Hi Chris:
Where did you get your aluminum sanding block & the ultra fine grit self adhesive sandpaper?
I'm having a hard time finding them locally.
On another issue:
I'm a retired electro-mechanical engineer. I've used all kinds of tapes, adhesives and insulating materials.
You might want to reconsider your use of (plastic) electrical tape on engine holders. It's adhesive allows creep and softens up under high heat. The tape also stretches. It's designed this way to allow it to conform to irregular surfaces and allow for future removal when changing electrical connections - not a good match for engine holders.
As you know, masking tape ages badly, gets brittle, loosens and tears. Not a good match either.
Earlier, I used masking tape but I sealed the edges with white glue. This helped a little.
Instead, give Kapton tape a try. It's what I use. It is high heat, has no creep and doesn't stretch. It's expensive, but at just a few inches per rocket, it doesn't cost much in that sense. Just goggle Kapton tape for sources. Let me know what you think.
Gary Minton
My response:
Hi Gary,
I got my Great Planes Easy touch Hand Sander from Hobbylinc: CLICK HERE
The finest grit they make for the hand sander is 220.
You can cut pieces of 400 grit and spray the back with spray adhesive.
Thanks for the tip about the Kapton tape. I'll have to check that out.
I use ST-7 tubing for engine mounts, it's thicker than a BT-20 and probably gives a little more insulation from the engine heat.
I never use making tape for engine hook retention anymore after cutting open a model that was a few years old. The old tape just flaked off!
I am aware of the electrical tape shrinking and the effects of heat on the tape.
I always do a 1 1/2 wrap over the engine hook. That puts two full wraps of tape on the hook.
Right now all my engine mounts are holding up pretty good with the black electrical tape.
I'll check into the Kapton tapes. I checked a website and they are good up to 500 degrees!
http://www.kaptontape.com/1_Mil_Kapton_Tapes.php
Pretty impressive.
Chris Michielssen
www.oddlrockets.com
www.modelrocketbuilding.blogspot.com
www.oddlrockets.com
www.modelrocketbuilding.blogspot.com
Why on Earth would you use tape at all? I coat an inch-wide strip of copier paper with yellow glue and wrap three to five thicknesses around the tube and engine hook. The yellow glue pulls the paper tight around the tube and seems to do a very good job of hook retention.
ReplyDeleteHi Chris,
DeleteIt's just the way I do it, no other explanation. I've also used 110 lb. card stock over the engine mount tube and hook. It depends on my mood and the rocket. You do what works for you.
It's just another option suggested by a reader of the blog.
I won't use masking tape again after seeing how it deteriorates.
I do it too, but won't paper and glue degrade in the same way masking tape does?
DeleteI mean like exactly the same way...
One the few models I've cut apart (after many flights and not worth repairing anymore) the tubes and glue joints were very strong. The masking tape wrap around the engine hook was never in very good shape.
DeleteI think paper and glue last much longer than masking tape would.
Looks like some good prices on Kapton tape on eBay. Even if you check North America only (the really cheap stuff labeled "KOPTAN" from China may be perfectly good, but who knows) I see for instance 20 mm x 100 ft (love the mixed units) at $5.49 shipped.
ReplyDeleteI bought the 30 mm (about a 1 1/4 inch) wide by 100ft for 5.98 shipped. Mine said Kapton tape and had a tone of buys with really positive reviews, so I expect it's legit - I guess well see.
ReplyDeleteSomeone in a decade please remind me to cut open one of my rockets so I can see how the tape performed.
I just hope I can remember which one has the fancy tape installed in it…
I just put in a calander reminder to check on the tape. now I just need to hope Outlook is still around in a decade.
DeleteI'll be the first one to email you in ten years. The calendar is marked!
DeleteThe Kapton tape comes in various thicknesses, from 1 to 5 mils. What thickness has Gary been using or what is the minimum thickness to ensure a quality build?
ReplyDeleteHi Andy,
DeleteI wouldn't know! Masking tape looks to be about 1 to 2 mils thickness.
I would gauge it that way. Again a guess on my part.