Converting this trailer for my Mirror dinghy to take my 3.2m SIB

Croolis · 25 February 2025, 12:05

At this moment in time, I have no better pictures of the trailer, but it's a combi trailer made to take the dinghy you can see in the picture.

I'd like to put my 3.2m air deck SIB on it. I think it would likely make sense to not have the engine on the back while on the road, but I'd be wanting to take the boat off the road trailer while still on the launch trailer, attach engine then use the launch trailer to put the boat in the water (then I can get rid of transom wheels hooray).

The other picture I provide shows about where the axle for the road trailer would lie (yellow lines). The launch trailer wheels would be a few centimetres further towards the rear. I would be needing to attach bunks I should think for the boat to sit on.

So my questions are, I suppose, is if this whole thing is feasible. As you can see from the top down picture, the transom isn't actually that far south of the road axle. So for just transporting the inflated boat (and bearing in mind I'll be doing 3-4 hours driving with it as a rule), do we think it would all be stable etc? Seems to me that it would but maybe there's things I'm not considering.

The second part is taking the boat off the road trolley on the launch trolley, then attaching the engine and moving the boat about in that state. So there's be no support for the engine directly under the transom unless I did something to extend the trailer backwards, say add some box section, so I can have a bunk directly under the transom. And I suppose, if I was actually doing that, would I be able to have the engine on the back while driving?

Or would I need to bother - does having the engine on the transom about a foot south of any underneath support a bad idea, in either the launch trolley only scenario on on the whole road trolley setup?

I should say the engine ins a 9.9 four stroke umm 38kg I think it is.

Thx for any help and suggestions.

User name · 25 February 2025, 12:24

I wouldn't let the engine overhang on a SIB, but depending on your metalwork skills, you might be able to knock up a removable outrigger that the lower unit could rest on when the engine is in the upright position, kinda like the 'transom saver' things.

That way, much of the weight would be inline/forward of the transom and the load would be distributed instead of weighing only on the tube mounts.

Croolis · 25 February 2025, 13:16

Yes, I guess some kind of diagonal bar that goes up from the axle to a little bunk that will sit under the transom. Easy to just bolt together from a bit of small box section. Only for the launch trolley. I won't try and drive with it. I think the weight (and it would be most of the weight of the whole damn thing) that far back, even if it was well supported, probably not the best idea.

Cool. I'll take that boat off of ebay then. Well, put it back up again without trolley. Which will probably mean I'll end up cutting it up, because sailing dinghys with broken rudders, split gaff mast and no trailers at all tend not to be desirable, no matter how old and classic. Hope not though.

Steve509926 · 25 February 2025, 16:32

Quote:

Originally Posted by Croolis

The other picture I provide shows about where the axle for the road trailer would lie (yellow lines). The launch trailer wheels would be a few centimetres further towards the rear. I would be needing to attach bunks I should think for the boat to sit on.

If you are fitting bunks, why don't you make them long enough to support the transom?
That's what I have done to my road base trailer.

chipko · 25 February 2025, 16:54

Agree with Steve above. Bunks will easily cantilever at least 500mm or so behind last support if required, even modestly sized ones like 38 x 69mm timbers. If you need to extend more upsize to 94 x 44mm or even upgrade to using two timbers in a T shape.

Pic below of an old jet ski trailer modified for our then T38. Cantilevered around 450mm with only 38 x 69mm section and rock solid.

Croolis · 25 February 2025, 18:02

All good suggestions, thank you. This needs looking into. And would you drive with the engine on the transom with those arrangements?

I shall have to get the boat off at the weekend and have a good look at the trailers, see what can be done.

What you mean by cantilevering in this context please? I'm not much of an engineer.

Steve509926 · 25 February 2025, 19:05

No reason why you shouldn't travel with the OB on the transom, but I always use a transom saver. If I travel long distances I tend to put the OB in the back of the truck but short distances when I'm on holiday it's fitted for the duration.
This thread may help re: transom saver, I nicked the idea off chipko.

https://www.rib.net/forum/f49/settin...ler-89643.html

Croolis · 25 February 2025, 19:08

Quote:

Originally Posted by Steve509926

No reason why you shouldn't travel with the OB on the transom, but I always use a transom saver. If I travel long distances I tend to put the OB in the back of the truck but short distances when I'm on holiday it's fitted for the duration.
This thread may help re: transom saver, I nicked the idea off chipko.

https://www.rib.net/forum/f49/settin...ler-89643.html

That's a useful thread

. Thank you.

Poly · 03 March 2025, 08:32

Quote:

Originally Posted by Croolis

it's a combi trailer made to take the dinghy you can see in the picture.

I'd like to put my 3.2m air deck SIB on it. I think it would likely make sense to not have the engine on the back while on the road, but I'd be wanting to take the boat off the road trailer while still on the launch trailer, attach engine then use the launch trailer to put the boat in the water (then I can get rid of transom wheels hooray).

Are you planning to keep the mirror? Just wondering if you would be better keeping it on its launching trolley but sharing the same base for road trailing. I'm not sure how easy it will be to add bunks, but they may actually not be a great solution for launch (and in particular recovery). Good transom wheels have advantages - not only where you launch but at somwhere you might stop for lunch, and ultimately mean you can prep everything and then step about and go whereas a trolley requires you to launch, then go and move the trolley meantime leaving the boat somewhere...

9D280 · 19 March 2025, 22:35

I was thinking same as Poly....

I have an old Snipe Combi which I got with a Laser. Later I got a used 470 with no road trailer. Road base was man enough for the 470';s weight (and thankfully the bow-to-balance-point of the two dingies was similar (more rear overhang on the 470, as pretty much an empy shell behind the Centrboard case), but I (got) made a gunwghale hiung launcher for the 470, and towed them both about on the same road base for years.

I no longer own the Laser, but I've been having similar thoughts for my SIB & that road base...

I've not done the geometry maths here, but am I correct in thinking the Yellow dimensions are the trailer? - If so Engine on might be a bit rear heavy, but do you have a close - up of the "nose end" - If i'm interpreting your picture correctly is the Trailer - trolley clip ahead of the mast support brackert and raised? - if so, could the SIB trolley be arranged to sit further forward to get the transom over the axle?

or.... when you make / modify the SIB launcher, use the mast support as the trolley fixing wiyth a short vertical down postr that clamps in using the mast support clamp? (Guessing that trailer wasn't specifically designed for a Mirror? )

Croolis · 20 March 2025, 09:48

Just saw Poly's post, sorry.

The Mirror has gone. It went for the princely sum of £25 on ebay auction lmao. That was after being up for weeks with no takers for the 100 quid starting bid so I went with 20 quid and it sold. But it had a split gaff mast, a broken rudder and no trailer, and it went to a young offender's institute who are going to restore it so I am content. Hopefully someone might not get stabbed or robbed from as a result of boat induced reform

.

To answer 9D280's questions. Yes the yellow lines are the ROAD trailer dimensions, which is like a T piece. The launch trolley sits on top of that and has a more triangular design. Now I've got the boat off of it, I can get some good photos. If I can get home before dark today, I'll get some proper measurements and pics.

I think the trailer was designed for the Mirror, because it has welded on short vertical pieces towards the rear that sat on the outside of the boat to keep it on (you can see them in the picture), plus it has an upturned part at the front with a blunt crossbar that fits the pram hull design of a Mirror very well. Finally, it has no mast support at all because the Mirror (at least that version) has a gaff mast which comprises two masts, that when taken down can lay flat inside the boat.

However, all of these things (if I remove the welded vertical pieces because too narrow) mean that it actually looks quite useful for the SIB.

I think I will not even attempt to take the engine on the back of the boat while in transport. Because this is amateur night I think I'm not up for the risk.

I'll get those pics up and folks can throw whatever advice they want at me

. Cheers.

Croolis · 20 March 2025, 10:37

If anyone can give me an idea where I should locate bunks, should I need to attach them, on this drawing, that would help a lot.

If I'm astonishingly lucky, the framing on the trailer will match where the bunks should go and I can just clad the frame in lagging, but seems unlikely.

Cheers

.

chipko · 20 March 2025, 11:05

Personally I’d position bunks under floor, tight up to tubes and extending slightly beyond transom.

Croolis · 20 March 2025, 12:10

Quote:

Originally Posted by chipko

Personally I’d position bunks under floor, tight up to tubes and extending slightly beyond transom.

Awesome thx

Croolis · Yesterday, 11:16

Here I have images of trailer. I've measured and, unless I've buggered it up, the launch trailer dimensions (not including the width of the road trailer wheels!) under the boat are marked out in yellow.

I think I'll need bunks - sadly the stretchers on the trailer are probably just a little too wide and on the vertical plane they don't sit quite right compared to the height of the welded on back bunk. The raised front part of the trailer looks like it will sit quite well with the raised part of the prow on the boat if I don't make the bunks too high. Can't really tell until I blow up the boat and start doing some real world checks.

As suggested, I'll extend the bunks out the back until they go under the transom. Maybe make some sort of detachable assembly that will extend a bit further backward for a trailer board mount.

The only things now I have to sort then is what to make things out of. I imagine some very short lengths of aluminium or galvanised steel box section to make pillars for the bunks held on to trailer frame by C clamps. I'll use properly varnished 2x3s for the bunks, maybe cover them in that carpet stuff.

Will use this for inspiration. smallribber has a vid up with it on that will help:
https://www.trailertek.com//extreme-...caAgeYEALw_wcB

I don't have an angle grinder and know nothing of metal work. I have a recep saw with a metalwork blade. That'll do it?