From: Wayne Hicks Subject: COZY: Hot-Wiring Questions Date: Tue, 26 Jan 1999 15:22:28 -0500 When cutting foam cores, the plans are quite specific to (a) weight down the foam, then (b) don't move the foam block. So, does this mean to: (1) Cut over the top of the template, then cut under the template (bottom curve) without flipping over the foam block? --or-- (2) It's okay to flip over the block to cut the bottom curve as long as the block is re-weighted as before? The local builders here are differing in opinion. Those that do #1 believe that cutting the cores release some of the internal cure stresses in the foam, and it's important to cut the bottom curve in place before unweighting. (Seems awkward to me...). If you unweight, flip over, and reweight, then you're bound to end up with warped cores. Those that do #2 claim that the #1's are wearing hip waders with the wool pulled over their eyes. Any thoughts? __________________________________________ L. Wayne Hicks SpaceTec Sr. Engineer 3221 North Armistead Ave 757-865-0900 phone Hampton, VA 23666 757-865-8960 fax http://www.spacetec-inc.com From: Todd Carrico Subject: RE: COZY: Hot-Wiring Questions Date: Tue, 26 Jan 1999 13:33:09 -0800 Never having done this myself, take this with a grain of salt: 1. Weight the foam enough to keep it flat, and stationary 2. Cut the top side, and keep the off-fall. 3. Flip the off-fall over and place your fresh cut core into it. 4. Weight the foam and cut the "Bottom" Alternatly: 1. Make your top cut. 2. Glass it. And allow it to cure. 3. Using bondo and some spare 1x2s, temporarily attach the 1x2's to keep the core from flexing. 4. Turn it over and repeat on the underside. I have never done this before so don't come down too hard on me if this sounds completely stupid. Todd Carrico, MCSD Senior Consultant ARIS Corporation 972-841-0077 -----Original Message----- From: Wayne Hicks [mailto:WHicks@SPACETEC.Zeltech.com] Sent: Tuesday, January 26, 1999 2:22 PM To: Cozy Builders Subject: COZY: Hot-Wiring Questions When cutting foam cores, the plans are quite specific to (a) weight down the foam, then (b) don't move the foam block. So, does this mean to: (1) Cut over the top of the template, then cut under the template (bottom curve) without flipping over the foam block? --or-- (2) It's okay to flip over the block to cut the bottom curve as long as the block is re-weighted as before? The local builders here are differing in opinion. Those that do #1 believe that cutting the cores release some of the internal cure stresses in the foam, and it's important to cut the bottom curve in place before unweighting. (Seems awkward to me...). If you unweight, flip over, and reweight, then you're bound to end up with warped cores. Those that do #2 claim that the #1's are wearing hip waders with the wool pulled over their eyes. Any thoughts? __________________________________________ L. Wayne Hicks SpaceTec Sr. Engineer 3221 North Armistead Ave 757-865-0900 phone Hampton, VA 23666 757-865-8960 fax http://www.spacetec-inc.com From: Fritzx2@aol.com Date: Tue, 26 Jan 1999 17:07:50 EST Subject: Re: COZY: Hot-Wiring Questions Wayne Hicks asks: >When cutting foam cores, the plans are quite specific to (a) weight down the >foam, then (b) don't move the foam block. >So, does this mean to: >(1) Cut over the top of the template, then cut under the template (bottom >curve) without flipping over the foam block? >--or-- >(2) It's okay to flip over the block to cut the bottom curve as long as the >block is re-weighted as before? I believe that the instructional portion of the Cozy plans specifically states that the block should NOT be moved until both the top and bottom of the core is cut. I think the reason is not because the the internal stresses being released, (although I do believe there could be internal stresses that are released when cutting but the weights and the cut off foam above the core keep the core in position until all the cuts are made, hence the need for the weights) but rather because the surface of the foam block is not going to be perfectly flat nor is the table that the foam block rests on. So, if you flip the core over between the cuts, you run the risk of twisting the core the opposite way that it was twisted (albeit slight) for the first cut. If the foam block is bent or twisted the same way for both the first cut and the second cut, (you didn't flip the block between cuts) then at the very worst you would have a core that had some banana shape or washout that you can correct when jigging. No big deal. But if you flipped the core over between the cuts, then you could, for example, possibly have positive washout on the top and negative washout on the bottom that could not BOTH be corrected by twisting the core in either direction. Same goes for any banana shape or worse yet some combination of the two. If you have a pretty flat table and both sides of the foam block are flat, then you could probably flip the block over in between cuts without having any adverse effects. Cutting the bottom of the airfoil by pulling up on the hotwire saw isn't any more difficult than pushing down on the saw when cutting the top half of the airfoil shape. Tax, tag, title and dealer options extra - your mileage may vary... :o) John Fritz fritzx2@aol.com From: cdenk@ix.netcom.com Date: Tue, 26 Jan 1999 16:18:43 -0600 (CST) Subject: RE: COZY: Hot-Wiring Questions This is the way I did it. The weight is only enough to hold in place, not enough to bend significantly. The free shape wants to be correct. You could even make 3 or 4 individual cuts if need be. The cutting position should be optimized to make cutting easier and therefore better quality. Can also hold pieces in place with nails, as long as they don't get in the way of the hot wire. > >1. Weight the foam enough to keep it flat, and stationary >2. Cut the top side, and keep the off-fall. >3. Flip the off-fall over and place your fresh cut core into it. >4. Weight the foam and cut the "Bottom" > From: Wayne Hicks Subject: RE: COZY: Hot-Wiring Questions Date: Tue, 26 Jan 1999 17:15:35 -0500 -----Original Message----- From: Bill Kastenholz [mailto:wkasty@ix.netcom.com] Sent: Tuesday, January 26, 1999 2:10 PM To: Wayne Hicks Subject: Re: COZY: Hot-Wiring Questions Wayne, I cut all of my own cores and tried both methods. I don't think flipping the cores over cause any harm. And sometimes, forcing down with the hotwire was a better situation than pulling up on the weighted cores. I am done with wings, winglets, and canard. I'm happy with them as is. Go ahead and practice cutting some pieces both ways. I didn't always have enough clearance to cut the bottom from the top side. Bill Kastenholz Wayne Hicks responds--> Yep, you bring up some good points about hotwiring logistics. As I was thinking, it would be awkward to pull up on the wire to get the bottom cut out. I've also seen what happens when you get halfway through the core only to find that your saw bone won't clear over the top of the weights. (This particular builder used water bottles, his car jack, jig saw, and tool box to weight down the foam...) Even if the cores do "spring", I've been assured that you can jig this out during the aligning process. Besides, it's not the "springy" cores that'll get you first, it's the hot wire lag, incorrectly-placed templates, and disfunctional hotwiring partners that will do you in. (HA!) Thanks for the advice! Wayne Hicks Cozy IV #678 Chapter 9 minus wheels and brakes, but going on to Chapter 10! Date: Wed, 27 Jan 1999 08:19 -0600 (CST) From: Michael Pollock Subject: RE: COZY: Hot-Wiring Questions >Wayne Hicks Hot-Wiring Questions Wayne, We completed cutting the canard and elevator cores last month and had no problem with them. They actually came out very good. We did flip the foam over during the cutting process because it was easier for us to keep the hot wire pressed firmly (but not too firmly) against the templates. We did, however, use 3M Adhesive 77 spray to stick the templates (made of 2 pieces of 7mm plywood stuck together) to the side of the cores before inserting the nails. It would not let the templates creep which really kept the cores to the correct size. Also, keep the wire as tight as possible and get the voltage across the wire proper. You can tell when the heat is right because these little spider looking webs come out of the cores with the wire. My voltage across my .032 safety wire was measured at 18 volts when cutting with a bow like Nat has in his plans set on the longest setting. The voltage across the wire was kept around 15 volts for the shortest setting of the bow. It will vary on your cutting speed, but those voltages worked well for us. Practice with your helper on your calling numbers and you will have no problem with the hot-wiring of your foam parts. Good Luck, Michael.Pollock@mci.com Flying Velocity N173DT Building Cozy MKIV #643 chapter 10 From: Wayne Hicks Subject: COZY: Suggestions for Cutting Canard Cores Date: Fri, 29 Jan 1999 09:39:06 -0500 Hey Gang! Well we took the plunge and started hot-wiring last night. Very exhilarating and not quite as scary as I imagined. I did underestimate the prep work involved (always the case, right?), and we spent about an hour practicing. I also flipped my cores. Sorry, we tried flip/no flip during practice and we found it easier to cut the cores with the help of gravity holding the wire to the templates. Some suggestions: 1. Go to the hardware store, buy a few 12-inch metal rulers and a few metal squares. Drill holes in them like you did on the templates. These make perfect straight edges for squaring and trimming the foam blocks. Get the rulers that are black with white-painted numbers and use the numbers for calling out the position of the wire. (Got this from a Long EZ builder who probably got it from the CP's...) 2. Get a clear plastic engineer's ruler, you know, the geeky looking thing that has all the parallel lines (1 mm) on it. Once you table is perfectly level and flat, it's very easy to look through the transparent ruler to set the level lines. 3. Don't be bashful about borrowing stuff from fellow builders. (Homebuilder's code......Ahhemm...) I borrowed bil kleb's templates and hotwire saw. His templates are fantastic and definitely saved a whole day's work. Thanks, bil!!! 4. We found the hotwiring to go easier when we dragged the wire along, i.e., with the 2x4 leaning 30 degrees or so in the direction of travel rather than holding the saw vertical. This helps to keep the wire from snagging. (I had NO snagging problems. Like I said, bil kleb's templates are first-rate!) __________________________________________ L. Wayne Hicks SpaceTec Sr. Engineer 3221 North Armistead Ave 757-865-0900 phone Hampton, VA 23666 757-865-8960 fax http://www.spacetec-inc.com Date: Tue, 07 Sep 1999 00:17:29 -0400 From: Rob Cherney Subject: Re: COZY: hot wire cutter At 06:33 PM 9/6/99 -0500, Paul Chumbley wrote: >Does anyone have the specs for the proper transformer / potentiometer combo >for the hot wire cutter? An old issue of Sport Aviation has a schematic >which recommends a 24v system, however the potentiometer specs do not seem >to be correct. Thanks Paul S # MK-805 Use an ordinary lamp dimmer on the transformer primary (120 V side). It works well. Rob- +------------------------------------------------------------------+ |Robert Cherney Home Phone: (410)465-5598 | |Ellicott City, Maryland e-mail: cherney@home.com | +------------------------------------------------------------------+ From: cdenk@ix.netcom.com Date: Tue, 7 Sep 1999 16:40:45 -0500 (CDT) Subject: Re: COZY: hot wire cutter For a wire about 7' long, we found about 20 volts A.C., and it seems I used a 10 amp fuse, if I accidently hit a water pipe or heating duct, since it wasn't an isolation transformer. Date: Mon, 06 Sep 1999 17:41:34 -0700 From: Eric Westland Subject: Re: COZY: hot wire cutter While I suppose one could rig up something pretty fancy, Jim White and I cut all our cores by just hooking two car battery chargers together in series. When the wire was a little too hot, we used the board with the zig-zag pattern of extra wire that I am pretty sure is shown in the plans. Eric Westland From: "Hunter Welch" Subject: Re: COZY: Quick build parts Date: Tue, 28 Sep 1999 21:50:20 -0700 -----Original Message----- From: John Slade To: Cozy builders Date: Tuesday, September 28, 1999 12:19 PM Subject: COZY: Quick build parts >John Slade wrote >I find it very useful to hear about other people's "deviations" [from plans] >but lately I only get this information privately. Publically no-one wants to >admit to changes they're making. 'Fess up people. What are you all up to? > I have a small but helpful thought for those who are coming up . I found that I could use some of the left over wing foam and by outlining a template from the large drawings of the side view of the thigh supports, I was able to hot wire a light and accurate piece. Covering with 2 layers of glass on each side, my thigh supports were complete and I can stand on them without problem. Bill W From: "John Slade" Subject: Re: COZY: Quick build parts Date: Tue, 28 Sep 1999 22:34:44 -0400 Bill, >I have a small but helpful thought for those who are coming up . I found >that I could use some of the left over wing foam and by outlining a template >from the large drawings of the side view of the thigh supports, I was able >to hot wire a light and accurate piece. I did something similar. I screwed up a couple of canard cores. Later I nails two 3/8 boards to the bench and hot wired 3/8 sheets out of the junked foam. Made all my seats and armrests that way.