How I build a Carson style roadster top.

WARNING---WARNING---WARNING----plastic drop sheets do not seal fiberglass resin from paint. Not even heavy plastic drop sheets!!!!
I came home this afternoon and removed all the clamps etcetera that were holding the plywood and fiberglass fabrications to the rear top of the roadster pickup body.
The resin has passed thru the dropsheets and really messed up the paint in the area around the top/rear of the body.----nothing that can't be fixed, but a real p#$$-off anyways. There were no holes in the plastic either. The resin seems to migrate right though it.
Anyone considering working with fiberglass mat and resin around a finish painted body should be aware of this.

 

I may have had an epiphany??? today.--I have ran into more problems than you would care to know about trying to find a shop that will bend the thinwall tube for my topbows to an exact radius without flattening or kinking it. I have only found one shop, they want $120 to make four 90 degree bends, I have to supply the material, and they won't gaurantee the accuracy and consistency of the bends.---and they want me to use a heavier wall tube than I would like.
-----So---today as I drove 200 kilometers to pick up my ancient mother and bring her to my place for Christmas, I got thinking-----I know that I can bend solid round rod consistently and accurately with my torch, my big hammer, and a peice of 1" flame cut plate to act as a jig to bend it around. That would make the top frame way to heavy, but---what if I just made the corners from solid rod, with a turn down on the ends to fit snugly inside the ends of my lighter gauge tubing---and weld the joints solid.
Damn, I bought a mig welder last year to use building the pickup body anyways.
The weld will be free. The bending will be free. The ability to use the lighter gauge steel tubing will almost offset the weight of the solid corners.
I think I'm onto something here----

 

Maybe you already thought of this or maybe it's too thin or the wrong radius or maybe I'm way off here but I'd be looking at some EMT bends for the corners. Just the way I think, don't know how much support you need. Looks great so far.

 

I have talked to a number of convertible top builders, because like you I thought emt electricians conduit would be exactly the right thing to use. They all told me that emt wasn't strong enough to stand up to sustained wind buffeting, and that I should use steel drawn over mandrel (DOM) tubing. Maybe thats just B.S., but I only want to build this thing once.

 

I'm sure DOM is stronger so I'd give the edge to the pros like you did. Don't need the top wrapped around your head at speed!

 

That is really going great all things considered. Great job with the renderings too!

 

I used 3/4" stainless tubing......sort of thick wall.....and bent it with an old "Cast iron" electricans tubing bender, that I bought at a rummage sale.....It worked out good.
You have to bend the radius from the same direction for each side....so the spring back will be symetrical. (start towards the center of the car and bend towards the outside for each side).

Good luck.

 

I agree. Seems to me that every Ford roadster ever made had oak top bows. As frugil as Henry Ford was he would have used pine if he thought it would hold up just to save $$$.So would Sid Chavers, who built my top with an oak front header.

 

Well, today I'm really pleased. I decided to mock up the top bows in wood to confirm the radius and positioning for the top bows before I had them bent for me in metal. I laid them out and cut them from 3/4" plywood, and spent the morning attaching them to the roadster pickup body as per the models and layouts I had made.
Then I lofted them in with 2" wide masking tape, to see the overall effect.
The really great news is that this is not going to have to be a flip up top. I can still, with relative ease, get this fat arthritic old body in and out with the top on the car. This pleases me more than you can ever guess.
I really like the shape of the top, and I have good vision to the side when I am setting in my comfortable "driving" position.
This is really great!!!!
Now that the holiday will soon be over, I hope that I can find someone this week to bend the tubing so that I can recreate the topframe in metal.
With this design I have lots of headroom, both below the center top bow and from the rear top bow.
The main reason that I didn't use a peice of tube around the rear of the*****pit area is that I don't have the top attachment tabs just behind the doors that roadsters and roadster pickups come stock with, and the fact that I wanted something a bit better structurally to attach the hinge to, as I had intended to make the top a flip up style. I am really happy that I can get in and out easily without having to flip the top up.
Now that weight is not really a big consideration, I am going to make the wooden header over the windshield from oak.

 

The plywood top bows look a bit too Fred Flintstone-ish for me to keep them. The idea was to check out the radius and the placement of the top bows so that I could loft things in with tape and check the profile before I have the top bows made from steel tubing.
Surprisingly, there are a lot of geometry considerations to the design of the top bows. The primary question of course, is what radius to use when bending the tubes. I was told by a top manufacturer out of Arizona that the radius of the bows should match the radius in the back corners of the*****pit, and in my particular instance that turned out to be an outside radius of 9". (I used an old drafting compass and some big peices of layout cardboard and scissors, and kept cutting out cardboard circles untill I got an exact match.)
I did a lot of measuring with me setting in the car to determine where my head sat in relationship to the top of the windshield posts (my posts extend 13 1/2" above the top of the doors), and I must have looked at 50 or 60 photographs and pictures of other vintage convertibles before building the cad models and establishing the dimensions for my layouts.
The center bow must have a radius equal to the rear bow for the canvas to loft properly, (it can only loft outward from the car to one "highpoint", never inward), and since the tube running back from the windshield header must in my opinion run parallel to the top of the door, that establishes how high above the door top the center bow actually starts to curve from the vertical.
I have talked to the people around here who make boat tops, but they all use aluminum tubing for the bows, and they all say that it is too light to stand up to wind buffeting at 60 Miles an hour (boats only travel at about 35 MPH top end)

 

Hurray, hurray---I found someone who can do my tube bending, in the west end of Toronto. I am going to use 1" outside diameter CREW tube (thats cold rolled electric welded if ya didn't know---I didn't) with a .083" wall thickness. Thats what the bender guy recommended for a smooth wrinkle free bend. I will buy the tube tomorrow and let you know what it cost me. The company that is doing the bending quoted $120 to do the bending. That works out to $30 per bend, but hey---I can't do it myself, and it will be highly visible when the top is finished.
I bit the bullet today and ordered a "smartparts" chrome roadster rear window frame 8" x 20" from Horton for the low low ???? price of $250 Canadian, and since I was in a spendthrift mood I ordered a chrome windshield wiper motor with blade and shaft for $60 at the same time. (since I am building the oak header that goes over the windshield, I wanted to incorporate a wiper motor into it ).

 

Jeez, I coulda built a whole friggin car in the time its taking to get started on this Carson top. I've got peices of tubing being bent in Toronto, but I phoned today and it'll be another 7 working days before theyr'e ready to be picked up. I've got a rear window frame and a chrome wiper motor****embly on order from Hortons, but it hasn't showed up yet.
I could have finished the fiberglass work on that plywood peice at the rear of the*****pit last weekend, but we had company coming and my wife threatened me with a horrible death if I got the house all "stunk up" with fiberglass resin.
Oh well,---I'll make it pay this weekend coming. I hope to do the final fiberglass work on the plywood, then do a bondo skim coat on the exposed surfaces and sand them smooth so it will be ready to be upholstered in the same red naugahyde as the roadster pickup interior. (there won't be any fiberglass on the outward facing surface, as that is where the canvas top will be stapled to, just like the tack strip on one of Henrys roadsters).
I apologize to anyone following the post for my slowness, but it will happen---we will have a beautifull top before spring comes.

 

Things are progressing on the great Carson top project. First off, I have been thinking I should have called this post "How I build a non-folding roadster top" as a true Carson top is built up with conduit, chicken wire, and padding, while mine is just going to be covered with canvas as were Henrys originals.--Oh well, ya win some, ya lose some. I have purchased an 8" x 20" chromed aluminum rear window frame from "Smartparts" in British Columbia, and it is out having safety glass cut and installed.
I ended up making the header over the windshield from Douglas fir---it is a much denser wood than common pine or spruce, yet is soft enough to accept the upholsterers staples, whereas my upholsterer had doubts about how well oak would have taken the staples. I have completely fiberglassed the plywood peices that fit around the*****pit together and on all exposed surfaces except for the exposed outer side, which will receive upholsterers staples to hold the canvas top material to it. (this peice bolts to the lip around the rear of the roadster*****pit with four 1/4" bolts)
I have cut the 3/16" plate to attach to the top of this rear peice, and that is what the tubular top bows will be welded to. (rearmost top bow welds to these 3/16" plates at each end, frontmost top bar welds to front of rearmost top bar about half way up.
I have attached 2" x 1/4" steel flatbar about 5 1/2" long to each end of the wooden header over the windshield. This will firstly give a place to weld the horizontal tube which runs above the sidewindow openings to, and secondly it will be drilled and tapped for a fully threaded bolt which will go through it and the header, and lock into a groove in pins which will be screwed into the tops of my steel window posts. (note that I have one eyebolt and one carriage bolt holding the header in place , as thats the first thing I came to in my "bolt drawer") however once the canvas is in place there will be no access to these bolt heads, so the final "pins" will set about flush with the top of the header.
The place that is bending my tubing was supposed to have the tubes finished this past week, but everybody has been off work with the flu.

 

I decided that I should probably do whatever was necessary to add a windhield wiper motor to the top header while I was building this top, as once it is done, and the header is covered with canvas, I will no longer have the opportunity. I purchased a 12 volt chrome wiper motor along with a chrome arm and wiper from Vintique. My intenetion is to leave the motor permanently in place attached to the inside of the header, but to have the wiper arm and wiper removeable so that I don't have to always be looking at it. The solid model I am ataching shows how I intend to do this. I will cut a clearance hole through the header on the "flat" side and drill a hole through the narrow side from inside, to accept the wiper motor. I have calculated the size of the large hole to accomodate the wiper at its maximum swing to either side, and there is enough clearance "front to back" to let me slip the wiper arm off the motor shaft and remove it after****embly.
I will keep the wiper and arm in a waterproof bag under the seat, along with a long handled hex. driver to tighten the screw which holds the wiper arm to the motor shaft.
That way, if I ever do get "caught out" a long way from home in a rainstorm, I will have a windshield wiper.---also, it makes the cops much happier at safety check time.

 

These are the tubes I picked up yesterday for the top bows. I am very pleased with the quality of the work. I paid $70 for two 20'-0 lengths of 1" O.D. steel tube with a 0.085" wall, (that includes 15% tax that we are lucky enough to get to pay here in Ontario), and the people that did the mandrel bending (four 90 degree bends) charged $138 including that damn tax.
I have had reams of advise on how I could have done this myself---i.e.--fill the pipes with sand---use an electricians bender----fill the pipe with ball bearings, yaddah, yaddah, yadah---- however I've lived a long time, and tried all that*****, and I know that the results are only marginal at best, and they don't make an electricians bender with the radius that I required. These tubes are going to be very visible on the inside of the finished top, and they are going to have convertible top material stretched over them on the outside, so they had to be perfect.

 

This is the method that I will use to attach the header to the top of the windshield posts. When I cut the top off the sedan posts, I capped them with a peice of 1/8" plate, with a 3/8" nut welded to the inside of it. I knew that someday I would want to make a removeable top, so wanted to make provision for it. I am going to attach a solid model, both exploded view and unexploded, to show what I intend doing. I could not simply bolt the header on, because once the canvas top is in place, I wouldn't be able to access the bolt head. So----the dark blue part is a shoulder bolt with a 1/2" diameter shank and a 3/8" threaded section, with the head cut off. The yellow is my header, the purple is the sedan post, and the green is a 1 1/2" x 1/4" steel flat bar which is the attachment point for welding the tube that runs foreward from the center top bow. This green bar has a 5/16" threaded hole in it, and the red fully threaded bolt runs foreward through the steel bar and the header, and locks into the groove cut into the shoulder bolt.---This will hold the top securely in place, but if I want to remove it all I have to do is back off the red fully threaded bolt, and the top will lift straight up off the shoulder bolts, which remain in place on the windshield posts.

 

Well, so far, so good. I just knocked off for the day. My back and feet are killling me (see, I'm not used to this real work). Things are looking great at this point, will weld in the second top bow and the struts that run foreward to the header tomorrow.

 

The top frame is finished, and the whole****embly/weld operation only took about 12 hours of my time, once I had all the bits and peices accumulated. (had the entire car covered with old bedsheets soaked in water to keep the "welding berries" off that pretty yellow paint).
The next thing I will do is remove the top****embly from the car to finish welding any areas that i couldn't get at. I plan on upholstering the plywood part that goes around the rear of the*****pit with more of the red nuagahyde that is used on the interior, and putting a stain and spar varnish on the header over the windshield.
The tubes will be painted the same yellow as the rest of the car.
Then, hopefully, off to the top sewer guy.

 

This picture shows the stainless steel shoulder bolts that will screw into the top of my windshield posts, to hold the top header in place (they are the dark blue parts shown in the solid model background).
I decided that I wanted some added insurance that the top wouldn't accidentaly blow off, so I had my machinist turn down an area in the center of the shoulder bolts, so that the red coloured full thread screws that clamp onto the shoulder bolts will fit into the turned area and not be able to slide up.

 

The way I have the header setting directly on top of the windshield, I have been concerned that in a rainstorm, rain would slide up the windshield and through the crack between the top of the glass and the underside of the header, and into the car.
To solve this problem, I decided to get a peice of aluminum glass channel from the autoglass shop and recess it into the underside of the wooden header part way, so that part of it hung down about 3/16" below the header to seal around the windshield. Now, its been many years since I bought any glass channel, and I found to my surprise that nobody stocks glass channel anymore. I found one glass shop that had a peice, but instead of rubber it had felt in the groove, which wouldn't stop the water anyways.
Just when I was about to give up on it, I went into an industrial glass shop, and found the perfect peice of aluminum channel. It has not got a rubber seal in it, but when I glue it into a slot in the wooden header I will coat the top of the windshield glass with vaseline, and squeeze a bead of silicone into the channel, then install the header. The silicone will extrude around the inside of the channel and "harden" in place, but the vaseline will keep it from bonding to the glass. This will give a perfect seal, but still allow me to remove the top when I want to.

 

I think your doing a GREAT job so far!

I'm a little bit concerned about the windshield hold down set up your using.
IMHO, I think you sould have a more positive attachment method up front where all the force of the "head-on" wind will be. And don't kid yourself into thinking it will only be a 60 mph wind (like any of us "don't" drive over 65!)
Think about driving into a 40 mph head wind at 80 mph. That makes it a 120 mph wind.

I've used the "bolt into perpendicular shoulder bolt" method on fixtures and speciality machines I've built in the past and it works nominal at best.
Most times it failed because the bolt that was holding the shoulder bolt in place would vibrate loose.

Maybe use an eye bolt, instead of a shoulder bolt with a turned area?
Kinda like this quick photoshoping i did of your rendering




An eye bolt would guarantee that it couldn't fly off at speed

Just an observation/thinking out loud. I could be, and often am, wrong.
When it comes to safety, I try to look at worst case scenerios.

 

Elcornus--thank you for your response. All of Henrys roadsters used the same setup as i am using, but without a "turned down" area on the pins. I thought that I was actually going one better than Henrys roadsters. I have gone too far to start changing that area now, but I will use locknuts on the full-thread bolts to ensure that they don't vibrate loose.----Brian

 

I phoned around yesterday untill I found a fellow with a router to put a radius on the top leading edge of the header---he was busy yesterday, but picked me today up and took me over to his very well equipped woodworking shop.
He used a 1/2" radius cutter in his router to put the nice edge on that you see. I also had him cut a 1/8" deep pocket above the cutout for my wiper motor so that I can flush-fit a peice of 1/8" deep wood in the recess and glue it in place. That will still give me access from the underside to install my wiper arm, but will prevent rain from blowing up through the hole into the inside of the car.
He also routed a 3/16" deep slot full length on the bottom side in which I will epoxy the aluminum channel that seals over the top of the windshield.
He didn't want to take any money for it, but I convinced him to take a $20 bill and promised him a hotrod ride when spring comes.
I finished welding the top frame this morning, and ground all the welds and primed the whole thing.
Think I'm done for the day now.

 

Priming and puttying and sanding, priming and puttying and sanding----Damn, I thought I was done with all that last year. Oh well, a little yellow from my touch up gun, and the frame will be ready to go back on. My top upholstery guy is coming down from Orillia on Thursday night for final inspection.---He was supposed to come down on Monday night, but we just had the snowstorm of the century here (21" in one massive dump) so I called him and said "don't come tonight if you value your life". I got the header stained last night, and varathane clearcoated tonight, and the house stinks like a bodyshop, but Sweetie is away on a training course in Toronto and won't be back till Friday night. Daughter (22) is complaining like hell, but daughter don't scare me (near as much as Sweetie)

 

If I remember correctly, my pop's '35 cabrolet has a notch in each of those pins. So the bolt isn't as much pinching the pin as it is hooking into it.

 

We are ready for canvas!!!

 

Okay---we're not quite there yet. I just had the top upholsterer to my house for final inspection, and there is one more thing I have to do. He is concerned that the top will "balloon" either upward or downward at speed. I am going to have to attach 3 peices of seatbelt webbing, running from the header back to the frontmost top bow, similar to the ones in this picture which I lifted from American Rodder. This isn't quite as simple as you think, because it has to set below the canvas enough that it doesn't create ridges in the canvas where the top material lays against it. This means that I will have to router 3 grooves into the leading edge of the wooden header just wide and deep enough to hold the seatbelt material, and weld 3 small peices of plate to the front edge of the topbow, just a bit lower than the top of the topbow, at the angle of loft between the topbow and the header, to rivet the seatbelt material to.

 

The game plan keeps evolving. I drove up to upholstery guys house today to get the maroon/red seat belt material, and surprise!!! It wasn't maroon/red as he remembered----it was black. Surprise #2---he showed me samples of the top material, and it is white on the outside, but black on the inside. Now, I didn't know that. I thought it would be white on the inside too. My plan was to paint the frame I built the same colour of yellow as I have on the roadster pickup, which is a special mix, and is not available in a rattle can.
Now that I know the top material is going to be black on the inside, I will paint the topframe with black paint from a rattle can---this makes my life simpler actually.
I got the 3 new tabs to attach the seatbelt webbing welded to the front topbow this morning, and primed. Tomorrow i will carve 3 pockets into the leading edge of the wooden header to receive the other end of the seatbelt material.
Good wife will be in Toronto again this week, so I will probably spray the topframe some evening this week, and then figure out how to get car to upholstery guys house 25 miles away.

 

Okay, thats my weekend gone. The frontmost top bow tube now has 3 new tabs, (see white tape) that are set 1/8" below the loft (an imaginary line running from the top of the topbow to the top of the wooden header). The wooden header now has 3 new notches 1/8" deep in the leading edge, and extending partway back on the top side (see white tape)---they hardly show up in the picture, as I have restained the milled out areas. ---I put a high speed carbide rotary rasp in the drill press, set the press on its highest speed, and very carefully milled out the pockets. The black 2" wide seatbelt webbing will rivet to the top of the new steel tabs, and nail to the pockets in the header. If I have calculated correctly, the top of the webbing will be about 1/32" below the inside of the top material, so as not to cause any humps or lines in the top.
Now the top upholstery guy is telling me he can't do my top untill "later in March".----thats okay though, as I can work a bit slower on finishing things up, and maybe some of this friggin snow will melt.

 

I just spent the morning making cardboard templates of the side window openings. I don't want to leave this to the discretion of the top maker, because his idea of what a side window opening should look like might be different than mine, and I have seen some roadster tops with downright ugly side window openings.
------And I just couldn't resist lofting in the finished frame with some 2" masking tape to see how it would look.
---I am very pleased with the side profile, and the window opening gives me a clear unimpeded view to the side. While I was at it I made a template to check out the height of the rear window opening as well.