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 what do you use to trim cured composites?

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runcyclexcski Posted - 05/08/2018 : 12:30:13
I've been making composite panels from Al and aramid honeycomb, and fiberglass, carbon,and kevlar skins. This is what I am planning to use for disk wheels and segments of the shell. I am getting better at making panels, but trimming off the edges of finished panels is quite a pain. Are there good life hacks for this? Tried dremel disks > mess, dust, and slow cutting.

Currently, I cure the panels against a thick flat piece of glass which I coated with 1 mm thick Teflon, and I vacuum-bag that. I make the fabric swatches over-sized and frame the honeycomb recntangles with wedge-shaped balsa pieces. The wedge lets the skins close over the honeycomb and stick to themselves neatly, then I trim it with Kevlar shears. This works, but shears get dull, and non-wedge shaped edges can't be done this way. So I wonder if there is a better way.

runcyclexcski
25   L A T E S T    R E P L I E S    (Newest First)
carolina Posted - 05/13/2020 : 16:59:33
another may 2020 update. have harbor freight and dewalt oscillating tool sander: these are ends l came up with over 3 years, if u do what l do.

https://youtu.be/mzBlFpP-PVU
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velosRus.com
carolina Posted - 03/30/2019 : 15:15:49
You should have these. Spend the money on ebay, get a vintage shipwrights divider. The lil profile gage from ebay too in different lengths also.




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velosRus.com
carolina Posted - 03/30/2019 : 15:10:08
I値l tell ya my invention here saves (土our fingers to the bone sanding) ya on contours or dimple areas on making plugs/masters: if ya can make a plug u can make a mold. Then you can make as many carbon parts as u want.

Video: couple post down.

Harbor Freight Oscillating tool and implements: Now also a cordless dewalt one for making plugs.
1) the lil blk cutter that comes with tool with hole drilled in it and mount different pads.
2) the lil yellow velcro pads at harbor freight. Just bolt it on to oscillating tools.
3) 1 key: choose high quality sand paper from auto body shop warehouse supplier.
4) Dow u-428 windshield adhesive on ebay.
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need more info? email me
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velosRus.com
carolina Posted - 03/30/2019 : 14:52:03
Don稚 be home without these two also: this belt sander works great from harbor freight, stuff i do with it is gentle. It will last long and belts too. The flex german buffer is money well spent.


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velosRus.com
carolina Posted - 03/19/2019 : 07:51:21
Rotozip if not but few layers of carbon. Small diamond dremel cut off wheel, die-grinder (harbor freight) with 4&1/2 cut off wheel.

The composite world is easier on tools that metal, i blow them off with air after each use.
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velosRus.com
carolina Posted - 05/15/2018 : 19:18:51
Never silicone, use only dow u-428 on ebay. Industry standard taught to me by netherlands companies. I have ryobi cordless caulk gun, love it. You can fix zillion things around house too with the u-428.
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velosRus.com
runcyclexcski Posted - 05/15/2018 : 14:27:04
Nice pics, many thanks! I own ~6 respirators, and I've made my own powered ones, too.

The path is to build the frame with cheap square wood planks, 25x50 mm sections, take measurements, optimize entry, then rebuild the frame in metal. I agree on shell attachments. I am a bit puzzled how to wateproof the joints between panels. Will use some silicon sealer, probably. but it would be nice to get away with gaskets (hence the need for good quality molds that can make smooth surfaces).

runcyclexcski
carolina Posted - 05/15/2018 : 12:53:08
Yes shell is great idea and by definition is a velomobiel.
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U can switch to carbon on next one.
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Be studing innegra, used in all velos of the big boys in Romania and used in my velo.
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Put your thoughts into how the shell attaches to trike frame, thats where you might need a tiny mold.
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Study the coroplast builders:







Heres a set of quest ww痴 on a trike w/diy shell.




Study the way this shell is mounted:/euro company. Also the challenger shell...



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Buy that full face respirator on ebay:
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runcyclexcski Posted - 05/15/2018 : 12:05:43
Hi Carolina --

Thanks for the great info. I order from easycomposites all the time, they are a great resource. I am familiar with their 10 gbp/meter carbin fiber, and I order it all the time. Fiberglass is still cheaper: I got a roll of 100 meters for 100 GPB (USD), and that pic was made with FG. So I experiment with FG and when I am happy with the result I make it in CF (if at all).

>> Some products i can稚 get in usa.

Interesting. I find the opposite to be true with most stuff DIY stuff. We do not even have McMaster in the UK. RS components UK is a joke compared to McMaster. McMaster does not sell to the UK.

I see, I guess by monocoque I meant unibody (i.e. the shell also is the load bearing component, and there is no frame). For my small DIY, it's easier to build small components, b.c. they are reusable. I do not like things made to serve only one purpose. Thus, I love my panels, they have so many uses. :) The most recent one just became the frame of an UL backpack.

I agree that the design based on a shell over a frame (which is what I am making) is not the neatest/highest end way, but it's more manageable for my purpose, and I am not looking to sell it for 10K+. Every component of my frame (Al U channels) can be reused for other projects. Plus, I can always remove the shell and ride the 'bare frame' on nice days, instead of being cooked alive in the shell.





runcyclexcski
carolina Posted - 05/15/2018 : 10:27:40
U came to a good place to do homework: heres a start from Daniel Fenn/DF . Subscribe to daniels youtube channel.

https://youtu.be/BQcGxwhdguw

https://youtu.be/tn1mW2PZSa0
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Your putting a shell on a trike?
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Your cut will heat a lil, but your gonna sand 1/16th or 1/8 or more off that.
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definitely would forget aluminum inserts like terry said, use cotton flox & maybe phonelic a few major places .
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Order the rivnut kit above.
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A velomobiel is not monocoupe, it is unibody like a smart car or toyota. Monocoupe is a piper or cessna airplane. I make unibodies, and not shells on trikes or 2 wheeler. Someone should make a unibody 2 wheeler.
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IMO , i wished you had used cf twill for your whole project only with innegra $9 yard. Your working yaself to much for nothing.
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Some places on your unit, you can use small mold, don稚 be scared. She want leave ya.
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You live in a town house with driveway in city? Keep huge shop vac around..

I do alot of wet sanding. Your water idea can help.
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Subscribe to easycomposites youtube channel of uk:


Also : east coast composites of uk youtube channel. I buy from both these people. Some products i can稚 get in usa.
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Don稚 make anymore panels, switch to 11 oz twill cfiber & sandwich in a lil innegra. Forget the vaccum bagging.
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All leading velomobiles are made in one factory in Romania. And you have waw from czech rebublic, (unibody made 2 hrs away in Lithuania).
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runcyclexcski Posted - 05/15/2018 : 09:28:27
Carolina, I just made small samples in which I deliberately let the two skins close together outside the honeycomb, and this edge seems much cleaner, and much easier to trim and to deal with. I can drill through this edge, perhaps, can reinforce it steel or Ti foil, and can use it to attach to a frame.

yet another attempt to attach an image... Google drive is a joke.

https://drive.google.com/file/d/1FNkFU6Mwyw4745EAIwG5OX244SIRY8J1/view?usp=sharing

https://drive.google.com/file/d/1FNkFU6Mwyw4745EAIwG5OX244SIRY8J1/view?usp=sharing

Regarding the fact that velomobile 'industry' does not use vacuum bagging... is that common? This is rather surprising, I did not know, thanks for pointing it out. To what extend to you think the absence of pressure would compromise the integrity and the strength of the product? The bike frame industry and the car industry use autoclaves, and the canoe industry uses bags, so one would think it's important to apply pressure for proper cure.

runcyclexcski
runcyclexcski Posted - 05/15/2018 : 09:00:33
>>>cut outside

Carolina, I work in a chemistry lab. And I live in the UK. Outside is a relative concept here :). BTW, why hurt precious air our evil fiberglass? Running water, I think, may work. Glass will end up in the sewer, OK with me, fishes do not mind (especially after Brexit, when the UK environment will go to hell anyway).

runcyclexcski
runcyclexcski Posted - 05/15/2018 : 08:58:15
Carolina -- this is an enclosed tadpole recumbent, yes. Instead of making a monocoque body with a full mould (which needs a garage and divorcing one's wife) I want to make small panels of nearly flat shapes and assemble them one by one. I make a few panels a weekend, so it's a slow, but sure, progress. The panel I showed you would become the part of the floor. Another advantage of these panels is that if I get bored with the recumbent project, I can reuse the panels for chairs etc.

Now that I am thinking further on this........ what do you think if I use a vertical banddsaw with a fine blade, and run tap water continously through the cutting edge? If yes, I need to look for a type of a saw that would survive being flooded with water. Motor on top, open design which can dry out. This trick did miracles for my glass micro-drilling project using a dremmel and a DRO endmill. I.e. I now can cut micro-holes in glass 0.5 mm in diameter, of similar quality as a high-end CNC for glass cutting (companies charge $50 per hole for this kind of job). I inspected my holes under a microscope -- chip size was 25 microns or so, I was quite pleased. My microholes are useless for composites, but the trick of running water may be borrowed.

BTW diamond blades that I used for cutting glass suck ass for cutting cured composites, in my hands at least. The epoxy gunks up the diamond burr and makes it smooth, almost oiled.

runcyclexcski
carolina Posted - 05/14/2018 : 21:07:26
I guess with the vaccum your screwed for trimming. That was terrys reminder. Velomobile industry does not vaccum.

I値l mention again full face respirator and cut outside.

You never told what your making. Are you building some kind of recumbent??
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velosRus.com
runcyclexcski Posted - 05/14/2018 : 17:12:42
Carolina -- the trick of curing while it's still wet and soft is a good idea... except that I would need to take it out of the bag before it's fully cured? Wouldn't that compromise the integrity of the panel (to remove vacuum before it's fully cured). If not, good to know, will try that.

Grinder: if I had a large shop with a HEPA filter all to myself, I would do it. I would prefer not to pulverize the fibers into the air. Something that my lungs may regret 10 years down the road, know that as a biochemist. Looking for smth something low-impact/low RPM. Of course that means time, I know. ANyway I think I will try the wet cutting trick.

Terry, thanks for your note. I have had T-nuts pulled out of my 7K Madone Bike frame before not a fan. I like large concact surfaces, and having those side plates redistributes the pressure and allows me some freedom on where exactly to tap, as I am experimenting with different shapes. At any rate, I am not sure why the metal plates matter for the trimming question: plates or no plates I still need to trim the cured fibers. Exacto knife: if I have a 3x3' panel, 12 feet of cutting is not what I am looking for. I tried it, yes.



runcyclexcski
carolina Posted - 05/11/2018 : 19:49:33
Ill mention 2 things again, a grinder (harbor freight) with 4 inch disc (metal ones and composition). I been in this shop 4 years every day cutting with grinder. Dremel is for fine stuff. Some don稚 want to get involved with gelcoat or duratec because of money or cutting corners.

You may consider a rivnut kit from ebay. I have one and love it. The china ones, u haf to tweek & file a bit but now works great and cheap. Just type in ebay.

What terry said too: trim your piece after its cured a while. Ive set clock and got up to trim, then no cutting next day. Just sanding.


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velosRus.com
Terry Posted - 05/11/2018 : 18:12:20
Well, if that is fibreglass on the outside of a wood boundary? You should be able to trim it with an exacto knife. Or any sharp blade!

Without further explanation , I am lost as to what you are trying to accomplish.....

Why on earth would you embed a metal piece in a layup just to tap some threads? Isn't that what T-nuts are for?

Way more info needed,,,,,,,
runcyclexcski Posted - 05/11/2018 : 14:24:46
it's a corner of a cured vacuum-bagged honeycomb. The brown stuff is the aramid honeycomb (6 mm cell, 10 mm thick) sandwiched between two clear fiberglass sheets. The wood pieces around it (10 mm thick) define the rectangular shape. There is also a steel 90 deg corner bracket on the outside of the wood frame, but underneath the fiberglass layer. The bracket will be used to thread tapping (2-56 or 4-40). I need to cleanly get rid of the fiberglass on the outsude, assuming that this panel may be quite large (say, 3x3"). I tried dremelling, it was slow/smoky/nasty.

runcyclexcski
runcyclexcski Posted - 05/11/2018 : 14:18:37
Carolina, I used to use a dremel for this, and it was a disaster... It was OK for small-dia tubes and pieces, but not for 1 foot + long pieces, particularly for those with any depth to them (i.e. honeycombs with two skins). I fully agree with the dust mask etc, I am pretty careful when it comes to air quality.

runcyclexcski
Garrie L Hill Posted - 05/11/2018 : 09:25:29



OK, here is Andrey's picture. Andrey; Why don't you start over, and ask your question referencing what we can see in your picture.

Garrie "carbon based lifeform" Hill
HPRA Co-Dictator of the East
for pics of some of my time and money sucking projects
http://s58.photobucket.com/albums/g277/cfbb/
and videos
http://vimeo.com/5513519


carolina Posted - 05/11/2018 : 09:22:49
Use a full-face respirator and do all cutting outside. Blown off with air hose, & yourself. I wear appron too. Hi-speed cutting disc痴 . Hom depot & lowes sell a metal disc for small dremel. And the grinder from harbor freight works great/$9 on sale days.
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velosRus.com
jjackstone Posted - 05/11/2018 : 09:03:22
I have had good luck using an oscillating cutting tool for this type of work. As long as the excess material you are trimming off has epoxy in it the tool will work pretty well. I haven't used it to cut through metal but the blades I use are rated for metal(I would assume light weight metal). Also haven't used it on Kevlar so I'm not sure how that would work. You can cover the area to be cut with masking tape to lessen the amount of dust but you're always going to get some. I usually try to place the shop vac hose right next to the area I'm cutting to suck the dust up immediately.



JJ
runcyclexcski Posted - 05/11/2018 : 08:13:26
Terry -- does it say permissions error? I posted it on my shared google drive.

runcyclexcski
runcyclexcski Posted - 05/11/2018 : 08:12:15
thanks, Garrie, just emailed one.

runcyclexcski
Garrie L Hill Posted - 05/10/2018 : 20:19:34
Send your pictures to me and I will post them.

Garrie@recumbents.com

Garrie "carbon based lifeform" Hill
HPRA Co-Dictator of the East
for pics of some of my time and money sucking projects
http://s58.photobucket.com/albums/g277/cfbb/
and videos
http://vimeo.com/5513519



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