Inside radius sanding

Post any and all methods for doing things here, if you think you have a good method, that you don't see most builders using
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Reid
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Inside radius sanding

Post by Reid » Fri Sep 25, 2020 2:59 pm

Hey Everyone,

I wanted to throw this out there and see what techniques or tools you are using to sand the interior radiused corners of your boats. This obviously didn't just randomly pop in my head. I was working on fairing the interior corners of the cockpit and hatch compartments of my FS18 and was having a hard time finding a tool that would help speed the process up but also produce a nice clean finish.
Here is an example of the areas that I am referring to:
This is the corner where one of my gunnel supports meets the side of the hull and the sole. There are three different planes converging into one corner which makes for a tight working space and difficult place to sand.
IMG_5739.jpg
Here are the tools that I have been working with:
I have a Dremel tool and a profile sander. The profile sander does a descent job on the straight runs but is difficult to get into the corners. I also have to change the paper quite frequently. The Dremel is a little easier to get into the corners but I have to be really delicate not to sand through my fairing compound and into the glass. The drum bit is also not the ideal bit to use.
IMG_5742.jpg
I think the ideal tool would be a set of round "ball" sanding bits for the Dremel. The set would come in different radiuses and various "grits". I have been searching for a while and can not find what I am looking for. The only thing I found that is similar are these Burr grinding bits. These are too small of a radius but they demonstrate what I am talking about.
Burr bits.JPG
Any suggestions?
Thanks,
Reid


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piperdown
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Re: Inside radius sanding

Post by piperdown » Fri Sep 25, 2020 3:45 pm

I've been using one of these.
https://www.harborfreight.com/53-amp-12 ... HJEALw_wcB

You can buy different grit sandpaper belts.
Eric (aka, piperdown)

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Jaysen
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Re: Inside radius sanding

Post by Jaysen » Fri Sep 25, 2020 4:29 pm

Get a flex extension for the Dremel and a slightly larger drum (pretty sure they make 3/4”). The. You only have to do the very end by hand.
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fallguy1000
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Re: Inside radius sanding

Post by fallguy1000 » Fri Sep 25, 2020 8:45 pm

I hate to tell you, but I jist take a piece of paper on the profile sander bits or pieces of black pipe or chunks of 3/4" coosa shaped with double radiuses. Then I grip Festool 80x133 paper and run progressions. I start at 60 grit. I also run 45 degree cuts into the corners and my corners look pretty decent. I sort of allow them to be a little less than perfecto. I have found pieces of black pipe to work best. The edge of the paper seems to find the edge of the pipe and I just keep driving the corner. I usually count strokes and find that 20-30 strokes is generally good. Then feel it and if the sides are high, I 45 or say 30 into the corners to smooth out any humps not hit by the radiusing sanding.
5BF298E6-8D7E-432F-97BB-27417CF50A07.png
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Aripeka Angler
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Re: Inside radius sanding

Post by Aripeka Angler » Sat Sep 26, 2020 6:22 am

Be neat as possible with the inside corner fillets. Mix very small batches of quick fair so you don’t get in a hurry. Remember, if you don’t make a mess you won’t have to sand off a mess. I like tiny silicone baby spoons and hand trimmed bondo spreaders for inside corner fillets. Kind of like trying to lose weight- doesn’t take long to put it on but it’s hard to take off. :lol:
Bowl turners have all kinds of abrasive gizmos to do inside corners. Google abrasive sanding balls, you will get tons of ideas.
Richard
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fallguy1000
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Re: Inside radius sanding

Post by fallguy1000 » Sat Sep 26, 2020 9:21 am

Aripeka Angler wrote:
Sat Sep 26, 2020 6:22 am
Be neat as possible with the inside corner fillets. Mix very small batches of quick fair so you don’t get in a hurry. Remember, if you don’t make a mess you won’t have to sand off a mess. I like tiny silicone baby spoons and hand trimmed bondo spreaders for inside corner fillets. Kind of like trying to lose weight- doesn’t take long to put it on but it’s hard to take off. :lol:
Bowl turners have all kinds of abrasive gizmos to do inside corners. Google abrasive sanding balls, you will get tons of ideas.
I must double down on this comment. I made a custom rubber tool with a vicegrip that I used to pull qf on all the inside turns. I left a little damn black mark, butgave me more consistent inside radiuses than anything else I found.

I used the black pipe I use for sanding to develop the radius, well, semi-circle for the tool. The vice grip handle allowed me to control the flex. Eventually the vice grip n rubber became one...but kleen edges is all that matter to allow for some flex, but not too much..

It is important the sanding tool and the filling tool radiuses match well or you will fight yourself in sanding n filling.
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mattkab
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Re: Inside radius sanding

Post by mattkab » Thu Oct 01, 2020 12:06 pm

piperdown wrote:
Fri Sep 25, 2020 3:45 pm
I've been using one of these.
https://www.harborfreight.com/53-amp-12 ... HJEALw_wcB

You can buy different grit sandpaper belts.
+1
I like it too. Changing belts and belt tensioning are PITA processes, but overall I'm happy with such a cheap sander. Does a great job with "inside radius sanding"

I also use a "mouse" sander, and do quite a bit of just hand-sanding with folded up bits.
Matt.
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