2nd Newbie Build- GP Super Skybolt
10-19-2006, 04:42 PM
#651
Senior Member
Thread Starter
My Feedback: (1)
Join Date: Jun 2005
Location: Antelope Valley,
CA
Posts: 825
Likes: 0
Received 0 Likes
on
0 Posts
RE: 2nd Newbie Build- GP Super Skybolt
ORIGINAL: bldrums
parrthd,
I was about to wonder if you could windex MC over UC and Minnflyer answered my question. I have only used MC ; Why do you guys think UC might be the better choice for the base covering?
I hate to cover a fuse anyway/ it would be so much nicer painted but paint would add too much weight ( IM told ) to an already fairly heavy airplane.
Bill
by the way , im close to sheeting the wings and although is seems like I have done enough to have a complete aircraft by now, ... I still see a lot left to go!
parrthd,
I was about to wonder if you could windex MC over UC and Minnflyer answered my question. I have only used MC ; Why do you guys think UC might be the better choice for the base covering?
I hate to cover a fuse anyway/ it would be so much nicer painted but paint would add too much weight ( IM told ) to an already fairly heavy airplane.
Bill
by the way , im close to sheeting the wings and although is seems like I have done enough to have a complete aircraft by now, ... I still see a lot left to go!
Mods
10-19-2006, 09:44 PM
#652
RE: 2nd Newbie Build- GP Super Skybolt
ORIGINAL: Mods-R-Me
That's what I did. The ultracote base w/ monokote trim worked very well. I convered the process in this thread and there is also another exception thread on how to do it in the tips and trick section by TERMIGATOR.
Mods
That's what I did. The ultracote base w/ monokote trim worked very well. I convered the process in this thread and there is also another exception thread on how to do it in the tips and trick section by TERMIGATOR.
Mods
Ken
10-20-2006, 08:31 AM
#653
RE: 2nd Newbie Build- GP Super Skybolt
Ok, here's the Good, the Bad, and the Ugly about Ultracote(UC) vs MonoKote (MK)
First, is one better than the other? No. They both have slightly different properties, so the one that's "better" is a personal preference.
So what are these properties? First, lets compare the material itself.
MK is a bit stiffer. It has more of a plastic feel to it, where UC feels a bit more rubbery. Mind you now, I am talking a VERY slight difference in "feel" - Don't go thinking that MK is like hard plastic and UC is like rubber. The feel is kind of like the difference between Cellophane and Saran Wrap.
Heat wise, I'm not going to look up what temps they shrink at, they both stick at a low temp and shrink at a higher temp, but UC does these at a slightly lower temp than MK.
Shrink-wise, UC shrinks more.
Now let's talk about the adhesive......................................
Both adhesives work great. The big advantage to MK's adhesive is that you can use the "Windex Trick" or Trim Solvent, or even acetone to stick it to a surface without heat. It's not so great for sticking it to wood, but it's excellent for sticking to a smooth surface. That smooth surface can be MK, UC, a window, your forehead, or whatever else you can dream up.
The other difference is that MK's adhesive is more permanent than UC's. What this means is once you iron down a piece of MK, it's pretty much there to stay. and the longer it stays, the harder it will be to ever remove. With UC, you can reheat the covering and easily peel it off again.
Now right away, you may see this as a good thing, but it has it's bad side too.
The good part is good in a few obvious ways. First, if you make a mistake, you can easily remove the piece and either rearrange it, or replace it altogether. It also makes it easier if in a few years you decide to remove the covering and re-do it.
But there is another benefit that is not so apparent...
There is a type of wrinkle that occurs while you are sealing the edges. Now you have to realize that whenever you heat something, it expands (Remember grade-school science?) Covering is the same. Before it shrinks, it expands a little.
Ok, so let's say that you're sealing the TE of a wing. You have the two ends tacked, then the middle, then a few places in between. But now you notice that where the covering used to lay flat between the two ends, it is now lifting slightly between all of the tacks. The covering has expanded slightly from the heat.
At this point, unless you are extremely careful, you are going to get a wrinkle.
Think of it this way: Put a table cloth on a table, put your hands on the cloth about 18" apart, and pull the cloth so your hands are only 16" apart. You can see how the cloth has raised slightly. The covering does the same thing as it expands. Now if you iron it down, you'll have a wrinkle (See pic below).
Now, if you are using MK, that wrinkle is there for good. Once the adhesive touches itself, it's done - and it aint gonna get un-done.
But with UC, because the adhesive releases, and combined with the extra shrink ability, all you have to do is turn up the iron heat (or use a heat gun) and go over the area, and the adhesive will let go of itself as the covering shrinks, and the wrinkle will magically disappear.
Ok, so how is this a bad thing?
This can be bad when you are using a heat gun near a seam or an edge. If you soften the adhesive near an edge, while you are shrinking a nearby area, the edge can pull away (Toward the shrinking area).
To avoid this, I always point my heat gun away from any edges. If it is unavoidable, I just lay a wet paper towel on the edge to keep it cool.
What about the "Other" kind of wrinkle? You know, the one you get from leaving the plane in the car on a hot day, or that just mysteriously appear after the plane has sat for a while?
Deal with it. Both coverings do it, and it is largely based on how good or bad of a job YOU did while covering (Or the manufacturer did).
So there it is - the "Good" and the "Bad".
As far as the "Ugly" goes, well, you'd have to see one of Ken's planes for that
First, is one better than the other? No. They both have slightly different properties, so the one that's "better" is a personal preference.
So what are these properties? First, lets compare the material itself.
MK is a bit stiffer. It has more of a plastic feel to it, where UC feels a bit more rubbery. Mind you now, I am talking a VERY slight difference in "feel" - Don't go thinking that MK is like hard plastic and UC is like rubber. The feel is kind of like the difference between Cellophane and Saran Wrap.
Heat wise, I'm not going to look up what temps they shrink at, they both stick at a low temp and shrink at a higher temp, but UC does these at a slightly lower temp than MK.
Shrink-wise, UC shrinks more.
Now let's talk about the adhesive......................................
Both adhesives work great. The big advantage to MK's adhesive is that you can use the "Windex Trick" or Trim Solvent, or even acetone to stick it to a surface without heat. It's not so great for sticking it to wood, but it's excellent for sticking to a smooth surface. That smooth surface can be MK, UC, a window, your forehead, or whatever else you can dream up.
The other difference is that MK's adhesive is more permanent than UC's. What this means is once you iron down a piece of MK, it's pretty much there to stay. and the longer it stays, the harder it will be to ever remove. With UC, you can reheat the covering and easily peel it off again.
Now right away, you may see this as a good thing, but it has it's bad side too.
The good part is good in a few obvious ways. First, if you make a mistake, you can easily remove the piece and either rearrange it, or replace it altogether. It also makes it easier if in a few years you decide to remove the covering and re-do it.
But there is another benefit that is not so apparent...
There is a type of wrinkle that occurs while you are sealing the edges. Now you have to realize that whenever you heat something, it expands (Remember grade-school science?) Covering is the same. Before it shrinks, it expands a little.
Ok, so let's say that you're sealing the TE of a wing. You have the two ends tacked, then the middle, then a few places in between. But now you notice that where the covering used to lay flat between the two ends, it is now lifting slightly between all of the tacks. The covering has expanded slightly from the heat.
At this point, unless you are extremely careful, you are going to get a wrinkle.
Think of it this way: Put a table cloth on a table, put your hands on the cloth about 18" apart, and pull the cloth so your hands are only 16" apart. You can see how the cloth has raised slightly. The covering does the same thing as it expands. Now if you iron it down, you'll have a wrinkle (See pic below).
Now, if you are using MK, that wrinkle is there for good. Once the adhesive touches itself, it's done - and it aint gonna get un-done.
But with UC, because the adhesive releases, and combined with the extra shrink ability, all you have to do is turn up the iron heat (or use a heat gun) and go over the area, and the adhesive will let go of itself as the covering shrinks, and the wrinkle will magically disappear.
Ok, so how is this a bad thing?
This can be bad when you are using a heat gun near a seam or an edge. If you soften the adhesive near an edge, while you are shrinking a nearby area, the edge can pull away (Toward the shrinking area).
To avoid this, I always point my heat gun away from any edges. If it is unavoidable, I just lay a wet paper towel on the edge to keep it cool.
What about the "Other" kind of wrinkle? You know, the one you get from leaving the plane in the car on a hot day, or that just mysteriously appear after the plane has sat for a while?
Deal with it. Both coverings do it, and it is largely based on how good or bad of a job YOU did while covering (Or the manufacturer did).
So there it is - the "Good" and the "Bad".
As far as the "Ugly" goes, well, you'd have to see one of Ken's planes for that
10-20-2006, 06:05 PM
#654
Senior Member
Join Date: Jan 2006
Location: Nettleton,
MS
Posts: 558
Likes: 0
Received 0 Likes
on
0 Posts
RE: 2nd Newbie Build- GP Super Skybolt
As far as the "Ugly" goes, well, you'd have to see one of Ken's planes for that
i've found most everything you're talking about to be true. (most of them i've found first hand on this covering job!!! )
i found that if i start by sealing a wing panel from the LE to the TE. next i pull one of the loose corners and seal down either the LE or the TE followed by pulling the last corner and sealing the last long edge that wrinkles are kept to a minimum, or at least small enough that they come out easily with a heat gun.
i've also found that i ( most people can, i can't ) can't use a hobby oriented heat gun (like hobbico or top flight) i use a milwaukee heat gun geared at paint removal etc. it has adjustable heat settings that i run at 650 degrees. (i work REALLY REALLY fast) i keep the gun 6 to 8 inches away from the covering and constantly moving. next trick is i apply heat ONLY to the covering that's NOT on the wood.
i've had mixed results so far but it's trial and error. i'm starting to make headway on my technique and it's starting to pay off. my wingtips are still a bit rough BUT the tail feathers are awsome. with the two compared side by side you'd think two different ppl covered each.
i think i'll try to get a few of the wingtips worked over tonight. then it'll be on to the fuselage.
10-21-2006, 07:45 AM
#656
Senior Member
Join Date: Jan 2006
Location: Nettleton,
MS
Posts: 558
Likes: 0
Received 0 Likes
on
0 Posts
RE: 2nd Newbie Build- GP Super Skybolt
Just be careful you don't melt a hole in the covering - Been there, done that, got the T-Shirt
the first wing panel i did on this project ended up with a hole in it LOL> luckily for me it was far enough down past the center line that i could trim it out and not have any adverse affects from it.
10-22-2006, 10:26 AM
#658
Senior Member
Join Date: Jan 2006
Location: Nettleton,
MS
Posts: 558
Likes: 0
Received 0 Likes
on
0 Posts
RE: 2nd Newbie Build- GP Super Skybolt
Great tips guys. Reading posts ahead of the build does wonders for the finished product
10-22-2006, 01:05 PM
#659
Join Date: Sep 2002
Location: C-Ville,
VA
Posts: 512
Likes: 0
Received 0 Likes
on
0 Posts
RE: 2nd Newbie Build- GP Super Skybolt
On the kit build , Skybolt thread
I am leary of not following the plans in order rather than the tempting :" think Ill go ahead and join this bottom wing now,see how shes gonna look " etc. I have run into problems doing that, so, moving along step by step is a little boring. This is the only kit that I have worried about the finish fit ; mainly the bi-wing set up. Everyone says its a great design but Im nervous that mine might end up skewed or too far out of specs when I finish. Single wing / bolt on / is the extent of my building experience, so , I hope for the best [8D] Each progression in the plan seems to get more and more critical........... So what, its just a hobby
I am leary of not following the plans in order rather than the tempting :" think Ill go ahead and join this bottom wing now,see how shes gonna look " etc. I have run into problems doing that, so, moving along step by step is a little boring. This is the only kit that I have worried about the finish fit ; mainly the bi-wing set up. Everyone says its a great design but Im nervous that mine might end up skewed or too far out of specs when I finish. Single wing / bolt on / is the extent of my building experience, so , I hope for the best [8D] Each progression in the plan seems to get more and more critical........... So what, its just a hobby
10-22-2006, 01:13 PM
#660
Senior Member
Join Date: Jan 2006
Location: Nettleton,
MS
Posts: 558
Likes: 0
Received 0 Likes
on
0 Posts
RE: 2nd Newbie Build- GP Super Skybolt
i tend to agree about going step by step is a bit boring but hang in there. this is my first bipe kit build as well. i had a million questions as the build began and as it progressed. BUT by going back over this thread and by asking questions most of my intimidations was overcome. some of our flyers have stopped by from time to time to "check" on the build and everyone has had nice things to say about the build. i just hope it flies as "nice" as they talk about it. and then again, if it doesn't, at least it'll be a little bit of a rush!!! LOL
it all actuality, everyone says the build is a LOT more critical than needed. the reason they make it so critical is a lot of people that would try to build this kit would build it very fast not taking time to check the "small things" --------from everyone i've heard and read, concerning the skybolt, the plane flies too good for it to be a REAL headache in the air. i've come to the comclusion that if something goes haywire, for whatever reason, it was in my build and not the design of the plane. (i really really REALLY hope my build is right!!!!!)
it all actuality, everyone says the build is a LOT more critical than needed. the reason they make it so critical is a lot of people that would try to build this kit would build it very fast not taking time to check the "small things" --------from everyone i've heard and read, concerning the skybolt, the plane flies too good for it to be a REAL headache in the air. i've come to the comclusion that if something goes haywire, for whatever reason, it was in my build and not the design of the plane. (i really really REALLY hope my build is right!!!!!)
10-22-2006, 01:16 PM
#661
Senior Member
Thread Starter
My Feedback: (1)
Join Date: Jun 2005
Location: Antelope Valley,
CA
Posts: 825
Likes: 0
Received 0 Likes
on
0 Posts
RE: 2nd Newbie Build- GP Super Skybolt
ORIGINAL: parrthd
i tend to agree about going step by step is a bit boring but hang in there. this is my first bipe kit build as well. i had a million questions as the build began and as it progressed. BUT by going back over this thread and by asking questions most of my intimidations was overcome. some of our flyers have stopped by from time to time to "check" on the build and everyone has had nice things to say about the build. i just hope it flies as "nice" as they talk about it. and then again, if it doesn't, at least it'll be a little bit of a rush!!! LOL
it all actuality, everyone says the build is a LOT more critical than needed. the reason they make it so critical is a lot of people that would try to build this kit would build it very fast not taking time to check the "small things" --------from everyone i've heard and read, concerning the skybolt, the plane flies too good for it to be a REAL headache in the air. i've come to the comclusion that if something goes haywire, for whatever reason, it was in my build and not the design of the plane. (i really really REALLY hope my build is right!!!!!)
i tend to agree about going step by step is a bit boring but hang in there. this is my first bipe kit build as well. i had a million questions as the build began and as it progressed. BUT by going back over this thread and by asking questions most of my intimidations was overcome. some of our flyers have stopped by from time to time to "check" on the build and everyone has had nice things to say about the build. i just hope it flies as "nice" as they talk about it. and then again, if it doesn't, at least it'll be a little bit of a rush!!! LOL
it all actuality, everyone says the build is a LOT more critical than needed. the reason they make it so critical is a lot of people that would try to build this kit would build it very fast not taking time to check the "small things" --------from everyone i've heard and read, concerning the skybolt, the plane flies too good for it to be a REAL headache in the air. i've come to the comclusion that if something goes haywire, for whatever reason, it was in my build and not the design of the plane. (i really really REALLY hope my build is right!!!!!)
10-22-2006, 01:23 PM
#662
Senior Member
Join Date: Jan 2006
Location: Nettleton,
MS
Posts: 558
Likes: 0
Received 0 Likes
on
0 Posts
RE: 2nd Newbie Build- GP Super Skybolt
ok mods, have you blew that evo engine out yet or are you waiting on me to finish mine and head to eglin so we can have a "skybolt duo" ???
you're forgetting, eglin is only around a 9 hr drive..........BUT i have family in gulfport!!!
you're forgetting, eglin is only around a 9 hr drive..........BUT i have family in gulfport!!!
10-22-2006, 01:27 PM
#663
Senior Member
Thread Starter
My Feedback: (1)
Join Date: Jun 2005
Location: Antelope Valley,
CA
Posts: 825
Likes: 0
Received 0 Likes
on
0 Posts
RE: 2nd Newbie Build- GP Super Skybolt
Are we talking about having a Club Skybolt fly in? Who's up for it? We tried to get one together a while back but interest faded.
10-22-2006, 08:27 PM
#664
Senior Member
Join Date: Mar 2006
Location: Sacramento,
CA
Posts: 1,977
Likes: 0
Received 0 Likes
on
0 Posts
RE: 2nd Newbie Build- GP Super Skybolt
I saw parrthd's Skybolt in person last night. He's an excellent craftsman. This is only his 2nd kit, as he said, so I can't imagine how good his work will be on his 10th, or 20th. I think he should just give up on kits and start plans-building/scratch-building.
10-22-2006, 10:06 PM
#665
Senior Member
Thread Starter
My Feedback: (1)
Join Date: Jun 2005
Location: Antelope Valley,
CA
Posts: 825
Likes: 0
Received 0 Likes
on
0 Posts
RE: 2nd Newbie Build- GP Super Skybolt
ORIGINAL: RVM
I saw parrthd's Skybolt in person last night. He's an excellent craftsman. This is only his 2nd kit, as he said, so I can't imagine how good his work will be on his 10th, or 20th. I think he should just give up on kits and start plans-building/scratch-building.
I saw parrthd's Skybolt in person last night. He's an excellent craftsman. This is only his 2nd kit, as he said, so I can't imagine how good his work will be on his 10th, or 20th. I think he should just give up on kits and start plans-building/scratch-building.
.Mods
10-23-2006, 08:33 PM
#667
Senior Member
Join Date: Jan 2006
Location: Nettleton,
MS
Posts: 558
Likes: 0
Received 0 Likes
on
0 Posts
RE: 2nd Newbie Build- GP Super Skybolt
ok guys, got the horizontal stab and fin finished today. looking toward the front fuse bottom and landing gear area tomorrow. the fin and stab came out really well and i'm pleased with the end result. it's the first part of the covering job i'm really happy with on the first attempt and haven't had to go back and touch anything up.
my next concern is the landing gear area. since the gear was made to detachable i'm concerned about the monokote staying sealed good right around the gear struts. i' don't know if i should flow a bit of thin ca under the covering once covered or not. what do you guys think?
mods - i'll be up for a skybolt meet, here, there, or in between. i've just got to get a bit of stick time on this plane and make sure it doesn't try to fly me!!! i also know a guy who just got a BRAND NEW fliton extra 300............(i know it's an arf and all but i fugured he'd be the only other one who would share the drive LOL).
anyway, here's some pics of the stab and fin.......see anything i could've done differently? i'm ALWAYS open to suggestions.
my next concern is the landing gear area. since the gear was made to detachable i'm concerned about the monokote staying sealed good right around the gear struts. i' don't know if i should flow a bit of thin ca under the covering once covered or not. what do you guys think?
mods - i'll be up for a skybolt meet, here, there, or in between. i've just got to get a bit of stick time on this plane and make sure it doesn't try to fly me!!! i also know a guy who just got a BRAND NEW fliton extra 300............(i know it's an arf and all but i fugured he'd be the only other one who would share the drive LOL).
anyway, here's some pics of the stab and fin.......see anything i could've done differently? i'm ALWAYS open to suggestions.
10-24-2006, 02:52 PM
#669
Senior Member
Join Date: Mar 2006
Location: Sacramento,
CA
Posts: 1,977
Likes: 0
Received 0 Likes
on
0 Posts
RE: 2nd Newbie Build- GP Super Skybolt
Since I'm probably not moving to the UK I hope to start on a plans-built Extra 300XS next year, if the funds allow. I just need a scroll saw and a disc sander and I'm set! [:-]
ORIGINAL: Mods-R-Me
This is very true. Those who are true builders at heart will eventually end up there. I'll see you on this side of the hobby when you get tired of kits parrthd .
Mods
ORIGINAL: RVM
I saw parrthd's Skybolt in person last night. He's an excellent craftsman. This is only his 2nd kit, as he said, so I can't imagine how good his work will be on his 10th, or 20th. I think he should just give up on kits and start plans-building/scratch-building.
I saw parrthd's Skybolt in person last night. He's an excellent craftsman. This is only his 2nd kit, as he said, so I can't imagine how good his work will be on his 10th, or 20th. I think he should just give up on kits and start plans-building/scratch-building.
.Mods
10-24-2006, 04:39 PM
#670
Senior Member
Join Date: Jan 2006
Location: Nettleton,
MS
Posts: 558
Likes: 0
Received 0 Likes
on
0 Posts
RE: 2nd Newbie Build- GP Super Skybolt
let me check around the pawn shops here. they usually have a good selection of used power tools. i'll see what i can come up with.
10-24-2006, 04:43 PM
#671
Senior Member
Join Date: Jan 2006
Location: Nettleton,
MS
Posts: 558
Likes: 0
Received 0 Likes
on
0 Posts
RE: 2nd Newbie Build- GP Super Skybolt
ORIGINAL: MinnFlyer
Now THAT looks NICE!
Now THAT looks NICE!
coming from someone who has made their own covering how to video, i'll take that as a compliment!! thanks for the kind words and thanks again for the tips, techniques, patience, and video!!!
10-24-2006, 08:59 PM
#672
Senior Member
Join Date: Jan 2006
Location: Nettleton,
MS
Posts: 558
Likes: 0
Received 0 Likes
on
0 Posts
RE: 2nd Newbie Build- GP Super Skybolt
today's update!!! the fuse bottom is complete from fore to aft leaving the bottom hatch and landing gear plate. the part pictured in the first two pics are compound curves (and i thought i was done with the heat gun!!! LOL) so out come the good ole heat gun AGAIN!!!
the third pic is the port side of the fuse, had to break away, post pics, and get ready for work
[sm=cry_smile.gif]
the last pic is what happened when i realized the hole for the pushrod should've been cut BEFORE sticking the panel on the fuse side. i had to cut the length of the rod and then tack the covering back in place. i'll either cover the cut line with a narrow peice of covering or flow a bit of thin ca into the cut. which would be better? the problem with the covering is the overlap will be going the WRONG way!!! maybe i'll get it looking decent though. at least this part is covered by the horzontal stab!!! LOL
the third pic is the port side of the fuse, had to break away, post pics, and get ready for work
[sm=cry_smile.gif]the last pic is what happened when i realized the hole for the pushrod should've been cut BEFORE sticking the panel on the fuse side. i had to cut the length of the rod and then tack the covering back in place. i'll either cover the cut line with a narrow peice of covering or flow a bit of thin ca into the cut. which would be better? the problem with the covering is the overlap will be going the WRONG way!!! maybe i'll get it looking decent though. at least this part is covered by the horzontal stab!!! LOL
10-25-2006, 07:52 PM
#673
Senior Member
Join Date: Jan 2006
Location: Nettleton,
MS
Posts: 558
Likes: 0
Received 0 Likes
on
0 Posts
RE: 2nd Newbie Build- GP Super Skybolt
well, i finished the fuse sides and the top fuse fore of the cockpit area........OH MY GOD i didn't think i was EVER going to get this done and looking half-way right.
i took conventional covering methods (i.e. bottom, sides, and then top) WRONG idea!!! you see in the pic, the fuse top is ONE peice and i should've made it two peices! talk about time consuming. i worked on ONE perice of monokote 8" wide by 18" long for over THREE HOURS!!!!! it took the time and there is still one small flaw that isn't to my standards but i'll have to live with it, i'm not going back and pulling that peice off!!! LOL
anyway here's todays installment of pics. i won't get a lot done tomorrow as i've got to carry my daughter to the dr. for a checkup. i'm hoping the next GOOD day i have, i can complete the fuse base coat and start on the trim scheme.
i also found out another trick. you know those t-bar sanders??? they make GREAT straight edges!!! even for cutting covering after it's on the fuse!!! i used a great planes easy touch bar sander 22" long. placed the edge on the line i needed trimmed andturned back the covering over the flat spot. then i laid the blade of my hobby knife (with a SHARP blade) flat against the flat spot of the sander and ZIP- perfect straight edge.
i took conventional covering methods (i.e. bottom, sides, and then top) WRONG idea!!! you see in the pic, the fuse top is ONE peice and i should've made it two peices! talk about time consuming. i worked on ONE perice of monokote 8" wide by 18" long for over THREE HOURS!!!!! it took the time and there is still one small flaw that isn't to my standards but i'll have to live with it, i'm not going back and pulling that peice off!!! LOL
anyway here's todays installment of pics. i won't get a lot done tomorrow as i've got to carry my daughter to the dr. for a checkup. i'm hoping the next GOOD day i have, i can complete the fuse base coat and start on the trim scheme.
i also found out another trick. you know those t-bar sanders??? they make GREAT straight edges!!! even for cutting covering after it's on the fuse!!! i used a great planes easy touch bar sander 22" long. placed the edge on the line i needed trimmed andturned back the covering over the flat spot. then i laid the blade of my hobby knife (with a SHARP blade) flat against the flat spot of the sander and ZIP- perfect straight edge.