wing cutting

[steve]

i have cut a wing and held the many pieces together with urethane spray can foam. it was going to be temporary. i later came back to separate the joints and found they were for the most part stronger than the wing foam, and is that not what we are looking for ?

so i glued up lots more and tested the joints and they all worked out well.

can anyone see this as a bad thing ?

i just glued up the big wing chunks and can if need be ,hot(cough) wire them back apart:confused:

[rickh]

A few things, could be minor depnding on your view.

 

The aerosol foam may emit fumes when cut, maybe the wrong kind?

How long will the aerosol foam last over the years? Will it make a difference?

Will the aerosol foam hot wire cut the same as the extruded styro?

 

From my dinking around, the latter may be the biggest issue. Especially if on a glancing/skewed cut.

 

Rick

[Steve Innova]

Some expanded foams will damage AL parts that they are in contact with.

[steve]

A few things, could be minor depnding on your view.

 

The aerosol foam may emit fumes when cut, maybe the wrong kind?

How long will the aerosol foam last over the years? Will it make a difference?

Will the aerosol foam hot wire cut the same as the extruded styro?

 

From my dinking around, the latter may be the biggest issue. Especially if on a glancing/skewed cut.

 

Rick

they are already cut, so cutting is moot now.

i did note that crushing the glue was the key, i had to get the foam down to the gluey stage so there was no air bubbles in it.

and that was easy to do, just crush the parts together with tape pulled very hard.

[steve]

Some expanded foams will damage AL parts that they are in contact with.

i cant see that this would apply here ? am i missing something ?

[longez360]

My 5 cents:

 

I'd stick to the plans.

 

Pour foam continues to expand with elevated temperatures beyond that which it was cured. Over a large area you will get bubbles as the part is cured, and at joints you can expect lumps and bubbles as well.

 

Micro is great. Use some 5 min to tack the parts together and micro everywhere else. Never squeeze out, just use it to within an inch of the surface of the joint.

[steve]

My 5 cents:

 

I'd stick to the plans.

 

Pour foam continues to expand with elevated temperatures beyond that which it was cured. Over a large area you will get bubbles as the part is cured, and at joints you can expect lumps and bubbles as well .

i don't see how that is a issue ie. 3 seams 1/6" think under a spar tape and under a sher web? thats a little like the ant lifting a car:rolleyes:

lumps and bubble sand off (as I'm doing now) non issue.

 

Micro is great. Use some 5 min to tack the parts together and micro everywhere else. Never squeeze out, just use it to within an inch of the surface of the joint.

yes," but" ii have foam in place NOW..see post one.

 

still looking for the show stopper...........more input plz

[Marc Zeitlin]

The aerosol foam may emit fumes when cut, maybe the wrong kind?...Will the aerosol foam hot wire cut the same as the extruded styro?

No one should EVER cut urethane foam with a hot wire cutter. Doing so emits isocyanate gas, which is extremely poisonous. Scaled explicitly prohibits doing so, for exactly this reason.

 

See:

 

http://www.cdc.gov/niosh/topics/isocyanates/

 

and:

 

http://www.aircraftspruce.com/catalog/cmpages/urethanefoam.php

[rickh]

still looking for the show stopper...........more input plz

I think you're nutz

Your plane, what's the worst that'll happen?

Two crossing plies of UNI on top/bottom, plus one span wise on top.

Got insurance? Kids? Wife?

 

Rick

[steve]

I think you're nutz

so

Your plane, what's the worst that'll happen?

I'm looking for answers not your questions

Two crossing plies of UNI on top/bottom, plus one span wise on top.

so ?

Got insurance? Kids? Wife?

not yet

that was not to helpful, just weird

do we have a IMO post some where, we should, all that have a ram chair could go there and impress them selfs whilst the rest of us try to build cool planes..........more impute plz

 

 

Rick

[Spodman]

No one should EVER cut urethane foam with a hot wire cutter.

Yes. BLOCKS of foam, hot wire cutter, clouds of poison gas, birdies fall off rafters leaving beakmarks in foam, homebuilders curse birds until conciousness lost. Got insurance? Kids? Wife?

 

Don't know that a thin smear of expanding foam BETWEEN the blocks of foam is going to have that significant an effect. Expanding foam to join foam blocks is included as a builder hint in newsletter #82, but without any comment from Nat on whether he thinks it is a good idea or not. For him to publish it implies he doesn't think it dangerous, even if he doesn't endorse it. I still hear some of these names on the forums, I don't think it killed them.

10) Gluing foam blocks together. Ken Brimmer recommends using “HOT STUFF”. It is a urethane foam which adheres well. Wayne Hicks recommends using 3M Temporary Spray Adhesive, available at Home Depot, but not 3M Super77, which dissolves styrafoam. Dennis Oelman recommends using Great Stuff expanding foam sealant available at hardware stores and Home Depot.

www.cozybuilders.org/newsletters/news_82.pdf

 

I must admit I was fairly keen on the concept and was intending to use expanding foam, or maybe the foam joining stuff my intended Oz supplier uses, when I get to see it.

[steve]

good on you mate, eh spot on !

so thats where the bugger was:D

thank you spodman!

i tryed to order the 76 but no go (home depot)

and 3m site said 176.00 for a case

so the gr8 stuff is the next best thing

Dust said the 3m is cats meow

[Spodman]

After a bit of thought my only reservation is the timing. Perhaps these good people nailed their blocks together with the dowels, hotwired, then joined the CUT blocks together with the variagated substances noted. It doesn't read that way to me though.

 

On the other hand, Wayne Hicks website says he used the tempo stuff when hotwiring, and micro to permanently join:

 

http://www.maddyhome.com/canardpages/pages/waynehicks/chapter_19_2.htm

 

Let me know how you get on.

[Wayne Hicks]

If i were building wings again:

 

(1) I'd buy the bigger foam billets if I could find them.

 

(2) If I had to use the plans-sized billets, I'd join them with a thin, but structurally sound, film of TWO-PART expandable foam. Mix, apply to both billets, hold together until cured. I would hotwire the blocks outside or in a well-ventilated area with plenty of air exchange. he key is a THIN layer. Too thick a layer is subject to the expansion/contraction issues that pour foam is famous for. (Note: I didn't do this on my wings because I was too lazy to order the TWO-PART pour foam in time to hotwire my wing cores.)

 

(3) Short of #1 and #2, I'd still use the 3M temporary spray to temporarily hold the cores together for hotwiring. Astute observers will also noticed that I held the blocks together with long composite clecos (drywall screws).

 

(4) I would NEVER EVER use the one-part canned stuff -- Great Stuff, Hot Stuff, or whatever other name it's masquerading as these days. Oelmann's experience might be different from mine, or maybe they make better stuff where he lives. All I know is the stuff I got from Lowe's or Home Depot is CRAP, CRAP, CRAP. It never hardened and I would never trust it as a structural adhesive between foam blocks.

[steve]

If i were building wings again:

 

(1) I'd buy the bigger foam billets if I could find them.

 

(2) If I had to use the plans-sized billets, I'd join them with a thin, but structurally sound, film of TWO-PART expandable foam. Mix, apply to both billets, hold together until cured. I would hotwire the blocks outside or in a well-ventilated area with plenty of air exchange. he key is a THIN layer. Too thick a layer is subject to the expansion/contraction issues that pour foam is famous for. (Note: I didn't do this on my wings because I was too lazy to order the TWO-PART pour foam in time to hotwire my wing cores.)

 

(3) Short of #1 and #2, I'd still use the 3M temporary spray to temporarily hold the cores together for hotwiring. Astute observers will also noticed that I held the blocks together with long composite clecos (drywall screws).

 

(4) I would NEVER EVER use the one-part canned stuff -- Great Stuff, Hot Stuff, or whatever other name it's masquerading as these days. Oelmann's experience might be different from mine, or maybe they make better stuff where he lives. All I know is the stuff I got from Lowe's or Home Depot is CRAP, CRAP, CRAP. It never hardened and I would never trust it as a structural adhesive between foam blocks.

i had the same thing happen in 05, but found out the foam was low expansion foam for windows and doors. the stuff i use is for cracks. and you are right..thin is the key

[Marc Zeitlin]

... HOT STUFF...

Hot Stuff is a Cyanoacrylate instant glue, not urethane, whatever Ken Brimmer or Nat Puffer might think.

[steve]

your right, again:p

hot stuff is not grate stuff

hot stuff is 15.oo a oz (balsa planes)

grate stuff is 4.00 a can( house insulation)

 

has any one hot wired into hotstuff ?

[Steve Innova]

All I know is the stuff I got from Lowe's or Home Depot is CRAP, CRAP, CRAP. It never hardened and I would never trust it as a structural adhesive between foam blocks.

It requires moisture to set. Mist the parts & glue joint lightly with water (use a spray bottle) and you'll have no problems.