How many BTUs of heating for 37' sloop?

[hpeer]

Just saw this portable unit.

No idea of price but may be just the ticket for you.

A portable diesel heater.

https://planarheaters.com/product/po...-planar-2d-12/

[hpeer]

Here is a better site for info on the Planar heater.

Lots more info here.

https://autoterm.com/air-heaters-overview

[thinwater]

Originally Posted by PaintedKite

Hello! My wife & I will live aboard our Dufour 382 in Annapolis for the second half of October and then sail south to FL in Nov/Dec. We will definitely need some heating, especially while in the northern latitudes.

It's been recommended to us to buy one of those plug-in, oil-filled heaters. (They look like small radiators.) The question is, "How many BTUs to buy?" I see 700W units for $50 and 1500W units for around $90. Those seem to be the primary choices.

The boat's got a very large interior for a 37-footer, and we will sleep in the forward V-berth. There's no insulation.

Is 700W enough?

Calculate.

How great a delta T (inside temp minus outside temp) will the 1500 W heater maintain at night? 1500 W = 5100 BTU. How great a delta T will you need (70-coldest night)? do the ratio and you will know how many BTUs you need to keep steady. You may want more for warm-up speed and wind (more drafts on windy nights).

While you are at it, consider all drafts and consider adding storm windows (double glazing) or insulated window covers. Carpet helps. A blanket over the companionway hatch helps.

Yup, this is when cored construction shines.

[donradcliffe]

Please put a CO alarm near the Buddy, and leave a hatch cracked open.

[Bill O]

Originally Posted by thinwater

Yup, this is when cored construction shines.

Just a curiosity question of what is repeated over and over, but never seen any R rating for a cored hull. (an R value of 5-6 is what I've seen claimed)

Yes, by observation the cored hull sections usually don't sweat, but has anyone confirmed (w/data) there really is an R value to a cored hull?

[GordMay]

Originally Posted by Bill O

Just a curiosity question of what is repeated over and over, but never seen any R rating for a cored hull. (an R value of 5-6 is what I've seen claimed)
Yes, by observation the cored hull sections usually don't sweat, but has anyone confirmed (w/data) there really is an R value to a cored hull?

Yes, a cored hull will have "some" appreciable R-Value. R-5 to R-6 seems approximately reasonable, depending upon core material & thickness, IMO. Solid fiberglass has an R-value on the order of R-0.4. (per inch thickness).

A well adhered installation of Armaflex type insulation, above the water line, should result in a warmer boat (or cooler), with reduced condensation.

The effectiveness of insulation is commonly stated in terms of its R-value, defined as
R = Delta T/Q
where Delta T is the difference in temperature between the inside and outside, and Q is the rate of heat flow through the wall.
The amount of heat lost is inversely proportional to the R-value.

[Bill O]

Originally Posted by GordMay

Yes, a cored hull will have "some" appreciable R-Value. R-5 to R-6 seems approximately reasonable, depending upon core material & thickness, IMO. Solid fiberglass has an R-value on the order of R-0.4. (per inch thickness).

A well adhered installation of Armaflex type insulation, above the water line, should result in a warmer boat (or cooler), with reduced condensation.

The effectiveness of insulation is commonly stated in terms of its R-value, defined as
R = Delta T/Q
where Delta T is the difference in temperature between the inside and outside, and Q is the rate of heat flow through the wall.
The amount of heat lost is inversely proportional to the R-value.

Gord,
Don't disagree w/anything you wrote except wanted to see some real (not just assumed) scientific data measuring the cored hull R value. Is it really out there?

[dannc]

Originally Posted by Bill O

Gord,
Don't disagree w/anything you wrote except wanted to see some real (not just assumed) scientific data measuring the cored hull R value. Is it really out there?

The best number I have ever come up with, for better or worse, is that rigid foam insulation used in house construction is rate for around R4-5 PER INCH.

Or roughly R1 per 1/4 inch.

How thick is the the coring in a cored hull? Any way I can see, the R value is not much in a cored hull.

Later,
Dan

[LouK]

Let's take a second look here. Not sure where you're parked in Annapolis but at the mom & pop marina where I keep my boat in Eastport, each slip has a power box with 1@30A , 1@50A in addition to a standard 110 volt outlet. A previous poster implied you won't get a full 30A shore power outlet to run two 1500w resistance heaters even though 1500w/110 VAC = 27 A. My suggestion is that you might do well to look around at other marinas in the area.

I spend a winter aboard a 40' sloop in New England twenty years ago & I know what a bear it is to stay warm (nothing more disappointing than having to shovel snow out of your cockpit). Heed well the comments regarding condensation; cracking the cockpit hatch was insufficient to prevent condensation but at least I didn't asphyxiate. Again, if you buy any kind of diesel or LP heater go large or don't go. I purchased the largest Dickinson available at the time; it kept me quite toasty almost to the end of November....

[GordMay]

Originally Posted by Bill O

Gord,
Don't disagree w/anything you wrote except wanted to see some real (not just assumed) scientific data measuring the cored hull R value. Is it really out there?

OK, you want me to tell you everything.
Would that be everything:
I know,
there is to know,
or
about your specific boat?


The most popular core materials are balsa, PVC cross-link foam (Klegecell, & Divinycell), and PVC linear foam (Airex & maybe Core-Cell).
End-grained balsa has a relatively poor thermal resistance (R-value) of 2.4, while the aged R-value of 2 lb/ft3 polyisocyanurate is closer to 4.5 to 5.4.
➥ https://www.dyplastcomposites.com/im...Composites.pdf

End grain Balsa has an R-vale of 2.3 per inch. ➥ https://www.fibreglast.com/product/e..._Sandwich_Core
Divinycell has an R-value of 6.0 (1")
➥ MatWeb - The Online Materials Information Resource
Klegell has an R-vale of ±7.0 (1")
➥ https://digital.library.unt.edu/ark:...metadc1212414/

So, I’d GUESS that a boat cabin about 24 Ft long x 8 Ft wide x 6 Ft high, with a cored hull, MIGHT require on the order of ABOUT ±12,000 BTU/hr or 3,500 Watts for a 25 deg. F rise.

See also ➥ https://www.cruisersforum.com/forums...ing-11920.html