It's my first thread on this forum, but I have always find very good information in the past about many topics. So I am sure I will have good advices here. I need to replace the chainplates on my Hughes
29 this season. This how I conceive the project
. Please feel free to let me know what you think about it.
First, the principal points I should keep in mind should be this:
1- To allow easy inspection
and to avoid corrosion
problem, the chainplates themselves should not be covered by fibreglass;
2- To minimize the stress on the chainplates and on the boat, the chainplates should be aligned with their respective shrouds;
3- To avoid exaggerated stress on hull
, I should prefer an installation
using mounting knees that needs to be glassed on the hull
This how I am now conceiving it:
1- Remove my current installation
2- Strengthen the hull by adding layers of glass from the inside (and probably also from the outside, to fill the depressions that have been made by the chainplates);
3- On that thickened hull, glassed in wooden knees correctly shaped to sit against the side of the hull and the deck
and to give the correct angle to the chainplates and their shrouds (but with no chainplates on them);
Question #1: Do you have any suggestion concerning the type of wood I should use? The backing blocks I've for my current
installation (shown on above pictures were made of IPE. I was planning to use the same type of wood, for is resistance to rot
and density, even though it would be hard to shape.
3.1- To prevent risk of rot
, I will first apply a coat of epoxy
on the wooden blocks.
Question #2: What do you think of penetrating epoxy
? According to West System website, it doesn't seem to be a good idea, especially if I am using high density wood. (WEST SYSTEM - Projects - Thinning WEST SYSTEM epoxy)
3.2- To also prevent risk of rot, I was thinking that it could no be a bad idea to first drill larger hole for mounting bolts, fill them with epoxy, and re-drill them the correct size.
Question #3: Do you think it is a good idea and, if yes, do you have any suggestion concerning the type of epoxy I should use (pure, with additives and which one?)
4- Flatten the "front side" of the glassed-in wooden knees so as the chainplates perfectly sit on them.
Question #4: Do you think it will work or should I better try to have the chainplate seats already molded in the last layers of laminate when I will be glassing in the wooden blocks?
5- Drill mounting holes for chainplates and their backing plates
through the glassed-in wooden blocks and through the hull.
Remark #1: I wasn't sure if outside backing plates
were still a good idea, because I was fearing that stress apply from the outside on a relatively small areas (the ones covered by the backing plates) will generate again the same problem (I have considered for a period to do something more like what can be found under "Option 2" there : Replacing The Chainplates | SEA SPRITE ASSOCIATION). But the way I figure it now is that having the wooden knees glued against the hull with epoxy and glassed in will made the whole "one block" that should work together (i.e. the load apply from the chainplate to its backing plate will be distributed to a larger part of the hull, because the backing plate will pull the whole glassed-in knee "through" the hull.)
Remark #2: What decided me to have outside backing plates is that it seems to me the only way to easily remove the mounting bolts to inspect them and change them if necessary.
Question #5: How many mounting bolts do you think I need (is there a formula to calculate this?) and is their a specific pattern to place them (vertically aligned, "Z shaped" pattern, etc?)
Question # 6: Do you have any comments concerning Remark #2 ?
Question # 7: One problems that I see with this is that having the chainplates aligned with their respective shrouds and the outside backing plate sitting against the hull will create a problem with the angle of the mounting bolts (they will not rest at perpendicular angle with the metal piece on one of their side, which, I assume, will tend to bend them). Should I be concerned with that (especially with the lower-shrouds)? To avoid that problem, I have imagined that I could use thicker chainplates and ask the shop to drill-in mounting holes that will be parallel with the hull axis. What do you think of that ?
6- Install chainplates and their backing plates with the mounting bolts, sealing them with appropriate sealant
Question # 8: Do you have suggestion concerning the material the chainplates, backing plates and mounting bolts should be made of? I've read that 316 stainless steel
should be OK.
What do you think of this project
? Am I doing it the right way ? If you have any suggestions of comments concerning the whole project or concerning specifically asked questions, I will be glad to read them.
Thanks in advance to everybody.