Carbon Boom Design

BalticBandit

Super Anarchist
11,114
36
The only issue I see with that plan is the fiber crimping (minor but research shows just 7 degrees of fiber crimp makes a significant impact on strength) If you wrap tight around the inflatable tube before going into the hard tube, you'd prolly be able to avoid that since the laminate would have to expand and the fiber crimps would get straightened out. this is why Hall spars exclusively use aluminum mandrels, when the part goes into the autoclave the aluminum expands with the heat and straightens any fiber crimps.
The plan is to wrap loosely around the inflatable tube offsetting the seams by 90 deg each layer. What I see this as allowing me to do is to eventually go to a female mold for oblong parts.

Another thought I had to experiment with was to use a discardable spacers to hold apart the wetted out layers and then fill them with self-expanding urethane foam as a way of getting the benefits of "inverted vaccum pressure" on foam core parts while mimimizing post cure sanding.

 
Hi Chris and Phil

not my orignal idea!!

The pressure I use is about 10-14 psi ( I have used up to 30 psi but that went with a loud pop and is not really required) , the batterns are bolted about every 6-8 inches and are about 35x 12mm , the fabric mould is tacked in place to them with double sided tape. The fabric for the mould is a industrial product, they use it in the composites industry as peel ply and in I think the baking industry as baking sheet (so the buns do not stick) It is a glass impregnated with ptfe (teflon?), you can find it on the aerovac web site http://www.aerovac.com/files/documents/ff0250w-ff0300w.pdf this is reasionably tough and it lets out all the excess resin. the ends I bung with round bits of mdf of about 25mm thick so I can put a jubalee clip around or last time I made a tube I held the ends in with tie wraps. The valve sticks through one end (valve from a bike inner tube) and is tacky taped to a standard bagging vac tube, nylon, we have this at work for bagging small internal moulds, same stuff as you would use to vac down your boat but a narrow tube of it.

The problem with using a solid outer layer/mould with wet rein systems is that you can not get the air bubbles out, with a pre preg layup you could debulk before you put the mould to gether.

Using a mandral is great however if they are not round and true the they lock when you try and take the spar off the mould, it also only really works well when you introduce heat and with my home set up thats not great.

Russell - in this instance you are no way near the critical limits of the material, do not worry about the crimp.

 

Steve Clark

Super Anarchist
I have heard of this being done with Mylar, and was thinking that a film sailcloth would work well.

On the other hand, the ability to bleed through the tube is pretty key, so I was wondering if conventional Dacron would work.

Probably a test is necessary.

SHC

 

usa7606

Member
195
0
I picked up a carbon tube for $100. I just asked around to all the riggers in the area and someone had a 76mm tube. Apparently it was a forespar spin pole. It has 2mm wall thickness, same as the CST boom. Here are some pictures of the mainsheet attachment and the carbon gooseneck I made. I made the carbon plate so I could tap into the boom, and made the white delrin shims to attach to the round surface. The gooseneck took a bunch of steps to make. Making the tube, making the block to raise it up, gluing them together, gluing to the boom and filleting, then taping it in.

carbon_boom_003_1.JPG

boom2_1.JPG

 
wind_apparent said:
I've been messing with 1.5'' and 2'' fire hose. Take a length of fire hose, make some plastic or aluminum endcaps. (drill a hole for an air valve in one). hold the endcaps in place with metal hose clamps. Inflate the hose to a semi-hard state. Wrap an overlapping layer of release film on the hose, followed by your laminate. (I've been using one wrap 3k, 2 wraps 12k, followed by a bi-axial carbon sleeve) Wrap a layer of peel ply and then spiral wrap with 2'' Teflon shrink tape. Then inflate the hose the rest of the way (it will take up to 125psi) and let it cure hanging vertically. after cure, take off the tape and peelply and hook the end fitting up to a vacuum pump to make the hose collapse. take the endcap off and pull hose and release film out. I have yet to try it with prepreg, but the hose is good to 220deg, I'm not sure if it'll last 3 hours in the oven. That's the next test. Fire hose is available in 1.5'', 2", 2.5", and 3" so pretty standard dinghy tube sizes.
The hose idea sounds good I was thinking a 4 or 5" at about 10 feet long. I'm thinking 3 wraps of 12oz double bias and a finishing layer of 6oz plain weave plus reinforcing. Not sure if this is the right layup but is worth asking

 

usa7606

Member
195
0
wind_apparent said:
I've been messing with 1.5'' and 2'' fire hose. Take a length of fire hose, make some plastic or aluminum endcaps. (drill a hole for an air valve in one). hold the endcaps in place with metal hose clamps. Inflate the hose to a semi-hard state. Wrap an overlapping layer of release film on the hose, followed by your laminate. (I've been using one wrap 3k, 2 wraps 12k, followed by a bi-axial carbon sleeve) Wrap a layer of peel ply and then spiral wrap with 2'' Teflon shrink tape. Then inflate the hose the rest of the way (it will take up to 125psi) and let it cure hanging vertically. after cure, take off the tape and peelply and hook the end fitting up to a vacuum pump to make the hose collapse. take the endcap off and pull hose and release film out. I have yet to try it with prepreg, but the hose is good to 220deg, I'm not sure if it'll last 3 hours in the oven. That's the next test. Fire hose is available in 1.5'', 2", 2.5", and 3" so pretty standard dinghy tube sizes.
The hose idea sounds good I was thinking a 4 or 5" at about 10 feet long. I'm thinking 3 wraps of 12oz double bias and a finishing layer of 6oz plain weave plus reinforcing. Not sure if this is the right layup but is worth asking
4 or 5" would be really big. 3.5" or 3" ID is more the size of a dinghy boom. maybe someone else can chime in but i think most booms are made of layers of unidirectional, mostly running the length of the boom(0). then there's +-45 and 90 layers of uni mixed in but the majority is uni running the length of the boom. it won't be very stiff just using +-45s and plain weave.

 

another 505 sailor

Super Anarchist
7,527
196
7.3.1 No dimension of the boom spar cross section shall exceed 102mm.

102 millimeters = 4.01574803 inches

Max size makes rigging the boom easier.

 

another 505 sailor

Super Anarchist
7,527
196
7.3.1 No dimension of the boom spar cross section shall exceed 102mm.

102 millimeters = 4.01574803 inches

Max size makes rigging the boom easier.
I hate to rain on your parade

rule 66; boom without fittings shall be able to pass through a circle having a diameter of 150mm.

I am thinking about going for an elliptical boom strength in form and the like
What's rule 66?

7.3 Boom

7.3.1 No dimension of the boom spar cross section shall exceed 102mm.

7.3.2 A maximum of 25mm boom spar curvature is permitted.

7.3.3 An outer limit mark not less than 10mm in width shall be placed around the boom spar. The outer point distance shall not exceed 2858mm.

7.3.4 The overall length of boom from the aft edge of the mast spar to outer end of boom shall not exceed 3308mm.

 

usa7606

Member
195
0
7.3.1 No dimension of the boom spar cross section shall exceed 102mm.

102 millimeters = 4.01574803 inches

Max size makes rigging the boom easier.
I hate to rain on your parade

rule 66; boom without fittings shall be able to pass through a circle having a diameter of 150mm.

I am thinking about going for an elliptical boom strength in form and the like
What's rule 66?

7.3 Boom

7.3.1 No dimension of the boom spar cross section shall exceed 102mm.

7.3.2 A maximum of 25mm boom spar curvature is permitted.

7.3.3 An outer limit mark not less than 10mm in width shall be placed around the boom spar. The outer point distance shall not exceed 2858mm.

7.3.4 The overall length of boom from the aft edge of the mast spar to outer end of boom shall not exceed 3308mm.
rule for the flying dutchman.

 
wind_apparent said:
wind_apparent said:
I've been messing with 1.5'' and 2'' fire hose. Take a length of fire hose, make some plastic or aluminum endcaps. (drill a hole for an air valve in one). hold the endcaps in place with metal hose clamps. Inflate the hose to a semi-hard state. Wrap an overlapping layer of release film on the hose, followed by your laminate. (I've been using one wrap 3k, 2 wraps 12k, followed by a bi-axial carbon sleeve) Wrap a layer of peel ply and then spiral wrap with 2'' Teflon shrink tape. Then inflate the hose the rest of the way (it will take up to 125psi) and let it cure hanging vertically. after cure, take off the tape and peelply and hook the end fitting up to a vacuum pump to make the hose collapse. take the endcap off and pull hose and release film out. I have yet to try it with prepreg, but the hose is good to 220deg, I'm not sure if it'll last 3 hours in the oven. That's the next test. Fire hose is available in 1.5'', 2", 2.5", and 3" so pretty standard dinghy tube sizes.
The hose idea sounds good I was thinking a 4 or 5" at about 10 feet long. I'm thinking 3 wraps of 12oz double bias and a finishing layer of 6oz plain weave plus reinforcing. Not sure if this is the right layup but is worth asking
I was also thinking of putting a spar down the middle of the hose so that when its inflated it has to take on an elliptical shape instead if round, but I haven't had a chance to mess with it yet.
have you played with the eliptical hose and tube idea yet

 

sadolph

Super Anarchist
1,903
1
Ottawa, Canada
Thinking about this some,

I have some clean unused 505 booms that are the old Schaffer section - not round. These could be a decent mandrel, using the technique where you put down one layer, then slice it down the center and pop it off the mandrel to get release, then laminate the final layers.

That section would offer a convenient flat surface for attachment of fittings - something I hate about round sections.

I may give that a try for fun.

Has anyone got a known good laminate schedule?

thanks, Steve

 
Thinking about this some,

I have some clean unused 505 booms that are the old Schaffer section - not round. These could be a decent mandrel, using the technique where you put down one layer, then slice it down the center and pop it off the mandrel to get release, then laminate the final layers.

That section would offer a convenient flat surface for attachment of fittings - something I hate about round sections.

I may give that a try for fun.

Has anyone got a known good laminate schedule?

thanks, Steve
One of my early thoughts was to do this with an old mast from a keelboat using the method as described a couple of posts above cleaning the first layer from the mandrel before laying up the rest same layup but eliptical

 
Regarding light bulbs as mandrels.... first reaction is no. I suppose you could test it by putting under vacuum and seeing if it holds up.

Regarding bare Shaffer booms as 505 boom mandrels, would prob work alright. The track for the sheet hangers and foot rope could pose problems, but wouldn't be impossible to work around. As far as layup is concerned.... without proper data the way to do it is to work backwards. You know the section dimensions and the material. Find the booms EI value, match your layup to meet or exceed the alum values. If you are truly serious about doing this, but aren't keen on the engineering to calculate this, call or email me and we'll discuss it. I'd be willing to collaborate on this project and have the necessary knowledge/education to work it out, but not the shop space, tools, or materials to complete the work. Find my contact info at www.505fleet25.com under the contacts section.

 

sadolph

Super Anarchist
1,903
1
Ottawa, Canada
Regarding light bulbs as mandrels.... first reaction is no. I suppose you could test it by putting under vacuum and seeing if it holds up.

Regarding bare Shaffer booms as 505 boom mandrels, would prob work alright. The track for the sheet hangers and foot rope could pose problems, but wouldn't be impossible to work around. As far as layup is concerned.... without proper data the way to do it is to work backwards. You know the section dimensions and the material. Find the booms EI value, match your layup to meet or exceed the alum values. If you are truly serious about doing this, but aren't keen on the engineering to calculate this, call or email me and we'll discuss it. I'd be willing to collaborate on this project and have the necessary knowledge/education to work it out, but not the shop space, tools, or materials to complete the work. Find my contact info at www.505fleet25.com under the contacts section.
Interesting offer. I have 3 clean new schaeffer booms, could laminate 3 booms at a shot.

I also have a nice vacuum system.

 

gui

Anarchist
wind_apparent said:
Has anyone tried using floresent light tubes as mandrels? was thinking you could tape the tube with flashbreaker, lay up, cure, then blow up the bulb and pull the mess out.
Yes yes yes, a body of mine or I did that exact thing. If I remember, we ended up with a lot of the broken glass still glued to the wall. Not a bad low tech method if you properly wax/pva the bulb.

 




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