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Thread: Advice / Help with Shaping?

  1. #1
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    Default Advice / Help with Shaping?

    Hi there guys – I have been reading and searching this forum with great delight, so much information on here about autobody 😊 So this is my first post and it is for help or more to the point what I am doing wrong...

    In short I have a handmade fuel tank, it was taken back to almost bare metal by me. I am getting a little stuck, mostly around shaping Filler. Have been applying Indasa Autofill filler on most of the tank to get me my rough shape before I go onto the easy sand filler (Upol Fantastic Filler). At the moment AutoFill is all I have been applying to the tank..

    I have the Durablock set (various shapes and sizes and some Soft Sanders also. Various grades of sandpaper, I have been mostly shaping with 60 grit by hand and some 80 grit on a DA. I bought a compressor and DA for this job and eventually this setup will be used for painting when I get to it.

    Fast forward 10-11 months into my attempt to do this myself so I apologize in advance if I have missed anything.

    I have been sanding mostly in criss-cross / diagonals, short and long sweeps. Now one bit I have plateaued on and its kind if difficult to explain is I seem to have two opposite corners that are a little ‘off’ or lower/less curved/more curved as opposed to the other two opposite corners when l look from certain height or angle. I feel like I am chasing curves and not getting anywhere (that probably does not make sense). Making simple cardboard cutouts of one side and flipping it over do not seem to work in my favour either.

    I am also not sure if I have inadvertently spent too long Sanding on one side of the tank making it look a little off shape or perhaps I have applied too much or little filler on some areas and not enough on other parts of the tank which could be what is making it look slightly off. I work on the tank when I have spare time, it is not continuous unfortunately as some days are but mostly its gaps between working on it.

    So my question is really, is there a technique that I am missing or is it a case of keep sanding until the desired shape is achieved using 60 and then 80 grit? Photos will probably explain a lot more hopefully. I shall try by best not to give up 😊 Any advice would be greatly approached!

    Many thanks,
    VJ
    Attached Images Attached Images

  2. #2
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    Be sure that you use a "guide coat" for helping adjust for surface irregularities. Also, once you get the shape corrected and you're ready to block the minor variations use a "good" spray-on filler like Slick Sand or Optex and again use a guide coat to help achieve perfection.


    Slick Sand can be sanding with some 220 to 400 before applying a 2K filler primer then guide coated and block sanded using 400 to 600 wet then you're ready for color.

  3. #3
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    Hi Len - thanks for replying back so promptly!

    I have guide coat (dry powder only) however not used it much thinking it is too early in the stage?! Thinking now guide coat can be used anytime right when blocking? I did briefly use guide coat… it sanded away really quick after a few hits of 60g.

    Question, is there a specific way to blocksand curves, concaves, convex shapes? I feel I cannot bring both sides down equally for some reason. I have bought 2k epoxy and spray on filler ready for when its needed, clearly a long way off applying this stuff.

    I have attached a couple more photos of how the tank is now (actually a few weeks back) and how the tank used to look like. The tank does not sit level so have to prop it up slightly from one corner to get it level.

    Many thanks again,
    VJ

    thumbnail_DSC_3215_resize.jpg


    tank_finished.jpg

  4. #4
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    getting round things flat can be very challenging. you will probably find the dura blocks will be too stiff for the tight radius sections you're working on. i keep a bunch of different hardness rubber blocks, long skinny ones, short fat ones, all different shapes and sizes. you need them to conform to the surface, but still be stiff enough to cut the high spots and not just conform to the irregularities you're trying to eliminate.
    b marler

  5. #5
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    On a shape like that I would normally sand at an angle around the shape. When sanding a guide coated filler be sure to sand on the high spots and NOT sand on the low guide coated areas. Sand on the high spots until they are level and the guide coat disappears.

  6. #6
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    Hi there b marler – you are spot on about the dura blocks being a bit stiff. I do have the round and the slim palm size dura block, which are not that rigid. These came as a dura block set, would this work? Any chance you would have a link to where I could get some of the rubber blocks from, did you make them yourself? I have a pack of soft sanders which are really soft, these have not worked that well for me, maybe later on after the high build stage these could come into use.

    Hi Len – I got you, I shall bring the surface down using guide coat and not labour on the low areas. It is difficult to have to think about every stroke I must admit… sand at an angle and around… repeat sand at an angle and around… and so on… get this into muscle memory and I will be a pro in no time he say

    VJ

  7. #7
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    Quote Originally Posted by tuffgong View Post
    Hi there b marler – you are spot on about the dura blocks being a bit stiff. I do have the round and the slim palm size dura block, which are not that rigid. These came as a dura block set, would this work? Any chance you would have a link to where I could get some of the rubber blocks from, did you make them yourself? I have a pack of soft sanders which are really soft, these have not worked that well for me, maybe later on after the high build stage these could come into use.

    Hi Len – I got you, I shall bring the surface down using guide coat and not labour on the low areas. It is difficult to have to think about every stroke I must admit… sand at an angle and around… repeat sand at an angle and around… and so on… get this into muscle memory and I will be a pro in no time he say

    VJ
    the thin block will help, but i would look for something a little longer and narrower, and just a tad firmer. i make mine from pieces of smooth rubber sheet, 3/4 thick. they will flex to the radius you want but still have the surface hardness you need to clip off the high spots of the filler. i get this rubber as cast offs from my work, but i'm sure it must be available to purchase in small quantities somewhere. mcmaster-carr maybe?
    not sure if the round one would have enough surface area. might be worth a try though. i generally use that one on fender lips and whatnot.
    b marler

  8. #8
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    Here are a few pointers that might help.

    When you stated:
    "I seem to have two opposite corners that are a little ‘off’ or lower/less curved/more curved as opposed to the other two opposite corners when l look from certain height or angle. I feel like I am chasing curves and not getting anywhere (that probably does not make sense). "

    Answer, yes it does make sense. You need to use pattern duplicators (shown in pic below) and trace onto poster board, not cardboard. Poster board cut outs give you a more accurate pattern duplication in order too measure opposing sides. For your tank it is imperative that you make X, Y and Z axis patterns in order to get this tanks shape correct. Poster board templets should have been used in the early stages during sheet metal shaping to bring the tank into symitry to the point all sides of tank are within 1/16" tolerance. This allows for the least amount of body filler to be used (I never allow my body filler to exceed 1/16") and makes shaping much easier to follow.

    After bare sheet metal is properly shaped I hit it with a coat or 2 of epoxy primer. Epoxy primer protects the bare sheet metal from rusting and gives me an indicator for sanding body filler prior to breaking through to bare metal.

    After epoxy primer dries for 24-48 hours I scuff the surface with 180g and apply a coat of body filler. I catch the body filler in the green stage and lightly hit it with 40g to “shape” the filler. On your tank I would use a combination of Dura-Block AF4400, Motor Guard MB-1 and SB-1 sanding blocks. These are the only blocks you will need to complete this project.

    After a quick, very light hit with sanding blocks using 40g to shape filler and removing the paraffin, hit it with dry powder guide coat (I use SEM 38203 spray guide coat for any grit above 180) and continue to shape the surface with180g.

    At this stage you should have a symmetrical part on all axis using your temples. Don't be afraid of sanding to bare metal during sanding as the part is either correct or it is not and needs more work.

    At this stage I am ready to apply my high build filler such as G2 Feather Fill, Slick Sand or Evercoat Optex 4:1 (my preference). I spray 2-3 coats and repeat the above sanding process starting with 180g and finish with 600g. If I break through to metal I apply an additional 2 coats and and sand out to 600g.

    The problem you present appears there is no way to gauge the amount of filler needing sanding vs symmetry of part as you have excess filler (sheet metal was not properly worked) and are attempting to “sculpt” the part as opposed to following the outline of sheet metal using the least amount of filler and guide coat.

    I personally would never allow a DA to touch that tank.
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  9. #9
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    As an example of working with templets for custom sheet metal patterns.
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  10. #10
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    Hi guys - Sorry for not replying sooner, I am just recovering from a common cold so was out for a little while, amazing what children can pass on to their parents. She has just turned 4... and passed on the most horrendous 'preschool' germs ever to me (my wife was perfectly fine). I have a cough now which is thankfully going, albeit slowly.

    @ b marler - That is superb, I have found a place online that does 'slabs' of the stuff but not cheap if buying a single piece at a time Not sure how easy it would be to cut to specific size / shape though.

    @Ronf – I am so glad I am making some sense, this stuff is all new to me and I apologize in advance. The metal work was done by the previous guy who built the bike over 10 years ago. How he got it looking like the original photo is beyond me – check it out, the bike being built here https://www.youtube.com/watch?v=txGjljMtBCY&t=2s

    I have ordered 10 sheets of A3 500gsm card (best I could find here) to help, I shall put the cardboard to one side 😊 I will also order the two Motor-Guard blocks, I have the Dura block already (long skilly one). I am truly amazed how this can be done using only three blocks. Also ordered a 10” contour duplication tool.

    I shall take heed and not use the DA on the tank, to be honest Ronf I used it mostly to DA off the old caked on paint and primer / sealers. I usually stop block sanding when I hit metal thinking i have gone to low. Sculpting is definitely the keyword here and perhaps the wrong way of working this project.

    Quick one Ronf, I shall use the pattern duplicator first to obtain the shape I want. Transfer that onto Card and use the card as my X,Y and Z guides?

    Can I start from where I am now or would I need to remove all my filler I have put on, which took me a very long time to do ☹

    Cheers in advance,

    VJ

  11. #11
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    Tuffgong,

    I looked through the Youtube video link you provided and found the fabricator has a very good understanding of metal work (I personally would have use my tig). However, there was not enough information provided to show how he fine tuned the shape of tank to ensure there was symmetry to all sides. It would not be unusual for a fabricator to allow a bit fudging without taking measurements, I just don't do it that way. I use wire cages all the time for producing sheet metal projects (ref: your youtube video at 2:13/5:24), this is when I begin using duplicators and cardboard to ensure parts align to symmetry. It is at this stage I can add more english wheel, planishing or H&D work to get part aligned. My goal is always to be within a 1/16" max for body filler. I would have produced the top part of tank with a wire cage and used the underside of tank to bring it into compliance, which he may have done.

    Should you strip back to metal at this point or continue on? That is for you to decide. Product manufactures of body fillers will normally state the maximum amount of filler to be used in the build, just remember the higher you build the filler the more chance of failure down the road. On your tank my first coat of filler would have been a short strand fiber filler sanded out with guide coat to bare metal or until I hit primer, followed by a standard body filler (I use Evercoat Rage Gold).

    My suggestion would be to keep what you have, just ensure your tank has the least amount of filler possible all the while making sure you stay under manufactures specifications for amount of build. If you find one side of tank is way out of compliance don't be afraid to drop down to 40g and sculpted it into compliance as you should be shooting a high build after sanding out to 180g. Use both your powdered and spray guide coats in every step, this ensures your tank is going to be dead on by the time you get to top coatings.

  12. #12
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    Here is an example of building primer and filler.
    Attached Images Attached Images

  13. #13

    Cool

    Quote Originally Posted by bmarler View Post
    getting round things flat can be very challenging. you will probably find the dura blocks will be too stiff for the tight radius sections you're working on. i keep a bunch of different hardness rubber blocks, long skinny ones, short fat ones, all different shapes and sizes. you need them to conform to the surface, but still be stiff enough to cut the high spots and not just conform to the irregularities you're trying to eliminate.
    Then make them unstiff

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    IMG_2137.jpg

  14. #14
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    How did you do that, did you cut those slots in yourself by hand? My skills are limited to what I know which is pretty much nothing, reading threads on this forum is where my learning curve starts

    Your ones look really good, can you still use them on flat parts perfectly fine? Thinking why Dura Blocks never made them with slots from factory.

    I have ordered Motor Guard MB and SB hand blocks also which are softer than the dura blocks I currently have. Having the right tool for the job eh, my wife thinks everything that comes in for me is £12 and bought really cheeeepp, like the budgie...

    VJ

  15. #15
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    Quote Originally Posted by MidnightOilJK View Post
    Then make them unstiff
    i love that. i love when someone points out something so simple that you think to yourself, how can it be that i never thought of that?
    thanks for posting.
    i'm assuming you cut those on a table saw right?
    b marler

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