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Rethinking the bunks, but the boat sits well on it

Whoops, can't get pictures to work...

Finally some pictures. After a DOH! moment and moving the bunk supports inboard to clear a lifting strake, I am contemplating how to modify them to sit on top of the I beams to lower the boat about 2-3" and get better support.

Nice trailer, what breaks are on her?

Can't you just move the bunk supports out some ?

I wish! There is a lifting strake right in the way. I had them out against the i beams. It was a unknown as I didn't haul boat to measure beforehand, I was hoping for the better luck


Kodiak stainless calipers, E coated slip
on rotors, Brake rite electric over hydraulic actuator. 7k Dexter torsion axles, 8" I beam, .25"
walled cross members. 316 hardware, Amsteel blue winch line, 8 lug wheels, each light has an individual wire to a junction box Ip front

CT', why can't the bunks be on a lift strake? Seems like as good a place as any for the support of the hull by the bunk? I've definitely had bunks on strakes (not this size hull) before- so just curious? Also, not knowing the ramp inclines you're using, or the tides, it seems that the depth of immersion to float off is pretty deep? So without side guides/uprights- if there were any current running or tidal action side to side on the ramp- seems like getting the boat onto the trailer that is so deep (?) would be a potential hassle?

Not familiar with your local details, just asking because of the waterline's relative height off the water? I've tended to V the cross pieces, lower the bents and get the chines to within as few inches of he fenders as I could to get on and off as shallow as I could?

This project, if I remember correctly, was to conserve some $ from purchasing a mainly aluminum trailer? How's the final cost versus planned saving end up? Is it worth others' asking for CT's Trailer Plan's package and trying their own version? Or, is the price of a new (existing mfg's) version a cost effective solution? Asking in generalities not about the final $'s spent. You have the perspective that others' reading would find very helpful to learn since you've explored and built your own; so a unique perspective I'd say?

Looking forward to learning more details- also how our various CAD solutions worked in the project? Also would appreciate any review of which joints are welded versus bolted and why 'that' joint's design was chosen? Thanks for posting, looks nice, it'll be interesting to learn more about what you've discovered in this project?

Cheers,
Kevin Morin
Kenai, AK

Kevin and the interwebs:

1) Placement of the bunks on the lifting strakes- The V of the strake was dead center on the bunk. The bunks are lined with UHMW. The high PSI of the entire weight being placed on the on the pointy end of the strake made it very difficult to get on the trailer. I believe the strakes are plenty strong, but it makes it difficult to load and probably would wear the bottom paint quickly.

2) As for the height, it is about where a production trailer would sit, especially some of the factory trailers under Duckworths that I have looked at. The boat would have sat lower if it had not been for me moving the bunks inward to avoid the strakes. I have about 5-6" between the keel and straight cross members. I want to gain back the 3-4" by rethinking the bunks. Looking at pictures, it is deceptive as I am standing down the ramp towards the water as well. I don't think it as bad as it looks in the photo. From the ground to the top of the pilothouse is 12'- which in my looking around is a little bit lower than a lot of plastic express style boats

3) Straight vs V bend bunks. Straight made it easier to construct- No welding or fabrication. There are prebent cross members available, but the price with shipping is prohibitive to the west coast. I don't have a high deadrise, which makes the V bend less necessary. I ordered the axles with a V bend in case I changed my mind or the trailer needed to be reconfigured for another boat. Hard to return the axles, easier to reengineer the cross members

4) Cost definitely saved some money I thought I could build the trailer for about $6000, but I ended up at about $7800. Some of it was for "oops" I need more hardware and having to run locally, some if it was outsourcing the bunk supports/bunks (almost $750), some of it was underestimating the amount of hardware needed. I have about $500 in stainless hardware. I bought USA made 316 stainless, and lastly, some of it was my obsessiveness for over doing things. For instance the winch line 7/16" Amsteel blue synthetic rope, Granted I bought a remnant at the supply house, but it was more expensive than a strap or cable. I got quotes for a similar trailer in the $13,000 to $16,000 range

5) Time, it has been spread over 10 months. Most of the build happened in June in two days. After I got the rolling frame done, it was nitpicky till I got all the bits and pieces. I bought what made sense, made other things I bought the winch post pre fabbed and it took almost 2.5 months to finally show up. I also did all the work on the trailer tongue (holes, hardware etc) and then disassembled it for galvanizing. I did not want to drill holes in newly galvanized piece of steal and compromise the rust resistance. Doing things that way takes time.

6) I have already walked someone else through the process, while the idea of commercializing my experience and ideas is exciting, the actual work is back breaking. I gain more satisfaction from sharing what I learned and the experience of completing the project. I would do it again. Anyone who wants help or info, I work for beer. Just 1, I am a lightweight (not physically, just with drinking)

7) I struggled with CAD. All I needed was the beams drawn. I ended up drawing them as far as I could take them, and then rang the bell for help with a friend. He cleaned them up and made the useable for the metal forming shop. During this time that I was building the trailer I was working full time AND going to college full time to finish my degree. I obtained my Bachelor's degree in September!!

8) There is very little welding on the trailer. I will take pictures of the parts that are- everything is bolted. All design was SWAGed and R&D by looking at many, many other trailers and mimicking what I felt was the best option. Anything that could be "upsized", was. Hardware, material thickness and cross section. Just because. The trailer ended up weighing about 2,150 lbs.

I am happy to share more pictures of the build as well as any details for anyone interested.

Did someone say "Build Pictures"

In sort of an order

More

And the winch post

And here you can see the lifting strake dilema

I'll suggest that you shorten the bunk brackets and weld them to the top of the main frame rails. It accomplishes three things, it moves the support outboard which would increase stability of the boat when making turns (or dodging crazies on the highway), it allows the bunks to easily clear the strakes and it enables lowering the boat right down to where it just clears the fenders which will make it easier to load and reduces the center of gravity which is safer for transport.

Chaps wrote:I'll suggest that you shorten the bunk brackets and weld them to the top of the main frame rails. It accomplishes three things, it moves the support outboard which would increase stability of the boat when making turns (or dodging crazies on the highway), it allows the bunks to easily clear the strakes and it enables lowering the boat right down to where it just clears the fenders which will make it easier to load and reduces the center of gravity which is safer for transport.

130% agree.. Trying to figure out the easiest way to accomplish this with as minimal cost.

measure, cut, weld . . . bet Goatram would knock that out for you cheap

Better get in the queue before his boat goes in for surgery.

Chtucker, one of the pic shows the bunk verticals bolted to the cross members- so the load to the main I-beam is not compression- its tension on the lower flange (bolts)? That sure seems less effective use of the I-beam than top down. So Chaps' idea of putting the verticals on the top of the I-beam seems a better design to me as well.

Next using the photo of the vertical and bunk rectangular extrusion as a model- the vertical positioned on the top flange only needs to be a few inches tall? So instead of the tall welded "T" columns that hold up the bunk extrusion- it looks like you'd get by with a few inches of 'blocking' instead of 16" (~" ?) vertical and that makes the entire structure more compact, less moment arm due to the boat in all hauling instances.

The load should be expressed on the centerline of the flange if you can- so a plate on the flange (load distribution) with a vertical plate upright, lengthwise, aligned and over the centerline of the beam's web with a bolt flange to support the bunk box extrusion seems best? If you weld that on, confine the weld (locator only) to the outer edge of the flange edges and run parallel to the beam not across it. Drill the flange atop the beam so the interface can drain dry.

Looks like very short supports would do the job, all they'd have to be for depth is enough for the chines to clear the fenders a few inches- but tall enough to get to the nuts of the bunk to support bolts' heads with a wrench.

Cheers,
Kevin Morin
Kenai, AK

I avoided the top of I beam bunks because I was so unsure of the ride height/tire fender clearance. That was unknown till the trailer was assembled. There were many different options on axle angle, and I guessed on what would work. Luckily that part came out spot on.

I don't like the idea of how the bunks are currently supported, but it mimics production trailers. I felt more comfortable when the supports where closer to the I beams.

I want to match my dead rise and put the bunk supports on top of the I beams. I need to haul the boat out again to take some more measurements, specifically, how far I can drop down and keep 2" between the keel and the straight cross members. I would imagine I can drop the boat 5-6". I don't know if this is the answer, but it is an option.

Next step-measurements x 2 or 3 times, then some thought and rework.

Nice job! Sure looks sturdy!