Fin box installment on Penetrator

In the last year I almost had enough money to order a Penetrator from respected Ventura surfer/shaper Dennis Ryder. Dennis kindly looked into shipping costs to get a board to me here in the UK. It was just horrendous…import duty and tax made it just too expensive. I ended up buying something else. I find I can’t get the concept out of my head and have approached the most experienced shaper in the UK to get a replica classic Penetrator made. One of the challenges is how to mount the fin box. The two Cedar stringers are 10” apart so the fin box is routed into the foam. My shaper says you can’t just route in to the foam. Now this is something I hadn’t thought about. Usually you are mounting the fin box over the stringer. He says one knock or even a hard bottom turn will stress it and cause cracks etc.
I’m just wondering what John, Dennis and Steve Walden (who made some Penetrators with Peck a few years back) do to get around this?
I know there is a wealth of knowledge on the forum so please guys, I’d love to hear your thoughts as my shaper is reluctant to go ahead with the project now.
Thanks guys…and if anyone has a used Penetrator they would be prepared to ship to the UK please please let me know!! Ha ha.

There is a nice used penetrator by Dennis , for sale at Ventura surf shop.

Thanks Matt…I will see if I can contact them. I think they have website so will go check it out.
Thanks again…I would rather have the real thing!

Dennis used to post on here once in awhile. If you get one of his you will be getting something that is more refined than the original MP’s. A much better board than the original or the ones Peck was doing. Dennis was working for Walden for quite awhile so he must have done some during that time frame. Dennis a much better shaper with regard to anything he shapes than Walden or Peck. Those boxes were and still are sunk in foam. With a fin patch over them and cloth under the box you should have no problem. Lowel

Dennis shaped them at MP, so one that he makes now is as real as it gets and more refined

Thanks McDing…much appreciated. I agree completely, back in 2004 I bought one of John’s Ultra Flight Penetrators from the Longboard House in Indiatlantic. It was extreme…ironing board flat in the nose and the dropped rail in the nose had an edge. Very challenging to ride in our beach break waves. The thing kept catching a rail and only worked for me off the tail or in bigger steeper waves. Dennis seems to have refined the shape and he is also a super nice guy to deal with. His prices are very competitive, it is just our stupid import taxes and customs charges that make anything from California expensive over here. Thanks for the info on the fin boxes, much appreciated.

As long as your not using light weight eps. Put glass in the box and then cap the box.

I’ve put quite a few long boxes into foam with no issues.

Back in the day they used to off set boxes because they didn’t want to cut into the stringer (or so I’ve been told)

Ps. It’s always a good idea to cap long boxes.




Honestly? Back in the day it had not occurred to them that a router and a jig would whip that puppy right out. Lol.

Contact Foam EZ for a shipping quote , import duty may be the problem .

The recent Thomas fire came quite close to Dennis’ place but he made it out okay. Still shaping and is one of the best and most prolific shapers in town. Dennis knows his stuff, has been around a long time, (back to the Front St. days) and can shape anything. Walden is…Walden.

What are the dimensions of that white board and how does it ride as a ‘twingle’?

9’10” - 22ish x 3-1/8 (off the top of my head)

Goes like a bat outta hell. One of my favorites and I really think the twingle thrives in big boards.

I’ve let others ride it and it’s never been a let down. (One guy is planning to build one in the next few months)

A  2 to 20 ?      A Twingle?       Or a 2 to 20, Twingle?

He wants to make something similar to the 2/20 - but 11ft long and run it as a twingle. - he rode mine and was blown away by the trim and really like response out of the square tail.

The old style Penetrators were intended for down the line noseriding at places like Rincon, Mary’s/indicators and Stables. I had a Prototype known as a “Snub”. When they went to lighter glass jobs they became more maneuverable and conducive to turns and cutbacks. I know Dennis shaped most of them, but it is possible Tom Hale may have done a few. By the time MP went full Shortboards with Mctavish, Cooper etc. The Penetrator had become fairly refined. The Front St. shop became William/Dennis Surfboards( Blinky Hubina and Dennis Ryder). Morey went on to other interests like the Morey Boogie. I don’t know what Pope did other than the Bisect. I didn’t go to school or grow up there. Just a Valley interloper who spent a little time around Front Street as a Gremmie. The rest is History.

I did a board recently that reminded me of those early MP boards. I’ll see if I can get you a pic. Lowel

I had a MP that had an off-set box with a wonder bolt to hold the fin in. It was pre- penetrator, and the box was just routed into the foam. I seem to remember somewhere in an old post that someone suggested placing strips of wood on each side of a box that wasn’t centered in the stringer. I don’t know if it would help. It wouldn’t hurt to line all sides of the routed out foam with a layer of glass as a reinforcement.

“Back in the day they used to off set boxes because they didn’t want to cut into the stringer (or so I’ve been told)”
Here are a couple that were done that way from that area (Santa Barbara) but not M-P. These are a little older - Yater and Owl labels. Not sure why they did it that way but preserving the stringer integrity is as good a guess as any(?)


Here are photos of a Phil Edwards board with a glass-on offset fin. I believe this one adds credence to the idea that by simply offsetting the fin, you create an asymmetrical board with one side ‘narrower’ than the other.



Not sure but I think it had something to do with keeping them higher in the pocket but I could be wrong…