randylervold

randylervold

moderator
Fiberglass gurus,

After trying to get the metal skirt to fit on my RV-3 I'm giving up -- I'm convinced God just didn't intend aluminum to be used for compound curves, fiberglass on the other hand is perfectly suited for that. No worries with laying it up and such (West Systems and 9 oz crowfoot e-glass), but what I'd appreciate are some ideas on are how to craft a molding surface. I will pop rivet my tipover plexi bubble to the frame in every other hole, which I will later drill out, so there won't need to be an clecos and thus I can layup onto the plexi. But what do I use to create a form from the plexi down to the fuselage, or to bridge the gap along the sides? This is way too much area for the traditional modeling clay we use for intersection fairings.

If I use any sort of tape it will create an uneven layup and require lots of sanding and filling, something I'd rather avoid. I was thinking of using expandable foam around the front and rear sections (won't work on the sides) and then sculpting it. Seems like I heard that the cans of foam you can buy at Home Depot aren't good because they contain formaldehyde, not sure why that's bad though.
Spruce has Poly-Cell 100 Polyurethane Foam
http://www.aircraftspruce.com/catalog/cmpages/polycel.php
and Liquid "X30" Foam
http://www.aircraftspruce.com/catalog/cmpages/x30foam.php

Anyone had an experience with either of these? When using foam, do you lay up directly on it, or coat it with something first?

And lastly, what would be a good way to create a surface on the sides? Here's a pic of what I'm dealing with...
http://www.romeolima.com/RV3works/Gallery/DSC_0899.jpg

Thanks!
 
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I considered this while making mine, but chickened out. I did destroy one skirt before I got the hang of things, however. I think the RC model crowd and the EZ crowd would be the guys to ask about your situation. I'll bet this is child's play to those guys. My feeling is that using glass is actually a much better way to achieve a good looking skirt, but wouldn't know how to go about it. Good luck and keep us posted.
 
canopy skirts

Randy
The guys @ www.showplanes.com are the experts. Lots of good pics on thier website.. They do the fastback mod for the RV8. Doubt if they'd do it for you but they can tell you how to do it for sure. They're down in Medford Oregon KMFR. Heard nothing but good things about them.
I did mine using 5 seperate pieces of aluminum. It staks up with the best. If you're interested in sticking with metal let me know and I'll take some pictures for you and try to explain it. It was not that big of a deal. Honest.
You will need a metal shrinker/stretcher tho.
Tom
RV3
 
InstaFoam

Randy,

The foam you want to use is InstaFoam

http://www.wicksaircraft.com/catalog/product_cat.php/subid=5830/index.html

You should mask the undersurface with 1 layer masking tape with one layer of clear 3M packing (shipping) tape on top of that. The clear shipping tape is the best release material.
Once you get the shape you want, cover the Instafoam with the clear tape. Then layup 6-8 layers of 8oz BID or carbon.
After it has cured, you should be able to pop it off by gently lifting the masking tape. Then separate the frame/skirt from the foam.

Greg Piney
RV-8 Soontobe
Setting up Shop
Tools Purchased
 
Question on InstaFoam

gpiney said:
Randy, The foam you want to use is InstaFoam
http://www.wicksaircraft.com/catalog/product_cat.php/subid=5830/index.html
You should mask the under surface with 1 layer masking tape with one layer of clear 3M packing (shipping) tape on top of that. The clear shipping tape is the best release material. Once you get the shape you want, cover the Instafoam with the clear tape. Then layup 6-8 layers of 8oz BID or carbon.
After it has cured, you should be able to pop it off by gently lifting the masking tape. Then separate the frame/skirt from the foam. Greg Piney RV-8
Click to expand...
Greg can the foam hold the vertical. You mix, it starts to expand how do you get it on the piece to work with. It seems if its too liquid it will just drip off the vertical. If its sets-up, it will set and attach to the workpiece?

Second after you have the shape to glass, you say use clear packing tape. I am guessing the tape sticks to the foam well?

In my mind I am guessing its like shaving cream and will stick till set. The description says you can work it like wood after set. Cool

Thanks George
 
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gmcjetpilot said:
Greg can the foam hold the vertical. You mix, it starts to expand how do you get it on the piece to work with. It seems if its too liquid it will just drip off the vertical. If its sets-up, it will set and attach to the workpiece?

Second after you have the shape to glass, you say use clear packing tape. I am guessing the tape sticks to the foam well?

In my mind I am guessing its like shaving cream and will stick till set. The description says you can work it like wood after set. Cool

Thanks George
Click to expand...


George,

Good question. I forgot that the area is near vertical. You will need to fabricate a small trough to catch it. The trough should look something like " |/ " where the red is the canopy and the blue is the trough. It can be a 2-3" wide section of posterboard sealed with packing tape and just taped on. Pour the instafoam on just above (1/2") the top line you want to fill. You will have to work fast. The time from mix to pour is about 2 minutes. You can do a bunch of small batches. Remember, you do not need to "fill it up" with liquid. InstaFoam expands 40 times the liquid volume. You will only need to coat the area
with liquid.

The packing tape is a release material. It will not stick well to the instafoam. It does stick well to itself. Make few horizontal 'bands' of tape, top down. Attach the first band just above the start of the instafoam. Then apply another band 1/2" above the bottom of the first band. Keep banding until you can attach a band to the structure again.
Then you should be ready to do the glassing.

Lastly, in re-reading my original post, when doing the initial mask-off with masking tape and packing tape, make sure you have an extra 4-6" all around. Epoxy does not like to come off. Keep a can of Acetone around and wipe up any
excess or drips immediately with an acetone soaked paper towel.

Greg Piney
RV-8 Soontobe
Setting up Shop
Tools Purchased
 
Styrofoam and Hotwire

Hi Randy,

I've played with molding objects out of urethane spray foam, and it's a mess. The worst thing is that the consistancy isn't homogeneous, big pockets are often formed that are discovered when you start carving. And as I'm sure you know, this stuff sticks to, and cruds up, everything in a 100yd radius.

This seems like a application for blue styrofoam and a hotwire, just like the Rutan squad uses. If it were me, I'd fill in the sides and hotwire to shape, then fill in around the canopy and sand to shape. Double stick tape, hotmelt, and or spray adhesive to attach / laminate the blue foam. Once the initial shape is complete I'd follow the process as shown on the rvpilot.com site.

Of course, I've never built an RV, I'm just guessing here. And this is my first post, so go easy on me. :eek:

Ted Johns
EAA-105
RV-7 dreamer
 
Ted Johns said:
Hi Randy,

I've played with molding objects out of urethane spray foam, and it's a mess. The worst thing is that the consistancy isn't homogeneous, big pockets are often formed that are discovered when you start carving. And as I'm sure you know, this stuff sticks to, and cruds up, everything in a 100yd radius.

This seems like a application for blue styrofoam and a hotwire, just like the Rutan squad uses. If it were me, I'd fill in the sides and hotwire to shape, then fill in around the canopy and sand to shape. Double stick tape, hotmelt, and or spray adhesive to attach / laminate the blue foam. Once the initial shape is complete I'd follow the process as shown on the rvpilot.com site.

Of course, I've never built an RV, I'm just guessing here. And this is my first post, so go easy on me. :eek:

Ted Johns
EAA-105
RV-7 dreamer
Click to expand...

Ted,

The foam in this case is just to fill a void that the fiberglass layup has to cover. The foam is not structural in any way. It is discarded after the layup is complete. You don't want to hotwire anything near plexiglass. Plexiglass melts.

Greg Piney
 
Hotwire Redux

gpiney said:
Ted,

The foam in this case is just to fill a void that the fiberglass layup has to cover. The foam is not structural in any way. It is discarded after the layup is complete. You don't want to hotwire anything near plexiglass. Plexiglass melts.

Greg Piney
Click to expand...

Um, the "voids" on the fuse sides under the canopy on an RV-3 are big enough to throw a cat thru. At least, thats what it looks like on Randy's site. Off with the canopy, hotwire some foam, back on with the canopy, no smokin plexy. :)

Heck, it seems to me that you could put some of that alum. hvac tape around the bottom of the canopy and hotwire small pieces of foam right up to the canopy edge, if a big "fillet" is what is required. Again, I'm just guessing.


Ted Johns
EAA-105
RV-7 Dreamer
 
Ted's on the right track. The Rutan disciples have this stuff down to a science so there's no need to reinvent the wheel (or wing).
 
Another idea that might work would be to use some heavy plastic poster stock (or a big ol piece of scrap Al., or even 1/8" bending plywood?) to wrap from fuse side to fuse side, just slightly overlapping the fore and aft cockpit opening. The stock would have to be stiff enough to fair the curve, but not so stiff that a reasonable temporary adhesive couldn't hold it. I can't quite tell from the picture if there is too much compound curve to fair in this manner. Then one would use the carving foam just to form the transition fillet.

Just an idea.


Ted Johns
EAA-105
RV-7 Dreamer
 
I thought several of you might want to see where I ended up with this. In the final analysis I used posterboard and packing tape to create a form and layed up on top of that. Actually it worked great and I now have a one piece canopy skirt. Of course it needs the usual sanding and filling, but I think this is really a great solution for this application. Here's the story.

Thanks to all for the advice and counsel.
 
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