Tow RIB with D-rings or welded aluminum tow eye

[Howler]

We happily towed a 9’ inflatable floor dinghy (65 lbs.) in all kinds of (Great Lakes) conditions using a bridle to two D-rings, motor removed, and bailing drain open. Always arrived dry and safely.

We recently upgraded to a 12” aluminum RIB (110 lbs.) Davits are on order but meanwhile we need to tow.

Question: Is it preferable to use the D-rings with a bridle or the welded tow eye near the bow of the rigid hull? Seems that would put a lot less strain on the rubber and distribute the force more evenly along the dinghy’s length

[alaskanviking]

it is possible to rip out d rings off of sponsons while towing, depends on the forces, and weather during the tow.

the welded aluminum tow point is better but it concentrates the forces on that single point. i have seen boats flip over while being towed from the tow eye. a bridle is better to distribute the load and keep the boat stable while towing

in the military we tow our zodiacs by splicing a bridle out of amsteel (amsteel floats). we splice big loops that fit snuggly over the back part of the sponson. we thread the ends through the sponson D rings, and ziptie the amsteel up to any eyelets along the sponson to keep it in the correct position.

from the D rings you can do it two ways;
Option one (preferred), connect a thicker amsteel tow line to the tow eye with a shackle, then grab your amsteel from both sponson D-Rings and splice them into that main tow line to create your bridle. this puts the tow forces at the stronger tow eye, but also spreads those loads out to the back of the sponsons/transom where its also strong. keeps tow forces from concentrated on the glued patches that hold the rings on. still retains a bridle to keep the boat stable. gives you redundancy if the tow leg or bridle leg breaks, you wont lose your boat. in this set up i make my tow line out of thicker line about 3-4ft longer than the bridle and the bridle legs out of thinner stuff. where the bridle legs meet the tow line i take them both forward inside the tow line and bring them back out maybe 6" from the eye slice or ring i spice in the end. then i splice the ends of the bridle legs into eye splices around the tow line eye so they're captured there. milk everything smooth. sew the end a bit, and the throat of all the eyes, and whip the throat of all the eyes. if possible match the bridle leg eyes to the tow line eye size, but have them spliced so they're in the tow eye. then you work the slack so all the eyes are close to matched and whip the two bridle eyes to the tow eye. this part is to allow you to connect to the eye easy with a shackle or 3 strand tow line and ensure they cant get loose if something breaks.

Option 2 - is bridle only, thicker though. splice like option 1 where there is a big loop over the aft of the sponson, and string through the d-ring. you can make this in one piece but its not as easy to make a big eye that is snug around the aft of the sponson when you do it that way. likewise zip tie it to any eyelets along the length to keep it in a position adequate to tow your boat. on my last aluminum rhib i was able to replace the polypropoline hand hold line with the amsteel tow bridle line. the polypro line doesn't last long in the sun. amsteel/dyneema is good with UV.

Picture is my last one. i did not splice a big loop around the aft sponson on this, but i should have. had i done it correctly i would have run the eye through that last eye/cleat that its spliced to in the picture, so that its captured to the boat and cant fall off into your prop. I used 3/8" or 1/2" amsteel when i did this last time. way stronger than required, but the thicker line is more comfortable to grab a hand hold. the line is spliced into itself around the two fabric loops the same as the original polypropoline hand hold line. this worked on this rhib to keep the line in a good tow position and double as the handhold. we picked up the boat with this to walk it up the beach. just keep in mind amsteel is much stronger than the fabric tabs, d rings and other attachment points on the sponson. you don't want to put a lot of force in a direction where it would rip off one of the attachments, and keep an eye on things over time. less of an issue while new, but later as the boat gets sun eaten....

[alaskanviking]

you can also install rings at the corners of the transom. the big eye goes around the sponson and through this ring as well. helps secure the eye and spread some load to the transom. you have to position the rings correctly, the goal is to have the eye snuggly fit around the sponson.

[C420sailor]

I tow from the bow eye on my 10’ RIB.

I use a very heavy piece of shock cord in parallel with the tow rope (about 3’ or so) to act as a snubber. It dramatically minimizes shock loading. I highly recommend doing this.

[Nicholson58]

On the rare instances when we tow it’s from the solid eye attached to the floor of the fiberglass RIB. Ours tends to whip side to side so we choke up on the painter so the dinghy bow is elevated to our transom. Noisy as heck but it is controlled and unlikely to flip.

[Howler]

Originally Posted by alaskanviking

it is possible to rip out d rings off of sponsons while towing, depends on the forces, and weather during the tow.

the welded aluminum tow point is better but it concentrates the forces on that single point. i have seen boats flip over while being towed from the tow eye. a bridle is better to distribute the load and keep the boat stable while towing

in the military we tow our zodiacs by splicing a bridle out of amsteel (amsteel floats). we splice big loops that fit snuggly over the back part of the sponson. we thread the ends through the sponson D rings, and ziptie the amsteel up to any eyelets along the sponson to keep it in the correct position.

from the D rings you can do it two ways;
Option one (preferred), connect a thicker amsteel tow line to the tow eye with a shackle, then grab your amsteel from both sponson D-Rings and splice them into that main tow line to create your bridle. this puts the tow forces at the stronger tow eye, but also spreads those loads out to the back of the sponsons/transom where its also strong. keeps tow forces from concentrated on the glued patches that hold the rings on. still retains a bridle to keep the boat stable. gives you redundancy if the tow leg or bridle leg breaks, you wont lose your boat. in this set up i make my tow line out of thicker line about 3-4ft longer than the bridle and the bridle legs out of thinner stuff. where the bridle legs meet the tow line i take them both forward inside the tow line and bring them back out maybe 6" from the eye slice or ring i spice in the end. then i splice the ends of the bridle legs into eye splices around the tow line eye so they're captured there. milk everything smooth. sew the end a bit, and the throat of all the eyes, and whip the throat of all the eyes. if possible match the bridle leg eyes to the tow line eye size, but have them spliced so they're in the tow eye. then you work the slack so all the eyes are close to matched and whip the two bridle eyes to the tow eye. this part is to allow you to connect to the eye easy with a shackle or 3 strand tow line and ensure they cant get loose if something breaks.

Option 2 - is bridle only, thicker though. splice like option 1 where there is a big loop over the aft of the sponson, and string through the d-ring. you can make this in one piece but its not as easy to make a big eye that is snug around the aft of the sponson when you do it that way. likewise zip tie it to any eyelets along the length to keep it in a position adequate to tow your boat. on my last aluminum rhib i was able to replace the polypropoline hand hold line with the amsteel tow bridle line. the polypro line doesn't last long in the sun. amsteel/dyneema is good with UV.

Picture is my last one. i did not splice a big loop around the aft sponson on this, but i should have. had i done it correctly i would have run the eye through that last eye/cleat that its spliced to in the picture, so that its captured to the boat and cant fall off into your prop. I used 3/8" or 1/2" amsteel when i did this last time. way stronger than required, but the thicker line is more comfortable to grab a hand hold. the line is spliced into itself around the two fabric loops the same as the original polypropoline hand hold line. this worked on this rhib to keep the line in a good tow position and double as the handhold. we picked up the boat with this to walk it up the beach. just keep in mind amsteel is much stronger than the fabric tabs, d rings and other attachment points on the sponson. you don't want to put a lot of force in a direction where it would rip off one of the attachments, and keep an eye on things over time. less of an issue while new, but later as the boat gets sun eaten....

Thank you for this very thorough response. Although extremely detailed, I'm still struggling to visualize the part where the bridle legs meet the main tow line and the various splices you describe. Could you possible add a picture of that part of the setup?

[Dooglas]

I tow a 9' RIB by D-rings in order to rig a bridle. I find a bridle and a short tow line are necessary to keep the dinghy from aggressively hunting back and forth.

[hlev00]

A three point bridle works the best. The main pull is on the welded bow eye. The D rings should only be to keep the dinghy tracking straight. I like the idea of some shock cord or rubber snubber to reduce the shock on the main line.

[Near2KR]

We towed an 11ft fiberglass RIB with a 9.9 mounted to the transom from Maine to Fl and back again with a single line attached to the eye mounted to the center of the bow. Not a single problem.

[alaskanviking]

I am at work, but managed to make a quick sketch for you and scan it.

its called a tri leg bridle. Ive seen it used in the military for some helocptor cargo lift slings and rescue swimmer slings. heavy duty especially with amsteel. center takes most of the force, the bridles are there to keep the boat from swinging back and forth or catching the bow and flipping. you should take pains to keep the bridle lengths the same or the boat will tow slightly off kilter.

size the bridles so they can take the full force if required, realistically for the 10-12ft boats we use 1/4" could do that, but like the picture i posted earlier thicker lines feel better in your hands and easier to grip

the center line is thicker so when you splice the bridle lines inside it burys them correctly. as an alternative you could sew the three lines together and extra wippings for the same length then cover with a chaff sleeve, but you wont have the same strength, would probably be good for smaller dyneema.

elastic is good but id only use it for short trips in good weather as it can break or stretch. correct towing is to have a long enough line so the boat being towed is at the same position as you on the following wave. that is enough length to use nylon 3 strand or plait as your shock absorber same as a snubber. you could use nylon double braid but that reduces the shock absorption. plait isn't similar but has more elastic shock absorption, however it doesn't kink badly like 3 strand can. give your self enough legth for your tow line so you can adjust the tow length for the conditions. ideally you would not be out towing in bad weather but sometimes weather changes on you fast and catches you. so better to plan for the worse and hope for the best.

[alaskanviking]

you could make brummel eye in the middle of the bridle to make the eye. that means there is only 2 eyes to deal with and that would keep the diameter in this area smaller. the problem is its not as easy to splice the opposite end of the bridle at the identical length. if your bridles are different length the boat will pull off kilter. too much soo and that adds a lot of friction force slowing you down.