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Thread: Bolger cartopper build without frames?

  1. #1
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    Default Bolger cartopper build without frames?

    I'm planning on building a Bolger Cartopper this spring to replacing my ailing PD Racer (failure to seal the upper edges of the ply has lead to major rot problems). Most of my boating is limited to inland lakes and rivers in Michigan, and although I have a trailer I can drag a boat on, I'll be mostly moving it around on actual car-top, so something that can be hefted by one person (even if it's awkward) is important.

    To the end of saving the most weight, I'll almost certainly leave out the permanent seats (although I will be including the centerboard and mast step/partner). I'm also considering leaving out the permanent frames.

    I'm wondering if anyone has an opinion about building a cartopper without the permanent frames on the inside? It seems to me that if the inside & outside of the boat were glassed, and an appropriately stiff gunwale was applied, the frames really wouldn't be needed. My suspicion is that all the hull panels are small enough and curved enough to prevent any significant oil-canning, and the general small size of the boat combined with stiff taped filets would prevent any undue twisting.

    Would a cartopper go taco-style amidships if it didn't have the frames to hold it open? Would the taped fillets and gunwales be enough to keep it shapely?

    Worst-case scenario, if I build it without frames and things go pear shaped, I can always come back after the fact and glue in some frames, but that's certainly more trouble than doing it right the first time.

  2. #2
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    Default Re: Bolger cartopper build without frames?

    I think when sailing you'll need those frames, as that tends to wrack / twist the hull pretty hard.

    I do a fair amount of cartopping, and it ain't getting any easier as I get older. Occasionally I'm stupid enough to cartop my Cosine Wherry when it can't be trailered, and at just over 100lbs it is very hard to manage singlehanded.

    Have you considered a SOF design?

    http://gentrycustomboats.com/Melonseed.html


    http://forum.woodenboat.com/showthre...rame-Sailboats
    Last edited by Thorne; 02-25-2018 at 10:43 PM.
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  3. #3
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    Default Re: Bolger cartopper build without frames?

    Nobody will know for sure before you try it. IMHO, dinghies are too wide to be built without frames. The wider the boat, the more it will twist, and the torsion will not only have an effect on sailing properties, but will also sooner or later damage the boat.
    You might consider building a decked sailing canoe, which can be built without stations. These boats can have cartop weights of less than 25 kg.

  4. #4
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    Default Re: Bolger cartopper build without frames?

    I would not leave the frames out. I would also keep the partners/forsheets and the stern sheets. These are good places to slide a block of foam under. I do not think a thwart is necessary. You can easily enough sit on the watertight box in which you carry some necessaries.

    If you don't mind spending a little on epoxy and good clear spruce, you can make laminated frames about half the dimensions shown. You'll need to make fussy blocks to fill in the corners between the continuous arc of the gunnel to gunnel laminations, which might be about 1/8" thick each.

    You can similarly save weight on the gunnel by making a laminated structure that's as wide as drawn but has 2/3 or so the depth. Add a stiffening block in the way of the oar locks.

    Assuming careful fits at the chines, you also don't need glass over the hull. Just don't drag her over rocks. The wheels on my dink flip up, as in the picture, or down for pulling the boat right side up. They are easily removed when the boat's afloat so you can toss them in the bow out of the way for a more aesthetic experience when rowing and no sheet tangles if sailing.


  5. #5
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    Default Re: Bolger cartopper build without frames?

    I’m not sure what the car topper is , but I’m assuming it’s a ply skiff built on frames .
    Can you induce a small amount of “torture” into the bottom and sides?
    It may change the shape a wee bit , maybe for the better.
    Torturing , putting a compound curve into thin ply , is of course not possible. That is why I always get a kick out of doing it !
    My little speedboats have no frames , they do not hand much of anything past the transom and stringers , and they take more beating than a sailing dingy .
    Maybe try it with a model of the boat . Cut a long thin dart in the bottom piece , pull it up with string and tape it . See that a piece of Matt board can be a stiff thing freestanding , rather than a floppy thing.
    Or just redesign ( model) a new boat based loosely on car toppers dimensions .

  6. #6
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    Default Re: Bolger cartopper build without frames?

    'twould be unwise IMHO

    Bolger HAD A CLUE when designing his minimalistic vessels and eliminated ALL unnecessary weight & components up front

    i suggest sticking to his plans

    btw, one of that design did complete the TEXAS 200 butt succumbed to edge grain rot due to the same issue you had w/ your PDR

    edge grain is the Achilles' heel of plywood so never leave any of it uncovered/unprotected if/when at all possible

    sw
    "we are the people, our parents warned us about" (jb)

    steve

  7. #7
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    Default Re: Bolger cartopper build without frames?

    I have on this Forum often mentioned that CPES put all over plywood surfaces and edges paying special attention to it really soaking in. This is a sealer/primer, not a top coat, but it will turn the plywood into a rather permanent, by human standard, structure. I know of a Gloucester Gull that was built in the early '80s, lives upside down on the beach spring, summer, fall, and winter when not being rowed. It does get a light sanding and a coat of exterior latex every forth or fifth year. Still looks great.

    The cost of CPES is not insignificant but it will make the difference between a boat that with luck might last five or ten years and a boat that needs no luck to last over a half century, perhaps more.

    G'luck

  8. #8
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    Default Re: Bolger cartopper build without frames?

    Very helpful!

    I feel very convinced to leave the frames in, some followups & clarifications:

    If you don't mind spending a little on epoxy and good clear spruce, you can make laminated frames about half the dimensions shown. You'll need to make fussy blocks to fill in the corners between the continuous arc of the gunnel to gunnel laminations, which might be about 1/8" thick each.
    I like that idea. I expect it would turn out looking nice too. Probably less likely to end up rotting too?

    You can similarly save weight on the gunnel by making a laminated structure that's as wide as drawn but has 2/3 or so the depth. Add a stiffening block in the way of the oar locks.
    Was thinking that. Also might do a wider slotted gunnel to make it extra stiff (and look nice and boat-ey)?

    Have you considered a SOF design?
    Definitely -- but this boat will probably get a lot of rougher use (too many people crammed in it for short evening rows, teaching myself to sail, teaching my teenage bud how to row and sail and crash into stuff, etc). I've made a couple SOF kayaks in the past and I really enjoy the build process, but probably not for this boat. I'd LOVE to build an ultralight SOF sailer someday in the future though.

    edge grain is the Achilles' heel of plywood so never leave any of it uncovered/unprotected if/when at all possible
    Yah I'm planning on glassing inside & out, radiusing the inside gunnel and wrapping the inside glass up around the gunnel. Have been pondering good ways to wrap the inside glass _all_ the way around the gunnel for total sealing. Maybe routing some kind of ogee-type shape on the bottom edge of the gunnel so the glass has a smooth surface to wrap all the way around to the outer hull glass? (maybe that's overkill)

    --------

    I'm also wondering about how folks usually go about attaching/sealing/glassing the joint between the bottom of the hull and the centerboard trunk to prevent water infiltrating into the ply around the trunk (and into the trunk itself). Do you run a roundover router around the inside of the centerboard trunk hole after attaching the trunk and then glass tape over that?

    I plan on glassing the inside sides of the trunk before constructing it, I'm mostly worried about end-grain penetration at the trunk-hull joint (am I just being paranoid?)

  9. #9
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    Default Re: Bolger cartopper build without frames?

    An engineered structure that uses glass makes sense. I am not convinced that a layer of glass makes much difference except maybe wraping the bottom and that first chine. I was surprised at how quickly the glass at the bow of my dory, the part that always got pulled up on the beach, wore down and surprised at how easily a rock could make a furrow right through the glass. I now preferr a sacrificial dimensional wood false bottom.

    Plywood must be fully sealed and that seal must be maintained.

    G'luck

  10. #10
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    Default

    I spent a good year considering the ideal car topping vessel and in the end designed and built a 12’ x 30” open canoe. I am now developing a sailing kit. It weighs in a 15kg and I can decide to go for a sail and ten minutes later be on the road. There are big benefits the other end and it expands the areas I can explore. Even my non boaty wife who grumbles at the 6 boats we have agrees it is pretty cool.

    Wouldn’t jump into building something until you consider all option as and what you actually want.



    This is a work in progress but everything for sailing I’d just strapped on with two straps


    https://tinkboats.wordpress.com
    http://proasail.blogspot.co.uk
    What I get up to
    https://youtu.be/X9NZEyvpb_Y Streaker dinghy
    https://youtu.be/oni-3rJzxqQ Sail Canoe
    https://youtu.be/eW078PPgJak Proa

  11. #11
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    Default Re: Bolger cartopper build without frames?

    hospader, may i take some of your thread to show you something of what you are dreaming about

    here is a pic of the Cartopper that did the Texas 200 taken early in the week



    later in the week on the beach AFTER THE INCIDENT

    hull still intact



    and the rest of the week she looked like this

    with borrowed rigging she forged on




    now she(a small piece of her) resides on the WALL OF HONOR @ FARLEY BOAT WORKS along side of a small piece of her sister(a Scamp) both having succumbed to water intrusion thru the edge grain of plywood



    both were built by ONE HELLUVA SAILOR

    both boats served their skipper well

    when you do get your dream on the water i expect she will serve you quite well

    sw
    "we are the people, our parents warned us about" (jb)

    steve

  12. #12
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    Default Re: Bolger cartopper build without frames?

    Hah! Love it. "Noble Plan" is a great boat name.

    I would _LOVE_ to do something like the texas 200 eventually (not why I'm building this particular boat, but I've always thought it sounded like a ton of fun). I was down in biscayne bay NP this winter (without a sailboat) and it really motivated me to get this project going.

  13. #13
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    When you look at a car topper with just the frames added it is hard to believe that they add much


    There is always a way around weight if you have not seen this classic (a Gypsy in this case)
    https://youtu.be/TIy3toNmUJQ

    Personally the Shellback would be my choice, I am sure weight can be saved with the thwarts. Note one frame.




    https://tinkboats.wordpress.com
    http://proasail.blogspot.co.uk
    What I get up to
    https://youtu.be/X9NZEyvpb_Y Streaker dinghy
    https://youtu.be/oni-3rJzxqQ Sail Canoe
    https://youtu.be/eW078PPgJak Proa

  14. #14
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    Default Re: Bolger cartopper build without frames?

    tink, that shellback is what I was sort of imagining re: a cartopper without frames.

    There's going to be at least a thwart at the location of the front frame no matter what (mast partner, front seat support, centerboard trunk support). Perhaps a single laminated frame at max beam (without the permanent seat like the shellback has)? I'm feeling like I want some interior framing, but I also want to try and keep the inside of the hull as uncluttered as possible for seating comfort.

    Not sure though, I do worry that without a fairly stiff frame somewhere in there there'd be some undesirable oil can/wracking/taco factor. Kinda want to just go ahead and try something more minimal. Worst case scenario I'm out a couple sheets of ply and I have to build another boat (oh no not that!)

    Still pondering.

  15. #15
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    Default Re: Bolger cartopper build without frames?

    It's NOT a canoe

    The shell back looks nearly identical!

    It will need framing or so much glass it would be too heavy. ( frames are not even the heavy part of the build)

    People that car top boats, learn early on how to get the boat up there, without being a world class weight lifter.

    Possibly you could use chine battens.

    I don't see that you will ever get to much less then 100 lbs. maybe if you left the C/B and case out.


    I have 15ft Ducker, cedar on light weight oak ribs. still around 100 lbs.
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

  16. #16
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    Default Re: Bolger cartopper build without frames?

    Can we assume you've done some cartopping with the vehicle in question? If not, borrow a friend's canoe or whatever and do it ASAP -- you'll find that loading / unloading on windy days can damage the boat, your car, your back or all three at once...

    Realistically I doubt you can get it built at under 100lbs, and anything that size is NOT fun to pull on and off a roofrack. As we say here on the WB Forum: Don't ask me how I know this.

    Last edited by Thorne; 02-27-2018 at 01:24 AM.
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  17. #17
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    Default Re: Bolger cartopper build without frames?

    I built a Cartopper and I liked the uninterupted space in the boat when sailing, for there is no central thwart. When rowing I had a small chest to sit on and that worked very well. Of course you could leave out the platform in the middle but the boat will be less comfortable.

  18. #18
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    Default Re: Bolger cartopper build without frames?

    https://www.amazon.com/Devlins-Boatb.../dp/0071579907

    If you haven’t seen Devlin’s book, it’s a good one. He talks you through how to build many different types of boats the stich’n’glue way. I bet if you followed his advise with a Cartopper, it would work out just fine. I would consider flotation compartments, they will also add to structural integrity.
    "Yeah, well, that's just, like your opinion man"
    -The Dude-

  19. #19
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    Default Re: Bolger cartopper build without frames?

    I don't see that you will ever get to much less then 100 lbs. maybe if you left the C/B and case out.
    I kinda thought about leaving the CB trunk out and building a removable-bolt-on-leeboard-twart, but that sounds generally kind of awkward and I think I'd rather just deal with the extra centerboard trunk weight. Also I've never built a centerboard nor had a boat with one, so I kinda just want to try it out.

    Can we assume you've done some cartopping with the vehicle in question? If not, borrow a friend's canoe or whatever and do it ASAP -- you'll find that loading / unloading on windy days can damage the boat, your car, your back or all three at once...
    Yah, have cartopped aSummer Breeze (2-sheet 12' skiff of similar size, but less hardware, no centerboard trunk, etc) and a very minimal PD racer (no floatation boxes, no sailing gear of any kind). The Summer Breeze was definitely heavier than the PD racer, it was a little awkward, but not ultimately a huge problem (unless super windy or otherwise bad as you say). Also drag a big plastic canoe around on top of it all the time. Actually for me, I find getting the boat up onto and off of the roof is the easy part (I just slide it off the back), my bigger beef is wrestling it into the water without a dolly (because I either don't have one, or forgot to bring it). 100lbs isn't a big problem as long as it's easy to pick up (I had one brick-like boat with side floatation boxes and no overhanging gunnels that was impossible to get a grip on).

    The more I talk about this, the more I think that having as open an interior as possible is really the reason I was rebelling against the frames (moreso than the potential extra weight). Cartopper's already pretty open in the grant scheme of thing, just that my previous 2 boats had no frames at all so it looked stuffed up to me. Also, I really like the decking in the bottom of the cartopper though, which need to sit up on the frames to make any sense anyways, and if you're putting the frames under where the decking goes, there's hardly any frame to remove anyways (so I should probably just keep the frames).

  20. #20
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    Default Re: Bolger cartopper build without frames?

    What about using beach rollers for both the launch method and buoyancy. What ever internals you use could center about turning the rollers into side tanks. Not my idea bean posted here before

  21. #21
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    Default Re: Bolger cartopper build without frames?

    tink I do have a spare gallon of HH-66 vinyl cement laying around and I was thinking about making some big floats that I could strap to the gunnels for floatation. Most places I go I don't think I really need any extra floatation because it's an easy swim to shore, but if I'm going out on bigger water I'd want something more to make her more recoverable (have heard it's hard/impossible to recover a cartopper without extra floatation)

  22. #22
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    Default Re: Bolger cartopper build without frames?

    Quote Originally Posted by hospadar View Post
    tink I do have a spare gallon of HH-66 vinyl cement laying around and I was thinking about making some big floats that I could strap to the gunnels for floatation. Most places I go I don't think I really need any extra floatation because it's an easy swim to shore, but if I'm going out on bigger water I'd want something more to make her more recoverable (have heard it's hard/impossible to recover a cartopper without extra floatation)
    Sounds like a nice plan. I think inflatable buoyancy has a lot of legs in a project like yours.

  23. #23
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    Default Re: Bolger cartopper build without frames?

    I built a Cartopper with no frames. No c/board either - lee boards & the mast was tied to the front bulkhead which supported the front deck & the compartment was watertight. I beefed up the gunnels with inner & outer wales with spacers on the inside wales so it made for a light stiff beam. The open area was wonderfully comfy...when dry, which it almost always was. Sailed fine but mostly I used it with an electric trolling motor to fish trout. Very nice design, sailed, rowed & motored fine. I cartopped it - when I was in my 40's - my version was heavier than Bolgers but a good trade off for me at the time, Moe

  24. #24
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    Default Re: Bolger cartopper build without frames?

    Moe - did you build in any of the interior decking that Bolger specifies? Do you know what kind of plywood/glass schedule you used? (1/4" ply and ordinary taped joints + single layer of glass inside and out?)

  25. #25
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    Default Re: Bolger cartopper build without frames?

    I built it a long time ago so I'm not 100% sure of the details but after a long look at the plans I believe this is how it went together.
    3/8 ply for the hull sheets & 1/4 on the deck & bulkhead (I think the bulkhead had some internal framing to support the mast) - nice occume ply.Stitch & tape - 6oz tape (maybe 4oz...?) on the joints, sheets were scarfed. No glass sheathing. My thinking was leave out the weight of the frames, timber stem, c/b board&case and whatever you had to put between the frames to make sitting down comfy to offset the greater ply weight of the 3/8" vs 1/4". So when lifting the hull all the sailing/rowing/sitting gear would be off the boat. It worked well & I think the weight was close enough to be a wash. I remember it being under 100lbs - but back then anything under 100lbs was easily handled...It sure went together quick! Easiest boat I ever built but (as usual...) I got bogged down making it glossy pretty with all the taped seams invisible...Now taped seams look business like & don't bother me...I always aim for a workboat finish & miss...Next time...
    It was very comfortable sitting for hours in a very small boat - that was the goal as my various back issues require specific postural alignments impossible using thwarts. Handy little boat highly recommended. Moe

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