DIY Kayak Trailer

Finally posting this after about 1 year of thinking about it.  I thought some folks who don't want to shell out $1600 or more for a kayak trailer might take some inspiration from my COVID project.  Please DM me with any questions and I'll be happy to elaborate.  Here are some bullet points which may or may not be so obvious...

--Base trailer is a Harbor Freight 40"x48" trailer that I purchased on CL for $125.  Here is a link to the HF product: https://www.harborfreight.com/1090-lb-capacity-40-12-in-x-48-in-utility-trailer-62645.html
--The previous owner installed galvanized sheet metal as the base instead of plywood which is totally sweet (highly suggested)
--I extended the tow bar about 3' based on the two boats we own, the biggest being 14'.  The tow bar was 2.5"x2.5"x3/16" HSS steel and cost about $50.  I used three fasteners for the bolted connection, but two is probably fine.  I bolted the new bar to the top of the stock one in case I ever wanted to convert the trailer back to a non-kayak trailer.
--I de-greased and ground down the mill scale off the new steel before painting (highly suggested to take the time to do this right)
--The main support frame is pressure treated lumber.  The vertical supports are keyed into the holes in the trailer frame for added strength and rigidity.
--The corners of the supports are reinforced with steel angles and screws
--Load carrying fasteners are SAE GR 8, 3/8" diameter (DO NOT use cheap fasteners on loaded towing components)
--Use nylok and washers on all loaded fasteners and lock washers with threadlok blue on all other nonstructural fasteners.  The leaf springs on this trailer are stupidly stiff (designed for 1000 lbs), so there is a lot of vibration.  Thread locking is super important here.
--Suggest to design the height of the support bars to keep the kayaks below the air stream of your car if mileage is a concern.  I can get 34 MPG towing a loaded trailer and car packed to the gills with two boats.  My Mazda 3 normally gets 38 to 40 MPG on the highway.  You probably also want to consider the height of your cooler before setting your bars too low.

That's a nice little trailer. I made a kayak trailer off the same frame and found it had a ton of value for the cost. I really appreciated how lightweight it was as I could move it around, even loaded, myself fairly easily.

I had several people tell me to be careful of the small wheels and the bearings getting hot. I packed the wheel bearings with top-shelf synthetic grease and never had any problems. I checked for wear on the bearings each season and replaced them once over 4 years.

EDIT: And thanks for the write-up, by the way! Some great advice in there for someone building a trailer.

That's a nice little trailer. I made a kayak trailer off the same frame and found it had a ton of value for the cost. I really appreciated how lightweight it was as I could move it around, even loaded, myself fairly easily.

I had several people tell me to be careful of the small wheels and the bearings getting hot. I packed the wheel bearings with top-shelf synthetic grease and never had any problems. I checked for wear on the bearings each season and replaced them once over 4 years.

EDIT: And thanks for the write-up, by the way! Some great advice in there for someone building a trailer.

Good point about the bearings.  Since my wheels are bigger thank yours there is a little less heat generated, but I am sure the bearings haven't been greased in a long time.  Since it's a HF product, I'm sure the original bearings and the grease applied in the factory are....suspect.  A good reminder to check on that before they burn up at 70 MPH....

Good point about the bearings.  Since my wheels are bigger thank yours there is a little less heat generated, but I am sure the bearings haven't been greased in a long time.  Since it's a HF product, I'm sure the original bearings and the grease applied in the factory are....suspect.  A good reminder to check on that before they burn up at 70 MPH....

Yes, and for anyone reading this: the HF bearings don't come packed with usable grease at all. They come from the factory packed with what looks like earwax, the only purpose of which is to keep things from rusting during storage and transit. When you're dealing with a new trailer or if you get new bearings you must strip all of that gunk off and pack them with actual bearing grease.

My brother got a HF compact car tow trailer and pulled the bearings as soon as he got home with it. There were metal filings in the grease. He repacked them with the good stuff.

I will suggest to anyone towing any kind of trailer whether its a camp trailer, boat trailer, or utility trailer, do yourself a favor and get one of those Infra Red Laser Pointer Thermometer guns and keep it in your Glove Box in the vehicle. Anytime I am going to be towing more that a short distance I'll pull over around 30 miles down the road and shoot the temps on my trailer bearings. They should remain at ambient air temperature if they are in great shape and should never get too hot to hold your fingers on in any case. You can purchase those thermometers on eBay for under $20.  It's money in the bank for insurance to prevent a bad day on the road.

I will suggest to anyone towing any kind of trailer whether its a camp trailer, boat trailer, or utility trailer, do yourself a favor and get one of those Infra Red Laser Pointer Thermometer guns and keep it in your Glove Box in the vehicle. Anytime I am going to be towing more that a short distance I'll pull over around 30 miles down the road and shoot the temps on my trailer bearings. They should remain at ambient air temperature if they are in great shape and should never get too hot to hold your fingers on in any case. You can purchase those thermometers on eBay for under $20.  It's money in the bank for insurance to prevent a bad day on the road.

Good advice!  Been doing it this way for years.  Establish a base line and then you'll know when one starts to drift out of normal. 

Never thought of a infrared thermometer.  I have always touched them (which can make you remove your hand in a hurry).

High quality Bearing Buddies are a must. 1 or 2 pumps onto the fittings every other trip works well.

I love DIY trailer talk and I am one to over build and carry spares.

I once had a Costco trailer that was probably built in the factory as the HF model.  Back then I hauled about 1000 lbs of ATVs and gear on it for about two years or so. The design of the tongue with the tilt scares the crap out of me after having my trailer develop a dead wobble and rocked so hard side to side it through my 300 lb ATV right off and onto the road. Luckily I was on a local back road near home when it happened. That trailer was decommissioned that day for good.

If I remember right, those factory wheels have a much lower max speed than a normal trailer. Something like 45 or 55 mph.

I would suggest putting together a small spares kit with bearings, seals, grease, grease caps, split pins, latex or nitryl gloves and some towels. When you start to see or hear a wheel bearing start to give, it will certainly be in an area nowhere near the proper parts store, or on a day or time they would even be open. Just pack some spares.