Fiberglass tips--Help/Technique

[jferraro17]

Okay, I feel like I'm spinning my wheels and need some help.

I've attached the tips to the rudder top, VS and Elevators. The aluminum had some residual pillowing from the initial construction (the lead weight wrap-around parts, and the open ended tip ribs), so I need to do some filling.

I'm using West Systems, including their micro/filler. My plan was a couple of layers of filler (sanded in between), then a layer of glass over the seam, then a layer of Super Fil or Rage Gold.

The problem I'm having is, when I sand, in an attempt to keep the shape formed properly, I sand away nearly all the filler. Or in the case of the glass layer, some of the cloth. I would describe the look as "scalloped" with a combination of gelcoat, aluminum and filler all following the shape of the pillowing. The VS turned out the best, as there seemed to be a pretty good alum-plastic transition to start with. The others, not so much. I don't understand how to get the finished shape I'm after...a nice smooth transition that when primed/painted won't show the line between the two materials.

I'm using a foam sanding block of various grit & and a square palm sander, should I use a more solid block? How about an orbital?

I'll try to get some pics posted in the mean time, but if my description sounds familiar, please help.

Very frustrating, so any tips appreciated!

Joe

[RV8TOR]

Joe, I filled in the rivets as well and smoothed the area about 2 inches inboard from the tip. Then I went back and redefined the gap line between the two so there would not be an opportunity for cracking later.

[jferraro17]

Charlie--

I'll give you a call tomorrow eve...around 6:30/7?

Joe

[RV8TOR]

Joe, my son has a Boy Scout meeting tomorrow at 7:00. Give me a call anytime before then or after 9:00. You are welcome to come over and take a look if you would like.

thanks

[adburhoe]

I would suggest ditching your power tools. They work for some folks, but not for me. For rough shaping, I start with 36 grit sandpaper, then 80 or 100. Get youself multiple sizes of flat wood. Use doublesided tape or spray adhesive to make a sanding block. In my shop I have everything from tounge depressors, to 2x4's with sandpaper around them. Use wood dowels or anything round to help make concave shapes. You'll be suprised at how quickly the material peels off with the 36 grit, and with this method you'll be evaluating the shape of your workpiece with every stroke. Foam blocks are OK for finishing, after the shape is mostly the way you want it.

Enjoy. Aaron

[DanH]

Listen to Aaron. Use hard blocks.

The goal is to develop a flat surface (flat as in "not wavy") while working across materials with different sanding properties. You only want to cut the high spots. That can't happen with a foam block, which follows every surface ripple. The ripples get worse and worse because the soft materials sand away faster than the hard materials. A hard block bridges the low spots and only cuts the high spots.

Using "a couple of layers of filler" tends to make the problem worse. Unless you're fanatical about measuring ingredients, it is hard to mix multiple batches of epoxy/micro and expect them to all have the same sanding density. Plus you need to roughen the surface everywhere to add the next layer...including the low spots, which is counterproductive. Mix one batch, lay it on thick, sand once.

I'd suggest you sand off everything you have on there now, except for what is down in the crack between the aluminum and the tip. Sand off the white gel coat in the bond areas too. Lay your glass fabric, then fill. Filler belongs on top of the fabric, not under it.

[szicree]

The previous posts are right on target. If I could emphasize one more thing it would be to use coarse paper like 40 for shaping. The whole idea is to cut off the high spots. A common mistake is to try to make it all buttery smooth by using a fine grit. All that happens is that the paper glides over whatever crummy contour you have and just makes it smooth.

Find a good sanding board and use 40 grit. Once it's nice and fair from the 40 grit, you can squeegee on a layer of micro and then sand with some 80 grit. This is about as fine as you need to go, as the rest can be done with high build primer.