QuickTalk 4 - Q-TIPS
- Category: Q-Talk Articles
- Published: Wednesday, 30 June 1982 07:11
- Written by Jim Masal
- Hits: 1607
Here's a HOT idea everyone should love. Instead of putting your hand on your canard (during post curing) and saying, "Ouch, it's hot!" or "Damn, I wonder if it's hot enough?", use a Tempil Stick. When canard reaches temperature desired, the stick will mark when scratched on the surface. Welding supply shops should have them for about $6.00 in temperatures desired. (Jim Wilker, #2294)
In the interest of attaining air foil surfaces that are smooth, correctly contoured and as light as possible, we have used the following technique on some of the components:
Rather than applying glass immediately to the slurry-covered foam core, we allow the slurry to cure. If the slurry was applied over the complete surface, then sanding does not gouge the surface. At this point, we again check the shape and contour of the part, and fill any low spots with micro. This will again be roughed up by sanding when hard. By now, we have a properly shaped core that has an airtight surface. (If you are extravagant, you can replace the sanding with peel-ply.) Next, we apply the glass and epoxy and cover the part with clear plastic (non-stick). We then further squeegee the layup to recover epoxy. It is absolutely critical that there be no pinholes in the core or the plastic sheet during cure. Air will enter the holes, leaving a very dry section in your layup. This method takes a little longer at layup time, but will save time and weight at final finishing time.
We have found that Handi-Wrap by Dow will separate easily, but Saran Wrap sticks badly and must be sanded off. Polyethylene does not stick, but it is not always transparent, which is useful to see how you are doing with air bubbles. A few other notes on this process:
a. Go back every half hour until hard to check for air causing dry patches.
b. Leave edges and cracks a little wet, so that air will not be sucked in.
c. Peel-ply can be applied before the plastic if a ready-to-bond surface is required.
d. Put some epoxy on top of the plastic so the squeegee will slide over the plastic easily.
e. Experiment with a small piece before committing yourself to a large layup.
You might call this a "poor man's vacuum bagging" process. (David Cyr, #2010)
Tailwheel vibration may be caused by the tailwheel being out of round. I put a dial indicator on mine and found that the wheel moved the indicator 0.2" plus it had lateral wobble. A competent machinist can freeze the rubber in dry ice and turn the wheel true on a lathe. (Tom Saunders, #2658)
When mounting my ailerons, I devised a gap-setting system which does away with those bothersome mixing sticks. Simply cut strips of paper about 1" wide and stack them to the proper gap thickness. Now, wrap them around the leading edge of the aileron (or rudder) and tape the ends. The idea is that no matter how you bend the stack, the thickness remains constant; thereby allowing you to position and reposition the piece several times without the bother of those mixing sticks. (Terry Hall, #196 and Ev Wieland, #126)
Sanding micro next to bare foam or any high spot next to an area you want to avoid can be done by cutting a hole of desirable size out of a manila folder, placing it over the spot to be sanded. Then sand away.
On surfaces you have not pool-plied (i.e. entire wing and canard), you can wait until the layup starts curing and is stiff but tacky, then spread on micro over laps and weave. It will all cure together with a possibly better bond and saves sanding. (Jim Masal, #457)
For a simple tie down get two of your wheel pant axle washers and trace on a piece of 1/16" stainless steel.
Make two and bend 45 degrees. The top will replace your axle bolt washer. This makes a good tie down and security point for the trailer.
A simple battery box can be made from the carton the battery came in. Cut the carton down to size (if necessary) and hold together with masking tape. Cover entire box with 2 BID. After cure, cut off top cover and pull the cardboard out (most will come). Use duct tape along top edge of this box and layup a box top, which overhangs the box sides by 1". After cure, take a knife blade and separate top and bottom. You now have a battery box, which you can mount in any location. (S. W. Hanke, #2148) /Ed. Note: Be sure to provide a battery drain tube if required and provide venting holes to prevent combustive gas formation in the box./
To turn over the wing or canard for glassing the top surface, attach a tapered 1x8 or 1x10 on the wing with bondo, 5 minute, hot glue, etc.
Install several 1x2 pieces crossways on top of the tapered boards. Level these carefully and reference one to the other for shimming, if necessary. This unit will be heavy, but solid, when you make your flip. (Bill Slattery, #2130)
After cutting UNI or BID for tapes or larger layup sheets, and before you handle them - take 1/2" masking tape and run it through your fingers 5 or 6 times. This will remove some part of the tack. (There is a masking tape for draftsman that has less tack, if you can find it.) Place the masking tape down the center of your cut tape. Make sure you don't go much more than half way. Put another piece down the other end and lap over slightly the other piece. This is to allow you something to start the peel-off. On larger pieces you can use two or more of these strips of masking tape. Roll up piece as usual. The tape will keep the shape of the piece, whatever size. When ready for use just lay it on, wet it out good and then peel off the masking tape - slowly, slowly. Pull the tape back off over itself - not up in the air, using a squeegee close to it to hold down the cloth, if necessary. Then finish wetting out the path of the masking tape. Do not try to peel off tape where it has not been wetted - again the reason for the overlap of tape somewhere in the middle of the cloth. For tapes to be laid up around a curve (i.e. firewall), put masking tape near the edge - layup on one side, wet out, remove masking tape, take cloth around curve and wet out. A perfect layup without narrow or wide places. (Bob Stillman, #2612 and David Cyr, #2010)
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