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Old 01-20-2021, 06:56 AM
1949MGTC 1949MGTC is offline
Join Date: Jul 2018
Location: Freeport,FL
Posts: 22
Default Bottom Rudder Fairing Advice

So I’m a newbie at fiberglass. What techniques and tools do you have for trimming the bottom rudder fairing down to the scribe line and how do you get it to be a perfectly straight line so it doesn’t look like a beaver chewed it?


Last edited by 1949MGTC : 01-20-2021 at 08:19 AM.
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Old 01-20-2021, 07:53 AM
rocketman1988 rocketman1988 is offline
Join Date: Jun 2010
Location: Sunman, IN
Posts: 2,340
Default Permagrit tools

I use permagrit tools and they make f/g work much easier...
Aerospace Engineer '88

Phase I as of 12-02-2020

Dues+ Paid 2020,...Thanks DR+
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Old 01-20-2021, 02:16 PM
DRMA DRMA is offline
Join Date: Jan 2016
Location: Sugar Land, TX
Posts: 450

I found that a Dremel tool with a diamond cutting wheel worked best for me on the fiberglass cuts. Then I used the PermaGrit tools and a 12" piece of 2x4 with #80 grit sandpaper attached to it using double sided carpet tape to smooth and straighten the edges after the cuts.

Just be careful to protect your skin and lungs while you are making fiberglass dust (sanding and cutting).
Dave Macdonald

RV-10 First Flight April 1, 2020. Phase 1 Complete
2021 VAF Dues Paid (plus a little more)
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Old 01-20-2021, 02:32 PM
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bjdecker bjdecker is offline
Join Date: Jun 2005
Location: Georgetown, TX
Posts: 491

Sioux RS10K recip saw with 32tpi blades, and a 3M 5444 "Stickit" sanding board w/ 60 or 80 grit paper.
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Brian Decker
Retired Firmware Guy and Airplane Builder

2020 RV-14 QB -- Under construction - Tailcone & Empennage Complete.
2018 RV-7 QB -- Built, Flying
2007 RV-7 QB -- Built, Drowned, Resurrected and flying
1998 RV-8 QB -- Started, Sold
1986 Mooney 205SE
1980 Mooney 231

Aided and abetted building a number of other RV's.
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Old 01-20-2021, 04:54 PM
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wirejock wirejock is offline
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 4,183
Default Dan Horton

Originally Posted by 1949MGTC View Post
So Im a newbie at fiberglass. What techniques and tools do you have for trimming the bottom rudder fairing down to the scribe line and how do you get it to be a perfectly straight line so it doesnt look like a beaver chewed it?

Best advise. Read every thread Dan Horton ever posted. Especially the Sticky on Fiberglass.
I made a feeble attempt to collect and share the high points. On my blog there are pages for fiberglass, paint, etc. Lots of lists of stuff.
I cut with a Dremel outside the line. Shape a little with a Vixen file then smooth with a board and 40, 80 grit. Dan's methods are awesome.
Larry Larson
Estes Park, CO
wirejock at yahoo dot com
Donated 01/01/2021, plus a little extra.
RV-7A #73391, N511RV reserved (2,000+ hours)
HS SB, empennage, tanks, wings, fuse, working finishing kit
I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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Old 01-21-2021, 01:48 PM
agent4573 agent4573 is offline
Join Date: Aug 2019
Location: Mountain view
Posts: 246

I used a dremel sawmax to make the initial cut, then a piece of 60 grit sandpaper wrapped around a 1/2x1x12" piece of wood to sand the edge straight.

2020 dues paid.
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Old 01-21-2021, 04:13 PM
BillL BillL is offline
Join Date: Sep 2007
Location: Central IL
Posts: 5,738

Dan would say the green 3m long board 40-80 grit lasts pretty well, I would agree. But, I switched to Permagrit for making a lot of plenums.

Pricey for a few uses but unbeatable for a lot of edges.

BTW - I use the dremel with HF diamond blades for well cured glass, for green glass a more coarse wheel is required.

If I built another plane, permagrit (or that style) countersinks would be purchased.

To the lower fairing, Vans has us put the attachment strip under the bottom rivets. I sanded the inside of the fairing to get the thickness even then added a spacer to avoid sanding the fairing to fit. Some outside (gel coat) sanding was done as the gel coat has no strength anyway. This way it was butted even along the length. The attach strip may have to be bent as the (my) fairing was not square. A lot of little fitting.

I saw one builder that split the fairing so the aft section could slide off (taildragger) and reach the electrical. I might try that on the next one too.

Lord Kelvin:
I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.

Last edited by BillL : 01-21-2021 at 04:19 PM.
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Old 02-03-2021, 03:10 PM
8MikeXray 8MikeXray is offline
Join Date: Aug 2006
Location: Santa Rosa, CA
Posts: 55
Default Best way to cut fiberglass

Use an oscillating saw with a 270 degree, round, fine tooth blade. Make a fence out of aluminum or wood, attach it to the fiberglass on the cut line with a hot glue gun and saw away. The kerf is 1/32”. Easy

I also used my Bosch oscillating saw to cut my canopy, works great and is very controllable.
MIke C
RV-8 IO-390-EXP

Last edited by 8MikeXray : 02-03-2021 at 03:34 PM.
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