Hi all! I was about to start a project making a fan shroud and had a few questions. I have seen where people use some basic fabric like an old table cloth and make shapes for speaker enclosures or fan shrouds by wrapping MDF and then coating the piece of fabric with fibergl*** resin, and then putting pieces of fibergl*** matt in the jelly, and then painting more jelly over the matt and so on until desired thickness is achieved. My questions are: 1) The matt... all I could find was a large (40"x40" or so) sheet of it. do I cut it up small, or as large as I can for the contours I am working with? I figured it would be in like, strands and pieces but all I can find is a sheet 2)I happen to have some woven fibergl*** CLOTH at home that's of course totally different and way stronger in and of it self than the matt... any good reason I wouldn't just simple stretch that over the MDF template and brush resin on it generously and call it a day? I know it would be thin but that's not a bad thing; this will for a mechanical fan, not supporting the weight of an electric one I hope I am not "off" but posting this here, but I just wanted to ask before diving into a 4ft^2 project as we are talking a decent materials cost and I hate to waste. I plan to use this more and more often; I know I will be making surface mounted speaker boxes for the bottoms of my doors as that's the only good place for a speaker and NOT somewhere I want to cut these doors... so the shroud will be good practice Thanks all! Drew
Hey Drew, I don't think you have to use the mat or cloth if you are covering the form with a fabric and then coating it with resin. I've done this using just a jersey / blanket type material with resin. If you want to use the mat you can either cut or tear it into manageable sized pieces.
I would make it out of steel or aluminum. You don't need any more **** under the hood that will catch fire.
I use that pink roll insulation. I can usually find it for free a construction sites in the dumpster, OK so I'm cheap.
Get the shape you want, use a couple layers of the woven, and once that's hard, rough it up a little and apply as many coats of matt to get the strength and stiffness you desire. The woven will sometimes take the shape and lay down better than the matt. Just remember the side toward he mold will get nice, however the other side will need some work. The entire tunnel was pieced together, from pieces made over 4 inch PVC pipe (tunnel) and boxes made from MDF, sanded and coated with wax paper, or painted with Krylon and several coats of car wax applied to the mold. Hope his helps!
Gudgeon Bros had a great book on Constant Camber boat panel building, in wood, then skinned in gl***. Gl*** cloth provides strength, the previous tips in posts ring true. Resin is the glue, or fudge, if overfilled. Good luck with it!
This is easy, chop strand mat is used first and before cure a layer of cloth is put over it and rolled out with steel roller. Chop strand mat has no strength as it is used to bond woven cloth. Woven cloth comes in in different weights so this is important as well. Woven cloth is used for strength and as also a top coat. For making tunnels and shapes you can use coragated card board as it is flexible. Then a quick shot of resin, then chop strand mat then cloth over it. You alternate chop strand mat and cloth you get a strong bond between layers . The reason for doing this is if you put cloth on cloth, it has too much resin and resin has no strength. It is just a glue to bond the gl*** mat and cloth together. You just want to saturate the gl*** and not too much resin as this makes the project weak. Over the years vacuum bagging was used to remove excess resin and this makes the item not only strong, but lighter as well. Good luck.
Wow guys thanks for all this info! So car wax works as mold release? I had wondered that. This will be over fabric stretched over a “buck” of sorts, so no need for a mold, but good to have in mind for another project Sent from my iPhone using H.A.M.B.
Try johnsons paste wax as a release, it worked better for me. Im sure there are specific mold releasers available as well. What kind of resin are you using theres better stuff out there than the hardware store kits, been years since I bought any. Ive used square PVC for structure, if you need it, gl***es right in.
Thanks for the advice. My resin is provost the hardware store stuff. Been on the shelf for years. What are you recommending? Also, by “gl***es Right in” do you mean it “sticks” Sent from my iPhone using H.A.M.B.
Here is an example of a fan shroud I made recently for a 34 Ford. It has interlocking tabs on the top and bottom half to index the two parts when it is installed and it does not require any fasteners in that area. The shroud has a small flange on the sides for the fasteners that hold it to the flanges on the radiator core. The shroud can be installed without removing the fan ***embly. I could post a couple more pictures of the fabricating process. John
John, that’s EXACTLY what I want to make. Thanks. Sadly, my trans cooler lines (which aren’t currently being used, and may never be in favor of the more heavy duty external type) require almost too hard of bend in the 5/16 line to leave the fan. I made one by hand in a vice that didn’t appear to be restrictive but was at the max or even beyond when I am capable of, and the fan blades were 1/2” away. This is because my fan is so low compared to my radiator, ifs below the core. Did you make the tabs after you cute it off the buck? I was thinking of doing the same, but with metal tabs and a 1/4” bolt fibergl***ed right into the piece. Tabs fixed on after its finished, of course. Bolt would be there from the beginning. Also, tabs to the radiator tab where it sits in my core support Also imagined rubber flaps that gravity/suction closes when idling and air flow opens when cruising. I think I’m gonna p*** on that idea, as the conical shape of the shroud will allow good airflow regardless. The Aforementioned would be much more important with both a flatter shroud, and with an electric fan Sent from my iPhone using H.A.M.B.
There is a tech article here from a few years ago. That I used to make a shroud for my 51 Fleetline. I made the buck and stretched a polyester shirt over the buck and stapled it on the back side. I think I did about 4 or 5 layers of matt. Came out very strong been on there now for a couple years.
I found a picture of the buck I made. I started with a piece of wood slightly smaller than the core of the radiator. This particular shroud was very difficult as there was no fudge room at all. It had to be made exactly to fit the radiator and the fan. Note that I covered the wood buck with aluminum foil to keep it from sticking.
Hello D, Don't forget to wear a good mask...not those white slip on kind that we see at hospitals and strange looking people walking around. Get one that will fit over everything and has filters. When you sand any kind of fibergl***, woven, flat cloth and resin, these things will happen. 1. If your arms and body are uncovered, you will start itching. 2. Super tiny sanding particles of gl*** will be floating in the air during sanding, so, it has to go somewhere. A simple white painters mask allows the small particles to get around the lip and into you. That is bad, a respirator will not. Wear goggles to keep the tiny stuff from going into your eyes. 3. If it gets in your eyes, a doctor has to somehow get it out, either a solution flush or what ever... not a good situation. Jnaki I have worked with all kinds of fibergl*** situations (speaker boxes and baffles) and I actually do not like it at all. (I gl***ed, sanded and made surfboard repairs in my backyard for my surfing friends... good money, but bad for health and the daily itching) A good friend of mine died from lung complications due to gl***ing, shaping and sanding surfboards. It included the dreaded three coats of sanding fibergl*** layers up to the gloss finish. (a surf shop production line workshop/warehouse, 25+ boards a week) I do not know how those TV show car guys sand and shape fibergl*** without good safety gear. Just my $.02 We even used mat and strands to form a gas tight bond on a corner of a metal gas tank from our 62 Rambler sedan that hit a rocky mound. The crack happened in Hawaii on a small dirt road leading into a secret waterfall area. We shaped the patch so we would not have to sand it ever...it looked professionally done, was air and gas tight. It lasted for years.
You really should use a laminating resin if you are going to be doing multiple layers. It remains tacky so the next layer will adhere to it. Hardware store resin is usually finishing resin which has a wax that floats to the surface so that it is not sticky. You will have to sand between every coat to get decent adhesion with a finishing resin.
Awesome I was going to ask about what you all did so it Didn’t stick to the wood. I was thinking masking or packaging tape; foil will do, Unless the tape idea will work as it is prolly easier. As for safety, thank you for the heads up. I am on the side of cautious when working on cars way more so than many of our car guy peers, so it’s taken to heart. I was thinking I’d ware an old diving mask and use the respirator I use for sand blasting, as long as wiping the gl*** particles off with a damp cloth won’t leave a hazardous situation for later.... if so, they sell disposable respirators for not too much maybe $10 that I can use for just this project. The doge mast I can simply wash in the ba*****t sink. I am thinking maybe I won’t smooth it out and avoid the sanding all together. It’s under the hood of a driver, and I don’t care for perfection it just has to work. I also wonder if going heavy on resin at the end allows for a little sanding of it (the resin) but not the gl*** it self. As for the speaker boxes, when I make those, I’ll probably smooth them with body filler so they require less sanding and make sure I don’t sand through the bondo. They’ll survive fine that way on a door. I just am not 100% sure yet that I want to open a 70 year old door and see speakers. But I am quite sure I wanna Jam out with more Than the two 3” 3 ways in the dash grille. Was thinking of eliminating b*** in those with a resistor thingy, and putting 6x9 on the front doors, low, with treble eliminated. 8” subs on the back doors with 3” full range (b*** eliminated) up on the top, front corner of the doors. I’ll also be considering getting rid of my foot operated emergency brake and building a 55-57 Chevy setup (hand pull) and building kick panel boxes Sent from my iPhone using H.A.M.B.
This is kinda the same Idea I did for my Plymouth but the shroud is integrated into the bracket that holds the radiator. The shroud itself is 1/4" rod and I stretched a old t shirt over it, no actual fibergl*** used. Here a a couple of pics, hope this helps.
Also… Using pink fibergl*** from insulation… That really works as well as the mat!?!? I have a bunch of it in my attic, and would certainly not mind saving the eight dollars on the mat… Sent from my iPhone using H.A.M.B.
Yup, three coats of resin. Sanding between each coat. A little bit of body filler to smooth out the not so pretty area's, and black appliance epoxy in the rattle can. On a side note, my wife was very happy that I got rid of a tore up old t shirt instead of wearing it until it fell apart!
Awesome! My thoughts on the fab blade hole was to make it with a 3/4” gap around the fan blade, and have it go about 1” past the edge of the blade toward the motor. That’s just in my own thoughts what makes sense. What did you all do? Sent from my iPhone using H.A.M.B.
Drew, I cant recommend a brand or type of resin, its been years since I layed anything. Used to buy mine locally in gallons from a boat shop. Can anyone share resin type, brand, source info.
I design the shrouds so that 1/3 of each fan blade is outside of the fan shroud and 2/3 of the blade is in the hole. It does not always work out to be exactly that amount but that is what I try to do. There have been some studies that indicate the fan will work best at this spacing. Sometimes I mix resin with body filler to make a thick paint that is brushable. I apply this over the sanded part that I have made. It is a cheap simple subs***ute for gel coat. It is in no way a good subs***ute for gel coat but it works well if the part is painted and it is easier to sand and finish. I certainly would not recommend this for an exterior body part. John
Boat shop... good call. We have tons of those here with all the lakes. Good call on the 1/3 2/3 I will aim for that. How about a perimeter (or I should ask cir***ference) gap? Sent from my iPhone using H.A.M.B.
{Good call on the 1/3 2/3 I will aim for that. How about a perimeter (or I should ask cir***ference) gap? } I try to keep it about 1/2" clearance for the blades but more allowances is might be best on your first effort. Remember that the engine will try to twist to the right side of the car. John
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