DIY custom frames, home carbon-fiber method simplified
- Thread starter spinningmagnets
- Start date
spinningmagnets
100 TW
Please add any links with pics that display the techniques that are being posted ! I am not experienced with any of these methods, but I am persuaded that vacuum bagging and spray-on fibers are mass-production techniques. If I only need to make one frame, and I can spend a dozen Saturdays making it, this thread has given me some great information.
I stll like the idea of cloth lay-up over a stiff foam form, but for those who want to run gear-shift/brake cables through the inside of the frame, it wouldn't be hard to split the foam core after shaping, and then slice out a round channel. You could even inlay aluminum tubing in most of the channel that has been radiussed by a tube bender (where curves are needed), and a tube bender can be easily made in a garage out of wood.
The adhesive that glues the two halves back together can also be the type that fills any voids between the foam and tubing.
Stainless steel hydraulic tubing can also be easily acquired and bent, and stright runs can be from thin-wall titanium tubing. With the CF skin handling the frame loads, the tubing doesnt have to be welded, brazed, or pretty...
I stll like the idea of cloth lay-up over a stiff foam form, but for those who want to run gear-shift/brake cables through the inside of the frame, it wouldn't be hard to split the foam core after shaping, and then slice out a round channel. You could even inlay aluminum tubing in most of the channel that has been radiussed by a tube bender (where curves are needed), and a tube bender can be easily made in a garage out of wood.
The adhesive that glues the two halves back together can also be the type that fills any voids between the foam and tubing.
Stainless steel hydraulic tubing can also be easily acquired and bent, and stright runs can be from thin-wall titanium tubing. With the CF skin handling the frame loads, the tubing doesnt have to be welded, brazed, or pretty...
John in CR
100 TW
JS Tyro said:
Constrained only by choice, and here in Costa Rica good stuff is hard to find and you don't know what's in the interior layers. Essentially making my own plywood with epoxy as the adhesive with fiberglass on one face and carbon/kevlar weave on the other will be exceedingly strong and rigid. Since Balsa grows here, I may be able to find some in sheet form for a thicker lightweight sandwich which drastically increases rigidity.
Regarding squeegee vs bagging, with large flat or gently curving surfaces like with a boat, I believe a skilled layup has an advantage. With a bike, bagging is probably better.
John
Just to be clear - I would never recommend that the average person not use vacuum bagging. The technique is relatively simple and very effective, especially for small stuff like a bike frame or other bike parts.
I don't know if I'd recommend using a food vacuum bagger. You can put a trap in the path to avoid having any surplus epoxy sucked into any vacuum pump you use. Some boat builders use old fridge compressors as pumps. If you can find some tubular polyethylene film to use on carbon/Kevlar/fiberglass sheaths, that's nearly perfect and a tad easier to use than flat sheets in some cases.
I don't know if I'd recommend using a food vacuum bagger. You can put a trap in the path to avoid having any surplus epoxy sucked into any vacuum pump you use. Some boat builders use old fridge compressors as pumps. If you can find some tubular polyethylene film to use on carbon/Kevlar/fiberglass sheaths, that's nearly perfect and a tad easier to use than flat sheets in some cases.
dave.com
10 mW
Interesting fairing construction method using foam strips. Kind of similar to strip plank hull construction used in kayaks and canoes.
http://www.wisil.recumbents.com/home.asp?URL=wisil/whatsup.htm#Fairing Building Projects The shell is made using wet layup, but later on in the article he uses vacuum bagging to make the subframe that supports the crank. This shell construction method interests me for 2 reasons, it's a double sided, cored structure, which is very stiff and light, and it is adaptable to moldless or female mold construction.
More fairing and bike construction info from wisil http://www.wisil.recumbents.com/home.asp?URL=wisil/whatsup.htm#Fairing Building Projects
http://www.wisil.recumbents.com/home.asp?URL=wisil/whatsup.htm#Fairing Building Projects The shell is made using wet layup, but later on in the article he uses vacuum bagging to make the subframe that supports the crank. This shell construction method interests me for 2 reasons, it's a double sided, cored structure, which is very stiff and light, and it is adaptable to moldless or female mold construction.
More fairing and bike construction info from wisil http://www.wisil.recumbents.com/home.asp?URL=wisil/whatsup.htm#Fairing Building Projects
Jeremy Harris
100 MW
I've posted this before, but the strip plank balsa technique used by Michael Storer looks pretty good, too. I had a play with this a while ago, to make a fairing, and found it to be easier than strip plank foam, as the stiffness of the balsa helps to get fair lines. Here's a link: http://www.storerboatplans.com/Balsacanoe/Balsacanoe.html
Michael is a member of this forum, so might chip in with some advice.
Jeremy
Michael is a member of this forum, so might chip in with some advice.
Jeremy
A bit heavier, but readily available is cedar strip. Around these parts, that's the only "respectable" canoe construction technique, short of birch bark.
Interesting - on the balsa strip canoe site you point to, he refers to 2.25 oz fiberglass as being "light." I know one guy that used 0.75 oz. fiberglass on a cedar paddle. Invisible under a sanded-smooth epoxy. You can get such fiberglass at (some) RC aircraft shops.
Interesting - on the balsa strip canoe site you point to, he refers to 2.25 oz fiberglass as being "light." I know one guy that used 0.75 oz. fiberglass on a cedar paddle. Invisible under a sanded-smooth epoxy. You can get such fiberglass at (some) RC aircraft shops.
dave.com
10 mW
Jeremy Harris said:
Yeah, thought the wisil stuff was pretty well known in the speedbike and velomobile world, but didn't search here. I think I'll pass the link along to the bentrider vm forum, there might be some interest in a 12lb velomobile fairing!
I like the basla for the same reasons you site. I presume Michael's joining method is also cove and bead? his page doesn't say specifically, but I can't really see an alternative that gives you closed joints. I despise CA glue for RC models because of the evil vapors, it's hard to beat for expedience though. Titebond works well with balsa, but requires more patience.
I can imagine a balsa sandwich of carbon/balsa/carbon would be hell for stout and very light.
If you're going to go with carbon/balsa sandwich construction, end-grain balsa is stronger and lighter than balsa strip would be. End grain means that the grain is nominally perpendicular to the carbon fiber layers rather than parallel. It is like having honeycomb core with very tiny tubes (the balsa cell structure). A little more awkward to work with for curved surfaces compared to strips, but with a router and a bead and cove bit you could make do (taking care, considering this stuff comes with a light fiberglass mesh backing). It's about CAD$2.00/sq.ft. in sheets that are 1/4"x2'x4' at a shop local to me. That compares to $5.83/sq.ft. for Core-Cell foam in bead and cove (but 1/2" thick, the thinnest they sell here - there's no difference in price between 1/2" and 3/4").
Jeremy Harris
100 MW
I agree that end grain balsa gives far and away the best strength as a core material, but the very significant advantage of using strip plank balsa is the ease of getting fair curves. I tried foam strip plank and, although it works well with thick planks, once you get down to sub-1/4 plank thickness you end up with a very rippled surface.
I built an experimental leading edge D box spar for an aircraft wing using 1/16" balsa planks, glassed inside and out with thin cloth. The result was plenty strong enough and very stiff; as with a lot of these composite structures stiffness is often more important than strength. I once made an undercarriage (landing gear) from foam cored carbon fibre, using the design tensile/compressive strength data for hand laid up unidirectional CF. The result was a part that was plenty strong enough, but ridiculously flexible. I ended up with a massively over-strength part, just to get the stiffness that was needed. I'd hazard a guess that a monocoque bike would be much the same, in that stiffness might well be far more important than strength, except around the high load points, like the steerer tube, seat mount, motor/pedal mount and rear wheel attachment.
I'm pretty sure Michael Storer did bead and cove his strips, but I found that when using thinner balsa sheet you can get away without doing this, if you temporarily support the back of each joint with tape, which also helps pull the strips tight together. I used ordinary PVA for edge joints as I'm no fan of isocyanate glues, either. PVA was easy to clean up on the outside, and as strength isn't really important for this joint it did just fine. One big problem with using balsa in this way is filling it to sand the shape fair. I've not found a filler that's as soft as balsa, which makes filling and sanding a real pain, as the balsa sands away faster than the filler. The secret is to make tight joints and get the strips as fair as possible, so no filler is needed.
Jeremy
I built an experimental leading edge D box spar for an aircraft wing using 1/16" balsa planks, glassed inside and out with thin cloth. The result was plenty strong enough and very stiff; as with a lot of these composite structures stiffness is often more important than strength. I once made an undercarriage (landing gear) from foam cored carbon fibre, using the design tensile/compressive strength data for hand laid up unidirectional CF. The result was a part that was plenty strong enough, but ridiculously flexible. I ended up with a massively over-strength part, just to get the stiffness that was needed. I'd hazard a guess that a monocoque bike would be much the same, in that stiffness might well be far more important than strength, except around the high load points, like the steerer tube, seat mount, motor/pedal mount and rear wheel attachment.
I'm pretty sure Michael Storer did bead and cove his strips, but I found that when using thinner balsa sheet you can get away without doing this, if you temporarily support the back of each joint with tape, which also helps pull the strips tight together. I used ordinary PVA for edge joints as I'm no fan of isocyanate glues, either. PVA was easy to clean up on the outside, and as strength isn't really important for this joint it did just fine. One big problem with using balsa in this way is filling it to sand the shape fair. I've not found a filler that's as soft as balsa, which makes filling and sanding a real pain, as the balsa sands away faster than the filler. The secret is to make tight joints and get the strips as fair as possible, so no filler is needed.
Jeremy
If you're really fanatical about it, you could use a mix of strips in some areas and end grain in others. 
Since balsa is so light and soft, you could probably run a bead and cove bit in a mini-router like a Dremel if you could get the shaft to fit. It would take very little time as well. I would much prefer that to a filler.
BTW - when you wrote PVA, I initially thought polyvinyl alcohol, the mold release and not polyvinyl acetate, the adhesive. It took a half second for my brain to sort it out.
Since balsa is so light and soft, you could probably run a bead and cove bit in a mini-router like a Dremel if you could get the shaft to fit. It would take very little time as well. I would much prefer that to a filler.
BTW - when you wrote PVA, I initially thought polyvinyl alcohol, the mold release and not polyvinyl acetate, the adhesive. It took a half second for my brain to sort it out.
12p3phPMDC
1 kW
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- Mar 16, 2009
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JS Tyro said:12p3phPMDC said:
<jealousmode>I hate it when people post stuff like that</jealousmode>
Very sweet design and construction.
Pretty inspiring build huh?
He also built one using straight wood. No carbon. Veneer it with ash burl instead
for a high end furniture look. Sweet!
After looking for a local source of CF sleeving and seeing the price/availability of that and Kevlar, I decided to experiment with basalt fiber biaxial sleeves. I'll be ordering some and making a seat frame and handlebar for my recumbent (I hate the fact that the seat back is fixed in place; being able to fold it down would allow me to put the bike in the back of my Civic hatchback).
Basalt fiber is heavier than CF or Kevlar but stronger and lighter than S- or E-glass. Anyone use it? Sounds like an interesting option for frame components that are essentially tubular (+/- a bit of shaping). If nothing else, I can say it's just like moon rock (nearly )
Basalt fiber is heavier than CF or Kevlar but stronger and lighter than S- or E-glass. Anyone use it? Sounds like an interesting option for frame components that are essentially tubular (+/- a bit of shaping). If nothing else, I can say it's just like moon rock (nearly
)John in CR
100 TW
Here's an interesting method for super lightweight but strong enough for boats. eg an 8lb canoe! I wouldn't trust a dacron skinned boat in the open water, but for a fairing it may be ideal, and easy to repair. http://www.gaboats.com/
John
John
I've considered skin-on-frame for a while as a fairing. The problem is that it is difficult to get a smooth shape. Every rib results in a peak in the surface, so it is rather uneven aerodynamically. It could be used along flat sections if the highly curved sections are rigid construction (such as composite).
I remember regularly seeing a guy cycling a recumbent with a plastic covered frame as a shell about 30 years ago. We'd pass on Sunday long rides in Hudson, Quebec (my rides started and ended at my apartment in downtown Montreal). While he may not have had the most perfect aerodynamics, he was still a lot faster than the rest of us. But then, we didn't have to contend with the humidity building up inside a shell; his transparent shell was often covered with condensation.
While ultralight Dacron (or Ceconite) (all just fancy brand names for polyester) paddle craft are too fragile for my tastes, heavier weights of polyester work quite well and are surprisingly strong. Many kayakers have made skin-on-frame with polyester (as well as nylon, cotton, hemp and other fabrics) and they serve very well. I've paddled a s-o-f kayak and they are very light and responsive; never got around to building one though...
I remember regularly seeing a guy cycling a recumbent with a plastic covered frame as a shell about 30 years ago. We'd pass on Sunday long rides in Hudson, Quebec (my rides started and ended at my apartment in downtown Montreal). While he may not have had the most perfect aerodynamics, he was still a lot faster than the rest of us. But then, we didn't have to contend with the humidity building up inside a shell; his transparent shell was often covered with condensation.
While ultralight Dacron (or Ceconite) (all just fancy brand names for polyester) paddle craft are too fragile for my tastes, heavier weights of polyester work quite well and are surprisingly strong. Many kayakers have made skin-on-frame with polyester (as well as nylon, cotton, hemp and other fabrics) and they serve very well. I've paddled a s-o-f kayak and they are very light and responsive; never got around to building one though...
John in CR
100 TW
JS Tyro said:
Ah, but what about a combination of methods, lost foam and geodesic structure.
eg
1. Fair a block of foam to the shape you want (easily done in a day).
2. Instead of covering the foam entirely with a material requiring resin impregnation (and weight, cost, and time), you use the kevlar roving triangulation approach of GABoats. If dead smooth curves are desired near the nose (to me only necessary for racing or going for a record), fully cover that portion of the foam with the lightest weight cloth you can find.
3. Remove the foam, leaving a rigid frame with smooth curves.
4. Add in a few cross members, which are also form the attachment to the bike.
5. Heat shrink the Dacron covering to the frame, which may not even require sealing of the dacron for a fairing, and then no finish is required.
If an 8lb canoe can be sufficiently strong and rigid, there's no reason a full fairing can't be 4-5lbs, since it supports little weight. The real challenge would be to make the geodesic structure strong enough for direction connection of the bike components to eliminate most of the traditional bike frame. That's where my interest lies, a one piece structure with a removable top that has a pivot for the rear swingarm, head tube, bottom bracket, and ventilated battery/electronics compartment built in. I have so many projects in que that this plan will probably change 20-30 times before any build.
John
There's a world of difference in the way a boat is supported on the water and the way a bike is supported on land. A canoe can carry an enormous load when in the water. Lift it out of the water while loaded, support it by the ends, and it can break. A bike is very much like the canoe out of water. When the canoe is in the water, the load is carried directly by the water, with the hull keeping the load separated from the water. The actual stresses on the hull are quite low compared to the load being carried. When the canoe is out of the water, the load has to be carried by the hull acting as a structural beam. This can put a lot of stress on the hull and particularly on the gunwales, which stabilize the hull along the open top. Kayaks are much less susceptible to this, as they have a monocoque shell hull rather than an open "bathtub" hull.
If you want to design a bike using this sort of technique, you'd need to create a skin-on-frame monocoque shell for maximum structural efficiency. Every opening in the shell (e.g. where the rider gets in and out) has to be reinforced to prevent it from being the weakest point in the design. For this reason, a light frame design like the geodesic boats would not work well. The skin/frame would be too flexible. Everything would have to be scaled up to stiffen and strengthen the design. You could use the lightweight approach on the ends where little load is carried.
If you want to design a bike using this sort of technique, you'd need to create a skin-on-frame monocoque shell for maximum structural efficiency. Every opening in the shell (e.g. where the rider gets in and out) has to be reinforced to prevent it from being the weakest point in the design. For this reason, a light frame design like the geodesic boats would not work well. The skin/frame would be too flexible. Everything would have to be scaled up to stiffen and strengthen the design. You could use the lightweight approach on the ends where little load is carried.
spinningmagnets
100 TW
"Lock" just sent me a useful link with good info and pics about making a curvy shape with cardboard (don't laugh) and then fiber-glassing it inside and out with cloth/epoxy.
http://microship.com/resources/cardboard-core-composites.html
http://microship.com/resources/cardboard-core-composites.html
John in CR
100 TW
For something as pictured above, I'd definitely go with very thin plywood...like cheap 3mm ply. It can easily bend that far, and if curved becomes extremely rigid with a single layer of glass and epoxy. Also, I see way too much in the way of flat surfaces in that build. With flat material you have to add a lot of weight and work in additional layers to achieve reasonable strength compared to a curved structure.
John
John
Lock
100 MW
Article posted August 1`09, sub-titled "Exploring some potential ultra light-weight vehicle building materials" here:
http://www.autospeed.com/cms/A_111401/article.html
Executive summary:
In AutoSpeed we've recently covered a couple of techniques for building ultra light-weight vehicles.
...composite fibreglass and aluminium honeycomb panels to form the monocoque...
...chassis...covered in expanded polystyrene modelling foam, carved to shape...covered in fibreglass cloth and resin.
also
...high strength chrome-moly steel tube, nickel-bronze brazed together.
...are there any alternatives?
Yes, there's a composite material that is very cheap, widely available in flat sheets, can be easily worked, has available excellent glues...
It's wood...
...composite wood sandwich construction...
Another wood-based material worth investigating is paper honeycomb paneling.
...and:
Conclusion
It may sound a bit down-market over the use of exotic materials like carbon fibre or Kevlar, but naturally occurring cellular composites (ie wood!) in either laminated, shaped form or as honeycomb panels, are cheaper, more easily worked, less energy intensive in production, and can be later recycled. As history shows, if it is used correctly, it can also be surprisingly strong and light.
If you're building an ultra light-weight vehicle, wood is definitely a material to investigate.
http://www.autospeed.com/cms/A_111401/article.html
Executive summary:
In AutoSpeed we've recently covered a couple of techniques for building ultra light-weight vehicles.
...composite fibreglass and aluminium honeycomb panels to form the monocoque...
...chassis...covered in expanded polystyrene modelling foam, carved to shape...covered in fibreglass cloth and resin.
also
...high strength chrome-moly steel tube, nickel-bronze brazed together.
...are there any alternatives?
Yes, there's a composite material that is very cheap, widely available in flat sheets, can be easily worked, has available excellent glues...
It's wood...
...composite wood sandwich construction...
Another wood-based material worth investigating is paper honeycomb paneling.
...and:
Conclusion
It may sound a bit down-market over the use of exotic materials like carbon fibre or Kevlar, but naturally occurring cellular composites (ie wood!) in either laminated, shaped form or as honeycomb panels, are cheaper, more easily worked, less energy intensive in production, and can be later recycled. As history shows, if it is used correctly, it can also be surprisingly strong and light.
If you're building an ultra light-weight vehicle, wood is definitely a material to investigate.
Thud
1 MW
Bump- never noticed this thread before.
here are some links for more eye candy.
Malric's blog shows the progesion of a hobby into Zochra Bikes
http://malricsworld.blogspot.com/2006/11/carbon-high-racer-construction.html
go to the home page & check his awsome links to other areas of like interests.
I wish we had a vocational class like this for me in HS. (carbon fiber was something you only read about in magazines)
http://www.blids.nl/gallery/Carbon-Recumbent-Workshop-2004
http://www.blids.nl/gallery/Carbon-Recumbent-Workshop-2005
here are some links for more eye candy.
Malric's blog shows the progesion of a hobby into Zochra Bikes
http://malricsworld.blogspot.com/2006/11/carbon-high-racer-construction.html
go to the home page & check his awsome links to other areas of like interests.
I wish we had a vocational class like this for me in HS. (carbon fiber was something you only read about in magazines)
http://www.blids.nl/gallery/Carbon-Recumbent-Workshop-2004
http://www.blids.nl/gallery/Carbon-Recumbent-Workshop-2005
etard
100 kW
http://www.plascore.com/marinevideo_lg.htm
Found this video after I did a search on honeycomb construction, thanks Lock. There is a snowboard made with this nomex honeycomb material. Right now I'm picturing a frame with two side panels, a wood skeleton to make seperate component layout with internal battery, controller, etc... and some sort of access panel for the whole thing. Something like this, but much smaller:
This Nomex stuff is suitable for forming simple curves. I would love to get a sheet of this stuff to mess around with. I wonder how much it costs?
http://www.plascore.com/pn1-nomex-aramid-fiber-honeycomb.htm
edit:
Wow, it's kinda expensive:
http://www.aircraftspruce.com/catalog/cmpages/01-00488.php
Found this video after I did a search on honeycomb construction, thanks Lock. There is a snowboard made with this nomex honeycomb material. Right now I'm picturing a frame with two side panels, a wood skeleton to make seperate component layout with internal battery, controller, etc... and some sort of access panel for the whole thing. Something like this, but much smaller:
This Nomex stuff is suitable for forming simple curves. I would love to get a sheet of this stuff to mess around with. I wonder how much it costs?
http://www.plascore.com/pn1-nomex-aramid-fiber-honeycomb.htm
edit:
Wow, it's kinda expensive:
http://www.aircraftspruce.com/catalog/cmpages/01-00488.php
AussieJester
1 TW
This is something i have been looking into for my next custom build, i shall go with a carbon
fiber/ vinylester resin over foam structure myself negating the need for vacuum bagging...
AFAIK the internal structure in this case the foam and in the case of the trailer a page back the cardboard
is there more for 'shaping' of the overlaid carbon fiber and provides very little if any strength...
curves in the carbon fiber give the strength, a flat piece of carbon fiber v's flat piece with ripples
ruts or curves in it is much stronger IIRC?... The Nomex pictured above
is sold by Fiberglass and Resin sales where i buy my glassing supplies from
i might look at the different sheets they have and contemplate using this over the foam!
Shall be a fun and possibly expensive flop when i attempt it, if i succeed though will be an oober light
weight rc cruiser , Hopefully my fiberglass experience will helpz me somewhat
KiM
fiber/ vinylester resin over foam structure myself negating the need for vacuum bagging...
AFAIK the internal structure in this case the foam and in the case of the trailer a page back the cardboard
is there more for 'shaping' of the overlaid carbon fiber and provides very little if any strength...
curves in the carbon fiber give the strength, a flat piece of carbon fiber v's flat piece with ripples
ruts or curves in it is much stronger IIRC?... The Nomex pictured above
is sold by Fiberglass and Resin sales where i buy my glassing supplies from
i might look at the different sheets they have and contemplate using this over the foam!
Shall be a fun and possibly expensive flop when i attempt it, if i succeed though will be an oober light
weight rc cruiser , Hopefully my fiberglass experience will helpz me somewhat
KiM