#284115 - 03/30/17 08:08 PM
Re: Using a lens to start a fire
[Re: Roarmeister]
|
Geezer in Chief
Geezer
Registered: 08/26/06
Posts: 7705
Loc: southern Cal
|
Actually, a hand lens for starting fire is not a prominent part of my plans. You need fairly robust sunlight to be successful, and that is not likely to be a situation where fire will be critical. Or to put it another way, when i have really needed a fire, it was after sunset, overcast, cold, etc.
Still, it is a worthwhile option, presuming one can plan ahead. It's been a long time since high school physics, but I daresay you are correct.
_________________________
Geezer in Chief
|
Top
|
|
|
|
#284116 - 03/30/17 08:57 PM
Re: Using a lens to start a fire
[Re: Roarmeister]
|
Old Hand
Registered: 08/10/06
Posts: 882
Loc: Colorado
|
I tried it last summer with a small hand lens.
Fail.
Even at 9,000' on a sunny day it failed. Atmosphere wasn't very clear due to forest fire smoke and I had difficulty holding it steady enough long enough.
More practice would be helpful I'm sure but it just doesn't seem worth the effort.
|
Top
|
|
|
|
#284117 - 03/30/17 09:28 PM
Re: Using a lens to start a fire
[Re: unimogbert]
|
Geezer
Registered: 06/02/06
Posts: 5357
Loc: SOCAL
|
A second Bic lighter is a better back-up IMO.
|
Top
|
|
|
|
#284119 - 03/31/17 03:02 AM
Re: Using a lens to start a fire
[Re: Roarmeister]
|
Carpal Tunnel
Registered: 04/28/10
Posts: 3152
Loc: Big Sky Country
|
I keep a credit-card-sized fresnel lens in most of my kits. As hikermor points out when you most need a fire it will least likely to work but I have used them to remove splinters, read small print on medicine bottles, etc. A fresnel is great since it's light, flat, flexible and very durable.
_________________________
“I'd rather have questions that cannot be answered than answers that can't be questioned.” —Richard Feynman
|
Top
|
|
|
|
#284120 - 03/31/17 05:28 AM
Re: Using a lens to start a fire
[Re: Phaedrus]
|
Addict
Registered: 05/23/08
Posts: 477
Loc: Somerset UK
|
A short focal length/high magnification lens has the slight advantage that it needs to be closer to the tinder. In most circumstances it is easier to hold the lens steady and at a short distance than at a longer distance. The actual light gathered is indeed in proportion to the area and not the magnification.
I have started fires in very marginal conditions by use of a large Fresnel lens, the smaller credit card sized ones only work reliably in ideal conditions IME.
As has already been posted, a fire is most needed in conditions when a lens is useless. Still worth carrying though IMHO, each fire started thus is one more match left for less favourable conditions.
A large Fresnel lens, say A4 sized will start fires in unfavourable conditions and is worth stocking in a long term TEOTWAWKI kit, but is unlikely to worth carry in a backpack.
In good sunlight an A4 Fresnel lens will light a fire of large sticks without any need to procure tinder.
|
Top
|
|
|
|
#284121 - 03/31/17 12:14 PM
Re: Using a lens to start a fire
[Re: Phaedrus]
|
Carpal Tunnel
Registered: 05/05/07
Posts: 3601
Loc: Ontario, Canada
|
I keep a credit-card-sized fresnel lens in most of my kits. As hikermor points out when you most need a fire it will least likely to work but I have used them to remove splinters, read small print on medicine bottles, etc. A fresnel is great since it's light, flat, flexible and very durable. Failing eyesight is the main reason I keep one in my kits too, Phaedrus. They are fun for firecraft practice but I wouldn't want to depend on that method in an emergency. Sidenote: a Fresnel lens and a pencil sharpener are a fun way to introduce kiddos to fire-making.
Edited by bacpacjac (03/31/17 12:16 PM)
|
Top
|
|
|
|
#284122 - 03/31/17 10:06 PM
Re: Using a lens to start a fire
[Re: Roarmeister]
|
Carpal Tunnel
Registered: 11/09/06
Posts: 2847
Loc: La-USA
|
Sidenote: a Fresnel lens and a pencil sharpener are a fun way to introduce kiddos to fire-making. wink
Jacque, I just put together 4 survival themed geocaches. I never thought about a magnifying hlass but included a pencil sharpener for the enclosed pencils (graphite won't run if it gets wet) and as fire starter material.
_________________________
QMC, USCG (Ret) The best luck is what you make yourself!
|
Top
|
|
|
|
#284124 - 03/31/17 10:15 PM
Re: Using a lens to start a fire
[Re: adam2]
|
Carpal Tunnel
Registered: 05/05/07
Posts: 3601
Loc: Ontario, Canada
|
As has already been posted, a fire is most needed in conditions when a lens is useless. Still worth carrying though IMHO, each fire started thus is one more match left for less favourable conditions.
I've never thought of it that way, Adam. I like your thinking. Thanks!
|
Top
|
|
|
|
|
|
|
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
9
|
10
|
11
|
12
|
13
|
14
|
15
|
16
|
17
|
18
|
19
|
20
|
21
|
22
|
23
|
24
|
25
|
26
|
27
|
28
|
29
|
30
|
31
|
|
|
1 registered (chaosmagnet),
335
Guests and
6
Spiders online. |
Key:
Admin,
Global Mod,
Mod
|
|
|