough) piping welded together. 10' centres and end pieces so 7 x 3= 21 pieces of 20' pvc pipe or thin wall electrical conduit.
-14x 2 or3' long spikes
-plastic circumf. would be 63'(or 60') x 60,2 layers so 7200 ft2.Can weld/tape smaller sections together,then tape/weld to make one big bag.Staple through slats to base 1x4 or whatever baseboard you use.


So price out:
- 420' of 1" (maybe 3/4-no snow in FLA) ID pvc pipe/conduit
-7200 square feet of poly (4 mil should be good enough)
-bunch of cheap white tarps for reflection and to protect the skin.
-45' of rebar for spikes
-300' of cheap 1x4 or 1x3
-300-400' of cheap rope to hold tarps on.
Blower-cheap

Could cut back on wood,no snow load

[CatBuilder]

Thank you for the hoop house ideas. However, I already have a fabric building quoted, pending an order from these guys:

http://www.teksupply.com/farm/supplies/home

It's basically the same thing you are describing, just a ready made kit and galvanized arches.

A couple more questions about the FL sun and heat:

1) You say get a white, reflective plastic. My supplier is selling me a black plastic. According to them, the white allows too much infrared through and actually makes it hotter inside than the black plastic which blocks all light. Any input to this from WestVanHan or any of the FL guys?

2) How big of an AC do I need (in tonnes or BTU) to cool a 60 x 30 tent with arches like described in WestVanHan's post?

[hoytedow]

You need white opaque, not translucent cloth. Or you can put a double roof on with an air space. That will provide a cooling space like campers' tents have. Black will get very hot inside unless there is a white upper surface.

[hoytedow]

Call these people for a/c. :
http://www.serviceexperts.com/Locations/FL/Air_Engineers_Jacksonville_FL_32246_(1).aspx

[WestVanHan]

You need white opaque, not translucent cloth. Or you can put a double roof on with an air space. That will provide a cooling space like campers' tents have. Black will get very hot inside unless there is a white upper surface.

Hoyts right but the inflated double layer I prescribed does the job of his double roof.
Air=insulation
The white tarps are opaque....

AC-I have no idea. Vents will be at the top of the arch,with an exhaust fan.
Close off both ends as well

At 60x40 (20 ft at peak) you're looking at.......... rough estimate.........38,000 cu ft total.

Something like this http://www.robert-bedard.com/ghouse/

Oh...and that "black plastic" they're selling you is called shade cloth. Google it.
If it were me,I'd throw on cheap tarps over the top half,and drape shade cloth on that for good measure

Basics:

http://www.robert-bedard.com/ghouse/

[hoytedow]

You only need to double tarp the sides hit by the sun. North side should not need it. If you have large trees near to the south they will also help cool.