converting to bunks on my trailer

[adam aunins]

I may be wrong but the way I under stand it is on a DS you want most of the boats wieght to rest along its keel and the outer bunks/rollers are more to help stabilize the boat on the trailer. If you can't set it up like that then very big bunks like Phil's that spread the load out are the way to go. I would try to get some rollers mounted under keel front middle and rear to take the load off of the rest of the hull. It made all the difference for my boat when I was able to set my trailer up that way, I can now go down the road and not sweet every bump along the way.

[persephone]

If the pivoting cross beams got to be a problem you could fabricate new cross members that bolt in. I get the impression that you are pretty handy, I don't think it would be too difficult to do. Where it is currently a bolt together trailer it is best to keep it that way (read as 'disregard my inquiry about welding'). Honestly I don't see them (the pivoting cross beams) being a problem. I try to balance out what is possible with what is necessary and beneficial. Anything is possible, but at what cost and to what end. Know what I mean?
I am fairing the underside a bit. I am using system 3 SilverTip QuickFair (jamestown distributors has it). So far it is going well. I can't say I'm going for the perfect bottom, just getting rid of the glaring problems. I have a pair of longitudinal indents from the bunks, and also have long cracks in the gelcoat at the seat junction. Where the indents run the length as opposed to the width of the boat I'm not as concerned about them. Also using the quick fair to fill in the hundreds of blisters I had to dremel out.
Mixing the compound can be difficult. It can be mixed by volume or weight, I have a very accurate scale at work and can mix it in 0.1 ounce increments. That is about enough as it kicks in 10 minutes and that is as much as I can spread cleanly in that time. That is a blob of mixed compound about half the size of a normal fist.
The bottom paint may be a racing paint, but I picked it for the color, and the fact that it is non-ablative.
I agree with Adam about the weight distribution. I'm planing on using wide bunks as a precaution, but hoping to set it up so that the center supports pick up as much of the weight as possible. I actually have 4 rollers, pics coming soon.
As to the stringers, I'm not really sure how they are structurally speaking. I'm not even sure I know how to tell if they are good or bad.
Thinking about it, are the stringers a stand-alone structural member, or are they there to support and spread the load in conjunction with the floorboards?

[K.C. Walker]

Thank you for your thoughts Adam. I'm glad to hear that the center rollers made the difference for your setup.

You are right that the recommendation for daysailers is to support them by the keel and stabilize them with bunks. However, I just tried an experiment with my boat. Thinking that I would try three center rollers front, middle, and rear. What I did was jack up the boat a little bit at the rear crossmember right in the center of boat where I would put a keel roller. This is about 18 inches in from the transom. What I found was that the hull deflected noticeably by putting localized pressure there. So yes, there is a substantial keel that can easily support the weight of the day sailor but that is from the rear of the centerboard trunk forward. So now I'm thinking the keel support should be mostly forward. Or, at least there should not be a lot of weight on the rear keel roller.

KC

[K.C. Walker]

Geoff,

Yes, the bolt together fabrication on this trailer makes it easy to modify. Good thoughts on an additional crossmember. I found that I can order one from EZ Loader.

Well, Dremeling out the blisters doesn't sound like much fun! Those longitudinal cracks where the seat meets the hull you might want to look at carefully if you haven't already. The crack I had in that same location went right through. It would be an easy repair to do now, grinding it out and putting some glass cloth in their. I drilled holes along the crack as a depth guide and then ground away until I was most of the way through. Sure enough, the crack really was most of the way through.

The stringers are an independent structural element. Though, they aren't very big so I don't know how much they add to the stiffness of the hull. AND, because mine are toast, I'm not sure what that area of the hull would be like with good stringers. Mine are obviously damaged from the floorboards. The previous owner repaired the floorboard "joists" (or what ever they're called in boats) with angle aluminum and it cut the stringers neatly into sections. The floorboards are originally designed with "joists" that have a profile that has feet on the ends and goes over the top of the stringers. Someone told me that the stringers were balsa wood core. Whatever was inside of them now looks like compost.

KC

[MarcCram]

It is balsa wood that was used in the core. And your right it looks like soggy cardboard or compost when it gets wet. I'm having the hardest time right now cutting my 3" SCH40 conduit in STRAIGHT thirds so I can glass them in place of the balsa that I cut out.

Sorry for the trailer digression.
marc

[quote="K.C. Walker"] Someone told me that the stringers were balsa wood core. Whatever was inside of them now looks like compost.[quote]

[persephone]

Here are some pics of hull and trailer.

http://s664.photobucket.com/albums/vv4/ ... udsbucket/

The pics of the trailer have information about what I like and dislike.
You can see I've already started the filling and fairing by the time I thought to take some pictures. Cleaning out the blisters wasn't as bad as finding them all. The coin tap test is pretty accurate, but time consuming. Tap test showed no delamination along the longitudinal cracks, so I'm leaving them alone for now.

[K.C. Walker]

Geoff,

Thank you for the detailed trailer pictures and analysis. There certainly seems to be no end of variations on trailers and setups. I see what you mean about getting low on the trailer and with a 3 foot overhang you ought to be able to get the transom in the water pretty easy.

The cross members on my trailer are semi-V-shaped and are now hanging pretty low beneath the frame. I'm thinking that the setup I can build in there will still have the boat pretty close to the height of the frame. So if I need to get lower I think your idea of the smaller tires would get me down as low as I can get without scraping the license plate. I've got some 12 inch tires from my other boat trailer that I'll try.

It looks like Persephone is about ready for paint! Nice Festool outfit you got there. That should keep the dust in check.

KC

[Phill]

...Phil Root has some very good pictures of his trailer on this website. I'm hoping Phil or anyone else would help me out on a few points. One of the things I was curious about was the wooden track up the middle next to the rollers on Phil's trailer. Does this help guide the boat on? One other thing, is that plywood for the main bunks on Phil's trailer?....

KC

The 2x4's are to keep my bow from loading into the sharp metal areas around the rollers when loading.

The bunks are made from outdoor grade plywood. Built in 1991, Thompson watersealled and then covered with in/outdoor carpeting.
Occasional watersealing the underside, but original carpeting on top of those bunks. I am fortunate to have a hoist at our club, so the trailer doesnt get dunked more that 10-15 times a summer. Lots of time to dry out. I keep waiting to hear cracking when I walk out on those bunks when retrieving at a ramp. So far, no creaking. so i have not replaced them.

Happiest DS'n..
phill

[K.C. Walker]

The 2x4's are to keep my bow from loading into the sharp metal areas around the rollers when loading.

The bunks are made from outdoor grade plywood. Built in 1991, Thompson watersealled and then covered with in/outdoor carpeting.
Occasional watersealing the underside, but original carpeting on top of those bunks. I am fortunate to have a hoist at our club, so the trailer doesnt get dunked more that 10-15 times a summer. Lots of time to dry out. I keep waiting to hear cracking when I walk out on those bunks when retrieving at a ramp. So far, no creaking. so i have not replaced them.

Happiest DS'n..
phill

Phill, thank you for your reply!

I'm thinking I will go with the plywood bunks, an 18 year life span seems plenty reasonable. And I like the idea of the 2 x 4 tracks for the bow. I doubt that I would launch more than 15 times a summer, so hopefully I'd get the same lifespan. Probably a longer lifespan than my sailing career will last.

Question on how you use your trailer. It sounds like you use the float on/float off, dunk the trailer method. Is that correct? I've got bearing buddies already installed and was thinking of going that way.

One other question how do you think the distribution of weight is as far as supporting by the keel and the bunks?

Thanks again!

KC

[Phill]

Yes, when ramp launching I back untill the rear of the boat floats off of the bunks,then as the boat starts to go back, all contact is then on the center rollers and bow support. If backed too far then too much pressure is applied to the bow and it tries to jump off of the rollers sideways when a boat wake or whatever else, that is what the wood in the center is for. Too keep the bow from scraping on the roller holder sides.


When resting of the trailer, my thoughts are to keep the wieght on the center keel line and only have the bunks keeping the boat from flopping side to side. With the large wide flattish areas from the CB pivot aft, it is a balancing (pun?) act to get the boat solid on the trailer and not put too much pressure on those flattish areas and cause oil canning of the bottom. Another thought, I tried to keep the bunks approximatly centered under the fore and aft seat tank sides. That edge should act like a stringer to spread the load and prevent oil canning. Kind of like a popcycle brace under the neck.

My thoughts on Bearing buddies. First, I never want to dunk my axles when the bearings are still warm, draws in moisture. fortunately, it takes time to rig mast etc... so that allows a cool down period. Adding grease occasionally is good. Too much and in the wrong way can be bad.
When putting grease in with the buddies, you are packing it in and it migrates to the rear seal, where it can, and often does blow out that seal. The only way to know if you have packed enough grease in is to see the leakage at the rear seal. No real winning here, just info to watch for. Newer trailer axles are being built now with a grease fitting that applies the grease at the inside rear seal and if you take the cap off of the hub, the grease migrates to the outside where it harmlessly oozees out. Wipe off the old replaced grease and replace the hub cap. My trailer came with that kind of fitting.

hope this helps