Hood scoop bonding part deux Terry PLEASE help New pix adde

[383 240z]

I posted this question a while back. Now I have a few photos to better explain my situation. I would like to know how to make this cowl induction scoop a bolt on or bonded on scoop. Terry has tried to explain to me how to do this but I just cant comprehend his instructions. maybe these photos can help with any help you all can give me. http://photos.yahoo.com/bc/rx7260z/lst?.dir=/RX-7+Hood+scoop&.src=ph&.view=t Thank you all again!! Keith

[blueovalz]

Your photos put your dilemma into better perspective. Let's try this. To begin with, I'd bolt this scoop on instead of bond it, but with the method I'll suggest, you will be able to do either. Being the scoop is so long, this causes the ends to be quite high off the curved hood's surface. My suggestion is (provided this is a glass scoop and not a plastic one) to cut or grind the bottom edge so that it more closely matches the contour of the hood all the way around the scoop (and remove any and all flanges that are on the outside edges of the scoop as you will not use these to bond the scoop onto the hood any more). Next rough up the surface around the scoop within 1" of the bottom of the scoop (especially on the inside edge) where it comes in contact with the hood using 36 grit or similar sandpaper, the rougher the better, to aid adherence to the fiberglass). Next, cover the hood with 2" masking tape (to protect the paint from stray resin, and the fiberglass part you are about to make), with a minimum of overlap (1/8" will be safe) between adjacent strips, then place the scoop on the taped hood where you plan to permanently locate it, and draw an outline (or footprint) of the scoop onto the taped hood with a Sharpie or something similar. Now, with the scoop removed, you now know exactly where the scoop will be placed because of this drawn outline. Next, cut out enough 2" wide strips of mat so that several layers of mat can be laid evenly along the inside edge of this outline. These pieces will be placed along the drawn outline or footprint so that about 1/2" of the mat will extend out past the outside of the drawn footprint, and the rest of the strip (1-1/2") will be on the inside of the drawn footprint. Thus you should have a 2" wide square-shaped "U" of mat resembling the outside shape of the scoop. Do all of this with dry mat as a trial run to make sure you have enough pieces to do this job and to make the total thickness of all the layers at least 1/8" thick. Thus with 2oz mat, you may only need 2-3 layers. With the cheaper, thinner mat, you may need 4-5 layers. Anyway, once you feel confident that you have enough strips of mat to do the job in one step, then clear everything off the taped hood, and mix up your resin (too much hardener will make it kick before you are finished, which is a big no-no). Before mixing the resin though, I'd suggest a light misting spray of WD-40 (if you don't have any mold release or wax around) onto the tape to assist the release of the fiberglass you are about to lay on it. Now comes the messy part. These pieces need to be dipped into the resin to ensure they are fully saturated, but not so much so that resin is running everywhere. Lay out the soaked strips onto the hood just like you practiced with the dry strips earlier. WHILE THE RESIN soaked strips are still WET and in place, place the modified hood scoop directly onto the strip of wet fiberglass so that it lines up with the drawn outline (which will still be visible through the wet resin) so that only about 1/2" of the mat is showing all the way around the scoop, and the rest of it is hidden because it is under and inside of the edges of the scoop. Make sure every thing is set (making sure the scoop will not slide away from it's location on the sloped surface) and let the fiberglass "kick". The roughed up edges on the scoop will give the mat a good surface to stick to. After it is hard, gently remove the fiberglass you laid out (with the scoop now bonded to it) off the hood, The bottom of the scoop (flange) now perfectly matches the hood's contour. Next, reinforce the joint between the scoop and the newly made and attached glass "flange" that you made, by applying strips (2" wide or so) of soaked mat on the inside of the scoop all along the joint where the two meet (otherwise, the scoop may separate from this flange because it currently is only held together through the thickness of the scoop's edge that was modified (perhaps as little as an 1/8" at most) to further strengthen the bonding of the flange and the scoop. Now, sometimes this reinforcing will slightly distort the shape of flange that you made, so you may have to repeat the flange making process one more time and with only one layer this time, to ensure a perfect fit after final reinforcement has been done. Now, trim (sand) the 1/2" of material off the outside circumference of the scoop, and then you are ready to either bolt the scoop down as I did in the previously sent photos on the last string (using the inside part of the flange), or you can use this same flange to bond it on, your choice. Sorry for the long post, but I hope this better helps you understand what I was describing on the earlier post.

[Guest Z-rific]

Man, that is one excellent how-to post. Great job Terry.

 

What do you think about rivets for this job?

[blueovalz]

Pop rivets work great. For years (still to this day) some of my bodywork is pop-riveted onto the sheet metal body, and fiberglass parts. Be sure to back up the blind side of the rivet with the appropriate washers to prevent pull-through if the part attached is fiberglass. I would also suggest using aluminum rivets instead of the steel ones if fiberglass is envolved too.

[383 240z]

Terry, I see said the blind man as he picked up his hammer and saw!!! I now understand your previous posts. Now all I have to do is convince the wife to let me fiberglass in the house. It is 22*F in the shop right now. Is there a good brand of resin you can reccomend.? I have used West System 105/205 before but lately I have been using the cheap BONDO brand sold at AUTOZONE. I have a bunch of mat here. What would you use for the mat I have both woven mat and chopped strand mat. Thank you again Keith

[Guest Anonymous]

Keith, Nate and I have been laying up fiberglass during the Thanksgiving holiday outside. Do not bring that resin inside because the fumes can be overpowering and long lasting. Open the garage door and work there in the cold. Slap a space heater up there with the piece while curing.We used one of those electric radiators with the enclosed oil heat conductor on a couple small pieces. I am not sure what temp the fiberglass quits curing at but the 40 to 60 temp may have helped more than hinder us (slower cure). We did the final lay up on a convertible top Sunday and put it in an unheated garage and it was dry to the touch this afternoon. Nor did we use a protective plastic wrap to aid in curing or as a moisture barrier on the final top lay up. We used plain old fool proof cheap polyester resin and fiberglass cloth and mat. Just follow Terry's instructions and you will come out fine. I use 3 M wide masking tape liberally applied on the area I do not want resin on...We used small pieces of woven cloth to get defintion on the buck and then switched to hand ripped (with latex gloves) mat in small pieces. The mat wetted very well in small ripped chunks by dabbing a 2 inch cheap bristled brush up and down. I dabbed and Nate ripped.

[blueovalz]

Tomahawk's words ring true. I don't even want to talk about the time in my youth when I did fiberglass indoors (bad scene!). Anyway, use the chopped mat because the woven cloth will not hold as much resin, and in this case you want the additional resin because when you place the scoop onto the wet mat, it will slightly "crush" the mat, thus filling in the rough cut (gaps, uneven edges, etc) you made on the scoop to match the contour of the hood. With the colder temps, I'd first warm up the motor to full operating temperature. This will heat the hood, and thus warm the resin. I'd shut the motor off when you place the wet mat onto the hood, due to the chance that the vibrations could cause all this stuff to start sliding down the sloped hood. Big thing to note: The warm hood will be the difference between night and day on the cure rate at the temperatures you've mentioned. Also, keep the resin (autozone/home depot stuff will work fine) inside where it's warm before you start. If you feel you have the patience, mix a small amount with some resin, place it on the warm hood, and time when it starts to gel (starts getting thick and gooie), then gets kinda "waxy" (is somewhat solid, but crumbly), and then fully, glassy hard. For ideal conditions and based on your job, I'd not want it to start gelling until at least 20-30 min. Once it starts gelling, it's too late to work it, and if you're not finished, then you will need to start all over again from scatch on the fiberglass part. It will be fine if the gelling takes an hour or so. If it kicks too fast, put less catalyst in it, too long, add more, but a longer cure time will allow you to finish the job, were a too short a cure time is a royal PITA 'cause "I gotta do this $#!t all over again" if I'm not completely finished once it does start to cure. Once fiberglass has reach the "waxy" stage (strands of glass will not pull out of the gel, but will break it apart), and you're happy with the job so far, then let it sit, carefully cover it with some plastic (don't move the scoop!!!), and then a blanket or something to insulate it and hold the heat in. The glass will create it's own heat on the reaction, so try to keep the heat held in. One good thing about slow cure rates is that the heat build-up is not so intense, and thus it will not distort the piece vs a fast cure on a hot day. If you still have time, then heat the motor up after the resin seems fairly hard, and give it one good cycle of heat to ensure it will be cured when you're ready to pull it off the hood. When you do pull it off, be patient, (work slowly from a corner first) if it wants to hold, and you will find puddy knife will come in handy at this point to help pry it off. Good luck and let us know how it turns out.

[383 240z]

Thanks for the responces guys I will take some pix when done I think I will just rent a good heater and warm up the shop when I have the time to tackel this job. It is about 12*F today and gonna stay that way for the rest of the week. If not my buddy will let me use a space in his heated shop. thanks again Keith

[383 240z]

OK I cut the large flats off the scoop. Then I transfered the contour of the hood to the side of the scoop. And cut them out. I then covered the hood with 2" masking tape overlapping each run by about 1/2" and layed garbage bags over the air cleaner and rest of the engine bay. (I cut a hole to clear the air cleaner before I bought the scoop)Now I just need to rent a heater to warm things up a bit and get out of a few X-mas shopping trips and get this thing inspected!! I THANK you all again this is not as hard as I had thought thank you for convincing me that I could do this my self! Keith

[Guest Anonymous]

Keith... we are having our "fiberglass lay up" curing as low as 40 degreess farenheight(polyester resin).The cold has been most likely helping us by extending the work time with slow hardening.The curing process does not like the humidity or air, so saran wrap was placed over the curing fiberglass for a seal.We quit sealing it with Saran Wrap and just let it cure for a couple days in the garage or the shed.Just mix the catalyst hardner and resin thoroughly in small lots or amounts.No need to make more than you can use because you can always re-group and re-mix rather tha pour out the excess I picked up a free syringe ( to draw medication out of a bottle) at a chain store pharmacy to measure the catalyst drawn fron a bottle. Use the cheap unpainted handled paint brush (2inch).. dab like a woodpecker.. don't brush stroke.

[383 240z]

They are calling for 45* and 50* for the next few days. So it is time to get this scoop project done. I'm not talking about heating the shop for the resin but for me I HATE the cold. Still tring to convince the wife to move to SW no rust and no SNOW!! I will be taking some photos along the way and will post them for you all to crituque (sp) my work.Keith

[blueovalz]

Let me add one more trick that I use when I make parts "on the car". This trick is one that I found accidentally, and works quite well IF, and its a big IF, you time it right. I've found that the bonding stage of the resin is at the very later stages of the hardening process. For example, once the resin gets that firm but crumbly stage, the adhesive bond that the resin has on the tape (or aluminum, paint, mold, etc) is only about 10% of what it will be with it fully hard and glassy. The bonding beyond this point starts improving quickly. So, with this said, my trick that I've used is to carefully test the waters (so the speak) of the resin's characteristics at the "firm but crumbly" stage. This can be done at a place where the resin was excessive and can be picked at with a pick or screwdriver to see how firm it is (it will be about like hard rubber), AND to see how well it separates from the tape. At a certain point, the resin will be firm enough to hold it's shape, but time wise, it's at a point before the "bonding" stage starts ramping up. At this junction, you can very easily and carefully lift the entire piece off the tape, and still have it hold its shape. Once the bond is separated, place the piece back down on the tape and let is cure completely. The piece will then lift off easily when hardening is completed. It may sound a bit tricky, but it works great in the absence of a good release agent. Good Luck.

With additional comments from others here, I feel this string could be a great archive for beginner fiber glassing. Please update this string with any photos on how your project came out. Oh yeah, the way I found out how this worked is I accidentally dribbled some resin onto the good paint not covered by tape. I found that instead of using a solvent to remove it, that if I waited till just the right time, the resin (firm but not hard) could be pulled off the paint in one whole piece, without maring the paint. Would not have believed it until I saw it.

[383 240z]

Terry I'm not sure I'm willing to try that(to afraid of if not being hard enough and damaging somthing)I think I will try your tip on spraying a liberal coat of wd-40. I'm not sure what to do with the peak and leading edge most likly I'll just build up a bulk of 'glass and sand it to the correct profile before it gets bolted down. I cut the side profile pretty close but it is not perfect the largest gap is about 1/16" is this ok or should I make it perfect? You all can see the new pix at http://photos.yahoo.com/bc/rx7260z/lst?.dir=/RX-7+Hood+scoop&.src=ph&.done Keith

[blueovalz]

It sounds like you've got a good grasp of what you need to do. The 1/16" is no problem. Like I said, the wet mat will crush and conform to the irregularities of the scoop's edging. In regards to the front point that was cut off? I would add enough mat just under this area so that it will fill in the small peaking gap in the center, and also jut forward a few inches. This way you will be able to shape it after it hardens to suit your needs (perhaps another point like it originally had). You will notice that once this scoop is removed that you will see a very slight scalloped surface on the bottom of the scoop where the tape on the hood was overlapped (from variations of tape thickness from single thickness to double, or even triple thickness if you did that). This is not a real problem being the scalloping is only as thick as the tape is thick. But this is why I try to make overlapping minimal, or as an option, overlap 1/2 width each time so that the end result is 2 layers with a thin single layer groove instead of one layer for most of it with a narrow double layered ridge (yeah, it's kinda confusing explaining this in text). Anyway, it looks good. I'm holding my breath waiting to see the final result.

[Guest Anonymous]

Though , I have never used it, I hear "cooking" Pam in the spray can makes a good parting agent

[383 240z]

I did not think about the scalloping effect on the flange portion. I guess I can sand that part out after it is finished I'm not worried about "show quality" this is my daily driver. I painted this thing in my driveway! It was the first car I ever painted. But I still want it to look presentable at the local car shows. But mostly I just like being able to say I did it all myself from the paint to wiring to rebuilding the transmission and tuning the carb. Keith

[383 240z]

I picked up some more mat and resin to day wife has me getting everything ready for the holiday parties she is throwing. as soon as that is out of the way I'll have some pix to post of the finished project wish me luck!! Keith

[Guest Anonymous]

Good luck, Keith.......I hope the pumpkin pie don't taste like napalm

[383 240z]

Looks like sunday is 'glassing day The weather is calling for 45* sat and sunday so I'll get everything ready on sat after work and give it a try on sun. hopfully I will have some good pix to post on mon with the new camera santa brought me!! Keith

[blueovalz]

Great! In your honor I’ve ripped a sacrificial amount of 2 ounce mat up into little strands, placed them on my Tesla Coil toroid, and zapped them with 500KV as an offering to the fiberglass gods in the hope they smile upon your adventure. This suspense is almost as unsettling on my nerves as Mikelly’s garage saga. I guess I need to get into the art of extended projects and share an essay on how, after 3 years, I’ve yet to get a bathroom vent that will keep bathroom dew point less than ambient whenever I take a shower. Tonight may be the night. I finally bought the brute of all bathroom vent fans. 300 CFM of squirrel caged, dim the lights monster motored, 8” orificed, supersonic air flowing, and mother of all vents. It may take a D-9 caterpillar and a come-a-long to get it up into the ceiling, but I will not be deterred. Oh yeah, good luck with the fiberglass.