I want to pickup and deliver my new kayak. The boat is an almost 19 foot Current Designs Extreme. The problem is my big car is out of state. The biggest vehicle I have is a Chevy Classic, think 4 door Chevy Malibu, which I am guessing to be a few feet shorter than the boat. My other resources are rope and some foam pieces,
http://www.austinkayak.com/products/129/Foam-Kayak-Saddle.html
http://media.ed.edmunds-media.com/pictures/VEHICLE/2003/Chevrolet/100080762/2003.chevrolet.malibu.2343-E.jpg
My plan is to tie the foam blocks to the boat with rope then tie the boat to the roof with rope through the front and back door windows then tie off the bow and stern to the front and back of the car.
The delivery home is about 40 freeway miles. I have never owned a boat or even worked with a boat like this (kevlar/carbon fiber)or had to ties a boat onto anything but a good rack. I do however have a lot of rope and know a lot of knots. Would you trust this configuration to such a nice boat just to get it home now?
I would
That sounds solid. I would only caution to make the bow and stern lines tight but not too tight at to break the boat in half.
Also, for the bow and stern lines, there should be four, meaning don’t use one for the bow that allows the bow to shift side to side much.
Finally, resistance increases exponentially with speed. While I recognize some freeways are madness, if you can go 55 or 65 you will have less worries than going 75 or 85mph.
If you do…
Take back roads. I dislike using just foam pads on a bare roof, I do not feel its very secure. I do think proper width foam pads on a rack are fine, and way cheaper and better contact than the $$$ saddles…
Or, find a fellow kayaker to help out who has a solid and secure rack system? Throw them a $20 for gas (should be plenty for an 80 mile trip in all but the worst MPG trucks…) and some beer for their time 
Heck if I lived near you I would have just talked myself into a favor lol. Or, just find someone with a Dodge Caravan with factory rack, and place the blocks on that. HUGE bar spread, very safe, IMO.
my girlfriend brought our 72lb Tandem Poly kayak home on her cavalier with just foam blocks, 50 miles. It is doable, she drove under 55 the whole way though. Stop often and check straps. I still prefer at least a factory rack over bare roof. Car roofs flex too much…
Should work
Just make sure you secure the kayak for side to side motion - either loop the tie downs holding the kayak to the roof through something on the kayak or make a loop around it so that the kayak would not slide sideways (that assumes that the tie downs will not slide about once secured through the doors - if necessary make a small loop through the inside door handle or similar inside the car to immobilize the tie downs).
As mentioned, front and rear tie downs should be pretty much mandatory with the foam block setup.
Make sure the roof and the foam are clean so that you don't end-up with scuff marks on the roof paint...
Find someone with a pick-up with
a ladder rack and pad the bars. Or buy a real rack. Don’t take chances with your new boat.
4 pads not 2
You can pull this off but if you buy 4 v shaped pads instead of just two you can spread the pressure out on the roof and better protect the kayak. I know a guy that drove from Michigan to Mexico with four good quality foam blocks that were roped like you describe. But his foam blocks had a non-skid finish on the contact side that resting on the metal roof and he felt that made all the difference as even when straps were not drum tight the blocks wouldn’t migrate east/west. I ditto the back roads at lower speed advice. Bow and stern lines an absolute must!!!
kayak rack
You’ve just spent over 3000$ for a new boat (I’m assuming its new) If you don’t already have one, spend the money and buy a kayak rack (thule or yakima are the two best known) Using foam blocks to transport a boat is not as good as having a rack.
rack not car matters
The size of the car don't matter. The length of the roof matters more. I have a boat that's longer than any of my cars (by different amount). And I've been transporting the boat to and from water for 4-5 years now. It only takes me 10 minutes to tie up the boat!
But I do have proper rack on the car.
I don't know if you already have racks on your "big" car or not. But whichever car you plan to used for primary boat transport better have a proper rack. Or you'll get tired of fussing with foam blocks and ropes real fast. And you won't paddle half as often due to the hassle of boat loading.
Assuming you have rack on the other car and wants to just transport the boat once on a car with rack, I will say it can be done, with caution.
I've transported boats without racks. But I also use straps with cam buckles instead of ropes. I'm not a rope expert so I don't know if you can get the rope as tight as with straps+cam buckles. The roof of the car is often quite soft. So the rope will develope slack as you hit the first couple of bumps. At the minimum, you'll have to stop after a couple blocks to re-tighen all the ropes.
I’ve been doing that for years
My only transport method for each of my sea kayaks over the years has been pretty much what you describe and I have a smaller car with a much much shorter roof line. I travel very long distances at freeway speeds with never a problem. I do have some important tips that I would highly suggest to you. First - use 12-15’ nylon cam-buckle straps. They are flat enough that you can easily close your car doors over them and the buckles allow you to tighten the straps quickly and safely. (unless you’re really confident tying a good trucker’s hitch) Second - wrap the straps around the circumference of the hull before it passes back through the car doors. That way it resists the sideways torquing wind force of passing trucks. (that’s why you want extra long straps) Third - put a few twists in the part of the straps that isn’t flush against the car or boat so it won’t vibrate in the wind. Fourth - try to strap the foam pads to the roof separately so that the front pad won’t get pushed backwards over time due to wind forces. I connected the foam pads together via 2 bent plastic conduit so they always stayed perfectly aligned, even if they weren’t connected to the car roof via a solid rack.
http://phrancis.com/test/dscf1486.jpg
As you can see, this kayak was much longer than my car, but I went paddling with it several times a month for years
http://phrancis.com/test/DSCF9304.JPG
At this point I had spent many months building a 17’ kit boat, but with more volume and only 43 lbs, it was buffeted by winds more. I then got rid of one roof strap and added bow lines attached to these custom strap tabs tucked under the hood.
I have it down to a perfect science for my boats and car. Although you have a much longer roof line, you’ll have to experiment and adjust a little, so take it slow and check often.
PVC
Rack is preferred. I ran across a great deal on a kayak in Indiana. I had to get it back to DC. I had foam blocks, straps and front/rear tie-downs. I bought some PVC pipe, angle and T fittings and made a rectangle. I put the foam blocks on the rectangle and carefully strapped it all down. The Prius and boat made the 600+ mile trip with no problems. I regularly checked the straps and boat. Repeated use of the roof could damage the paint.
JimZ
Straps, not rope
I would use webbing straps with cam lock buckles. They are a little more secure than rope and they will do better when you close the doors on them.
Straps v. Rope
Straps work, and rope works. Straps are nice if you cannot tie knots, and they do go through the car better in that they don’t interfere with the doors as much. As to them being more secure, it seems to me that rock-climbers still use rope, as do tugboat operators, so I’d be confident in either.
got a hitch?
Try this. It’s what I use to carry a near 18’ Canoe on top of a PU. Works slick. Makes loading a breeze and supports everything well
We have 17ft kayaks on an Accord
we use a trailer or our newest roof racks - "Springcreek Outfitters suction cup racks" - they are extremely well made and are completely adjustable to fit various roof configurations. We were a little worried what they would be like until we recieved them! We like them alot and can use them on other vehicles so the investment in our eyes is worth it.
We also bought their kayak cradles (reviewed on pnet) and find they are excellent also.
Thanks its already home
The extenuating circumstances are I have just moved to San Diego (kind of) and don’t know any other boaters yet. My Ford explorer with a Yakima and two kayak specific saddles is still in Utah.
I took lots of rope and some webbing. I used some twine to tie the foam to the boat, just about the location of the bulkheads. Wrapped the webbing around this boat once in the same area as the bulkheads and through the car door and secured with a truckers hitch. I used rope to create two secure independent bow and sternlines. Then drove it home 40 milea at 55. Felt as secure at the end as it did in the beginning. The hardest part was trying to find a place to tie off the bow and stern of the boat, had to get very creative. Pictures to follow.
The boat was $1600 used but immaculate and included a paddle. I will report on its maiden voyage.