Dew heaters

[emyliano2000]

Hi guys.

I just received the kendrick 8" primary mirror heater and the dewzapper split heater for the secondary mirror and I was wondering if you would know what to use to stick them to the mirrors. I wouldn't wanna use something that is inappropriate for it considering the heaters are gonna be warm.

Thanks

Emil

[NigeB]

Hi Emil

The dew heaters are attached to a large heat sink (your mirrors) so I would not be worried about them getting overly warm (even on full power, my heaters feel barely warm to the touch because they're attached to a big cold lump of metal and glass which soaks away the heat).

In my view a more significant consideration is the longevity of the adhesive on the tape, which can "let go" if subjected to damp conditions over a period of time. I've had good success with this type of stuff:

https://www.amazon.co.uk/Roll-Aluminium-Insulation-Bright-Silver/dp/B0153IC8L2/ref=sr_1_3?ie=UTF8&qid=1481670578&sr=8-3&keywords=aluminium+tape

(similar to car exhaust tape). I use this not because of its thermal properties, but because the adhesive on the tape is really strong, and it provides a good, long-life, moisture-resistant fix. But you definitely don't want this to get anywhere near the optical surfaces!

Nigel

[emyliano2000]

41 minutes ago, NigeB said:

longevity of the adhesive

On the kendrick website it advises to use silicone caulk. What is that?

 

43 minutes ago, NigeB said:

I've had good success with this type of stuff:

Does this tape go over the heater? How do you fix the heater with it?

[NigeB]

12 minutes ago, emyliano2000 said:

On the kendrick website it advises to use silicone caulk. What is that?

 

Does this tape go over the heater? How do you fix the heater with it?

Silicone sealant - the sort of stuff you can seal window frames with. If you're going that route, use one rated for exterior use - the interior sealant is less able to deal with very low temperatures and can degrade over time. E.g.

 

https://www.amazon.co.uk/Evo-Stik-483422-290ml-Multi-Purpose-Silicone/dp/B0041WB7G4/ref=sr_1_3?s=diy&ie=UTF8&qid=1481674163&sr=1-3&keywords=exterior+silicone+sealant

 

Regarding the Al tape - for narrow heaters I cover the entire heater strip with it and stick down on either side. For large areas, I use the tape to stick down around the edge. 

[emyliano2000]

2 minutes ago, NigeB said:

Silicone sealant

? I know what that is, I just thought the silicone caulk is something else. I know the decorators use caulk and I thought the silicone caulk might be some kind of silicone mixt with decorator's caulk ?

[emyliano2000]

21 minutes ago, NigeB said:

Silicone sealant

The other thing is that I painted the back of the mirrors with blackboard paint. Will that affect the adhesion in any way?

[NigeB]

7 minutes ago, emyliano2000 said:

The other thing is that I painted the back of the mirrors with blackboard paint. Will that affect the adhesion in any way?

Should be ok; I think the silicone, or the tape, should stick to the paint (take note of any directions regarding minimum temperature at time of application). The bond will only be as strong as the weakest link, which is probably the paint-mirror interface. If it flakes, just clean off the tape and the mirror back and re-stick on a clean glass surface.

[emyliano2000]

Thanks Nigel.

[N3ptune]

I have this solution also.. which is a non invasive way to hold a primary heater onto the primary mirror.

Inside the bathing cap there is a small pillow of bubble wrap to push on the foam which is pushing on the heater.

http://imgur.com/SaUX4Tt

http://imgur.com/F0TqhdU

http://imgur.com/JBbNlxw

http://imgur.com/30jbWgY

The final image, the whole assembly with a simple strap around the bathing cap, to keep it in place.

http://imgur.com/hDB14YB

It's working quite well so far for really cold days.